Tag Archive | viticulture

Grape Leafhoppers

By: Andy Muza, Penn State Extension – Erie County

There are several species of leafhoppers in the genus Erythroneura that feed on grape foliage. Research conducted in New York showed that the eastern grape leafhopper Erythroneura comes (Say) is the most common on American varieties (e.g., Concord, Niagara) while E. bistrata/vitifex complex were more common on Vitis vinifera and interspecific hybrids. Other species found in commercial grapes included E. tricinta, E. vulnerata and E. vitis. (1). Regardless of which of these species is prevalent, their life cycles are similar and the injury caused by these leafhoppers and their management is the same.

Life Cycle and Description

The various Erythroneura leafhoppers overwinter as adults in leaf litter in the vineyard or in plant debris around the vineyard. As temperatures increase in the spring, adults begin feeding on a variety of weeds, bushes and trees. Adults then migrate into vineyards to feed when leaves emerge (2). Eastern grape leafhopper adults are small (only about 1/8”), white-pale yellow, with darker lemon colored markings on the wings, and 3 black spots towards the posterior portion of the wings (Figures 1 & 2).  Other Erythroneura species have varying coloration and markings (3).


Figure 2. Adult grape leafhoppers on underside of Concord leaf. Photo: Andy Muza, Penn State.

Initial feeding occurs on sucker growth and basal leaves on shoots in the trellis. Females lay eggs on the undersides of leaves just below the leaf surface. Nymphs of the first generation hatch in mid-late June. Immatures are wingless, pale yellow in coloration with tiny wing pads (Figure 3). Nymphs develop through 5 instars with wings fully developed after the fifth molt (2). Nymphal development to adulthood takes about 30 days or less depending on environmental conditions. In northwestern Pennsylvania nymphs of the second generation can be found in vineyards in mid-late August. There are 1.5 – 2 generations/season in the Lake Erie Region, depending on seasonal temperatures, and in the southwestern portion of the state likely 2.5 – 3 generations.

Grape leafhopper (GLH) adults and nymphs have piercing – sucking type mouthparts and feed on the underside of leaves extracting the contents of leaf cells resulting in white – yellow spotting of the foliage (stippling). Moderate – Heavy feeding causes yellowing and browning of tissue while severe injury can result in premature defoliation (Figure 4).

Figure 4. Concord leaf with stippling and browning of leaf tissue caused by GLH feeding. Photo: Andy Muza, Penn State.


The greatest risk for economic losses due to grape leafhopper (GLH) feeding occurs during hot, dry years in vineyards with heavy crop loads and high leafhopper populations (4). In most years, the majority of vineyards in Pennsylvania should not require an insecticide treatment specifically for management of grape leafhopper. Therefore, routine, prophylactic insecticide treatments for leafhoppers are unnecessary and not recommended. Insecticide applications should be based on scouting information and threshold levels.

Scouting – Tim Martinson at Cornell designed a scouting procedure for leafhoppers which corresponds to the timings when sampling for grape berry moth injury are conducted (5).

10 Days Postbloom – Usually population levels and feeding is minimal at this time of the season. If however, early in the season, high numbers of adult leafhoppers migrate into the vineyard this can result in enough leaf feeding to reduce bud fruitfulness in the following year (4). Scouting should be conducted to look for leaf feeding on interior leaves in the canopy. If leaf stippling is noticeable throughout the vineyard then an insecticide application is recommended.

Third week in July – Check 4 different areas in the vineyard (2 exterior and 2 interior). At each area look at lower leaves on shoots and check for leaf feeding. If no – minimal injury is observed, proceed to the next sampling site (Figure 5). If moderate-heavy leaf stippling is observed then begin counting nymphs on the undersides of leaves (Figure 6). Examine 5 leaves (leaves 3-7 from base of shoot)/shoot on 5 different shoots at each location. If a threshold of 5 nymphs/leaf is reached then an insecticide application is recommended.

Figure 5. Minimal GLH stippling on Concord leaf. Photo: Andy Muza, Penn State.


Figure 6. GLH nymphs, cast nymphal skins and adults on underside of leaf. Photo: https://ecommons.cornell.edu/bitstream/handle/1813/43102/grape-leafhopper-FS-NYSIPM.pdf?sequence=1&isAllowed=y

Late August – The scouting protocol at this time follows the same procedure as the July sampling. However, the threshold for the August sampling period is 10 nymphs/leaf before an insecticide application is recommended.

Based on scouting data, if an insecticide application becomes necessary during the season, there are a number of options available. Consult the “2017 New York and Pennsylvania Pest Management Guidelines for Grapes” (6) for a list of insecticides which are effective for grape leafhopper management.

Shoot and leaf removal practices conducted in many wine grape vineyards may reduce leafhopper population levels, if the removed leaves are harboring nymphs of this pest. In addition, these practices will open up the canopy for better spray penetration.

A number of predators (e.g., spiders, green lacewings, lady beetles, etc.) and egg parasitoids (Anagrus species) which occur in vineyards contribute to reducing leafhopper population levels (7). Therefore conserving these beneficial insects, by avoiding unnecessary applications of broad spectrum contact insecticides, is advised. Good weed control in the vineyard and the prevention of overgrown areas around the vineyard will also reduce leafhopper overwintering sites.


  1. Martinson, T. E. and T. J. Dennehy. Varietal Preferences of Erythroneura Leafhoppers (Homoptera: Cicadellidae) Feeding on Grapes in New York. Environ. Entomol. 24:550-558 (1995). https://academic.oup.com/ee/article/24/3/550/2394852/Varietal-Preferences-of-Erythroneura-Leafhoppers
  2. Grape Leafhopper. Grape Insect IPM Insect Identification Sheet No. 4 (1984). NYS. Ag. Exp. Station, Cornell University. https://ecommons.cornell.edu/bitstream/handle/1813/43102/grape-leafhopper-FS-NYSIPM.pdf?sequence=1&isAllowed=y
  3. Leaf- Stippling Leafhoppers (Ontario GrapeIPM). Ontario Ministry of Agriculture Food & Rural Affairs, Canada http://www.omafra.gov.on.ca/IPM/english/grapes/insects/ls-leafhoppers.html
  4. Martinson, T. E., et al. Impact of Feeding Injury by Eastern Grape Leafhopper (Homoptera:Cicadellidae) on Yield and Juice Quality of Concord Grape. Am. J. Enol. Vitic., 48:291-302 (1997). http://www.ajevonline.org/content/ajev/48/3/291.full.pdf
  5. Martinson, T. E., et al. Risk Assessment of Grape Berry Moth and Guidelines for Management of the Eastern Grape Leafhopper. New York’s Food and Life Sci. Bull. 138. 10 pp. (1991). http://nysipm.cornell.edu/publications/grapeman/files/risk.pdf
  6. Weigle, T. H., and A. J. Muza. 2017. “2017 New York and Pennsylvania Pest Management Guidelines for Grapes”. Cornell and Penn State Extension. 150 pp. https://store.cornell.edu/p-197039-2017-new-york-and-pennsylvania-pest-management-guidelines-for-grapes.aspx
  7. Williams, L., III, and T. E. Martinson. 2000. Colonization of New York Vineyards by Anagrus spp. (Hymenoptera:Mymaridae): Overwintering Biology, Within-Vineyard Distribution of Wasps, and Parasitism of Grape Leafhopper, Erythroneura spp. (Homoptera: Cicadellidae), Eggs. Biol. Control 18:136-146.   https://pubag.nal.usda.gov/pubag/downloadPDF.xhtml?id=43140&content=PDF

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.


Harvesting the Knowledge Accumulated at Penn State on Grapes and Wine

By: Denise M. Gardner

Early in 2016, I was asked to create a “behind the scenes” event in late October to feature our research winemaking program and share this with alumni to introduce them to some of the things that Penn State offers in the fields of viticulture and enology.  This was, by far, one of the most interesting events I have organized during my time with Penn State, and it ended up being a very rewarding experience, personally, to see the pride and talent that contributed to make the event a success.

The challenge: teach a group of adults about wine production… most of whom have probably very little knowledge about or experience in actual wine production.

As many of us know, making wine is not really the romantic ideal that is often portrayed and associated with the wine industry.  We all know that we aren’t overlooking our vineyards with a glass of wine in hand 24-7.

It’s hard work.  It’s dedication.  And it’s farming.

When I introduced this event idea to the Extension Enology Advisory Committee – a group composed of 13 volunteers from Pennsylvania’s wine industry and several representatives from various academic communities – they all jumped on the idea of showcasing the Penn State Extension Enology presence and the impact it has had on the local industry in addition to Penn State’s research programs.

Starting in April 2016, I went to work on developing a short [film] script to organize and develop a small video that highlighted our research initiatives and student involvement around winemaking at Penn State.  The hope was that this video would feature how students, faculty, and staff are getting involved with industry members via Penn State Extension’s programs while also explaining how wine is generally produced.

With this video, I ended up interviewing two faculty members from our research team, Dr. Michela Centinari from the Dept. of Plant Sciences and Dr. Ryan Elias from the Dept. of Food Science.  We collected their perspectives and opinions on various activities that they have been involved in and related it back to the growth and development associated with Penn State offering educational and research experiences in viticulture, enology, and wine marketing.

Figure 1: Filming Day! Dr. Ryan Elias, Dr. Michela Centinari, and Denise Gardner get interviewed and video taped for a small presentation on winemaking at Penn State. Filming completed by media guru, Jon Cofer. Photo by: Denise M. Gardner

Figure 1: Filming Day! Dr. Ryan Elias, Dr. Michela Centinari, and Denise Gardner get interviewed and video taped for a small presentation on winemaking at Penn State. Filming completed by media guru, Jon Cofer. Photo by: Denise M. Gardner

Luckily, one of the media specialists within the College of Agricultural Sciences, Jon Cofer, had a collection of footage that we had shot during wine processing days just in case we ever needed video footage for anything.  As luck would have it, we did need the media footage!  Jon sifted through hours of film to find the best footage, which we then tied back into the explanation on how research wines are generally processed at Penn State.

During our travels around the state, whether it was to check in on research trials or visit with industry members during Regional Winery Visits, Michela, a group of dedicated graduate students, and I collected video footage in commercial vineyards in an attempt to highlight what goes on during the growing season.  And finally, I met with some recent graduates that experienced educational opportunities through Penn State and Extension, and who both work in Pennsylvania’s wine industry today.  I have to admit, one of the most awarding experiences in being Penn State’s Extension Enologist is that I have watched several “students” graduate and find full-time job placement within our state’s wine industry.  It is an absolute joy to see these young adults exceed in a growing industry.

The result of this event couldn’t have been better received.  Instead of making wine with a group of non-winemakers, we set up three educational stations to teach about:

  1. wine grape properties and vineyard management by highlighting how to conduct a berry sensory analysis, explaining berry physiological differences, and teaching how to read a refractometer.
  2. the chemistry behind fermentation and sensory training associated with wine tasting through analytical demonstrations and “aroma guessing” with aroma standards.
  3. and evaluating the end result (finished wine!) of some of our best research wines and commercial winery collaborators.
Figure 2: Graduate students, Maria and Drew, get ready to teach attendees about wine grape properties. Maria and Drew are members of Dr. Michela Centinari's research lab. Photo by: Tom Dimick

Figure 2: Graduate students, Maria and Drew, get ready to teach attendees about wine grape properties. Maria and Drew are members of Dr. Michela Centinari’s research lab. Photo by: Tom Dimick


Figure 3: Jared Smith (Dept. of Food Science Teaching Lab Support Specialist and previous graduate supported by the Crouch Endowment) explains how winemakers monitor fermentation and the use of temperature-controlled fermentation tanks. Photo by: Tom Dimick

Figure 3: Jared Smith (Dept. of Food Science Teaching Lab Support Specialist and previous graduate supported by the Crouch Endowment) explains how winemakers monitor fermentation and the use of temperature-controlled fermentation tanks. Photo by: Tom Dimick


Figure 4: Graduate student, Laurel, tests attendees on their ability to smell and aroma and guess what it is. Laurel works within Dr. Ryan Elias's lab. Photo by: Tom Dimick

Figure 4: Graduate student, Laurel, tests attendees on their ability to smell and aroma and guess what it is. Laurel works within Dr. Ryan Elias’s lab. Photo by: Tom Dimick


Figure 5: Denise Gardner pours some of the commercial wines for attendees and explains how to pair them with locally produced cheeses. Photo by: Tom Dimick

Figure 5: Denise Gardner pours some of the commercial wines for attendees and explains how to pair them with locally produced cheeses. Photo by: Tom Dimick


Figure 6: Dr. Michela Centinari pours and explains the research wine trials. Attendees loved this portion of the program and were truly impressed with the quality wines produced by our research team! Photo by: Tom Dimick

Figure 6: Dr. Michela Centinari pours and explains the research wine trials. Attendees loved this portion of the program and were truly impressed with the quality wines produced by our research team! Photo by: Tom Dimick

The educational portion of this program was a big success.  Attendees learned about native and wine grape varieties grown in Pennsylvania, and how those grapes compare to table grapes that people see in grocery stores.  At the fermentation booth, participants learned how to measure Brix to determine potential alcohol and how a temperature-controlled stainless steel tank can be useful in wine production.  Additionally, our graduate students put guests’ nose-sniffing skills to the greatest test in seeing if they could guess various wine aromas without peaking at the answers!  It was enlightening to see our students teach the importance of these skills to develop a career in the wine industry.

The Penn State research wines that are made at University Park were also a big hit.  Explaining the purpose of research wines can be a slight challenge, as most of our wines are never finished.  This means that in order to emphasize a vineyard or winemaking treatment, fining, stabilizing, and finishing treatments (like oak aging) are kept to an absolute minimum or completely avoided.  In many cases, bottled wines will never see any oak or fining other than getting racked off of their lees.

Our primary display was on the Noiret wines, which was a project funded by the PA Wine Marketing and Research Board to determine if vineyard management treatments affected the concentration and perception of rotundone, the primary aroma compound associated with the Noiret variety that exudes a black pepper aroma.  The rosé wine, also made from Noiret, was an excellent contrast to the red wines produced from the same variety.  Pairing the wines with various cheeses produced by Berkey Creamery was an excellent way to also talk about wine styles produced in Pennsylvania and the importance of food and wine pairing with many of the local wines.

If you are interested in tasting many of our wine trials, please join us at the annual PA Wine Marketing and Research Board Symposium.  The 2017 Symposium will be held in University Park on March 29th(More details on this conference will be released soon!)

But what happened to that video?!  If you are still interested in evaluating our winemaking program, curious about what we have been up to for the past few years, please feel free to enjoy our short 12 minute video that highlights a small portion of our efforts to work with industry and participate in viticulture and enology research.  While the program is young, we have truly been fortunate to work with some pretty amazing people: commercial growers and producers that are interested in research, students developing expertise, and other academic colleagues that have been willing to collaborate with us as we build our programs.

We truly hope that you have seen or experienced some of the benefits of our programs, but if you would like to know more about what we do, please do not hesitate to contact us!  Our email addresses are readily available and we also try to document our regular activities on Facebook.  We honestly couldn’t do it without the support of people like YOU!

Enjoy the video!  We think it is fairly entertaining, a lot of work went into it, and it showcases a small fraction of the things we are trying to do at Penn State to help progress and educate the local wine industry:

Winemaking At Penn State Video

(If you do not have a dropbox account, simply hit “No Thanks” when the pop up window is displayed.  You can also do this if you would like to avoid logging into dropbox.)

Figure 7: Bottled research wines ready for tasting. Photo by: Denise Gardner

Figure 7: Bottled research wines ready for tasting. Photo by: Denise Gardner


Looking back at the 2016 season

By Michela Centinari, Bryan Hed, and Kathy Kelley

The 2016 growing season was a rewarding one for many Pennsylvania (PA) wine grape growers. But before we move on with plans for next year, let’s review this past season using some interesting data we gathered from PA grape growers. In November 2016, we sent out a 5-min Internet survey developed by our team and housed on SurveyMonkey.com. A link to the survey was sent to 90 members of a PA wine grape grower extension electronic mailing list. Thirty-seven participants clicked the link and responded to questions related to the 2016 harvest and growing season.

All procedures were approved by the Office of Research Protections at The Pennsylvania State University (University Park, PA). Upon completion of the survey, each participant was entered into a raffle to win one of three $25 gift certificates that could be redeemed toward any Penn State Extension wine or grape program fee.

This article is based on our observations and feedback we received from survey participants. We welcome more PA wine grape growers to share their stories and to send us (Michela Centinari; Bryan Hed) their contact information so they can be included in future surveys (where else do you have a chance to win a gift card for a Penn State Extension event?).

First, some information about the respondents

Thirty-three survey participants (89%) indicated the region where they grew grapes. The majority of the respondents (11) were from the Southeast region, followed by Northwest (7), Northeast (6), South Central (4), North Central (3), and Southwest (2) regions.

Data that described what species of grapes survey participants grew were: Vitis vinifera (e.g., Riesling, Cabernet Franc, Chardonnay), Vitis interspecific hybrid (e.g., Chambourcin, Traminette, Vidal Blanc), abbreviated in Table 1 as vinifera and hybrid, respectively, and native (e.g., Concord, Niagara) cultivars (Table 1).


What did we ask the survey participants?

Participants were asked to rank the average yield of the grapes they grew in 2016 from “poor” to “record crop.” They were also asked to rank the average quality of the fruit from “poor” to “excellent,” and the insect and disease pressure experienced from “below average” to “above average.”  Respondents were then directed to open-ended questions where they indicated what cultivars performed below or above average and why.

 Survey participant responses  

  • Yield: The majority of the respondents (88%) indicated that average crop yield was “average” “above average,” or “record crop” (Figure 1). Only four participants (12%) indicated that average yield was “below average” or “poor.”screenshot-2016-12-14-15-41-31

Of those four respondents, two attributed “poor” or “below average” yield to disease issues (e.g., powdery mildew, black rot). One survey participant from the Southeast region indicated problems with freeze injury as the vines were approaching bud burst.  Specifically, the participant wrote: “My whites especially Chardonnay were light (lower crop yield than average) this year. I believe the whites were hit hard with the early April freezes when we had three nights in a row dip down into the 20’s. I believe many of the primary buds froze. Most of the white grape clusters were much smaller than usual.”

An unusually warm March was indeed followed by a very cold start to the month of April. Between April 3 and 10, there were several nights in the 20’s ºF in many regions of PA. While there was no sign of bud burst, as far as we are aware, for grapevines grown in central or north PA, some were approaching bud burst in several areas of south central and southeast PA.

The fourth respondent from northwest PA commented that “Vines are still recovering from 2014 winter injury, and that is too expensive to replant large percentage.” Despite long-term issues with winter injury recovery, finally, after two harsh winters (2013-2014; 2014-2015) PA grape growers were able to enjoy the winter without having to worry about their vines. In many regions of PA, winter temperatures did not reach critical low values that tend to injure many of the cultivars grown in the Commonwealth. However, on February 14 temperatures reached -10°F and below in northeast PA.  The lowest temperature recorded (-19°F) was in Potter County. Despite this isolated event, we did not receive inquires of growers concerned about winter injury.

  • Fruit quality: The majority of the respondents (83%) ranked fruit quality as “above average” or “excellent,” which was consistent across cultivars and regions. Only one grower rated fruit quality as “below average” as a consequence of high disease pressure.


A few survey participants from southeast PA who rated fruit quality from “above average” to “excellent” commented:

“Early veraison and high heat degree days in September allowed the early varietal to ripen in almost perfect condition. The Bordeaux reds .. in late September and early October soaked up a lot of rain and didn’t recover completely from this. I harvested Merlot clusters bigger than I have ever seen them”

“Bordeaux varieties (Cabs, Merlot, Petit Verdot) were at least 23ºBrix with a high of 25. Nice and ripe with good flavors”

“Grüner, Riesling, Merlot, Chambourcin, and Cabernet Franc achieved mature ripe flavor. Acids were in ideal range”

Other survey participants from across the state also indicated that in 2016 the grapes reached “Optimal ripeness and acidity level,” “Good acid balance,” “Berry size, color, acids, pH, and sugars were the best ever,” “Excellent cultivar character.”

Several respondents pointed out that “Hot and dry weather played an important role in the quality this year” and commented that fruit was clean from major diseases.

  • Insect and disease pressure: Almost half of the growers who participated in the survey (47%) experienced “below average” insect and disease pressure during the 2016 growing season, while 41% answered “average” and only 12 % “above average.”


Of the four participants who reported “above average” disease pressure, one indicated problems with spotted Lanternfly an invasive insect who unfortunately is making its way to some areas of PA (Spotted Lanternfly: A new invasive pest detected in Pennsylvania).  Two respondents reported issues with powdery mildew. Powdery mildew was indeed very much “alive and well” in many vineyards in 2016.  In Erie County, we witnessed flare-ups of this disease on fruit during late June and early July, despite relatively prudent control measures and relatively few primary infection periods. This disease requires rainfall events early in the season for spore release only (minimum of 0.1 inches of rain and temperatures above 50ºF), but once spores are released the pathogen does not require wet plant surfaces to infect susceptible tissue and generate subsequent waves of its parasitic life cycle. This is very much unlike most of the other fungal pathogens we deal with each year. Note that even California growers spend a boatload of time and treasure controlling this disease every year. In short, it is a disease management issue wherever grapes are grown, every year, everywhere. Fortunately, aside from a few horror stories where there were gaps in spray intervals around bloom, most growers managed to get decent commercial control of this disease on their grapes in 2016.

Weather conditions during the growing season

A look at the weather conditions through the online network for environment and weather applications (http://newa.cornell.edu/) can help interpreting survey participant responses. In Figure 4 and 5, we reported data collected by the two new weather stations located nearby the Penn State Fruit Research and Extension center (FREC) in Biglerville (Adams County, south central PA) and at the Lake Erie Regional Grape Research and Extension center (LERGREC) in North East (Erie county, northwestern PA). We compared the 2016 monthly growing degree days (GDD) (index of heat accumulation) and precipitation to the mean values for April through October for a three-year period (2013-2015) (Figures 4, 5).

Temperature: Despite a cool start to the 2016 season (see April and May) the rest of the season was warmer than average in PA and other parts of the eastern U.S. Indeed, the heat accumulated (GDD) from June through October in 2016 was above that of the previous three-year average (Figure 4).


The warm weather led in many cases to great fruit ripening conditions, as indicated by the majority of the respondents, but in a few instances may have hindered fruit sugar accumulation as noticed by one of the participants: “I think that heat in August slowed ripening and resulted in lower Brix than other years but all fruit did achieve ripeness.” High temperatures might increase plant respiration rates to a greater degree than photosynthesis rates, which in other words means lower carbon gain /sugar accumulation for the vine and fruit. A detailed explanation of why this happens can be found in the September issue of Viticulture notes edited by Tony Wolf (Professor and Viticulture Extension Specialist at Virginia Tech).

Precipitation: Rainfall in the spring and early summer was well below average in Erie County (northwestern PA) with 2.1, 1.9, and 2.7 inches of rain in May, June, and July, respectively (Figure 5B). Dry weather often comes hand in hand with a higher number of sunny days and higher temperatures; two additional factors that stymie fungal pathogen growth.


Peak grape disease susceptibility generally occurs during June and early July in PA. Both June and July were drier than average in many parts of the state: see for example Biglerville (south central PA) with only 2.7 and 0.2 inches of rain in June and July, respectively (Figure 5A), or other sites across the state (Table 2: Lewisburg, State College, and Cabot). This helps to explain the large percentage of growers reporting average to below average disease pressure. However, in other parts of the state or near the eastern PA border it was not quite as dry but still warm (Table 2, numbers in bold font).


In places and months where rainfall amounts were well above average, rainfall was often heavy and punctuated by well defined, often lengthy dry periods in which growers could easily keep up with their protective fungicide sprays. Unfortunately, there were a few locations where diseases like black rot flared out of control, but those were the exceptions rather than the rule (Figure 3).

In summary “dry, sunny, and warm” sums up the weather for the majority of the growing season for many regions of the state, with local and ample variations on precipitation amount. For the most part, these conditions are rather hostile to the fungal or fungal-like pathogens that are responsible for the majority of our grape disease issues every year. This was very fortunate for a number of reasons, not the least of which was the fact that 2016 was following a year that left many vineyards with well above average levels of overwintering inoculum for diseases like black rot and downy mildew. This was especially true in northwestern PA; downy mildew could be found in pretty much every vineyard in Erie County in 2015, despite the fact that the vast majority of the grape acreage is planted to Concord, a variety with relatively low susceptibility to downy mildew. A wet spring and early summer could have left growers really struggling hard to keep those diseases under control on fruit this year. But downy mildew literally “took a vacation” in the Lake Erie region in 2016. It was the most downy mildew-free season Bryan experienced over his 18 seasons of working with grapes. You might say that many PA grape growers got a small taste of what it’s like to grow grapes in California.

When ripening begins, our attention naturally turns toward controlling bunch rots on susceptible varieties. Varieties that produce “tight,” compact clusters are most at risk, and for these control measures are essential. Fortunately, survey participants did not indicate bunch rot issues this season. In Erie, as well as many other locations in PA rainfall resumed by the second week in August (Figure 5), and the ripening period was actually relatively wet through September. As you know, rainfall during ripening leads to bunch rot problems (Late summer/early fall grape disease control) and we did see rot problems develop early in vineyards of Pinot Gris and Pinot Noir with extremely tight clusters despite measures to reduce cluster compactness and a barrage of fungicide applications. In those vineyards, the crop had to be harvested early, before optimum ripeness. However, at LERGREC, rot control was especially good in Vignoles (another cultivar susceptible to bunch rot) where we applied mechanized pre-bloom fruit zone leaf removal in combination with Botrytis specific fungicides at veraison and beyond.

In conclusion, it was a rewarding growing season for many PA wine grape growers. Warm, (mostly) dry conditions favored the production of a high-quality vintage and we are looking forward to tasting this season’s wines!

How does delaying spur-pruning to the onset or after bud burst impact vine performance? Insights from recent studies

By Michela Centinari

Now that harvest is finally over and wines are tucked away in the cellar, it is time to prepare for the next year. One of the first concerns that many growers feel in a new growing season is that worry of spring frost and the associated potential risk of vine injury. In the spring of 2016, for example, an unusually warm March was followed by a very cold start to the month of April, which resulted in damaging frost incidences in some vineyards of the Mid-Atlantic region.

Susceptibility to frost injury increases with advanced phenological growth stage [1], therefore, growers and scientists have explored different techniques for delaying bud burst of grapevines to increase the chance of avoiding spring frost damaging events. Vegetable-based oils (e.g., Amigo oil) can be sprayed on the canes/buds during the winter to slow down bud de-acclimation and delay the resumption of vegetative growth in the spring [2; 3; study at Penn State]. Delaying pruning until late winter can also be used to delaying bud burst of vines growing in frost prone areas.

Canes of cordon-trained vines can be pruned to 2-3 node spurs late in the winter or even when apical buds begin to open to delay bud burst of basal buds. Due to the strong apical dominance of Vitis vinifera cultivars, apical buds of an unpruned cane tend to burst first, which inhibits development and growth of median and basal buds [4] (Figure 1).

Figure1. Spur pruning vines while the apical buds are bursting. Photo source: McGourty, The case for double—pruning. Practical Winery &Vineyard.

Figure1. Spur pruning vines while the apical buds are bursting. Photo source: McGourty, The case for double—pruning. Practical Winery &Vineyard.

What may happen if we wait until the onset of bud burst or even later to prune the vines?

Spur-pruning the vines when the apical buds of un-pruned canes are already open may not only delay bud burst of the basal nodes, but may also postpone other phenological growth stages such as bloom, fruit-set, or even veraison with potential consequences for vine yield and fruit chemical composition at harvest [4].

I recently read two articles on this topic published in the American Journal of Enology and Viticulture (Post-bud burst spur-pruning reduces yield and delays fruit sugar accumulation in Sangiovese in central Italy [5] ) and in Frontiers in Plant Sciences (Phenology, canopy aging and seasonal carbon balance as related to delayed winter pruning of Vitis vinifera L. cv. Sangiovese grapevines [6]).

The studies described in these articles aimed to assess if and how delaying winter spur-pruning of Sangiovese vines to the bud swelling stage or later, after bud burst, impacted the annual growth cycle of the vines and its productivity.

The studies were conducted in Italy and the researchers were specifically interested in assessing if vines pruned around or after bud burst exhibited a delay in grape ripening as compared to those pruned during the winter, resulting in lower sugar accumulation and higher acidity in the fruit at harvest. A steady trend of increased warming is, indeed, pushing some Mediterranean grape growing regions toward accelerated ripening [7], which could lead to excessive or overly fast sugar accumulation in the fruit, high alcohol in the wine, unacceptably low acidity, high pH, and also atypical grape flavors and aromas [5].

Although excessive or overly fast sugar accumulation may not be a problem in our region, it’s still important to understand if delaying winter pruning to extremes could be used to delay bud burst and reduce risk of frost damage, as well as the impact this practice may have on vine yield, and fruit and wine chemistry. This is a topic of further interest in light of changing climatic conditions and the potential increase of unpredictable weather patterns like early spring warming and late spring frosts [8].

Below, I will summarize the two previously mentioned studies emphasizing results which can be of interest to wine grape growers in our regions.

Both studies were conducted on mature Sangiovese (Vitis vinifera L.) vines. The first study was established in a commercial vineyard in central Italy, whereas the second study was conducted on vines growing outdoors in 10-gal pots at a research station in northern Italy. Groups of vines were assigned to different pruning treatments. Vines assigned to the standard grower practice treatment were spur-pruned to 2 basal nodes during the winter when buds were dormant. Vines assigned to the other treatments were spur-pruned at more unusual times from the bud swelling to full bloom (Figures 2 and 3A).

Figure 2. Phenological growth stages of the apical shoot at the time vines were pruned to 2-node spurs. *BBCH scale was used to assess phenological stages [9] in studies described below.

Figure 2. Phenological growth stages of the apical shoot at the time vines were pruned to 2-node spurs. *BBCH scale was used to assess phenological stages [9] in studies described below.

Did delaying vine spur-pruning to after bud-burst consistently delay the whole annual growing cycle?

Basal buds of Sangiovese vines spur-pruned when apical shoots were about 1.6″ long (called late pruning treatment; Figure 3A central panel) burst 17 days later than those of vines pruned in the winter, when buds were dormant (called standard pruning treatment; Figure 3A left panel). Pruning the vines even later, when apical shoots were about 4.7-5.5″ long (called very-late pruning treatment;  Figure 3A right panel) extended the delay in bud burst to 31 days as compared to vines pruned in the winter Unfortunately no phenology data were recorded for vines pruned at bud swelling stage (study 1).

The delay in phenological growth stage decreased over the season. For example, late-pruned and very-late pruned vines reached veraison 3 and 13 days, respectfully, after those pruned in the winter (Figure 3C). Shoots of vines pruned after bud burst developed later in the season under higher air temperature than those of vines pruned during the winter. Greater air temperature may have helped shoots of late- and very-late pruned vines to reach bloom and veraison in fewer days as compared to those pruned earlier [6].

By harvest the delay was fully off-set for the late-pruned vines: they reached the sugar level set for ripening (~ 19 ºBrix) three days before those pruned in the winter. Grapes of very-late pruned vines reached 19 ºBrix 6 days after those pruned in the winter.

Figure 3. Vine appearance at the time of pruning (A) and at bloom (B) and veraison (C). Note: standard winter pruning was taken as a reference for bloom and veraison. Photo courtesy Dr. Stefano Poni (professor of Viticulture, Universita’ Cattolica del Sacro Cuore, Italy).

Figure 3. Vine appearance at the time of pruning (A) and at bloom (B) and veraison (C). Note: standard winter pruning was taken as a reference for bloom and veraison. Photo courtesy Dr. Stefano Poni (professor of Viticulture, Universita’ Cattolica del Sacro Cuore, Italy).

Spur-pruning vines after bud burst significantly reduced crop yield compared to standard winter pruning

Vines pruned at bud swelling growth stage had similar crop weight, number of clusters per vine, and cluster weight than those pruned when buds were still dormant. Pruning vines after bud burst, however, reduced yield as compared those pruned during the dormant season. For example, late pruned vines (spur-pruned when apical shoots were about 1.6″ long; Figure 3A central panel) had 26% lower crop yield as compared to those of the standard pruning control group (spur-pruned before bud burst). Reduction of crop yield was related to lower cluster weight and lower number of berries per cluster. While there is not a clear explanation on why late-pruned vines had fewer berries per cluster, several hypotheses were presented including increased production of gibberellins during the initial flush of growth in the late-pruned vines [6].

Waiting even longer to prune the vines had a detrimental effect, reducing not only cluster weight but also the number of clusters per vine. For example, vines pruned to two basal nodes when the apical shoots were already flowering had no crop at harvest. When vines were pruned so late the basal shoots did not develop flowers and remained vegetative after pruning. I am not sure why any growers would want to wait until bloom to prune the vines, but it’s still interesting to see how such a drastic treatment may limit sources of carbohydrates for developing cluster primordia [5].

Although uncertainty still exists, the authors suggested that delaying spur-pruning until after bud burst, but not to extremes, may have the potential for reducing crop yield in high-yielding cultivars such as Sangiovese planted in specific regions of Italy. However, long-term field studies are necessary to assess if it is possible to calibrate winter pruning date for managing yield reductions and/or fruit maturation rate.

Did delaying vine spur-pruning to bud swelling stage or after bud burst consistently impact fruit chemistry?

The effect of the timing of spur-pruning on fruit composition at harvest varied between studies and with the extent of the pruning delay. For example, Sangiovese vines late pruned (apical shoots 1.6″ long) had higher total soluble solids (+ 1 °Brix), total anthocyanins and phenolics than winter-pruned vines. However, vines growing in a commercial vineyard (study 1) and spur-pruned to two basal nodes later in the season, when inflorescences of apical shoots were already swelling (Figure 3C), had lower sugar concentration (-1.6 °Brix) and higher TA (+1.8 g/L tartaric acid) than those pruned during the winter, but at the same time they also had higher anthocyanins and phenolic concentrations.  This result suggests that spur-pruning canes after bud burst may decouple the accumulation patterns of total soluble solids and anthocyanins, phenolic metabolites. This could be intriguing for growers trying to delay fruit sugar accumulation and acid degradation, while maintaining wine color, but on the another hand it could also come with a  reduction in crop yield, quantified to over 50% in this study [5].

Did delaying winter spur-pruning have negative carry-over effects on the following season?

Pruning vines at the bud swelling stage did not have negative effects on vine growth in the following year. It did not impact bud fertility (number of clusters per shoot) or winter carbohydrate storage, which is important for winter vine survival and following year resumption of growth. However, pruning the vines to two-nodes after bud burst, specifically when inflorescences of apical shoots were already swelling (Figure 3C), reduced bud fertility by 50% in the following year. Those vines were able to recover once standard winter pruning was applied again at the end of the study.

In conclusion:

These studies conducted on Sangiovese vines grown in Italy found that:

  • Winter spur-pruning can be applied up to bud swelling without adversely affecting vine yield, grape composition at harvest or bud fertility in the following year.
  • Vines pruned after bud burst show pronounced delay in shoot development at the beginning of the season, which increased as the pruning time was further delayed. Under the warm conditions of these studies the delay in phenological growth stage decreased or even disappeared over the season. This could be partially explained by the fact that late-pruned vines needed less time than vines pruned during the winter to reach maximum photosynthesis efficiency.
  • Delaying spur-pruning to after bud-burst may reduce vine yield, decrease sugar accumulation and bud fertility in the following year.

Delaying winter pruning of vines located in frost prone areas to the onset of bud burst or shortly after that may be used as frost avoidance technique. However, we need to further understand how a delay in shoot development and potentially a shorter growing season (number of days from bud burst to harvest) may impact fruit ripening, yield component, vine over-winter carbohydrate storages and susceptibility to winter cold temperatures, as well as the following year growth. The studies summarized here were conducted in a warm region with a growing season longer than many areas of Pennsylvania.  Further research is necessary to corroborate those results under our regional climatic conditions.


Literature cited

  1. Centinari M, Smith MS, Londo JP. 2016. Assessment of Freeze Injury of Grapevine Green Tissues in Response to Cultivars and a Cryoprotectant Product. Hortscience 51: 1–5.
  2. Dami I, and Beam B. 2004. Response of grapevines to soybean oil application. J. Enol. Vitic. 55: 269–275.
  3. Loseke BJ, Read PE, and Blankenship EE. 2015. Preventing spring freeze injury on grapevines using multiple applications of Amigo Oil and naphthaleneacetic acid. Scientia Hort. 193: 294–300.
  4. Friend AP, and Trought MCT. 2007. Delayed winter spur-pruning in New Zealand can alter yield components of Merlot grapevines. J. Grape Wine Res. 13: 157–164.
  5. Frioni T, Tombesi S, Silvestroni O, Lanari V, Bellincontro A, Sabbatini P, Gatti M, Poni S, Palliotti A. 2016. Post-bud burst spur pruning reduces yield and delays fruit sugar accumulation in Sangiovese in central Italy. J. Enol. Vitic. 67:419–425.
  6. Gatti M, Pirez FJ, Chiari G, Tombesi S, Palliotti A, and Poni S. 2016. Phenology, canopy aging and seasonal carbon balance as related to delayed winter pruning of Vitis vinifera cv. Sangiovese grapevine. Frontiers in Plant Sciences 7:1–14. Article 659.
  7. Jones GV, White MA, Cooper OR, and Storchmann K. 2005. Climate change and global wine quality. Climatic Change 73: 319–343.
  8. Mosedale JR, Wilson RJ, and Maclean IMD. 2015. Climate change and crop exposure to adverse weather: Changes to frost risk and grapevine flowering conditions. PLoS One 10:e0141218.
  9. Lorentz DH, Eichorn KW, Bleiholder H, Klose R, Meier U, and Weber E.1995. Phenological growth stages of thegrapevine (Vitis vinifera ssp. vinifera). Codes and descriptions according to the extended BBCH scale. Aust. J. Grape Wine Res. 1, 100–103.

Resources for Identification and Management of Vineyard Pests

By: Andy Muza, Penn State Extension – Erie County

Another harvest will soon be over for grape growers in Pennsylvania and the winter season is fast approaching. Take the time this winter to explore the resources below to prepare for next season’s pest problems.

Hardcopy References
The following 5 references provide information on identification and management of insect, disease and weed problems in vineyards. I suggest purchasing these items before next season begins. Although the cost will be over $250 it is well worth having these invaluable resources in your viticultural library.

  1. New York and Pennsylvania Pest Management Guidelines for Grapes: Every commercial grape grower in Pennsylvania should have a copy of the current guidelines. This guideline provides a wealth of information on insect, disease and weed management with pesticide options, rates, and schedules, as well as, a chapter on sprayer technology.
  2. A Pocket Guide for Grape IPM Scouting of Grapes in North Central & Eastern U.S.:This pocket reference book is for use while scouting in the vineyard. The guide provides concise information and color photographs on insect/mite pests, natural enemies, diseases and disorders.
  3. Compendium of Grape Diseases, Disorders, and Pests, Second Edition: This new edition is an expanded version of the original Compendium with 375 photos and drawings and containing updated information about pathogens including additional diseases. The second edition is divided into 4 parts covering: diseases caused by biotic factors (e.g., fungi, bacteria, viruses etc.); disease – like symptoms caused by insects and mites; disorders caused by abiotic factors (e.g., environmental stresses, nutritional disorders, etc.); and fungicides/spray technology.
  4. Weeds of the Northeast: Described as the first comprehensive weed identification manual available for the Northeast enabling identification of almost 300 common and economically important weeds in the region. The manual contains color photos of vegetative and flowering stages of weeds, as well as, seed photos.
  5. Wine Grape Production Guide for Eastern North America: A comprehensive reference on all aspects of wine grape production (e.g., varieties, canopy management, nutrient management, etc.) including chapters on disease management, insect and mite pests and vineyard weed management.
Important viticulture resources for vineyard managers in the Mid-Atlantic region. Photo provided by: Andy Muza

Important viticulture resources for vineyard managers in the Mid-Atlantic region.

Insect and Disease Resources – 2016 articles

Articles from the 2016 season that should be reviewed include:

GRAPE DISEASE CONTROL, 2016 by Wayne F. Wilcox, Cornell University (74 pages). Dr. Wilcox provides comprehensive coverage of relative research and disease management options.

Grape Insect and Mite Pests – 2016 Field Season by Greg Loeb, Cornell University (21 pages). Dr. Loeb provides a thorough review of insect pests that you might see throughout the season in the vineyard. Included are 18 photos of pests/injury along with management guidelines.

Insect and Disease Resources – Web sites

IPM –Grapes (Cornell): Information is available on diseases, insect and mites, weeds, wildlife, organic IPM, spray technology and pesticides.

NYS IPM : Fruit IPM Fact Sheets (Cornell): Fact sheets on diseases and insects on grapes, tree fruit and small fruit. A total of 22 fact sheets pertain to insects and diseases on grapes.

Identifying Grape Insects (Michigan State University):  The information on this site is from the previously mentioned resource, A Pocket Guide for Grape IPM Scouting of Grapes in North Central & Eastern U.S. and is categorized by: Pests attacking; buds, leaves, fruit, root, during harvest. Also includes beneficial insects and mites.

Mid Atlantic Vineyards Grape IPM (Virginia Tech): Insect fact sheets categorized by: direct pests – fruit; indirect pests – leaves; trunk and cane feeders; and root feeders.

Ontario Grape IPM: This site provides information on a variety of topics including: insects and mites; diseases and disorders; weeds; herbicide injury; identification keys; etc.

Growing Grapes – Vineyard IPM (eXtension): Articles both in English and Spanish on: insects, diseases, weeds, animal pests and problems not caused by insects or diseases.

Weed Resources – Web sites
New Jersey Weed Gallery (Rutgers): Photos and descriptions of weeds found in New Jersey. Weeds can be viewed by common name, Latin name or thumbnail images.

Weed Identification Guide (Virginia Tech): These pages are intended to aide in the identification of common weeds and weed seedlings found throughout Virginia and the Southeastern U.S. The weed pictures are arranged alphabetically by common name.

UMass Extension Weed Herbarium (University of Massachusetts): Identification notes and color photos of over 500 weeds.

UC-IPM Weed Photo Gallery (University of California): Common names link to pages with weed descriptions and photos often showing several stages of development.


What is Enology?

By: Denise M. Gardner

By definition, (o)enology is the study of wine and winemaking (Robinson 2006).  The field of enology differs from that of viticulture, the science of grape growing, although the two are often intertwined in academic departments across the United States.

An (o)enologist is one that practices the field of (o)enology, and often understands the scientific principles associated with winemaking, including desirable characteristics associated with the grape itself.  Enologists tend to understand wine analysis and can make educated decisions during wine production based on the analytical description and, potentially, sensory description of a given wine.  Many enologists do not actually have a degree in “enology” per se, although enology degree programs exist throughout the world.  In fact, many industry enologists have a science degree in chemistry, microbiology, biology, food science or another related field.

I find myself often making the argument that an enologist is actually a food scientist that specializes in the production of wine.  While it may appear less glamorous in words, many enologists that have studied in the U.S. have Bachelors of Science degrees from institutions in which “enology” is embedded within the food science department.  While the art of crafting a quality wine is unique to the product, and can require years of adequate sensory training or experience, the equipment and production techniques associated with winemaking are also utilized in the commercial production of many food and beverage products.

Penn State Food Science undergraduate students learn pilot scale research winemaking techniques associated with commercial winemaking practices and enology.

Penn State Food Science undergraduate students learn pilot scale research winemaking techniques associated with commercial winemaking practices and enology. Photo by: Denise M. Gardner

What does an (o)enologist do?

Being an enologist does not necessarily indicate that that individual is also the winemaker.  In the book, “How to Launch Your Wine Career,” the authors (Thatch and D’Emilio 2009) explain the two arms associated with wine production in California: the winemaker and the enologist.  For a head winemaker position, one typically has to work up the ladder from assistant winemaker, and may find themselves in several assistant winemaker positions prior to holding a head winemaker position.  The enologist position develops through a different ladder within the winery: from a crush (or harvest) intern to a cellar worker to a lab assistant and finally a cellar master before reaching the enologist position.  Note that this development may not always be the case in smaller, commercial wineries.

In larger wineries, many enologists focus on working within a winery’s lab.  Their primary duties could range from conducting daily wine analysis and monitoring quality control parameters of all of the wines, to training additional employees (lab assistants, lab technicians, harvest interns) in running analysis, to assisting the winemaker with specific tasks (e.g., setting up blending trials, recording data on blending trials, field trials, or wine trials, and accomplishing cellar tasks).  In smaller wineries, the enologist will tend to wear several hats, and may also be associated as the head winemaker for the establishment.

Understanding analytical techniques associated with the quality control of wine production is an essential component of being an enologist.

Understanding analytical techniques associated with the quality control of wine production is an essential component of being an enologist. Photo by: Denise M. Gardner

Is an enologist the same thing as a sommelier?

Enologists should not be confused with sommeliers, which the Oxford Companion to Wine defines as a “specialist wine waiter or wine steward.”  Sommeliers are typically employed by restaurants, distributors, or other retail entities to advise consumers on wine purchases at a specific establishment.  It is not uncommon for sommeliers to determine a wine list for a restaurant or to advertise food and wine pairings based on the restaurant’s menu and available wine selection.

Education in a sommelier certificate program focuses on introductory viticulture and winemaking knowledge; a broad overview of terms and basic production practices (i.e., how to make a white wine versus a red wine).  Their focus will feature global wine producing regions (e.g., regions within France like Bordeaux, Burgundy, the Loire, etc.), wine styles and the characteristics associated within specific regionally (terroir-driven) produced wines. Written knowledge is supplemented with educational tastings, and most sommelier and sommelier-like programs have a unique tasting method that is taught and practiced by all pupils.  Additionally, some sommelier programs feature education on the various types of spirits produced internationally and the sensory evaluation thereof.  Sommeliers understand how to interpret wine regions and what to expect stylistically from a wine that is presented to them.  Despite the depth of knowledge in these areas, sommelier training does not focus on actual production techniques.  A sommelier is not trained in a wine processing facility, nor taught the scientific component to winemaking, and their approach to wine tasting often differs from those in production.  I have often found that sommelier’s evaluation of a wine can supplement that of the winemaker in a positive way, and emphasizes how varied sensory perceptions of wine truly are based on one’s training and experience.

Wine sensory evaluation – an educational tasting session – hosted by a Wine and Spirits Education Trust class.  Flights of wine are chosen to emphasize regional and stylistic characteristics that are specific to a given region.

Wine sensory evaluation – an educational tasting session – hosted by a Wine and Spirits Education Trust class. Flights of wine are chosen to emphasize regional and stylistic characteristics that are specific to a given region. Photo by: Denise M. Gardner

There are several organizations that train sommeliers.  The most famous and prestigious organizations for sommelier credentials include the Court of Master Sommeliers and the Masters of Wine (MW) programs.  Certification typically requires participants to pass several exams, written and oral (i.e., mock sommelier serving exams or blind wine tastings with adequate identification of each wine).  The Masters of Wine program also includes a written research paper on a select wine topic.

There is also a number of regional and local sommelier training and certificate programs, or wine education courses, available to interested parties.

Is it important for a winery to hire an enologist?

For a smaller, commercial winery (<10,000 cases), having an on-site enologist is beneficial for a winery, especially if the enologist is trained to make wine, run and interpret lab analysis, and adequately taste wines.  Essentially, their role takes can take the “guess work” out of winemaking.  An enologist’s skill and expertise can completely transform a winery’s brand and quality, especially if that individual is employed to accomplish two production tasks: enologist (i.e., lab analysis) and winemaker.  Additionally, a winemaker can also train to improve their skills in the lab to also act as the winery’s enologist.

How to become more affluent in enology?

In Pennsylvania, there are a number of ways that one can improve their knowledge in enology.  First, it is best to identify what you want to do.

  • Are you interest in making or producing wine on the production floor?
  • Do you have an interest in science and lab analysis?
  • Or are you looking into a broader knowledge for making wine and food pairings?

For the first two points, if you are looking to switch careers or already employed by the wine industry, but think you need a more in-depth background in the scientific principles associated with wine production and/or analysis, a good starting point is Harrisburg Area Community College’s (HACC) online viticulture and enology Associate’s Degree program: http://bit.ly/HACCVandE

Additionally, Penn State Extension offers several workshops, short courses, webinars, and educational events that are designed for the commercial wine industry: http://extension.psu.edu/food/enology

Penn State Extension Enologist, Denise M. Gardner, tastes wines with Wine Quality Improvement (WQI) Short Course attendees to diagnose wine defects/flaws within commercial wines.

Penn State Extension Enologist, Denise M. Gardner, tastes wines with Wine Quality Improvement (WQI) Short Course attendees to diagnose wine defects/flaws within commercial wines. Photo by: Michael Black/Black Sun Photography.

Sometimes, it is beneficial to enroll in broader food production short courses to enhance one’s baseline knowledge.  Such short courses include like:

Additionally, many other Extension programs feature wine- and grape growing-specific workshops tailored towards to the commercial wine industry.

How to broaden your wine knowledge

However, if you found yourself wanting a broader background in understanding wine regions, wine styles, and wine (in general), without getting into winemaking, then you may want to look into a wine education course that follows a sommelier curriculum.  Several are featured in Pennsylvania, and offer a wide range of expertise levels:


Robinson, J. 2006. The Oxford Companion to Wine. Oxford University Press, New York.

Thach, L. and B. D’Emilio. 2009. How to Launch Your Wine Career. The Wine Appreciation Guild, San Francisco.