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
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.
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.
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.
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
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.
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.
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.
- NYS IPM Fact Sheets for Grapes; Identifying Grape Insects (Michigan State);
- Midwest Grape Production Guide (Bulletin 919) – (Chapter 4 – information on grape insect pests);
- Mid Atlantic Vineyards Grape IPM (Virginia Tech) ;Ontario GrapeIPM – Grape Insects
- Another valuable, compact resource that can be taken along in the vineyard as you are scouting is A Pocket Guide for Grape IPM Scouting of Grapes in North Central & Eastern U.S. This guide provides concise information along with color photographs on insect/mite pests, natural enemies, diseases and disorders.
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
IRAC Number (Modes of Action – MoA – Classification) : Insecticides for management of grape berry moth
Components of a Resistance Management Strategy
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.
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 ; Altacor ; or Delegate ) 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.
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
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.
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 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.
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.
By: Jody Timer
Lake Erie Regional Grape Research and Extension Center
The grape berry moth, Paralobesia viteana, (GBM) is, by far, the most destructive insect pest in the Eastern vineyards of the United States. Often the damage from these insects goes unnoticed until late in the season, which makes controlling them, and the damage that they cause, difficult.
This blog will be a brief overview of the grape berry moth’s life cycle, what to scout for, and some suggestions on how to control their infestations.
GBM has three, and often four, generations a year with larval infestation in vineyards increasing from generation to generation. These numerous generations contribute not only to their ability to be so ruinous, but also to their ability to build up a resistance to insecticides. The GBM overwinters in the pupae stage. The adults emerge in the spring from overwintered leaf litter and debris that gets blown from the vineyards to protected sites.
The mated females oviposit on developing buds, flower clusters, or grape berries. Upon hatching, 1st instars burrow into the grape and feed. There are four larval instars, and larvae fully develop in approximately 10-13 days. Typical loss of berries is due to GBM larva feeding internally, but additional significant losses can occur as a consequence of fruit rots brought on by this pestiferous insects’ damage to berries. The damage can extend to entire clusters resulting in major crop losses. Once the larva enters the berry, they are protected from insecticides.
Compounding these management decisions are the late season generation’s infestations in recent years that have caught growers unaware, resulting in additional crop losses. Growers need reliable and effective methods for assessing risk from GBM, and precise control options in many regions, to avoid significant economic damage. One tool, originally developed in the in the 1970s and 1980s, is a trap baited with synthetic sex pheromone. Unfortunately, the pheromone-based lure, as currently employed, is useful for indicating the first flight of overwintered male GBM, but cannot out-compete the female GBM in the vineyard. This causes the captures to be sporadic and consequently makes detecting the spray timings for subsequent generations difficult. A grape berry moth model was developed by Tobin et al. (2001) and was incorporated into Cornell’s NEWA website http://newa.cornell.edu. This website uses the wild grape bloom in a particular area as the starting point for degree day calculation. Once the wild grape bloom date is entered the website will give the growing degree day accumulation in your area, and spray timing recommendations.
According to the Grape Berry Moth Model found on the NEWA website, we are past, at, or rapidly approaching, the 1720 DD timeframe in the southeastern part of the state. The northwestern part of the state will have another 10 days at least, but scouting should be started now. When scouting for GBM, make sure to separate the berries. GBM tend to lay their eggs in- between berries which often makes their holes hard to detect. The 1720 DD timeframe is when contact insecticides should be applied for GBM in high risk vineyards and in low- and intermediate-risk vineyards where scouting showed damaged clusters above the 15% threshold. The best way to use the model would be to plug in the wild grape bloom date that you know for your region. The location and wild grape bloom date can make a significant difference in spray timing. If you do not know the wild bloom date, the model calculates one for your region. The GBM DD Model provides the optimum timing for an insecticide application. However, the decision to apply an insecticide should depend on scouting data and history of GBM injury at the site. (http://lergp.cce.cornell.edu/submission.php?id=69&crumb=ipm|ipm) contains a table listing the modes of actions of insecticides used, and which insecticides have shown efficacy, in New York and Pennsylvania vineyards.
|Tobin, P.C., S. Nagarkatti, and M.C. Saunders. 2001. Modeling development in grape berry moth (Lepidoptera: Tortricidae). Environ. Entomol. 30: 692-699.|