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Grape Leafhoppers

By: Andy Muza, Penn State Extension – Erie County

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

Life Cycle and Description

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

 

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

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

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

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

Management

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

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

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

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

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

 

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

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

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

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

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

References

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

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.

Will The Brown Marmorated Stink Bug Be A Problem In Wine And Juice?

By: Jody Timer, Research Technologist

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stal) is an invasive species that has become a major pest in the eastern United States. This pest originally became a sizable problem in Mid-Atlantic vineyards, including southwestern Pennsylvania, during the 2010 growing season and continues to be a large-scale problem. The Lake Erie grape belt is the largest Concord grape growing region in the world. The recent appearance of the brown marmorated stink bug in Lake Erie vineyards has the potential to become problematic. After the mild winter of 2015-2016, the numbers of BMSB in this area began to increase rapidly. This winter, frequent complaints have been received from homeowner concerning the presence of BMSB in their houses.

BMSB have been found in both grape foliage and grape clusters; they seek the moisture, sugar, and warmth on the inside the clusters (especially overnight) and they often migrate to the cluster’s interior close to harvest. This makes the possibility of BMSB inside the cluster very likely when these grapes are mechanically harvested and transported to the processor.

Brown Marmorated Stink Bug in a Grape Cluster

All BMSB life stages (5 instars) have been observed in vineyards indicating that grapes are a suitable crop for BMSB development, and all stages have been found to cause direct damage to grapes (Bernon 2004). At the Lake Erie Grape Laboratory, we have maintained an adult BMSB colony on a diet of Concord grapes with no apparent development problems. It has also been estimated that the presence of 5 BMSB per grape cluster may lead to 37% loss in grape yield as a result of BMSB damage (Smith et al. 2014). With the yearly increase of numbers of BMSB in the Pennsylvania vineyards, the possibility of BMSB tainting the juice produced in this area is becoming a primary concern to processors, growers, marketers, and consumers.

Life stags of the Brown Marmorated Stink Bug. Photo from: http://www.mda.state.mn.us/plants/insects/stinkbug.aspx

Insects produce small, volatile molecules that may be imparted to juice and wine during crush. Humans are able to detect these molecules at extremely low concentrations. For example, 2-isopropyl-3-methoxypyrazine (IPMP) from Multicolored ladybeetles (ladybug taint) is detectable at 0.30 ng/L concentrations in Concord grape juice (Pickering et al. 2008). BMSB have a distinctive odor which has been described as green, cilantro-like, which may or may not be off-putting within grape juice aroma. BMSBs produce taint associated compounds as allomones, alarm pheromones, aggregation pheromones, and kairomones. These compounds are mainly released from the dorsal abdominal glands in nymphs and paired metathoracic glands in adults (Baldwin et al. 2014). When BMSBs are crushed along with grape clusters, release of these compounds could potentially taint in the juice.

Multidimensional gas chromatography mass spectrometry (MDGC-MS) analysis of stressed BMSB, adults and nymphs, has been used to identify more than 39 compounds. The volatile compounds in the taint are tridecane, dodecane, trans-2-decenal and trans-2-undecen-1-ol. Tridecane and trans-2-decenal together constitute at least 70% of BMSB taint (Baldwin et al. 2014; Solomon 2013). Trans-2-decenal, is the major irritant and is believed to be responsible for the potent stink odor from BMSB. However, being an extremely unstable compound it can easily break down, and its degradation products lack the distinctive BMSB odor (Baldwin et al. 2014). When trans-2-decenal was added to red wine (Pinot Noir) the morning of testing, the detection threshold was in the low microgram per liter (ug/L) range (Mohekar et al 2015). However, because trans-2-decenal is unstable, this may not reflect what happens when juice is processed and stored. Joe Fiola from University of Maryland, reported that while 5-10 BMSB per 25 pound lug of white grapes imparted a perceptible taint in raw juice for up to four months in some cases, the taint was not perceptible in the wine after fermentation (Fiola 2011).  Mohekar and colleagues, from Oregon State, reported that trans-2-decenal, has a detection threshold in the ug/L range in Pinot Noir wines, and was able to be detected by tasters (Mohekar et al 2016).

Informal sensory testing with the on-site staff was performed at the Lake Erie Regional Grape Research laboratory. Small batches of grape juice were produced using a residential Kitchen Aid® juicer, and increasing numbers of BMSB were added. Batches of juice containing the equivalent of 0, 2, 10, and 25 BMSB per lug (~35 lbs. of Concord grapes) were tasted raw and after high-temperature, short-time pasteurization (HTST) by five staff members. In blinded triangle tests (2 blanks and 1 spiked sample), 5 of 5 individuals correctly identify the spiked sample of the 25 BMSB/lug juice (both raw and pasteurized); for the 10 BMSB sample, 4 of 5 correctly identified the spike in raw juice, and 5 of 5 identified the spiked sample for the pasteurized juice. The following month the pasteurized juice was re-tasted by 10 individuals and similar results were obtained.  These tests suggest 25 BMSB/lug are sufficient to induce a perceivable flavor change in Concord grape juice. Following this testing, a set of samples were processed at the Food Science laboratory of Penn State, using industrially relevant methods (equivalent to Welch’s Corporation processing techniques), to assess if the odor-causing compounds secreted by BMSB were stable enough to transfer through the juicing, processing, pasteurization, and storing of grape juice and therefore cause it to be rejected by consumers. Large scale sensory tests were then run with regular grape juice consumers to quantify rejection thresholds for BMSB-spiked, processed grape juice.

Grape clusters, with varying amounts of BMSB (0, 4, 8, 16, 24, and 32 BMSB, per 35 lbs), were crushed and destemmed; the juice was pasteurized, clarified and blended. Following storage for 8 weeks (2 months after initial processing), sensory testing was performed with grape juice consumers in the controlled sensory testing facility to determine rejection thresholds for different levels of BMSB. Sensory testing was then repeated 8 weeks later (4 months after initial processing).

Despite the use of BMSB levels that clearly caused a noticeable change in the flavor of processed juice in pilot testing, we were unable to find a level of BMSB that caused rejection in consumers following processing and storage at either time point.

As the area’s BMSB population increases, this research will be notably important for processor to determine threshold levels at harvest. This research suggest that taint from BMSB at high but realistic doses for the Lake Erie grape-growing region will not influence consumer acceptability. Conversely however, our results may not generalize to smaller producers in the area who make grape juice using exclusively from Concord grapes. Typically, this juice is sold as fresh juice with a limited shelf life. These smaller growers and producers should be aware of the possibility of taint in their juice especially with the increasing numbers of BMSB in the region. Pre-harvest scouting for BMSB should be conducted to determine if a pre-harvest BMSB insecticide spray should be applied.

https://youtu.be/VzIpLHatLHc

https://youtu.be/el9HLnMLN90

 

References:

Baldwin, R.L. IV, A. Zhang, S.W. Fultz, S. Abubeker, C. Harris, E.E. Connor, and D.L. Van Hekken (2014) Hot topic: Brown marmorated stink bug odor compounds do not transfer into milk by feeding bug-contaminated corn silage to lactating dairy cattle. J. Dairy Sci. 97. 1877-1884.

Bernon, G. (2004) Biology of Halyomorpha halys, the brown marmorated stink bug (BMSB) Final Report—USDA APHIS CPHST Project T3P01. USDA APHIS.

Fiola, J.A. (2011) Brown Marmorated Stink Bug (BMSB) Part 3-Fruit Damage and Juice/Wine Taint. Timely Viticulture. University of Maryland extension,

http://www.grapesand fruit.umd.edu. Accessed October, 2016

Mohekar. P. (2016) Brown Marmorated Stink Bug (BMSB), Halyomorpha halys Taint in Wine: Impact on Wine Sensory, Effect of Wine-processing and Management Techniques. Dissertation Oregon State University

Mohekar, P., Tomasino, E., Wiman, N.G., (2015) Defining defensive secretions of brown marmorated stink bug, Halyomorpha halys. Presented at the 2015 Annual Meeting of the Entomological Society of America, Minneapolis, MN

Pfeiffer, D. G., T. C. Leskey and H. J. Burrack, (2012) Threatening the harvest: The threat from three invasive insects in late season vineyards, pp. 449-474. In N. J. Bostanian,

Pfeiffer, D., J. Fiola, B. Lamp, K. Rane, A. Nielsen, D. Polk, B. Petty, D. Ward, M. Saunders, J. Timer, C. Hedstrom, P. Mohekar, N. Wiman, E. Tomasino and V. Walton, (2013) BMSB in Vineyards and Wines. www.stopbmsb.org/stopBMSB/assets/File/Research/BMSB…/Vineyards-Vaughn.pd . Accessed September 2016

Pickering, G.J., Karthik, A., Inglis, D., Sears, M. and K. Ker, (2008). Detection Thresholds for 2-Isopropyl-3-Methoxypyrazine in Concord and Niagara Grape Juice. Journal of Food Science, 73 (6): S262-S266.

Prescott, J., Hayes, J. E., & Byrnes, N. K. (2014). Sensory Science. In N. K. V. Alfen (Ed.), Encyclopedia of Agriculture and Food Systems (pp. 80-101). San Diego: Elsevier.

Smith, J.R., Hesler, S.P., and Loeb, G.M., (2014) Potential Impact of Halyomorpha halys (Hemiptera: Pentatomidae) on Grape Production in the Finger Lakes Region of New York. J. Entomol. Sci. 49, 290–303. doi:10.18474/0749-8004-49.3.290

Solomon, D., D. Dutcher, and T. Raymond, (2013) Characterization of Halyomorpha halys (brown marmorated stink bug) biogenic volatile organic compound emissions and their role in secondary organic aerosol formation. J. Air Waste Manag. Assoc. 1995 63, 1264–1269.

Welch’s Corporation, www.Welch’s.com Accessed August 2016.

Resources for Identification and Management of Vineyard Pests

By: Andy Muza, Penn State Extension – Erie County

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

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

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

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

Insect and Disease Resources – 2016 articles

Articles from the 2016 season that should be reviewed include:

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

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

Insect and Disease Resources – Web sites

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

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

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

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

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

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

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

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

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

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

 

Is Spotted Wing Drosophila a Problem in My Wine Grapes?

By: Jody Timer, Penn State Dept. of Entomology, Lake Erie Regional Wine Research and Extension Center

Research has been conducted recently at the Lake Erie Grape Research and Extension Center, to determine the prevalence of spotted wing Drosophila throughout the Lake Erie grape growing region. Spotted wing Drosophila, Drosophila suzukii, Matsumura (Diptera: Drosophilae) (SWD) is an invasive vinegar fly of East Asian origin, that was recently introduced into the United States. It was first found in California in 2008 and is now found in all major fruit-growing regions of the country including Pennsylvania. It was first discovered in Pennsylvania’s Lake Erie grape growing region in the late fall of 2011. The potential infestation rate of spotted wing Drosophila differs from other vinegar flies because the female possess 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: https://youtu.be/dPr61VC2gyo

Aug 2016_Jody_Fig 1 SWD

During egg-laying, it is believed that sour rot and fungal disease can also be introduced, further affecting the fruit quality. SWD are thought to overwinter primarily as adult females, and they prefer moderate, cool wet climates similar to the Lake Erie grape belt. Adults live approximately two to nine weeks. During this time, one adult female can lay 100 to 600 eggs in fruit. 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 field or a vineyard. Eggs hatch in two hours to three days with the larvae feeding in the fruit for about 3 to 13 days before pupating into adults. Thus, multiple generations occur per year. Drosophila suzukii is now one of the most serious pests of thin-skinned fruits including blueberry, raspberry, cherry, grape, and strawberry. Because this pest is similar in appearance to common vinegar flies, the greatest problems have occurred when populations went unnoticed and thus remained untreated until they caused considerable damage to crops.  A good YouTube video on how to identify SWD damage is: https://youtu.be/DLNDnMMfWfs

In our research we sent up 25 traps for SWD though out the region.  By harvest SWD were found in all of the traps. They began to attact the grapes at verasion, and by harvest the SWD outnumber the other vinegar flies (fruit flies) in all of the traps. Over the entire season, the percentage of SWD to other vinegar flies caught in our traps over the last three years is approximately 25-30%. We also found numerous SWD in the traps we placed by cherries, strawberries, raspberries, and corn. Females SWD were caught in traps before males and males were caught in the fall after the females. It is believed that the overwintering populations are mostly female.

We then conducted 2 and 4 choice and no-choice test with common wine and juice grape varieties SWD infested all of the grapes we tested. They showed no strong preference for cultivar of grape, color of grape, or brix’s (as long as the variety was past verasion). An interesting side discovery from our research was that SWD does not appear to attack native wild grapes.  Even given no other source (no choice testing) it only laid a few eggs on the wild grapes. SWD do attack injured grapes before non-injured.

These vinegar flies become a greater problem the later the grapes are harvested, due to late season rots, which makes the later ripening wine grapes particularly at risk.  Although this insect is a concern of juice grape growers, it should be of decided concern to wine grape growers. Besides the problem of late season rots this insect can impart, there is the problem of wine taint. The beneficial aspects of fruit fly infestation of grapes are stated in a TreeHugger article. It states that the fruit fly also helps the wine by carrying yeast on its body on imparting this to the grapes. Saying that the new knowledge about the interaction between fruit flies and yeast “helps us understand why yeasts make interesting aromas, and opens up the possibility of using flies to help find new yeasts.” Matthew Goddard, from the School of Biological Sciences at the University of Auckland, studied the matter. Goddard’s studies found that when fruit flies had a choice of yeasts, they carried the aromatic wine yeast 100 times more – showing that the smell did have an effect. According to LiveScience, they can find wine or fermenting juice from half a mile away. These beneficial effects are decidedly outweighed by the negative effects from fruit fly infestation. The alcohol in the wine softens the fly’s body and it releases a nasty-smelling enzyme into the wine, they can also transmit large Acetobacter populations. Acetobacter can cause of host of other problem with wine making such as acetic acid.  SWD is of special concern because of their ability to lay eggs in otherwise healthy fruit. Often the fruit will not look damaged until the larval populations, which have hatched from the internally laid eggs, grow and feed internally on the grape berry till it eventually collapses. This can happen after seemingly healthy fruit has been harvested and sent to wineries.

Trapping and forecasting can lead to improvements in grower’s capability to optimally time pest management decisions which should reduce both the direct cost of pesticide treatments and the indirect cost to wineries.  Photo from: https://byo.com/hops/item/1265-preventing-three-big-stinks https://www.therealreview.com/2015/02/27/waiter-theres-a-fly-in-my-wine/

Trapping and forecasting can lead to improvements in grower’s capability to optimally time pest management decisions which should reduce both the direct cost of pesticide treatments and the indirect cost to wineries.
Photo from: https://byo.com/hops/item/1265-preventing-three-big-stinks
https://www.therealreview.com/2015/02/27/waiter-theres-a-fly-in-my-wine/

Japanese Beetle: A Common Pest in the Vineyard    

By: Andy Muza, Penn State Extension – Erie County

Distribution

The Japanese beetle has been in the United States since 1916 when it was first discovered in New Jersey. By 1920, this pest had migrated to southeastern Pennsylvania and by 1957 this insect could be found in every county in the state. Currently, this pest can be commonly found in all states from Maine to Georgia and as far west as Illinois and Tennessee. Japanese beetle has also been found in parts of Nebraska, Kansas, Oklahoma and in Utah.

Life Cycle and Description

Japanese beetle has 1 generation/year with 4 life stages: egg, larva, pupa and adult. The beetles are almost ½” in length and ¼” wide with a metallic green body and bronze colored wing covers. An identifying characteristic is 12 patches of white hairs on the abdomen around the outside edges of the wing covers (Figure 1).

Beetles can live for 4 – 6 weeks and they spend this time voraciously feeding and mating. Females deposit their eggs in the soil and can lay up to 60 eggs during their lifetime. Eggs hatch in 10 – 14 days and larvae (grubs) begin feeding, mainly on grass roots, near the soil surface. A fully grown larva is about 1” long with a soft, white body, 3 pairs of legs, and a light brown head capsule. Grubs are described as having a curled or C-shaped body (Figure 2). In the fall, larvae move deeper into the soil (4” – 8”) to overwinter. As soil temperatures warm in the spring the mature grubs (Figure 3) return to the soil surface to feed and pupate.

 

Figure 3: Mature Japanese beetle larva (grub). Photo from: S. Hesler

Figure 3: Mature Japanese beetle larva (grub). Photo from: S. Hesler

Emergence

On average in southern Pennsylvania, adult beetles begin emerging from the soil about the third week of June and in other areas of the state about 7-10 days later. This season, during the week of June 19 – 25, significant buildups of this beetle were reported in many orchards in southern Pennsylvania.  In Erie County, Pennsylvania observed the first beetle in a vineyard on June 22 but by July 6 there was a noticeable increase in beetle numbers.

Feeding Injury

Adult Japanese beetle feed on over 300 species of plants including grape, tree fruits, small fruits, vegetables, ornamentals and various weeds. The larvae are serious pests of turfgrass. On some crops, (e.g., peaches) beetles can cause significant injury on both fruit and leaves. However, on grapes, feeding is mainly on leaf tissue. Beetles are most active on warm, sunny days and tend to congregate on vines to feed and mate in groups on the top leaves of the canopy. Feeding injury, depending on severity, can result in leaves having a skeletonized appearance due to consumption of the soft leaf tissues between veins (Figure 4). Research and field observations indicate that Japanese beetles prefer smooth, thinner type grape leaves which are characteristic of many wine grape varieties (e.g., Chardonnay, Traminette, and Vidal Blanc). However, large populations of beetles can also cause considerable leaf injury to lesser preferred varieties such as Concords (Figure 5).

Figure 3: Traminette leaves skeletonized by Japanese Beetle. Photo by: Andy Muza

Figure 4: Traminette leaves skeletonized by Japanese Beetle. Photo by: Andy Muza

 

Figure 4: Concord leaf with feeding injury from Japanese Beetle. Photo by: Andy Muza

Figure 5: Concord leaf with feeding injury from Japanese Beetle. Photo by: Andy Muza

 

Management

A presentation “Managing Japanese beetles in vineyards” (Rufuus Isaacs) (http://www.isaacslab.ent.msu.edu/Images/talks/Isaacs%20Viticulture%202010%20JB%20for%20web.pdf) provides information on various management strategies, scouting, leaf area loss tolerance and insecticide option information.  Definitely worth checking out.

Biological and cultural management tactics are also discussed in various fact sheets about Japanese beetle but currently the most practical management in commercial vineyards requires insecticide application(s) aimed at adult beetles.

There are numerous insecticides registered on grapes for management of Japanese beetle in Pennsylvania, which can be found in the 2016 New York and Pennsylvania Pest Management Guidelines for Grapes. For a concise explanation of insecticide options refer to “Managing Japanese beetles in fruit crops” (R. Isaacs and J. Wise) (http://msue.anr.msu.edu/news/managing_japanese_beetles_in_fruit_crops).

Research has shown that grapevines can tolerate a fair amount of leaf area loss without detrimental effects. However, no economic threshold level has been established for leaf injury on grapes caused by Japanese beetle. Therefore, growers have to rely on their judgement and experience to determine leaf injury levels they can tolerate.

Before deciding if an insecticide application is needed in any of your vineyard blocks consider:

  • Japanese beetle population levels,
  • varietal susceptibility,
  • age of vineyard (i.e., young or mature),
  • canopy size, and
  • crop load.

Heavy infestations in vineyards may require more than 1 insecticide application so frequent and thorough scouting of vineyards is necessary throughout the season. Many wine varieties, young vineyard blocks and vines in grow tubes are especially vulnerable to serious leaf loss by Japanese beetle feeding so consistent monitoring is critical.

Resources:

Japanese beetle, Popillia japonica Newman on Grape. (D.G. Pfeiffer and P.B. Schultz) http://www.virginiafruit.ento.vt.edu/JBGrape.html

Managing Japanese beetles in fruit crops (R. Isaacs and J. Wise) http://msue.anr.msu.edu/news/managing_japanese_beetles_in_fruit_crops

Managing Japanese beetles in vineyards (R. Isaacs) http://www.isaacslab.ent.msu.edu/Images/talks/Isaacs%20Viticulture%202010%20JB%20for%20web.pdf

Managing the Japanese Beetle: A Homeowner’s  Handbook  https://www.aphis.usda.gov/publications/plant_health/2015/japanese-beetle-handbook.pdf

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.