Tag Archive | grape berry moth

Late harvest insect problems

By: Jody Timer, Entomology Research Technologist, Erie County

The grape berry moth (GBM): The most destructive grape insect pest in the Eastern US is the native Grape Berry Moth, Paralobesia viteana. This insect is becoming increasingly harder to control as result of shorter residual time of insecticides, resistance to insecticides, and abandoned vineyards. GBM larval burrow into the grape berry soon after hatching, making precise timing of spray applications a critical component of control. This insect has four generations per year. Each generation increases in number exponentially if control measures are not applied to the early generations. Although in early season this insect pest has distinct peaks in generational emergence, by August the peaks have overlapped making complete control almost impossible. Growing areas with large populations require a second generational spray in July and/or August.  If these sprays have not been applied and there are GBM problems in your vineyard, it is a good idea to spray for this fourth generation in September. Spray timings can be calculated by following the NEWA model recommendations. Although much of the damage may have already occurred, this spray will help prevent the generations from starting the season next year farther into your vineyard. If you are dropping your crop from the end rows because of the excessive berry moth damage, collecting the dropped grapes as opposed to dropping them under the trellis will greatly reduce overwintering populations from remaining in your vineyard.  More GBM information can be found on extension pages and on the LERGP Podcasts.                                                            

Screenshot 2018-08-30 13.44.36

Spotted wing drosophila (SWD): Spotted wing drosophila, Drosophila suzukii,(SWD)is an invasive vinegar fly of East Asian origin that was recently introduced into the United States. It was first found in Pennsylvania in 2010. The potential infestation rate of spotted wing drosophila differs from other vinegar flies because the female possesses a serrated ovipositor that cuts into healthy fruit to lay eggs. Consequently, spotted wing drosophila (SWD) larvae can be found in fruit that is just ripening. During egg-laying, it is believed that sour rot and fungal disease can also be introduced, further affecting the fruit quality. All fruit flies carry yeast which can affect the quality of wine if these flies are present during winemaking. During peak temperatures, a female can lay more than 100 eggs a day. Such a high reproduction rate indicates the SWDs’ high potential for fruit infestation and their potential for spreading rapidly through a vineyard, with multiple generations occurring each year. Spotted wing drosophila is now one of the most serious pests of thin-skinned fruits including grapes. At this time, no action threshold is available for SWD, so the common recommendation is to increase monitoring when one fly is captured on a farm and began a spray regiment continuing through harvest, making sure to protect fruit through to harvest using registered insecticides. Female SWD are able to lay eggs into fruit from the time of first coloring through to harvest, so this period is the window of susceptibility to SWD. Because SWD populations tend to increase in the later part of the summer, we expect late-harvested fruit, such as grapes, to experience higher pressure from SWD than those that are harvested earlier in the summer such as strawberries and summer red raspberries. A number of registered insecticides have been very effective against SWD in laboratory trials, the most effective chemicals are organophosphate, pyrethroid, and spinosyn class insecticides. Under field conditions, insecticides with fast knockdown activity have performed well at protecting fruit immediately after application. When SWD are detected it is recommended that the spray intervals be tightened to prevent crop infestation before and during harvest.

Screenshot 2018-08-30 13.45.13

Spotted Lanternfly (SLF):  This newest invasive insect has the potential to be devastating to the grape growing industry. Its preferred host is the Tree of Heaven (Ailanthus altissima) and grapevines. SLF aggregate feeds on vines by piercing the vines and feeding on the phloem and xylem. This feeding causes intracellular damage as the insects siphon vast amounts of phloem which reduces the vine’s health and vigor. The insects excrete honeydew and the feeding sites leak sap, which causes sooty mold to form on the leaves reducing the photosynthesis. The sap also attracts secondary pests such as wasps and bees. The wounds make the hosts more susceptible to disease. Systemic chemicals are preferable and highly effective, but insect feeding is still damaging as there is a constant influx of insects from forest margins. Eggs are laid at the end of the season and the adult insects die. If discovered, egg masses should be removed immediately. Thirteen counties in southeastern PA are now under quarantine for this insect.

Screenshot 2018-08-30 13.45.23

Multicolored Asian ladybird beetles (MALB):  Although these insects cannot be effectively sprayed at harvest, vineyards should be scouted prior to harvesting to see if they are present.  MALB feeds on damaged fruit and causes taint to wine and juice in very small numbers if harvested with the grapes.

Screenshot 2018-08-30 13.45.33

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.

Grape Pests Updates – Spring 2016

By: Jody Timer

As a new grape season approaches, you all may be asking yourselves, “What is going to be my biggest headache this season?” As far as insects go, I would have to answer, as always, the grape berry moth (GBM).  In this blog I would like to touch on the most recent research regarding the grape berry moth, as well as, other insects to scout for in your vineyards in the early part of the growing season.

The last two growing seasons, growers expected to see a dramatic decline in GBM populations, due to the harsh winters and record breaking cold. The opposite scenario occurred when greater than average GBM infestations materialized.  So, what can we expect from this growing season?  The winter of 2015-2016 was mild, the spring started off warm, and then April slowed down the accumulation of degree days. The total accumulation of degree days for this season is only slightly ahead last season’s and is forecasted to catch up in the next week to within two days, with average temperatures throughout the rest of May.  With our current research, we aim to enhance the temperature-based phenology model to provide more detailed recommendations.  We are researching ways to optimize the timing of generation-specific interventions, thereby providing prevention of economic damage of subsequent generations. The number of generations of grape berry moth has been increasing from the traditional three generations per year to four plus. First, and most obvious, adding generations increases the overall attack potential. Second, and largely ignored, adding generations may increase the developmental asynchrony of the population. Given the already narrow time-window of vulnerable life stages, and changes in current and future insecticides, such developmental asynchrony increases the risk that late-season generations will require more than one insecticidal application to achieve control below industry-mandated economic thresholds.

The timing of chemical control of GBM is particularly challenging because the stages most vulnerable to insecticidal applications reside inside the berry for the majority of their life cycles. The result is an extremely narrow management window. (See http://newa.cornell.edu/index.php?page=berry-moth for the online forecasting tool for your growing regions). The early season developmental synchrony in GBM is caused by the relatively synchronous forcing of diapause, as adults emerge from diapausing pupae in late spring. Later in the season the generations become less and less synchronized and the peaks of emergence become blurred.  We are exploring the correlation with GBM spring emergence (DD) and the timing of wild grape bloom and the resulting asynchrony of the subsequent generations. Presently the wild grape bloom is used as the biofix for the NEWA GBM phenology forecast model. We expect GBM developmental synchrony to be dependent on multiple factors, most importantly, the rate of emergence in the spring. Our research is exploring the possibility that the closer the GBM spring emergence coincides with grape bloom the greater the survivorship of the first generation of GBM. Consequently, a large first generation emergence would result in subsequent generations, all of which would emerge in the presences of suitable hosts, exponentially proliferating. For example, in the Lake Erie grape growing region the wild grape bloom usually occurs around the first week in June and the GBM peak in emergence occurs around the end of May.  However, if we experience a very warm spring and the GBM emerge sooner than the wild grape blooms, they will emerge with no suitable host and less of them will survive. Such enhanced models will allow for more adaptive generation-specific protocols of management, and could include novel control strategies.  According to this model, we are expecting another heavy infestation of grape berry moth this year.

Early Season Insects:

Grape Flea Beetle– also known as the steely beetle. These beetles are small (3/16”) and metallic blue in color. Beetles overwinter in the adult stage and emerge as grape buds begin to swell, with one generation per year.  This beetle primarily attacks buds of wild and cultivated grapevines.  They are one of the first insect pests to appear in the vineyards in the spring. The most significant injury caused by this pest is due to adults feeding on swollen grape buds, often destroying the developing bud. They have the potential of causing considerable damage under the right conditions; specifically when we get a prolonged swollen bud stage. Look for damage from steely beetle along the edges of the vineyard. By about 1/2” growth the threat of economic loss from this pest is over. Infestations are worse on wooded edges. They get their name from their ability to jump.

Climbing Cutworms: There are several species of cutworm larvae feed on grape buds during the swell stage. The injury to buds can be confused with grape flea beetle damage. The moths are night flyers and the larvae are night feeders. Both stages hide during the day. Larvae have a brown to gray coloration with darker stripes or dots along the body, and are 30-36 mm long. Vineyards with weed cover under the trellis and areas with sandy soils are at greater risk for injury. The greatest economic injury occurs during bud swell in the spring. Scout frequently during this time.

3 – 12 INCH SHOOT GROWTH

Banded Grape Bug and/or Lygocoris inconspicuous – both of these insects have piercing and sucking type mouthparts. Banded grape bug nymphs have antennae with black and white bands, green/brown bodies and are <1/2”. Lygocoris inconspicuous nymphs are slightly smaller with light green antennae (no bands) and light green bodies. Nymphs (immature stage) of both insects feed on developing flower clusters by piercing florets, pedicels and rachises. Begin scouting when shoots are 3 – 5” in length and continue until shoots are at least 12”. See scouting video, below – Banded Grape Bug LERGPvids:

Grape Phylloxera (leaf form)Grape Phylloxera. Grape phylloxera is an aphid-like insect with a complex life-cycle that causes feeding galls on either roots or leaves. The life cycle is different for the foliar and root forms of this insect. The root form is the more destructive of the 2 forms but is managed by grafting susceptible varieties to phylloxera resistant/tolerant rootstocks. Leaf galls are in the shape of pouches or and can contain several adults and hundreds of eggs or immature stages. Root galls are swellings on the root, sometimes showing a hook shape where the phylloxera feed at the elbow of the hook. At high densities, leaf galls can cause reduced photosynthesis. Root galls likely reduce root growth, the uptake of nutrients and water, and can create sites for invasion of pathogenic fungi. There is a wide range in susceptibility of grape varieties to both gall types. Begin scouting early in the season. Galls may become evident as soon as the 3-5 leaf stage so carefully examine the undersides of terminal leaves for warty looking, green to reddish growths. An insecticide application can be applied when first galls are forming. The most reliable method to determine if crawlers are active is to cut galls open and observe for presence of nymphs. Crawlers are extremely small so a good hand lens is needed.

Phylloxera Nymphs (Crawlers) Photo From: http://www.virginiafruit.ento.vt.edu/phylloxera.html

Phylloxera Nymphs (Crawlers) Photo From: http://www.virginiafruit.ento.vt.edu/phylloxera.html

Additional Insect Pests – During this time period a number of other insects (i.e., grape plume moth, grapevine epimenus, 8 – spotted forester, tumid/tomato gallmaker, grape cane gallmaker, and grape cane girdler) may also be present in the vineyard. Although injury from these insects may look alarming, damage is usually cosmetic and insecticide applications are rarely needed.

For more detailed information, please see: Andy Muza’s blog last spring: Grape Insect Pests to Watch for from: Bud Swell through Immediate Pre-Bloom Stages

Fact sheets on grape insect pests can be found at the following sites: Please click on the links below for more fact sheets specifically on insect pests found in the vineyard.

Components of an Insecticide Resistance Management Strategy for Grape Berry Moth

Andy Muza, Penn State Extension – Erie County

In this blog I will discuss insecticide resistance management pertaining to grape berry moth control.  But first, information concerning insecticide classification and modes of action is necessary.

Insecticides are classified based on the similarity of the chemical structures of their active ingredients. Therefore, all insecticides in a certain group/class have similar characteristics. It is the chemical structure of the insecticide’s active ingredient that defines how it works (i.e., mode of action, MoA) at the target site.  The target site is the location within the insect where the insecticide acts.

Understanding modes of actions can be difficult due to the complex biochemical processes that occur within insects upon exposure. Fortunately, due to the efforts of the Insecticide Resistance Action Committee (IRAC) in classifying the Mode of Action (MoA) of insecticides, and assigning numbers to the mode of action groups, a detailed understanding of how insecticides work is not required. However, a basic knowledge regarding modes of action and the MoA classification scheme is useful for developing an insecticide resistance management strategy.

There are at least 8 different modes of action groups [IRAC Number – 1A, 1B, 3A, 5, 11, 18, 22A, 28] that are rated good to moderate for management of grape berry moth (GBM) in the 2016 New York and Pennsylvania Pest Management Guidelines for Grapes

https://store.cornell.edu/p-193185-2016-new-york-and-pennsylvania-pest-management-guidelines-for-grapes.aspx

IRAC Number (Modes of Action – MoA – Classification) : Insecticides for management of grape berry moth

Apr 2016_Andy_Insecticide Table

Components of a Resistance Management Strategy

Cultural Practices

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, trashy 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.

Figure 1.  Weeds under the trellis can harbor grape berry moth pupae.

Figure 1. Weeds under the trellis can harbor grape berry moth pupae.

Figure 2. Overgrown areas around the vineyard can be overwintering sites for grape berry moth pupae.

Figure 2. Overgrown areas around the vineyard can be overwintering sites for grape berry moth pupae.

Figure 3. Wild grapevines near the vineyard are potential reservoir sites for grape berry moth.

Figure 3. Wild grapevines near the vineyard are potential reservoir sites for grape berry moth.

Scouting                             

Insecticides should be used only if needed. Regular scouting throughout the season is a critical component in determining if and where applications should be applied for GBM.  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”  –  http://nysipm.cornell.edu/publications/grapeman/files/risk.pdf

Timing of insecticide applications using the GBM Degree–Day Model

GBM Degree–Day Model is incorporated into Cornell’s Network for Environmental and Weather Applications (NEWA – http://www.newa.cornell.edu/) and many grape growers in the Lake Erie Region have adopted this model to more accurately time insecticide applications for GBM management.

Spray Application Practices

Obtaining good spray coverage on clusters is critical. Calibrate sprayers at a minimum in the beginning of each season. Preferably 2 – 3 times/season as canopy growth increases.

  • 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.

Rotate chemical groups/classes of insecticides                                                                                                           

An important component in preventing or delaying insecticide resistance is to rotate insecticides with different modes of action into your GBM spray program. Use the MoA classification information above and consult the 2016 New York and Pennsylvania Pest Management Guidelines for Grapes   https://store.cornell.edu/p-193185-2016-new-york-and-pennsylvania-pest-management-guidelines-for-grapes.aspx  to develop a rotational plan.

Be sure to incorporate GBM selective insecticides such as (Intrepid [18]; Altacor [28]; or Delegate [5]) into your spray program which will also aid in conserving natural enemies.

Understanding insecticide modes of action may not be easy but following the IRAC MoA Classification for resistance management is as simple as rotating the numbers.

 

References:

Brown, A.E. and E. Ingianni.  Revised August 2013.  “No. 43: Mode of Action of Insecticides and Related Pest Control Chemicals for Production Agriculture, Ornamentals, and Turf.” University of Maryland. 13 pp. http://pesticide.umd.edu/products/leaflet_series/leaflets/PIL43.pdf

Insecticide Resistance Action Committee (IRAC) http://www.irac-online.org/

Suiter, D.R. and M.E. Scharf.  Reviewed January 2015. “Insecticide Basics for the Pest Management Professional (Bulletin 1352). University of Georgia. 28 pp. http://extension.uga.edu/publications/detail.cfm?number=B1352

                                                                                                     

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.

What’s Bugging Your Vines?

By: Jody Timer

Insect problems in the vineyards do not stop after bloom when Rose Chafer, Flea Beetle, Banded Grape Bug and other early season insects cease to create problems. This blog will briefly describe other important insect pest to be aware of during the ensuing months of the grape growing season.

The grape berry moth remains the most important grape insect pest. Their numbers exponentially increase during the growing season with each subsequent generation. GBM larvae feed directly on berries causing yield loss as a result of loss of berries and crop rejection. In addition, feeding injury provides entry points for fungi and bacteria which can cause cluster rots. This year the Erie County grape growing region has experience extremely high infestation rates during the first generation. Scouting each of your vineyards, paying close attention to wooded edges, is critical to GBM management and will divulge if this pest is present in your vineyard. Infestation can be determined by looking for any of the following signs; holes in berries, webbing in clusters, splits or dark tunneling underneath berry skin, reddish or brown discoloration of berries, and frass in injured berries. 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”.  Scouting can also help growers decide if spraying the entire vineyard is necessary or, if the injury is confined to the wooded edges, just applying a spray to that portion of the vineyard. Spraying just the edges as opposed to forgoing a spray completely will help prevent GBM from moving further into the center of the vineyard with each generation. It is important to time the sprays for GBM to coincide with the generational peaks. Once the GBM larvae are inside the berries, the sprays become ineffective.  There are NEWA weather stations throughout the state which can be accessed through Cornell’s NEWA website http://newa.cornell.edu this has been described in previous blogs. When choosing a spray material to apply to GBM infections unfortunately, you get what you pay for. With some minor exceptions, the quality of GBM materials relate closely to the price of those materials. GBM materials seemed to be priced relative to their effectiveness. Anecdotal observation shows crop losses have the potential to exceed 90% if inexpensive materials are used.

July_Jody1

We have received many inquiries regarding Japanese beetle damage; questioning how much damage is acceptable before spraying becomes necessary. The simple answer to this is: “It depends on what type of grapes you are growing.” Managing adult Japanese beetles is challenging because of the large numbers that can occur throughout the summer. The hard bodies of the Japanese beetles make them relatively unattractive to many predators.  During the latter part of the growing season, several growth processes take place within the vine which requires carbohydrate supplies. Under favorable environmental conditions, the leaves supply the needs of all these carbohydrate sinks. However, premature defoliation or a reduction in effective photosynthetic area within the vine canopies caused by Japanese beetles can adversely affect vine health. Japanese beetles show strong preference for susceptible vines. They prefer Vitis vinifera, followed closely by hybrids, and then juice grapes. Scouting for Japanese beetle is relatively easy.  They feed primarily on the top portions of the vines, and are easy to spot especially between 12 p.m. and 2 p.m. Monitoring traps baited with floral lure (for female) and sex pheromone (for male) are very effective at attracting beetles, however, they must be used sparingly because they attract beetles to your vineyard and do not trap and kill all of the beetles. Like most insects they are more abundant at the vineyard borders. When making spray decisions for Japanese Beetles an important factor to consider is: how much damage are they actually causing. Concord vines can stand up to about 30% damage to leaves without suffering damage to the vine. It is essential to remember this percentage is all the leaves not just the top leaves. Also, a percentage of leaf damage is usually lower than growers estimate by just observing the leaves. In a study by Rufus Isaacs of Michigan [http://www.isaacslab.ent.msu.edu/Images/talks/Isaacs%20Viticulture%202010%20JB%20for%20web.pdf] he discovered that in Seyval vines, natural levels of Japanese beetle feeding (6.5% leaf area loss) had no effect on vine growth or fruit quality. Intensive feeding after verasion inside cages (11% leaf area loss) reduced fruit quality. Newly planted and younger vines cannot tolerate Japanese beetle damage as well as established vines.

July_Jody2

The spotted wing drosophila (SWD) has become widely established in Pennsylvania over the last couple of years. This insect has many generations per year which leads to their abundance late in the grape growing season. This fruit fly is of importance because it possesses a serrated ovipositor which allows the females to lay their eggs directly into undamaged fruit. These eggs hatch in the fruit and the larvae will then consume the fruit from the inside out. Their microscopic holes also establish pathways for fungi and bacteria to enter the grape berries. Although raspberries, blackberries, and blueberries are the fruit crops most seriously affected by SWD, our research has shown that they will attack all varieties of grapes. The easiest way to monitor for SWD is by simple plastic cup traps containing apple cider vinegar. To determine if they are infesting your grapes it is recommend that you place undamaged grapes in a salt solution and observe if larva float to the top. There is excellent information on identification, monitoring, trapping, and damage detection by SWD at: http://extension.psu.edu/pests/ipm/agriculture/fruits/spotted-wing-drosophila

July_Jody3

The brown marmorated stink bug (BMSB) is currently a very serious pest in tree fruits and vegetables, and can be a household nuisance. Although BMSB prefer other fruits and vegetables to grapes, they do feed on grapes. Their damage can cause ugly scars on table grapes and grapes grown for sale at fruit stands. This type of damage is not important to juice growers, however, the holes open pathways for fungal and bacteria late season infections. They may also be easily harvest with the grapes. The insects tend to move to the interior of the cluster when disturbed and are hard to see. When killed they give off a foul odor which is how they got their name. Our research has shown that this odor and resulting taste do not survive the pasteurization of juice grapes. There is conflicting research on whether this taint transfers to wine, more research is ongoing. BMSB can be most easily found by putting a cloth under a grapevine and shaking the grapevine. These insect will then, in most cases, drop to the cloth. There are traps commercially available to trap these insect, but their efficacy is very low.

Asian Lady Beetle (MALB) has not been seen in abundant numbers in the past four years. MALB are predators to many insects and are considered a valuable biological control agent in many agroecosystems. When there is a larger than average population of MALB as there was 5 and 6 years ago, they become a problem late in the season. When injured or alarmed they secrete bodily fluids containing alkaloids which can taint the flavor of wines should the insect be processed with the harvested grapes. Since MALB tend to seek sources of carbohydrates before overwintering, they will congregate on ripened grape injuring the grapes and possibly being harvested with the grapes. As recently as 6 years ago, it appeared as if MALB was going to be a major problem with massive populations developing in the late summer. Since that time, MALB populations have not been as numerous and the concerns over this insect and its impact on wine production have lessened.

July_Jody5

As you approach harvest, be sure to take the time to check your vineyard for the presence of these pests. If you plan to use any insecticides, be very mindful of the preharvest restrictions and be sure to

Life cycle information for the majority of the important grape pests can be found at: http://www.nysipm.cornell.edu/factsheets/grapes/ ; NY IPM Program; Grapes.msu.edu; Mid-Atlantic Vineyards Grape IPM; and Ontario GrapeIPM.

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.