Tag Archive | NEWA

Do you NEWA?

By Jody Timer, Entomology Research Technologist, Penn State’s Lake Erie Regional Grape Research and Extension Center

What is NEWA?

NEWA is The Network for Environment and Weather Applications network which has the capacity to connect you with data from weather stations across the Northeast. NEWA was created in 1995 by the NewYork State IPM. It is an online agricultural decision support system that uses real-time weather data, streamed over the internet from 573 weather stations throughout the Northeast, Midwest, and mid-Atlantic. (newa.cornell.edu) NEWA models and resources are available free of charge and are used to make informed localized crop management decisions.

Although provided free on the internet, it is funded through the New York State IPM program. It provides insect and plant disease pest management tools, degree days, insect models, crop production models, National Weather Service forecasts, and localized weather information for growers, consultants, Extension educators, faculty, researchers, and others. Interactive forecast models automatically compute and display results to inform crop production and precision IPM practices.

The information specific to grape production includes; Downy mildew, Phomopsis, Black rot, Powdery mildew, and Grape berry moth. This information can advise grape growers of best spray timing, wetting periods, and peaks in Grape berry moth generations specific to their area. A weather station at your farm or business improves the precision and accuracy of NEWA tools. NEWA interfaces with RainWise stations.

On the home page of NEWA (newa.cornell.edu) is a map of the Northeastern U.S. marked with the locations of hundreds of weather stations where historical and ‘up to the hour’ weather data can be viewed. Click on a weather station near enough to you (denoted by a leaf/raindrop icon) to get weather, insect pest, and disease information you need to make important management decisions. Clicking on ‘grapes’ under ‘crop pages’ will give you access to forecasting models for all the major diseases, as well as the grape berry moth degree-day model that will improve your timing of grape berry moth insecticide. You can replace your own grape bloom date with the one provided on the NEWA page to get a more precise prediction of recommended spray timings for grape berry moth generations.

Each model forecast is accompanied by helpful disease management messages and explanations. These suggestions for grape production are reviewed yearly by the Cornell and Penn State research and extension grape team.

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Contact your NEWA state coordinator before making any station purchase decision. NEWA partners with member states throughout the eastern and central United States to provide local grower support and expertise. Your coordinator can provide information specific to your state, answer questions about the NEWA platform, direct commodity questions to appropriate extension or university resources, and identify possible training opportunities for you. Click here to view a list of NEWA state coordinators

There is also a youtube video on the NEWA weather station network: https://youtu.be/Av8mlZEXZ8M?t=30

 

Three Phases to Managing Grape Berry Moth

By: Andy Muza, Penn State Extension – Erie County

As the season begins, growers should be prepared to manage a serious pest which can cause substantial economic losses. The grape berry moth (GBM) is a prevalent pest of grapes throughout Pennsylvania and the eastern United States. The larval stage feeds on berries and causes yield losses due to consumption and shelling of berries and by providing entry sites for fungi that can cause cluster rots.

I consider management of this pest to be a three phase process which includes: 1) PRE –TREATMENT  Phase; 2) TREATMENT  Phase;  3) POST – TREATMENT  Phase.

1) PRE-TREATMENT PHASE

Sprayer Maintenance

Follow maintenance procedures outlined in your sprayer manual. Check pump, hoses, filters, nozzles, etc. to be sure that everything is in good working order before your first pesticide application.  Also practice routine sprayer maintenance during the season such as lubrication of bearings and cleaning and flushing of the sprayer after each use.

Calibration of Sprayer

Sprayers should be calibrated early in the season well before any insecticide or fungicide spraying is required. Calibration of sprayers ensures that the appropriate amount of spray material is being applied where it is needed to manage pests. The sprayer should be calibrated in the vineyard under conditions in which the sprayer will be operated. Ideally, sprayers should be calibrated 2-3 times during the season as canopy growth increases.

Classifying a Vineyard Using the GBM Risk Assessment Program 

The GBM Risk Assessment Program was developed by Hoffman and Dennehy (Cornell University), (“Bulletin 138, Risk Assessment of Grape Berry Moth and Guidelines for Management of the Eastern Grape Leafhopper”  –  http://nysipm.cornell.edu/publications/grapeman/files/risk.pdf).  It is a method of classifying vineyard blocks for risk (e.g., High, Low or Intermediate) of receiving damage from grape berry moth. The criteria used for assigning risk include: Value of the varieties being grown; Surrounding Vineyard Habitat; History of GBM injury; Climatic factors related to the region where grapes are being grown.

High Risk Classification  

Value of the varieties being grown – if higher value varieties such as Vitis vinifera, many hybrids, or table grapes are being grown then these vineyards should automatically be assigned a High Risk Classification. Therefore most vineyards in Pennsylvania, outside of the Lake Erie Region, should initially be classified as High Risk. This classification can be adjusted later if scouting history reveals that GBM injury is consistently low at your vineyard site.

Surrounding Vineyard Habitat – if wooded edges or hedgerows/weedy areas are present around vineyards.

History of GBM injury – if scouting reveals that damage is often above 6% cluster damage in July and /or above 15 % cluster damage (2% berry damage) at harvest. These injury levels were developed with processed juice grape varieties in mind and injury levels may be lower for varieties that command a higher value/ton.

Climatic factors related to the region – if a region has prolonged winter snow cover or mild winter temperatures.

Low Risk Classification

Value of the varieties being grown – if lower value varieties (e.g., juice grapes) are being grown.

Surrounding Vineyard Habitat – if no wooded edges or hedgerows/weedy areas are present around vineyards.

History of GBM injury – if vineyards seldom have problems with GBM. The history of GBM injury for each site is acquired by maintaining scouting records of vineyards over the years.

Climatic factors related to the region – if permanent snow cover is rare and site is prone to severe winter temperatures.

Intermediate Risk Classification – is a catch all classification.  If it isn’t High or Low risk then site is classified as Intermediate risk.

Life cycle and description of GBM

Knowledge about the life cycle and ability to identify the pest and injury caused is important for successful management. Moths emerge from the overwintering pupal stage in spring. Emergence in Erie County, Pa. occurs in late May but in other areas of the state this may occur 2 -3 weeks earlier. These moths are small (about 6 mm), brownish with grey-blue coloration at the base of wings (Figure 1). Unless pheromone traps are used it is unlikely that moths will be observed. Adults are active around dusk and have a distinctive zig zag pattern in flight. Mated females lay eggs singly on flower clusters or berries. Eggs are very small (< 1mm), scale-like and whitish, opaque (Figure 2). Due to their size, eggs are difficult to observe without a hand lens. Early in the season larvae hatching from eggs will web together small berries to feed. However, when berries reach about 5 – 7 mm in size, larvae will bore directly into berries to feed. Newly hatched larvae are tiny with white bodies and black head capsules. Later stages are brownish to purple in coloration (Figure 3). Upon completing development larvae exit berries and either drop to the ground to pupate in leaf litter or some will pupate in the canopy in a semicircular leaf flap. Pupae which are encased in leaf sections are light brown to greenish in coloration (5 mm). Leaves with pupae will remain underneath the trellis if there is poor weed control or will be moved by the wind and collect along wood edges, or in brushy areas. Adults will emerge from pupae to begin the next generation. There are usually 3 – 4 generations of GBM per year in Pennsylvania, depending on temperatures during the growing season.

Figure 1. Grape Berry Moth adult on Concord leaf. Photo by: Andy Muza, Penn State

 

Figure 2. Grape berry moth eggs on Concord cluster. Photo by: Andy Muza, Penn State

 

Figure 3. Grape berry moth mature larva on berry. Photo found at: Grape Berry Moth fact sheet http://nysipm.cornell.edu/factsheets/grapes/pests/gbm/gbm_fig3.asp

Scouting                                                                                                                                                                                           

Regular scouting throughout the season (at least weekly) is critical in determining if and where applications should be applied for GBM.  A scouting protocol for GBM is described in “Bulletin 138, Risk Assessment of Grape Berry Moth and Guidelines for Management of the Eastern Grape Leafhopper” .

This protocol recommends selecting four different areas in your vineyard to be sampled during each scouting event. Two different areas should be checked in the interior of the vineyard and two different areas along the exterior (border) portions of the vineyard. At each of the four sampling sites, randomly select 5 vines and examine 10 clusters/vine for GBM injury. Determine separate injury levels (# injured clusters/100 clusters = % injured clusters) for the interior and exterior portions of the vineyard. It is important to keep separate injury levels for the interior and exterior areas because border areas near woodlines/hedgerows will usually have higher levels of injury. Therefore, border areas may need an insecticide application while interior areas may not.

When scouting early in the season look for webbing in the clusters (Figure 4). Until berries are large enough to enter, larvae will web together multiple berries and feed from inside webbing sites. Some varieties (e.g., Concord) may exhibit a distinct reddening of portions of the berry if injury occurs before veraison (Figure 5) while other varieties do not (Figure 6). Later in the season look for holes, splits, webbing or dark tunneling underneath berry skin (Figure 7).  If injured berries are broken open then larvae may be found.

Figure 4. Webbing in cluster from GBM larva. Photo by: Andy Muza, Penn State

 

Figure 5. Reddening of Concord berries caused by GBM injury. Photo by: Andy Muza, Penn State

 

Figure 6. GBM entry holes in Niagara berries. Photo by: Andy Muza, Penn State

 

Figure 7. Late season GBM injury on Concord berries. Photo by: Andy Muza, Penn State

Map vineyards and keep scouting records – Develop detailed maps of your vineyards and surrounding topography. Keep records of GBM injury levels for each scouting date and vineyard sections checked. These records will provide a GBM history per site.

Pheromone Traps – GBM flight periods can be monitored using commercially available pheromone traps (Figure 8). Traps and pheromone caps can be purchased from a number of sources such as at Great Lakes IPM, Inc.  and  Scentry Biologicals, Inc.  Monitoring traps are baited with small rubber lures impregnated with GBM female sex pheromone for attracting male moths. Pheromone traps may provide an idea of population levels at your vineyard site and can be used as a scouting tool to indicate flight periods. However, trap data are not used for timing of spray applications due to ambiguity concerning correlation of capture numbers and berry injury levels.

Figure 8. Pheromone trap for monitoring GBM flight periods. Photo by: Andy Muza, Penn State

Cultural Practices

Cultural practices are integral for any integrated pest management program. Therefore, maintain good weed control under the trellis. Poor weed management resulting in excessive vegetation under the vines can harbor grape berry moth (GBM) pupae.

Viticultural practices that promote a more open, less dense canopy resulting in better exposure of clusters to sunlight (e.g., shoot thinning, leaf removal, judicious use of nitrogen) will not only improve quality of fruit but will enable better spray coverage.

Vineyard area maintenance such as preventing overgrown, weedy areas around the vineyard will reduce overwintering sites for GBM pupae. If possible, removal of wild grapevines near the vineyard will decrease potential reservoir sites.

2) TREATMENT PHASE

Spray Timing

To accurately time insecticide applications it is recommended that the Grape Berry Moth Degree-Day Model be used. The GBM DD Model is a temperature-driven developmental model developed by Tobin and Saunders at  Penn State. This model is incorporated into Cornell’s Network for Environmental and Weather Applications (NEWA).  Collaborative research at Penn State, Cornell and Michigan State Universities has shown that use of this developmental model can improve GBM management. For a comprehensive explanation concerning the development and use of this forecasting model consult   “Focus on Females Provides New Insights for Grape Berry Moth Management” , Issue 14, May 2013.

Use of the GBM DD Model:

  • CHECK the NEWA weather station closest to your vineyard. There are a number of NEWA weather stations located throughout Pennsylvania.  However, the majority of vineyards outside Erie County, PA will probably not be close enough (i.e., within a few miles) to a NEWA station for this option to be useful. But you can still use the GBM DD Model by recording daily maximum and minimum temperature data on your own. Options include either purchasing a max/min thermometer or weather station for your site. The RainWise AgroMET & IP-100 Package   http://www.rainwise.com/  is the authorized choice for participation into the NEWA network.
  • MONITOR and RECORD the date of wild grape bloom (i.e., when approximately 50% of flowers open) for each vineyard site. Research has shown that egg laying by females that emerge in the spring (first generation) is closely associated with bloom of wild grapevines. Therefore, the majority of eggs from this generation are laid on wild grape clusters and not in cultivated vineyards. NOTE: If using a NEWA site then enter the date of wild grape bloom into the model. If you do not record a wild grape bloom date for your site then the model does provide an estimated date for the weather station that is used.
  • TRACK GBM degree days using a NEWA station closest to your vineyard site OR keep a running total throughout the season of GBM degree days [(Daily MAX + MIN Temperatures)/2) – 47.14 F] starting on the recorded date of wild grape bloom.
  • SCOUT to determine injury levels.
  • SPRAY (if needed) as close to the designated degree day timings as possible.

The model recommends an insecticide treatment in high and possibly intermediate risk sites when: 810 GBM degree days are accumulated for the second generation; 1620 GBM degree days for the third generation; and 2430 GBM degree days (if harvest has not yet occurred) in years that a fourth generation occurs. Insecticides such as Intrepid, Altacor, and Delegate are suggested for these timings.

If using broad spectrum contact insecticides (e.g., pyrethroids) then applications should be delayed about 100 GBM degree days for each generation (i.e., 910, 1720, 2530 GBM degree days).

Insecticide Choices/Application Practices

There are numerous insecticides effective for GBM which are registered for use in Pennsylvania. Consult the 2017 New York and Pennsylvania Pest Management Guidelines for Grapes (https://store.cornell.edu/p-197039-2017-new-york-and-pennsylvania-pest-management-guidelines-for-grapes.aspx).

Rotate insecticides with different modes of action into your GBM spray program to prevent/delay insecticide resistance. Read the label to determine if a spray adjuvant and/or pH adjustment to spray water is required. Also, incorporate more selective insecticides (e.g., Intrepid, Altacor, Delegate) into your spray program which will aid in conserving natural enemies.

Good spray coverage on clusters is critical. Therefore, spray every row and use appropriate gallonage, speed, pressure, and nozzles for good cluster coverage as the size of the canopy increases throughout the season.

3) POST-TREATMENT PHASE

Evaluate efficacy of applications

Don’t assume that because an insecticide was applied that GBM was controlled. After an insecticide application check areas that were sprayed to determine the effectiveness of the application. High Risk sites in Erie County, PA have benefited from back to back applications (about 10 days apart) per generation due to extremely high population levels at these sites.

Continue to Scout                                                                                                                                                                        

Monitoring your vineyard(s) not only for GBM but also for other insects, diseases and weeds should continue through harvest.

Keep Accurate Records

Accurate records should be kept each season for: scouting (e.g., dates, pests observed, vineyard location where observed, injury levels); pesticide applications (e.g., pesticides used, rates/acre, gallons/acre applied, etc.) and weather data.

Re – examine management practices

At the end of the season, especially if GBM was not adequately controlled, re – examine management practices by reviewing your records. A few factors to consider that contribute to poor control include: Inadequate Spray Coverage; Inaccurate Spray Timing; Too Few Applications; and Choice of Insecticides.

Change/Fine Tune management practices

The results of re-examining your practices may reveal flaws in your management strategy. If flaws are identified then be prepared to make the necessary changes in the future. Fine tuning your pest management strategy is an ongoing process which should evolve as long as you continue to farm.

2017 Pre-Bloom Disease Management Review and Discussion

By Bryan Hed

Another season of grape growing is upon us and it’s a good time to review important disease management principles and be aware of some of the tools to consider integrating into your vineyard management programs this spring.

First is your annual reminder to check out the NEWA website (Network for Environment and Weather Applications) found at http://newa.cornell.edu. On the home page is a map of the Northeastern U.S. marked with the locations of hundreds of weather stations where historical and ‘up to the hour’ weather data can be viewed. Although is provided free on the internet, it is funded through the New York State IPM program. Click on a weather station near enough to you (denoted by a leaf/rain drop icon) to get weather, insect pest, and disease information you need to make important management decisions that could save you time and money. Clicking on ‘grapes’ under ‘crop pages’ will give you access to forecasting models for all the major diseases, as well as the grape berry moth degree day model that will improve your timing of grape berry moth insecticide sprays later this summer. Each model forecast is accompanied by helpful disease management messages and explanations.

Next, let’s move our minds into the upcoming pre-bloom disease management season. It’s important to recognize that the threat of disease this spring (pre-bloom) is largely determined by the amount of overwintering inoculum in your blocks. The amount of overwintering inoculum is dependent on the amount of disease that developed in your vineyard last year or in previous years. In other words, if you have kept diseases well under control in the past, especially last year, then there will be relatively little for pathogen populations to build on and cause damage, at least initially, this year. Some very practical research by Wayne Wilcox at Cornell nicely illustrates this point with powdery mildew (pm) development in susceptible wine varieties. In blocks where pm was well controlled all season, fewer overwintering structures of the fungal pathogen (chasmothecia) were available the following spring to jump start disease cycles. Early disease pressure was relatively low and early sprays were less critical to good commercial control than in blocks where disease control was poor the previous year. Where there was poor control the previous year, more of the pathogen overwintered to start disease cycles the following spring and early sprays were critical to maintaining successful commercial control. This is not to say that a bad year of pm will automatically be followed by another bad year. But it certainly tilts the odds in favor of the pathogen, especially if for some reason, you can’t manage the timely application of your early disease control program (stuff happens). It also doesn’t mean you can slack off this year if you had good control last year. Remember, there’s the weather. The weather ALWAYS plays an important role too. A good illustration of this is an experience by an organic grape grower who, in an extremely wet season, developed a serious, economically damaging case of black rot. In conventionally managed vineyards there are several very effective chemistries to control black rot, but in organic production there are no real effective fungicides, and control of this disease in organic vineyards must rely heavily on cultural measures that reduce the pathogen’s overwintering population. Of course, the grower did everything he could to sanitize the trellis of overwintering fruit mummies and bury mummies that had fallen to the ground to reduce overwintering inoculum. But fortunately, the following year was bone dry during the fruit susceptibility period and black rot was not even an issue. Had the previous wet season been followed by another wet one, I’m quite certain, the battle for control of black rot in that organic vineyard would have required ‘the kitchen sink’ to avoid losses. Unfortunately, we have no control over the weather and accurate forecasts, especially long term, are not something to rely on. But, we can (and should) strive to control overwintering inoculum levels every year and the best way to do that is good, practical, season-long disease control.

So, begin to wrap your minds around the campaign ahead. If you had poor disease control in some blocks last season, have you reviewed your spray records where control failed AND where it worked well? Where it failed, did you use the wrong material at a critical time?  I’ve had growers discuss their control failures with me only to discover that their timing was fine, but their choice of material did not cover the disease(s) they intended to control. The number of spray materials, what disease each one controls, and how well each one controls each disease, can be bewildering at times…and the list keeps growing and changing. Also, materials that used to be good choices may have become ineffective due to the development of resistance by the pathogens. For example, materials like the strobilurins (Abound, Sovran, Flint, Pristine) are no longer effective at controlling powdery and downy mildew in many parts of the east. In vineyards where this has occurred, using them during the critical fruit protection period (which used to be a great idea!) can now prove disastrous. The sterol inhibitor fungicides (Rally, Elite, Orius, Mettle, Tebusol, Tebustar, Procure, Viticure, etc) are also exhibiting the effects of resistance by the powdery mildew fungus. Though in most cases they still work on powdery to some extent, they are not appropriate for the critical fruit protection period anymore, around and shortly after bloom (products that include the more active difenoconazole are an exception on less susceptible varieties). However, they may be acceptable for maintaining a clean vineyard outside the critical period. Do you have an accurate grasp on that?

Do you have a firm grasp on the critical fruit protection period? The critical period for fruit protection from all diseases generally extends from ‘just before bloom’ to about 4 weeks later. This is the period when you need to be especially vigilant about minimizing spray intervals, using your best materials that cover all the major diseases (Phomopsis, black rot, powdery and downy mildew), focus on good coverage, etc. It is never profitable to try to cut corners during the critical period. However, if you had heavy amounts of black rot in your vineyard the year before, you should assume you have an unhealthy dose of overwintering inoculum in your vineyard this spring, and prevention of leaf lesions in the fruit zone (which would need to be addressed during the first 3-12” of shoot growth, well before the fruit protection period) would also prove to be critical. This goes for other diseases as well (refer back to the previous example with Wayne Wilcox’ powdery mildew experiment). The pre-bloom presence of visible disease in the fruit zone is a big red flag; it means you’ve got potential for serious fruit loss ahead, especially if weather conditions favor the pathogen (wet, warm, humid, calm, cloudy) during the fruit protection period that follows.

Did you record the relative levels of disease that developed in years past for each of your blocks? In order to do this, you need to be able to identify the various diseases and then scout regularly for them. This takes up valuable time but you can streamline your scouting efforts in many ways. Do you know when you would expect to first see each disease? Downy mildew doesn’t become active until about the 5-6 leaf stage. So, you know you can’t expect to see it until about that time or shortly after that. In which blocks are diseases most likely to occur first? Your block or rows next to the woods would be a good place to start, or perhaps your most susceptible variety. Blocks with the most disease last year would be a good place to start. On which parts of the vine do you expect to see diseases appear first? Can recent weather data help you to determine where to look for the disease? For example, if a black rot infection period occurred 2 weeks ago (and you can find this out easily by searching the NEWA website), would you examine the newest growth, the oldest growth, or would you look for lesions on leaves that were currently expanding and most susceptible 2 weeks ago? The answers to these questions can help you streamline your scouting efforts, save time, and improve your expertise.

Do you fully comprehend the susceptibilities of all the varieties you’re growing? You cannot spray premium Vitis vinifera like the hybrids or natives and expect the same results. What are you going to change this year to address disease control breaches in your vinifera? If you had good control last year, are you ready to do it again this year? OR, do you feel lucky and plan to back off until close to bloom to apply your first spray? I always plan for the worst when it comes to the weather and assume it’s going to be wet, cloudy, and warm; ideal for fungal disease epidemics. Consider that here in the east we are growing a highly vulnerable, susceptible host (wine grapes) on the pathogen’s ‘turf’ (the wet, humid eastern U.S.). The good news is that disease control during the pre-bloom period is generally easier (good spray coverage not a problem, low initial disease/inoculum levels, etc.) and cheaper (can use lower fungicide rates, lower spray gallonage, less expensive materials, less time, etc) than in the post bloom period, and a well prepared pre-bloom disease management program will provide extra insurance against problems during bloom and early fruit set, when your fruit ($) is most vulnerable. Now let’s review the common diseases with some of these questions and concepts in mind.

Phomopsis cane and leaf spot is often the first disease problem we face in the pre-bloom period, particularly where trellis systems maintain lots of old and/or dead wood. That’s because old and/or dead wood is where the pathogen overwinters. Therefore, the more old wood you have in your trellis, the more inoculum you can expect to be battling with this spring. Conversely, cane pruned systems have fewer problems with Phomopsis, and cane pruning/minimizing older wood is an important cultural control for this disease. Fortunately, many areas of PA and other parts of the east experienced a relatively dry spring in 2016, helping to minimize new overwintering infections on year-old wood. But, older cordons and especially dead wood and pruning stubs, can carry overwintering inoculum into many subsequent springs. So, if there was little opportunity for new Phomopsis infections to occur last year, you can still be carrying a fair amount of overwintering inoculum in old cordons and pruning stubs.

During early spring rains, Phomopsis spores flush from lesions on wood and are splashed about to invade any new shoot, leaf, and inflorescence they land on…provided the wetting period/temperature combination falls within a minimum range for infection. The basal-most (oldest) internodes of new shoots are the most susceptible to shoot infections simply because they are closest to the inoculum source; wood. In every trial where I have rated shoot infection of Phomopsis, the most severe lesion development was ALWAYS found (on average) on the first (oldest) internode region of the shoot. Lesion development typically got less severe as my rating progressed through internodes 2, 3, 4, and 5. However, once these internodes become fully expanded after the first few weeks in the season, they are no longer susceptible to lesion development. I rarely see Phomopsis lesion development beyond the fifth internode region. That’s why this disease is best dealt with preventatively, very early, during the first few inches of shoot growth. Infections that occur on the first few internodes of new shoots are not only the most likely to occur, but also the most critical; infections of inflorescences (generally on nodes 2-5) can lead to crop loss early (parts of the inflorescence may be ‘bitten off’ by the pathogen) or later during ripening (cluster stem infections in spring move into berries and cause fruit rot and shelling after veraison). And, infections that occur on the basal-most internodes, can’t all be eliminated by judicious hand pruning during the dormant season. So, in blocks where you suspect any risk of early Phomopsis infections, applications of a fungicide (mancozeb or captan are good choices) at no later than 3-6” of shoot growth are a good investment, particularly if you are not cane pruning. Following up with fungicides at 8-12” shoots and immediate pre-bloom are also important pre-bloom applications. Below are some pics from last year’s blog (Figures 1, 2) to help you get a handle on the appearance of lesions on year-old canes. Unfortunately, determining the presence of Phomopsis on older wood generally involves more than just a visual assessment.

Figure 1. Dark brown lesions on the first few internodes on these Chancellor canes are from Phomopsis infections that occurred during early shoot growth in the previous year (when these were green shoots). The buds present are just ready to burst open with new shoot growth that will be very vulnerable to infection during subsequent rain periods.

Figure 2. Although the 1” shoot stage can be vulnerable to damage from this pathogen, the more critical stage is at 3-6” shoots, when more shoot, leaf, and cluster tissue is exposed and is highly susceptible (below). Note the inflorescence in the upper right picture from which Phomopsis has “bitten off” whole branches, dramatically limiting yield potential for that cluster.

Pre-bloom fungicide applications for Powdery mildew are also prudent during early shoot growth for Vitis vinifera cultivars and highly susceptible hybrids, especially in vineyards where control of this disease may have slipped last year (again, because of lots of overwintering inoculum). The primary inoculum for this pathogen generally comes from overwintering structures of the fungus that are lodged within cracks in the bark of cordons and trunks. Spring rain periods of at least 0.1” of precipitation and temperatures of 50 F or more, are the requirements for release of primary inoculum (ascospores) from the overwintering structures. The more mildew that was allowed to develop the year before, the larger the release of spores in early spring, the more primary infections that are likely to occur, and the more critical the need to control the disease early. Sulfur, oils, monopotassium phosphate, and potassium bicarbonate materials can be good choices for mildew management early on. All of these materials can eradicate small existing powdery mildew infections on leaves and cluster stems. Most do not generally offer any protection from future infections and therefore work best if applied often. Sulfur is an exception, and has the added benefit of providing a week or more of protection against future infections. Many of the more experienced growers like to utilize a mancozeb/sulfur combination to control all diseases during the pre-bloom period. This combination is relatively inexpensive, there are no resistance issues, and it works. Remember to read labels and be aware that you can’t mix sulfur and oils, or oils and captan. The tebuconazole products can be used during early pre-bloom to control powdery mildew as well, especially at the 8-10” shoot stage. These materials are very inexpensive and generally provide enough powdery mildew control to keep vines healthy until the immediate pre-bloom spray (they will also nicely control early black rot infections). At immediate pre-bloom and first post bloom, you want to apply your best powdery mildew chemistries like quinoxyfen (Quintec), difenoconazole (Revus Top), metrafenone (Vivando), fluopyram/tebuconazol (Luna Experience), etc. For native juice grapes, powdery mildew is rarely a concern during the early shoot growth stages, especially in the cooler Lake Erie region of Pennsylvania.

A note about fungicide resistance management and powdery mildew: It’s important to plan your powdery mildew management choices ahead of time with resistance management in mind. The easiest way to do this is to become familiar with FRAC (fungicide resistance action committee) codes listed prominently on the first page of fungicide labels. Fungicides with the same FRAC group number can be considered similar enough in their mode of action/chemistry that resistance to one is resistance to all others within that group. Therefore when you rotate fungicides for resistance management, you’re essentially rotating FRAC groups. Some good rules to remember are to avoid using the same FRAC group consecutively, or more than twice in a given season. The development of powdery mildew resistance is always a concern when using materials like the strobilurins (FRAC 11), the sterol inhibitors (FRAC 3), Quintec (FRAC 13), Vivando (FRAC U8), Luna Experience (FRAC 7, 3), Torino (FRAC U6), and Endura (FRAC 7) to name a few. Resistance is generally not a concern for uses of sulfur, oils, bicarbonates, and the potassium salts (mentioned above), or copper.

Next, black rot: One of the best ways to reduce overwintering inoculum of black rot is to scout your vineyard for old fruit mummies and eliminate them from the trellis. Black rot infected fruit mummies that have overwintered in the trellis are the most potent source of inoculum for infections the following spring. No matter how cold it gets over the winter, the pathogen survives just beautifully in colonized fruit remaining in the trellis. But, dropping this inoculum source to the soil, allows microbial degradation/weathering to reduce the potential for mummies to release spores the following spring. It also places the inoculum source much farther from new, susceptible plant tissue up in the trellis. The best time to ‘sanitize’ the trellis is during dormant pruning; weathering has already accomplished some of the removal of last season’s infected fruit from the trellis, and what remains is relatively easy to see and remove by hand. Experiments we conducted several years ago clearly showed that the earlier the mummies are knocked to the ground during the dormant period, the more time for decomposition to break them down before the next season, and the fewer spores released from the ground the following spring to start new disease cycles. Nevertheless, some inoculum on the ground will survive to release spores in spring, and burial of mummies with cultivation will go a step further to eliminate the threat. Removal of ALL old cluster material from the trellis before bud break is important to maintaining good control of this disease.

It may not be necessary to apply a fungicide for black rot at early shoot stages IF good control of this disease was achieved the previous year AND conscientious scouting and trellis sanitation has been implemented. However, the importance of early shoot infections should not be underestimated as I mentioned above, especially if they result in leaf lesions in the fruit zone. For example, inoculations we performed from early May to early June (simulating wet weather and an overwintering inoculum source (mummies) in the trellis) resulted in leaf and shoot lesions in the cluster zone (Figure 3). Those lesions went on to release spores during the critical fruit protection period, resulting in crop loss of 47-77% on those shoots with infected leaves!

An application of mancozeb, ziram, or captan for Phomopsis will also provide control of early black rot infections. The sterol inhibitor fungicides and strobilurins are also good materials for black rot that are more rainfast than mancozeb, ziram, and captan. The sterol inhibitors also provide excellent post infection activity that can be very useful at terminating an infection that has already occurred (but not yet manifested itself).

Figure 3. Early (pre-bloom) black rot leaf infections in the cluster zone provide inoculum that can add to problems with controlling fruit infection after capfall. The two small tan lesions on the leaf at node 2 are just inches from the developing inflorescence found at node 3 (picture on the right). These lesions will release spores during rainfall periods that could easily be splashed to highly susceptible cluster stems pre-bloom, and developing fruit after capfall. Resulting fruit infections will lead to crop loss.

Downy mildew and the 5-6 leaf stage: This stage marks the point at which the downy mildew pathogen first becomes active and is capable of releasing primary spores from inoculum sources that have overwintered on the ground (leaves and other plant material that was infected during the previous season). As with all other diseases, vineyards that developed a fair amount of downy mildew leaf/cluster infection last year will be at higher risk this spring than vineyards that were kept clean. However, overwintering structures of the downy mildew pathogen can survive more than one season in the soil.

Periods of rainfall with temperatures of at least 52 F meet the requirements of spore release and the first infections; plant surfaces must be wet for infection to occur. While scouting for this disease, expect to see it first in wetter areas of your acreage and pay close attention to leaves near the ground (sucker growth, grape seedlings that germinated from shelled berries last fall) which are most likely to become infected first. Therefore, keeping such low growth to a minimum in spring is a prudent control measure that can delay the development of the disease. It also suggests that if you’re planning vine trunk renewal from sucker growth, you will need to apply fungicides to protect that growth from the ground up as the pathogen becomes active.

Spring leaf infections are identified by the yellow ‘oil-spots’ seen on the tops of leaves (Figure 4), coinciding with white, downy sporulation of the pathogen on the undersides of leaves. Inflorescences can be blighted and show sporulation as well. Sporulation occurs during darkness under high relative humidity, and can typically be seen during a morning scout of the vineyard following a wet/humid night. Under optimum temperatures (70-75F), only an hour or two of plant surface wetness may be required for infection to occur, and new infections can produce their own spores with just 5 days.

Many parts of the northeast experienced drought conditions last year, which severely inhibited the development of this disease. Up in Erie County PA, the disease basically took a vacation in 2016, and I could barely find a handful of lesions on unsprayed ‘Chancellor’ leaves and fruit near the ground all summer: it was the perfect year to start renewal trunks! It wasn’t until later in August that rains finally returned and we began to see a few more infections, but for the most part the disease literally could not get off the ground in Erie county PA in 2016. What does this mean for 2017? The great lack of downy mildew in drought hit areas last year means that pre-bloom disease cycles this year will have to rely on overwintering inoculum from previous years (although spores of downy mildew can travel long distances between vineyards, the first infections will arise from inoculum within your vineyard). I have not found any detailed information as to how long the pathogen can survive in the soil, but I guarantee that if you’ve had downy mildew before, then it’s still there. Whether your area was wet or dry last spring, the principle described earlier still applies: vineyards devoid of downy mildew last year (whether from drought or just plain good control) will be easier to keep ‘clean’ in the pre-bloom period this year.

Mancozeb products are good options for the first downy mildew, Phomopsis, and black rot sprays in the pre-bloom period. Ziram and Captan have a similar spectrum of control, but Ziram is a little weaker on downy mildew, and Captan a little weak on black rot.  However, these may be a viable option if these diseases are not a huge threat early on (that is if you had good control last year). These materials are all surface protectants subject to wash-off by rainfall, which means that under heavy, frequent rainfall conditions, application intervals will need to be minimized (7-10 days?) especially for highly susceptible varieties. For that more critical ‘immediate pre-bloom’ spray (and the first post bloom spray), there are other materials like Presidio, Revus, Revus Top, and Zampro that are quite rainfast, very effective, and will provide longer range protection under wet conditions (when you need the protection most and are least likely to be able to stick to shorter spray intervals). However, products like Presidio also require a second active ingredient (like mancozeb) in a tank mix for resistance management purposes (which isn’t a bad idea at this critical spray timing in any case). Other materials like the phosphonates, Ranman, and the strobies /Reason, are probably best utilized outside the critical two sprays around bloom (especially for V. vinifera and highly susceptible hybrids), unless they’re used as tank mix partners with other effective materials. They’re very good materials, but they’re just not the ‘best of the best’.

Figure 4. Yellow oil-spot symptoms of downy mildew on young spring leaves.

One more time for emphasis: the immediate pre bloom and first post bloom (7-14 days later) fungicide applications are the most important you’ll make all year, regardless of variety grown and disease pressure. These two sprays protect your fruit from all the major fungal diseases (Phomopsis, black rot, downy and powdery mildew). Make sure sprayers are properly calibrated and adjusted for best coverage on a bloom-period canopy, spray every row at full rates and shortest intervals, and NEVER extend the interval between these sprays beyond 14 days.

‘Newer’ Fungicides: Aprovia (solatenol) may be worth a try for powdery mildew control (received federal registration in 2015). The active ingredient is related (same FRAC group) to Boscalid (found in Endura and Pristine) and Fluopyram (found in Luna Experience). It also has activity against black rot, but should not be expected to control this disease under high pressure on a susceptible variety.

***Lastly, to help you with all your grape management decisions this year, you should have…

New York and Pennsylvania Pest Management Guidelines for Grapes. An inexpensive, excellent source of research based information for commercial growers; some information in this blog was gleaned from it and it is revised every year to include the newest information. Copies can be purchased at the Cornell Store at https://store.cornell.edu/c-875-pmep-guidelines.aspx. It sells for about $31.

 

2016 Pre-Bloom Disease Management Review

By: Bryan Hed

Spring has arrived, but it sure doesn’t feel like it in many parts of the Northeastern U.S. However, the cool weather is buying us some extra time that can be used to review our pre-bloom disease management plans and familiarize ourselves with all the tools at our disposal. First, if you haven’t done so yet, acquaint yourself with the NEWA website (Network for Environment and Weather Applications) found at http://newa.cornell.edu. This is your annual reminder! On the home page is a map of the U.S. with every location of a weather station (391 locations!) that can be tapped into for historical and ‘up to the hour’ weather data. From the convenience of your computer screen, you can view weather information from eastern Nebraska to the eastern seaboard, and many places in between. In connection with each weather station is a pest forecast to help you make insect pest and disease management decisions. Use your cursor to navigate the map and click on the weather station nearest you (denoted by a leaf/rain drop icon) to view nearby temperature, rainfall, leaf wetness duration, wind speed, etc.  Clicking on ‘grapes’ under ‘crop pages’ will give you access to disease forecasting models for Phomopsis cane and leaf spot, black rot, and powdery and downy mildew. You can also access the grape berry moth degree day model that will improve your timing of grape berry moth insecticide sprays later this summer. Research has shown that use of the berry moth model can improve control of this pest (and of the Botrytis and other rot that develops as a result of the damage it causes) without any increase in your management costs. Each model forecast is accompanied with helpful disease management messages and explanations. This is a great way to make use of one of those cold, rainy mornings to educate yourself and prepare for the challenges ahead.

Disease concerns during early shoot growth stages

Phomopsis cane and leaf spot is our first concern during the early stages of growth in late April and early May. This is because inoculum sources overwinter in woody tissues (alive and dead) right on the vine, and often on wood you can’t just prune out (basal nodes on year-old canes). Infected wood releases spores of the fungus during the first rain periods in spring. The inoculum sources  which appear as dark scabby lesions on the first few inches of year-old canes, may be just millimeters from the first susceptible green tissue after bud break (Figure 1) and spores can infect within relatively short time periods (24 hours) at very cool temperatures (upper 40s). An examination of your vines now can provide you with some idea of the amount of inoculum present in your vineyard, and the need for early fungicide applications to prevent infections in the cluster zone.  Look specifically for lesions along the first (oldest) few inches of year old canes (again, see Figure 1). Also, old pruning stubs are classic sources of inoculum, and according to work performed at Cornell University, dead wood is probably the most potent source of spores of Phomopsis as the fungus grows and sporulates especially well on this material; removal of all dead wood from the trellis at dormant pruning will help control this disease. Where inoculum sources have built up in the trellis (which is particularly a problem in machine pruned vineyards) applications of mancozeb, ziram, or captan during early shoot growth stages are a cost effective way to control shoot and cluster stem infections (Figure 2) that can lead to crop loss. It will also help to prevent the build-up of inoculum on tissues that you can’t just prune out during dormancy (those first 4-5 nodes of shoots that you need for next year’s crop!).

Figure 1. Note the dark brown lesions on the first few internode regions on these Chancellor canes. The lesions are from Phomopsis infections that occurred during early shoot growth in the previous year (when these were green shoots). The buds present are just ready to burst open with new shoot growth that will be very vulnerable to infection during subsequent rain periods.

Apr 2016_Bryan_Phomopsis

Figure 2. Although the 1” shoot stage can be vulnerable to damage from this pathogen, the more critical stage is at 3-6” shoots, when more shoot, leaf, and cluster tissue is exposed and is highly susceptible (below).

Apr 2016_Bryan_Phomopsis 2

Sprays for powdery mildew may be prudent during early shoot growth for Vitis vinifera cultivars and highly susceptible hybrids, especially in vineyards where control of this disease may have slipped last year (lots of overwintering inoculum). Unlike the fungi causing Phomopsis and black rot, the powdery mildew fungus has to have live grape tissue to grow and reproduce. It survives the winter by going dormant itself, just like their grapevine host. According to work at Cornell University overwintering inoculum will come primarily from infections that occurred before Labor Day of last year. This is because infections that occurred after that, likely do not have time to prepare for winter dormancy and overwintering survival. Then, during the following spring, primary infection periods occur with the completion of two simple weather factors: at least a tenth of an inch of rain with temperatures above 50 F. When those two factors occur in concert, overwintering inoculum (spores of the fungus) has been unleashed from its dormant stage and the potential for infection is there if green tissue is present. Applications of sulfur, oils, Nutrol, and potassium bicarbonate materials can be good choices for mildew management early on. Remember to read labels and be aware that you can’t mix sulfur and oils, or oils and captan. Powdery mildew is rarely a concern during the early shoot growth stages for growers of juice grapes, especially in the cooler Lake Erie region of Pennsylvania.

As for black rot, scout your vineyards for old fruit mummies and clusters (infected from the previous season) in the trellis. Removal of ALL old cluster material before bud break is essential to maintaining good control of this disease. Once on the ground, mummies/clusters can be buried with cultivation, reducing or eliminating their capacity to fuel new infections in spring. As I mentioned in last year’s blog, a fungicide application for black rot may not be necessary at these early shoot stages IF good control of this disease was achieved the previous year AND conscientious trellis sanitation has been implemented. On the other hand, the importance of early shoot infections should not be underestimated. For example, inoculations we performed at these early shoot growth stages (from early May to early June) simulating wet weather and an overwintering inoculum source (mummies) in the trellis, went on to produce leaf and shoot infections in the cluster zone (Figure 3) that released spores during early berry development stages and resulted in crop loss of 47-77%! An application of mancozeb, ziram, or captan for Phomopsis will also provide control of early black rot infections.

Figure 3. Early black rot leaf infections in the cluster zone provide inoculum that can add to problems with controlling fruit infection after capfall. The two small tan lesions on the leaf at node 2 are just inches from the developing inflorescence found at node 3. These lesions will release spores during rainfall periods that could easily be splashed to highly susceptible cluster stems pre-bloom, and developing fruit after capfall. Resulting fruit infections will lead to crop loss.

Apr 2016_Bryan_Black Rot Leaf

At about 10-12” shoot growth or the 5-6 leaf stage: The importance of applying sprays at this stage is also dependent on the level of overwintering inoculum, that is, the level of control maintained the year before. In other words, if you had trouble controlling diseases last year, a fungicide spray at this time is going to be more critical than if you kept your vineyard clean last year. This is particularly true for the more susceptible V. vinifera and French hybrid varieties.

This stage also marks the point at which the downy mildew pathogen first becomes active. The first infections arise from inoculum that has overwintered on the ground; leaves and other plant material that was infected during the previous season. Therefore, vineyards that developed a fair amount of leaf/cluster infection last year will be at higher risk than vineyards in which infections were controlled. Infection of grapevines by downy mildew is very dependent on the creation and maintenance of wet plant surfaces by rainfall.  Pay close attention to spring precipitation periods: when temperatures are above 52 degrees F during rainfall, infective spores are produced that cause the first infections. Spring leaf infections are identified by the classic yellow oil-spot symptom on the tops of leaves (Figure 4), coinciding with white, downy sporulation of the pathogen on the undersides of leaves. Inflorescences can be blighted and show sporulation as well. Sporulation occurs through night time hours under high relative humidity, and is often readily apparent during a morning scout of the vineyard. First symptoms are most likely to be seen on leaves close to the ground or on sucker growth (because the pathogen comes from the ground) in wetter areas of your vineyard (because of longer hours of wetness after rainfall and higher humidity in these areas); start your scouting there first. Like a flame, the downy mildew pathogen kills everything it ‘touches’, and infected material eventually turns brown and dies, as if scorched by fire. Good control early is very important in years with frequent wetness. Under optimum temperatures of 70-75F, only an hour or two of plant surface wetness may be required for infection to occur. Once established, downy mildew can spread very quickly under wet, warm conditions; it only requires 4-5 days at those optimum temperatures for new infections to go on to produce more spores for the next round of infections.

Mancozeb products offer some of the best control options for downy mildew, while also controlling Phomopsis and black rot infections at this time. Ziram is a little weaker on downy mildew, and Captan a little weak on black rot, but these may also be a viable option at this stage if these diseases are not a huge threat at this time (but they are all a priority at this time on Vitis vinifera and susceptible hybrids). Keep in mind that all these materials are surface protectants; they do not penetrate plant tissue (they are designed that way because they can injure plant tissue) and are therefore subject to wash-off by rainfall. This means that under heavy, frequent rainfall conditions, application intervals will need to be squeezed down from 14 days to more like 7-10 days between sprays, especially for highly susceptible varieties. Other options for downy mildew exist that are more rainfast, like Presidio, Revus, Revus Top, Pristine, Reason, Zampro, Ranman, and the phosphorous acid products.

Keep in mind that shoots are growing at break neck speed at this time of year, and may double or more in length within a short period of time. This leaves increasingly larger amounts of unprotected, highly susceptible tissue within that typical two week fungicide interval, regardless of what fungicide is used.

Figure 4. Yellow oil-spot symptoms of downy mildew on young spring leaves.

Apr 2016_Bryan_Yellow Oil Spot Downy

One last reminder with regard to black rot that I mentioned earlier; black rot leaf infections at this time will create more sources of inoculum in the cluster zone (often on leaves at nodes 4-7) and can make black rot control more problematic during the fruit protection period (after capfall). If you see lesions on leaves in the cluster zone, make sure your subsequent black rot sprays are applied effectively and timely over the next several weeks during the fruit protection period.

Powdery mildew (Figure 5) should also be addressed at this time for Vitis vinifera and susceptible hybrids, but this disease is much less of a concern for juice grapes. Sulfur is an inexpensive option for powdery on non-sensitive varieties at this time and a reliable standard, even at cool temperatures. The sterol inhibitor fungicides may also be good choices at this time, providing they are still effective in your vineyard. The sterol inhibitor and strobilurin fungicides have been in use for many years in Pennsylvania vineyards and are considered at high risk for the development of resistance by the powdery mildew fungus. Research at Virginia Tech and Cornell has indicated that powdery mildew resistance to strobilurins is common in parts of those states. On the other hand, resistance appears to be less common in Pennsylvania, for the moment. If you suspect powdery mildew resistance to these materials in your vineyard and you are applying them for the other diseases they still control, apply them in a tank mix with another active ingredient for mildew (like sulfur) or discontinue their use and use an alternative active ingredient. Just because we have few documented cases of powdery and downy mildew resistance in Pennsylvania at present, be vigilant in your observations regarding potential resistance and control failure. This is even more critical for the next two fungicide application timings; the immediate pre-bloom/first post bloom sprays, where fruit protection ($$$$) is top priority.

Immediate pre bloom/first post bloom fungicide application.

The immediate pre bloom (just before the beginning of capfall) and first post bloom (7-14 days later) fungicide applications are the most important applications you’ll make all year, regardless of variety grown and disease pressure. These two sprays are designed to protect your annual investment (fruit) from all the major fungal diseases (Phomopsis, black rot, downy and powdery mildew) and cost cutting over these two sprays will often result in economic losses (unless you can reliably predict bone dry weather). There is little or nothing to be gained by doing these two sprays ‘on the cheap’, even if disease control was ‘stellar’ last year. This is because young fruit of every variety are most susceptible to all the major diseases during the period stretching from bloom (capfall) to about 2-3 weeks after bloom. I cannot overemphasize how important it is to apply your most effective materials at this time. This is generally a good time to try some of the newer active ingredients in products like Vivando or Torino (for powdery mildew only), Revus Top (for powdery and downy mildew and black rot), Inspire Super (for powdery mildew and Botrytis), Luna Experience (wine grapes only, for powdery mildew, Botrytis, and black rot) and the newer downy mildew materials (listed above). Just remember that you will need to limit the use of these materials to about two applications per season for resistance management purposes. Sulfur can also be included in a tank mix (on non-sensitive varieties) to further improve control and aid in managing powdery mildew resistance, especially in cases of high disease pressure on highly susceptible varieties. Make sure sprayers are properly calibrated and adjusted for best coverage on a bloom-period canopy, spray every row at full rates and shortest intervals, and NEVER extend the interval between these sprays beyond 14 days.

Some growers may be thinking of applying the phosphorous acid products (aka phosphites, phosphonates) for downy mildew at this time. These products are readily absorbed into plants and are rain-fast, effective, and relatively pleasant to work with. However, if you use these materials at this time, be mindful that they provide only limited protection against new infections (7-10 days under high disease pressure). They can provide excellent control of downy mildew under very high disease pressure, but that level of control can deteriorate after 10 days leaving a way in for the pathogen and potential crop loss.

Bloom may also be a time when Botrytis infections can become established in clusters. These infections do not immediately rot fruit, but remain dormant until activation during the ripening period. Though this is mainly a concern for growers of bunch rot susceptible varieties, a bloom spray for Botrytis can significantly impact fruit health and crop loss at harvest.

Figure 5. Powdery mildew symptoms on grape.

bryan_june_powderymildew

I am anticipating a new material, Aprovia, to be available for 2016, mainly for powdery mildew. This material is related chemically to Boscalid (found in Endura and Pristine) and Fluopyram (found in Luna Experience).

Finally, a shortened recap of some relevant main points from last year’s blog.

  1. Good overwintering inoculum control (good control last year, good trellis sanitation) will make seasonal disease control more effective and more forgiving (‘I can’t get a spray on because it won’t stop raining; good thing I controlled diseases well last year’); consider it an insurance policy.
  2. Early spray programs are relatively inexpensive. If disease control was lacking last year, higher overwintering inoculum levels will require that you fire up your seasonal spray program earlier this year, especially if conditions are wet.
  3. The bloom and early post bloom periods are the most critical for protecting your crop ($) against all diseases; it is never cost effective to cut corners during those stages of crop development.
  4. Scout your vineyards and develop your skills at identifying diseases. Focus on vineyard areas where disease control has been most challenging. Know what plant parts to examine for first symptoms and at what stage of plant growth to anticipate seeing them.
  5. Know your fungicides; their strengths, weaknesses, specific diseases they control, their tank mix partners and their rotational partners for resistance management.
  6. Read labels
  7. Make good use of the NEWA system. It will help you make pest management decisions while teaching you a little about pathogen and insect pest biology, and it’s free!

Some information in this blog was gleaned from the New York and Pennsylvania Pest Management Guidelines for Grapes. This publication is an excellent source of research based information designed to help commercial growers make important grape production decisions. Copies can be purchased at the Cornell Store at https://store.cornell.edu/p-193185-2016-new-york-and-pennsylvania-pest-management-guidelines-for-grapes.aspx

As we get closer to bloom, another article will be posted to cover important disease management concepts for the post-bloom period.

2015 Late Season Disease Management

By: Bryan Hed

In many parts of the Eastern United States, 2015 will be remembered as one of the wettest fruit development periods in recent memory. Here at our Penn State research farm in North East PA, rain fell consistently, to the tune of about 2 inches per week, from late May through the middle of July! This level of wetness creates ideal conditions for diseases like downy mildew and black rot, of which there is abundant proof in our unsprayed check plots this year. Even growers of Concord grape, which has limited susceptibility to downy mildew, have been faced with downy mildew pressure they haven’t seen in a long time. Acreage under organic management where synthetic pesticides are prohibited, has, in some cases, suffered heavy losses from black rot. The wet weather also created perfect conditions for the establishment of latent infections of Botrytis during bloom and the early berry development period. These infections lay dormant in clusters until the ripening period (now), when factors related to high humidity, cluster compactness, and berry skin integrity, bring about the activation of these infections and the initiation of bunch rots.

More recently however, we have seen drier conditions prevail (only 2.62” rainfall over the past 7 weeks at our site) that have brought some relief, mainly from downy mildew (the danger of black rot fruit infections was past somewhere around the middle of July). The drier, sunnier conditions are more hostile to the survival of the downy mildew spores and can inactivate much of the sporulation so that an occasional wetting period will probably not amount to much additional leaf infection, at least not in vineyards that have kept this disease under control. Nevertheless, according to DMCast, (the downy mildew infection model developed at Cornell and loaded into the free NEWA website at http://newa.cornell.edu/), occasional wetting events may generate a downy mildew infection period in some locations IF there is active sporulation.  This is why it’s so important to continue scouting leaves for the distinctive white ‘downy’ sporulation of this disease (Figure 1). Growers of susceptible varieties need to keep closely monitoring their vineyards for active sporulation and use that information in combination with the DMCast model on NEWA. If conditions turn wet more consistently, this disease can quickly spiral out of control, strip vines of their leaves and effectively end the season (and the ripening of canes for next year’s crop). So, despite the drier, hotter weather, the solid establishment of this disease across our region in June and July will likely mean that this disease will remain a serious potential threat for the rest of the season! If you find yourself trying to control this disease well into the ripening period, be aware that your list of chemical control options will start to become shorter as we get within 30, then 21, then 14 days of harvest, until in the end you’ll be left with some formulations of captan, copper, and phosphorous acid products.

Figure 1. Late summer downy mildew lesions on a mature leaf of Vitis labrusca ‘Niagara’. Note the absence of the more typical ‘oil spot’ symptoms that are observed on immature leaves in spring. Rather, lesions on mature leaves in mid-late summer take on a blockier appearance but still have the typical white downy sporulation underneath.

Sep_Bryan_Fig 1

The threat of powdery mildew fruit infection (Figure 2) was over weeks ago. But as with downy mildew, leaves are susceptible to powdery mildew all season. However, powdery mildew leaf infection has been building rather slowly from our perspective along Lake Erie, and I see relatively little development of this disease on mature, exporting leaves of Concord and Niagara at our location. In fact the south side of our unsprayed east-west oriented rows are practically mildew free (sunlight is lethal to powdery mildew). Shoot tips, of course, are a different matter; we are seeing the classic distortion of new growth caused by heavy and rapid colonization by powdery mildew. This is nothing unusual, especially for this time of year. After more than 3 months of inoculum buildup in the air, unprotected new growth, which is highly susceptible to infection, is literally thrust into a hornet’s nest of powdery mildew spores and becomes infected as soon as it emerges. In vineyards that have largely controlled this disease to this point, infection of new growth is less severe and less rapid. These infections are also of much less concern (probably of no concern) in juice grape vineyards than in susceptible wine grape vineyards and will have little or no impact on the ripening of juice grape crops in the Lake Erie belt. And, according to work performed by Wayne Wilcox’ program, leaf infections that occur after Labor Day will probably not add to the burden of over-wintering inoculum for primary cycles next year; they likely don’t have time to mature before leaf fall. However, protection of new shoot and leaf tissue may still be important in wine grapes, especially Vitis vinifera. New growth is not only incredibly vulnerable to infection at this time (for the reasons stated above), but collectively serves as the perfect substrate for even more rapid generation of inoculum levels in the air; infected shoot tips represent an important source of late summer inoculum for powdery mildew. Sulfur is often the material of choice for late season control of powdery mildew; it’s relatively inexpensive, it’s effective, and you don’t have to be too concerned about the development of resistance. But too much sulfur on grapes during fermentation can lead to production of hydrogen sulfide which produces off aromas in the wine. When should sulfur applications be terminated before wine grape harvest? Of course, this depends to some extent on rainfall during ripening and sulfur rates. However, recent findings at Cornell (Kwasniewski et al. 2014) have shown that growers of red wines (for fermentation on the skins) should allow at least 5 weeks between that last application of sulfur and harvest (right about end of August for us in the northeast).  With white wines (not fermented on the skins) late sulfur sprays are not thought, generally, to lead to issues with hydrogen sulfide. Other materials that have been used to successfully control this disease on leaves during ripening are things like monopotassium phosphate and formulations of potassium bicarbonates. These materials are not effective on heavy leaf infections but, according to one of my colleagues in Ontario, can work reasonably well if applied often (weekly?) to maintain relatively clean canopies, especially if you’ve exhausted your options of single site synthetic materials (Vivando, Quintec, Torino, Luna, strobies, sterol inhibitors).

Figure 2. Late summer powdery mildew on fruit and leaves. Skins of fruit that are severely infected may split and lead to additional problems with bunch rots during ripening.

Sep_Bryan_Fig 2

As for Botrytis bunch rot, every grower of a susceptible variety (particularly the tight clustered varieties like Riesling, Vignoles, Pinot gris, Pinot noir, Chardonnay, Seyval, etc.) should have applied a Botrytis-specific fungicide around veraison.  Keep in mind that these materials will not control sour bunch rots. However, Botrytis often opens the way for nastier sour rots and control of Botrytis can therefore indirectly improve control of other rots as well. Additional application(s) may be warranted about 2-3 weeks after the veraison application. Pay close attention to pre-harvest intervals for the Botrytis specific fungicides as they range from 14 (Boscalid, found in Endura) to 7 [cyprodinil (Vangard), pyrimethanil (Scala), iprodione (Meteor, Rovral), fludioxonil (Switch)] to 0 days [fenhexamid (Elevate)] pre-harvest.  Pulling leaves in the cluster zone is a great way to reduce Botrytis bunch rot every year, but should be done much earlier in the season for maximum effectiveness. For example, in a 3 year trial to examine the timing of leaf removal (Chardonnay), we found that the earlier leaves were pulled, the less Botrytis, and other rots, that developed in the crop. In fact, when leaf removal was delayed until around veraison, there was relatively little benefit in terms of rot control, and the risk of sunburned fruit was greater, especially on the south (or west) side of the trellis. So, if you decide to pull leaves in late summer, it may be best to limit your investment in time and money and limit your risk of sunburn, by only removing leaves on the north or east side of the trellis. Other forms of canopy management, such as judicious shoot trimming and positioning, can improve deposition and efficacy of late season fungicide applications and may in some cases be a better cultural investment than cluster zone leaf removal at this time.

Figure 3. Botrytis bunch rot development during ripening (Vitis interspecific hybrid ‘Vignoles’). Berries in overly compact clusters can be forced off of their pedicels, leaving open wounds that are easily colonized by Botrytis (grey sporulation seen in photo on right).

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Lastly, if you’ve had trouble controlling black rot fruit infections this season, you’re not alone. There is nothing you can or should spray at this point in time to reduce further infection; fruit are already resistant and black rot leaf lesions can only develop on immature leaves at shoot tips and are probably of little to no significance at this time. The focus, before next spring, should be to reduce the level of overwintering inoculum that is left in the trellis and vineyard, that can jump start new disease cycles in 2016. Dormant pruning is a good time to cleanse the trellis of any and all black rot fruit mummies. Remove them from the trellis and plow them into row middles (especially if you have large amounts of them, and/or are farming organically) or remove them from the vineyard (if practical). We have also found that the sooner mummies are dropped to the ground at the end of the season, the fewer spores they release in the following spring. In other words, mummies removed from the trellis and dropped in November or January, generally released fewer spores the following spring than mummies dropped in March. However, this is not to suggest you should prune your vines in November rather than March, especially with the potential threat of another brutal winter. But, the longer mummies spend on the ground through the fall and winter months, the less potent they are as inoculum sources the following spring. If you suspect you have black rot lesions on canes (usually these are most commonly found on the oldest, most basal, internodes/nodes and can often be accompanied by leaf lesions in the cluster zone), prune them out as best you can as they can also be a hefty source of spores in spring.

Figure 4. Black rot cane lesion (top), leaf lesion (bottom left) and fruit mummies (bottom right).

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In conclusion, 2015 has been a banner year for downy mildew and black rot in many parts of Pennsylvania and the Northeast. The impact on bunch rot disease development is yet to be seen. If this season has left more of these diseases in your vineyard than you’re used to seeing in a given year, there will be more overwintering inoculum to start new disease cycles next year and less forgiveness for mistakes in disease management in spring, especially if conditions are wet. Diseases like black rot and downy mildew emanate from the vineyard soil in spring (and from the trellis in the case of black rot) and are initially, from very local sources of inoculum.

Make note of which vineyard blocks were most troublesome this year as they will likely be the places from which these diseases will appear earliest next year.

 

References

Kwasniewski, M.T., G.L. Sacks, and W.F. Wilcox. 2014. Persistence of elemental sulfur spray residue on grapes during ripening and vinification. Am. J. Enol. Vitic. 65(4):453-462.

Grape Berry Moth: Answers to questions you should be asking about this native pest

By: Andy Muza, Penn State Extension – Erie County

In Erie County, Pennsylvania, grape growers are more than familiar with the perennial, insect pest known as grape berry moth (GBM). However, as more vineyards are being planted throughout PA, growers in other areas of the state may be unaware of the threat that this destructive insect poses to grapes. Therefore, in this blog I will be discussing grape berry moth (GBM) by answering questions that a grower should ask if they are unfamiliar with this pest.

1) What is Grape Berry moth and why should I be concerned about this pest?

GBM is an insect in the Order: Lepidoptera (moths and butterflies) and Family:Tortricidae. It is native to the eastern U.S. and has evolved with wild grapes (e.g., Vitis riparia). GBM larvae feed on berries of grapevines which are spread throughout eastern woodlands. As commercial vineyards are being planted in counties across the state this insect will readily take advantage of the newly available food sources.                                                                                                                                                                        Grape Grape berry moth is considered a serious pest of grapes throughout all of the eastern U.S. GBM larvae feed directly on berries causing yield loss due to: consumption of berries; berry shelling; and crop rejection due to contamination. In addition, feeding injury provides entry points for fungi (e.g., Botrytis) and bacteria which can cause cluster rots.

Shelled Concord berries due to GBM infestation. Photo Credit: A. Muza, Penn State

Shelled Concord berries due to GBM infestation. Photo Credit: A. Muza, Penn State

Chardonnay cluster with Botrytis bunch rot. Photo Credit: Greg Loeb, Cornell

Chardonnay cluster with Botrytis bunch rot.
Photo Credit: Greg Loeb, Cornell

2) How do I identify grape berry moth and what is the life cycle?

GBM HAS FOUR LIFE STAGES: EGG, LARVA, PUPA AND ADULT 

Egg – Laid singly on berries; very small (< 1mm); whitish, opaque; flat, oval, scale-like. Hatch in 3 – 8 days (temperature dependent).

Larva – 4 larval stages; Newly hatched – tiny, creamy white with dark head capsule; Later stages – greenish to purple coloration (10 mm).

Pupa – Light brown to greenish coloration (5 mm). Pupae encased in leaf sections which are easily moved by wind to wood edges, trashy areas.

Adult – Small moth (about 6 mm); brown coloration; base of wings grey- blue; brown patches at tips of wings. Moths active at dusk and fly in a zig zag pattern.

LIFE CYCLE                                                                                                                                                           This pest has 3-4 generations/year in PA, depending on seasonal temperatures. This insect overwinters in the pupal stage in plant debris on the vineyard floor or in protected sites, such as wooded areas, where leaf debris has collected. The adults emerge in spring (late May in Erie County, Pa.), mate, and females lay eggs on flower clusters and berries. Larvae hatch and web together small berries (early in the season) and feed, or bore into berries (at about 5 – 7 mm in size). Larvae exit berries after completing feeding and either: cut a semicircular flap in a leaf to pupate in the canopy; or drop to the ground and pupate in leaf litter. Adults emerge and continue this cycle for several generations throughout the season.

Grape berry moth pupating within leaf flap. Photo credit: A. Muza, Penn State

Grape berry moth pupating within leaf flap. Photo credit: A. Muza, Penn State

Grape Berry Moth Fact Sheets containing additional pictures of life stages, injury and life cycle information can be obtained at the following sites: NY IPM Program; Grapes.msu.edu; Mid-Atlantic Vineyards Grape IPM; and Ontario GrapeIPM.

3) How do I know if GBM is present and causing problems in my vineyard?

Indicators of potential GBM problems include: Feeding injury (small holes) in berries, shelling of berries, rotting clusters.

Scouting                                                                                                                                             Regular scouting throughout the season is a critical component of GBM management and will reveal if this pest is present in the vineyard. A scouting protocol and assigning a GBM risk rating is outlined in “Bulletin 138, Risk Assessment of Grape Berry Moth and Guidelines for Management of the Eastern Grape Leafhopper”

When scouting, pay particular attention to areas most susceptible to infestations such as: border rows near woods, overgrown areas, tree lines, or any protected areas around the vineyard where leaf debris might collect.

Since other disease causing organisms may also cause injuries similar to GBM damage, examine clusters closely. What to look for: webbing in clusters; berries with holes, splits or dark tunneling underneath berry skin; reddish or brown discoloration of berries; presence of larva and/or frass in injured berries. Observation of eggs can be difficult due their small size so a hand lens is useful. Positioning clusters towards the sunlight as they are examined will aid in revealing eggs. Practice is required to acclimate your eyes for observation of eggs.

Webbing in cluster caused by GBM larva. Photo credit: A. Muza, Penn State

Webbing in cluster caused by GBM larva. Photo credit: A. Muza, Penn State

GBM entry holes in Niagara berries. Photo credit: A. Muza, Penn State

GBM entry holes in Niagara berries. Photo credit: A. Muza, Penn State

Grape berry moth eggs on Concord cluster. Photo credit: A. Muza, Penn State

Grape berry moth eggs on Concord cluster. Photo credit: A. Muza, Penn State

Map vineyards and keep records – Make detailed maps of your vineyards and surrounding topography. Keep records of GBM injury levels for each scouting date and vineyard sections checked. These records will provide a GBM history per site.

Pheromone Traps – GBM population levels can be monitored using commercially available pheromone traps. Monitoring traps are baited with small rubber lures impregnated with GBM female sex pheromone for attracting male moths. Pheromone traps can be used as a scouting tool to indicate flight periods and can provide an idea of population levels at your vineyard site. However, trap data are not used for timing of spray applications due to ambiguity concerning correlation of capture numbers and berry injury levels. Monitoring traps are available at Great Lakes IPM, Inc. and Scentry Biologicals, Inc.

4) How do I manage Grape Berry Moth?

CULTURAL PRACTICES                                                                                                                                                Maintain good weed control under the trellis. Poor weed management resulting in excessive vegetation under the vines can harbor GBM pupae. Viticultural practices that promote a more open, less dense canopy resulting in better exposure of clusters to sunlight (e.g., judicious use of nitrogen, shoot and leaf removal) will not only improve quality of fruit but will enable better spray coverage.                                                                                                                                                              Vineyard Vineyard area maintenance such as preventing overgrown, trashy areas around the vineyard will reduce overwintering sites for GBM. Removal of wild grapevines near the vineyard will decrease potential reservoir sites.

GRAPE BERRY MOTH DEGREE-DAY MODEL

The temperature-driven developmental model for GBM was developed by Tobin and Saunders and is now incorporated into Cornell’s Network for Environmental and Weather Applications (NEWA). Currently, many grape growers in the Lake Erie Region have adopted this model to more accurately time insecticide applications for GBM management. Prior to the GBM forecasting model, grape growers in New York and in Erie County, PA used the grape berry moth risk assessment program to time insecticide applications. However, collaborative research at Penn State, Cornell and Michigan State Universities has shown that timing of insecticide applications using the GBM degree-day model results in less injury compared with the grape berry moth risk assessment protocol ( “Focus on Females Provides New Insights for Grape Berry Moth Management” , Issue 14, May 2013 ).

(I highly recommend reading this article by Saunders, Isaacs and Loeb which provides an excellent background concerning the development and explanation on use of this forecasting model).

Use of this developmental model can improve GBM management. However, to ensure the greatest efficacy a few steps are required:

  • Check the NEWA weather station closest to your vineyard. If a weather station is not located close enough to your vineyard site then you will have to record temperature data on your own and follow the procedure outlined in “Focus on Females Provides New Insights for Grape Berry Moth Management” .
  • Monitor and record the date of wild grape bloom (i.e., when approximately 50% of flowers open) for each site and enter these dates into the model. If you do not record a wild grape bloom date for your site then the model will provide an estimated date for the weather station that is used.
  • Regularly check the model to track degree days.
  • Scout both before and after insecticide applications.
  • Incorporate GBM selective insecticides (i.e., Intrepid, Altacor, Belt, Delegate) into your spray program which will also aid in conserving natural enemies. Obtain a copy of the 2015 New York and Pennsylvania Pest Management Guidelines for Grapes . This guideline provides insecticide recommendations and efficacy information for grape berry moth management in Pennsylvania vineyards.
  • Spray as close to the designated degree day timings as possible (i.e., the day of or within 1 or 2 days of the recommended date).
  • Evaluate efficacy of applications.

It is important to be aware that the model provides the optimum timing for an insecticide treatment. However, the decision to apply an insecticide depends on your scouting data and the history of GBM injury at your site.

SPRAY APPLICATION PRACTICES

Obtaining good spray coverage on clusters is critical. However, this can be a challenging feat, particularly later in the season due to the extent of canopy growth. Therefore, it is important that diligent spray practices are adopted.

  • Check equipment for proper working order (Hoses, pumps, nozzles, etc.).
  • Calibrate Sprayer – sprayers should be calibrated at a minimum in the beginning of each season. Preferably 2 – 3 times/season as canopy growth increases. Consider using a patternator to check nozzle output and spray cards or fluorescent dye to check spray coverage. Two YouTube videos which are available to assist in calibration of an airblast sprayer for vineyards include: Calibration of Airblast Sprayers for Vineyards: Part 1 – Selecting and Changing Nozzles. U.S. version and Calibration of Airblast Sprayers for Vineyards: Part 2 – Measuring Liquid Flow. U.S. version by Andrew Landers – Cornell University.
  • Be Aware of: Pesticide registrations; pesticide preharvest intervals; reentry intervals and pH of water sources. (The pH of water can vary throughout the season depending on source). Adjust pH if necessary according to the pesticide label.
  • Use appropriate gallonage, speed, pressure, and nozzles for good cluster coverage as the size of the canopy increases throughout the season.
  • Spray Every Row.
  • Minimize Spray Drift.

2015 Pre-Bloom Disease Management Review

By: Bryan Hed

Well spring is here, and with a new season of grape production soon upon us, a review of pre-bloom disease management topics is in order. In addition to adjusting and carefully calibrating sprayers, take some time now, before bud-break, to acquaint yourself with the NEWA website (Network for Environment and Weather Applications) found at http://newa.cornell.edu . This website gives you easy access to a wealth of weather and pest forecast information from an extensive network of weather stations positioned all over the Northeast…and it’s free. When you first access the site, you’ll see a map of the northeastern U.S. You can use your cursor to navigate the map and click on the weather station nearest you (denoted by a leaf/rain drop icon) to tap into daily and hourly weather (temperature, rainfall, leaf wetness duration, wind speed, etc) near your vineyard or any location you choose (hmm, we had 21 below zero on February 16, I wonder how badly southern PA was hit…). Clicking on ‘grapes’ under ‘crop pages’ will give you access to disease forecasting models for the ‘big four’ like Phomopsis cane and leaf spot, black rot, and powdery and downy mildew. You can also access the grape berry moth degree day model that will help to take a lot of the guesswork out of timing your berry moth insecticide sprays later this year. Each model forecast is accompanied with disease management messages and explanations. For example, at our present stage of development, ‘dormant’, the website has this to add about Phomopsis control: ‘Dead and diseased canes, arms, and pruning stubs should be pruned out to reduce inoculum. Dead canes and stubs can produce extremely high levels of Phomopsis spores over several years. In particular, growers seeking to minimize fungicide use should pay strict attention to the removal of infected wood from within the canopy’. This is a great way to educate yourself on the challenges ahead as we strive to make the most effective and cost worthy decisions in our efforts to grow healthy grapes. Check it out!

For many of us, Phomopsis cane and leaf spot will be the first fungal disease we encounter during the early shoot growth stages in late April (?) and May. I have included several pictures below to help reacquaint you with symptoms on shoots, canes, and leaves. This fungus is often a threat during those long rain periods in May. Young shoots are capable of becoming infected as soon as they emerge and inflorescences ($) can be impacted by this pathogen around the 3-6” shoot stage (basically when they become visible). Infections on newly emerged inflorescences can literally ‘bite off’ whole sections of the cluster and reduce crop potential very early in the season. Early infections on flower stems can move into berries later in the season, during ripening, and cause fruit drop or even fruit rot (either way, you lose). So, If weather is wet at this stage (3-6” shoots), an application of mancozeb, ziram, or captan will limit these infections that can lead to early destruction of clusters or sections of clusters, fruit rot, and ultimately, reductions in yield. Work by Wayne Wilcox has shown that this fungicide application can significantly increase yields and easily pay for itself (sprays at this time are generally pretty inexpensive). This spray can also protect against early shoot infections that become a source of inoculum (canes) in the following year. So, fungicide applications at the 3-6” shoot stage double as an insurance policy against crop loss in subsequent years.

For symptoms on wood (below), look for scabby lesions on the first 2-4 internodes of year-old canes (from last year’s infections in early May), and/or an abundance of old pruning stubs and older and dead wood.

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Although the 1” shoot stage can be vulnerable to damage from this pathogen, the more critical stage is at 3-6” shoots, when more shoot, leaf, and cluster tissue is exposed and is highly susceptible (below).

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Sprays for powdery mildew will likely be necessary at very early shoot growth stages for highly susceptible Vitis vinifera cultivars and/or where control of this disease was lacking the previous summer. Research at Cornell has shown that vineyards harboring high overwintering inoculum levels may require that control measures commence earlier the following season to avoid epidemic development and crop loss. A tenth of an inch of rain with temperatures above 50 F constitute a primary infection period for powdery mildew. Materials like sulfur, oils, Nutrol, and potassium bicarbonate materials may be good first choices for mildew at this stage. Keep in mind that you can’t mix sulfur and oils, or oils and captan (read the labels!). For juice grapes like Concord and Niagara, powdery mildew control is generally not a concern at this time.

For black rot, old fruit mummies and clusters (infected from the previous season) are prime sources of inoculum in spring and early summer, and thorough removal of all this material from the trellis during dormant pruning is essential to maintaining good control of this disease. Once on the ground, mummies can be buried with cultivation or mulch, reducing or eliminating their capacity to fuel new infections in spring. A fungicide application for black rot may not be necessary at these early shoot stages if good control of this disease was achieved the previous year and conscientious trellis sanitation has been implemented. On the other hand, inoculations we performed at these early shoot growth stages (simulating wet weather and an overwintering inoculum source in the trellis) can produce leaf and shoot infections in the cluster zone, that go on to release spores during early berry development stages, and that result in fruit infection and crop loss. An application of mancozeb, ziram, or captan for Phomopsis will also provide control of early black rot infections.

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At about 10-12” shoot growth or the 5-6 leaf stage, a fungicide application at this time will limit infections of Phomopsis on shoots, and cluster and berry stems, especially in vineyards at high risk. Black rot control may not be critical for juice grapes at this time if excellent control of this disease was maintained in previous years and conditions are dry. However, it would be advisable to apply a fungicide for black rot if conditions are wet and warm, especially to Vitis vinifera and susceptible hybrids. As mentioned earlier, black rot leaf and shoot infections at this time can increase inoculum levels in the cluster zone, making black rot control more problematic during the fruit protection period (after capfall). If scouting reveals black rot lesions on leaves in the cluster zone, this is a great big red flag! Make sure your subsequent black rot sprays are effective and timely, especially during the fruit protection period. Downy mildew becomes a concern at this stage as well and fungicide sprays for this disease will be necessary for susceptible varieties, especially if conditions are wet. Mancozeb products offer one of the best control options for all three diseases. Ziram is a little weaker on downy mildew, and Captan a little weak on black rot, but these may also be an option if these diseases are not a priority at this time.

Powdery mildew is less of a concern at this time for juice grapes than for wine grapes, but may be necessary if susceptibility and risk of disease is high, especially for growers of Vitis vinifera and sensitive hybrid wine grapes. Sulfur is an inexpensive option for powdery on non-sensitive varieties. The sterol inhibitor fungicides may also be good choices at this time, providing they are still effective in your vineyard. Note that the sterol inhibitor and strobilurin fungicides have been in use for many years in Pennsylvania vineyards and are considered at high risk for the development of resistance by the powdery mildew fungus, that is, they may not be as effective as they used to be, or are ineffective. If you suspect powdery mildew resistance to these materials in your vineyard, either apply them in a tank mix with another active ingredient for mildew (like sulfur) or discontinue their use and use an alternative active ingredient. This is even more critical for the next two fungicide application timings; the immediate pre-bloom/first post bloom sprays.

Immediate pre bloom/first post bloom fungicide application.

These next two sprays – immediate pre bloom (just before the beginning of capfall) and first post bloom – are critical for every vineyard, every year, for control of every disease!!! Young fruit of every variety are most susceptible to all the major diseases (Phomopsis fruit rot, black rot, downy and powdery mildew) during the period from bloom to about 2-3 weeks after bloom. Apply your most effective materials (Strobies (if no resistance issues), Quintec (powdery only), Manzates/Ziram/Captan (for Phomopsis, black rot, downy mildew)). This is also the perfect time to consider some of the newer products like Vivando or Torino (for powdery mildew only), Revus Top (for powdery and downy mildew and black rot), Inspire Super (for powdery mildew and Botrytis), Luna Experience (wine grapes only, for powdery mildew, Botrytis, and black rot) and the newer downy mildew materials (listed below). Plan to apply for best coverage, every row, full rates, and shortest intervals (NEVER extend the interval between these sprays beyond 14 days).

Phosphorous acid products (aka phosphites, phosphonates) have become favorites for many growers as a means of controlling downy mildew. They are effective and ‘friendly’ to work with. However, if you use these materials at this time, be mindful that, although they are extremely rain-fast, they still provide only limited protection against new infections. Do not expect phosphorous acid sprays to provide more than 10 days of protection, especially under high disease pressure.

Relatively new downy mildew materials

  1. Revus; contains mandipropamid, registered in 08. Very effective on downy mildew in PA and NY trials.
  2. Presidio; fluopicolide, registered in 08. Very effective on downy mildew in PA and NY trials. Label requires that Presidio be applied as tank mix with another downy mildew fungicide.
  3. Reason 500 SC; fenamidone, which is a quinone outside inhibitor; same mode of action as strobies, but not technically a strobie. However, treat it as a strobie with respect to resistance management. Provided excellent control of downy mildew in Cornell trials.
  4. Quadris Top; azoxystrobin + difenoconozole; for downy and powdery mildew, black rot, and Phomopsis. New combination of current chemistries. Its use on grapes in the Lake Erie region will be greatly restricted: with azoxystrobin in the mix, this can’t be used in Erie county PA, and with difenoconazole in the mix, this can’t be used on Concord.
  5. Ranman; cyazofamid, a new chemistry for downy mildew. PA and NY trials show good to excellent efficacy against downy when applied alone and mixed with phosphorous acid.
  6. Zampro; ametoctradin + demethomorph. The newest of the new downy mildew materials; a combination material that is very effective on downy mildew.

 

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A new material, Aprovia, may be available for 2015 (?), mainly for powdery mildew. Federal registration is anticipated in April of this year. This material is related chemically to Boscalid (found in Endura and Pristine) and Fluopyram (found in Luna Experience).

And finally, a short recap of some main points – in no particular order of importance – when planning your pre-bloom disease management programs…

  1. Overwintering inoculum control = maintaining a relatively clean vineyard through to harvest (in the previous year) and subsequently, thorough sanitation during dormant hand pruning activities.
  2. Good overwintering inoculum control will make seasonal disease control more forgiving (‘I can’t get a spray on because it won’t stop raining; good thing I controlled diseases well last year!!’); consider it an insurance policy. Your pre-bloom spray programs will also be more effective as they are applied to control a smaller initial pathogen population this year.
  3. Early spray programs are relatively inexpensive. If disease control was lacking last year, higher overwintering inoculum levels will require that you fire up your seasonal spray program earlier this year, especially if conditions are wet.
  4. The bloom and early post bloom periods are the most critical for protecting your crop ($) against all diseases; it is never cost effective to cut corners during those stages of crop development.
  5. Scout your vineyards and develop your skills at identifying diseases; know what it is you’re trying to control. Focus your scouting efforts in vineyards/vineyard areas where disease control has been most challenging (where you expect disease to show up first). Discovering disease in its earliest stages is key to controlling it, and you can’t discover it early if you don’t scout!
  6. Know your fungicides; their strengths and weaknesses, the specific diseases each material controls, and their rotational partners for resistance management.
  7. Read labels!
  8. Prepare yourself to make the most of the 2015 growing season with a run through the NEWA system.