Growth Regulator Herbicides Negatively Affect Grapevine Development: Identification of Herbicide Drift Damage, How to Prevent it, and What to do if it Occurs in your Vineyard
By: Michela Centinari
The Penn State Extension grape team has been receiving reports on herbicide drift damage in vineyards from a number of Pennsylvania wine grape growers this growing season, definitely many more than in previous years. All herbicides registered for grapes can potentially harm the vines if not applied in accordance to the pesticide label (e.g., glyphosate products) . However, in many of the reported cases through the 2017 growing season the damage was caused by herbicides not registered for grapes, which drifted into the vineyards from nearby fields.
Damage from herbicide drift is, unfortunately, something that grape growers across the country are too familiar with. It represents an economic threat for the grape and wine industry and should not be underestimated. Herbicide drift damage can, indeed, result in significant crop losses which may extend to multiple seasons, and in some cases it also results in vine death. Several extension web resources are available to assist grape growers in preventing and dealing with herbicide drift damage. Some of them are listed at the end of this article, including one from Andy Muza, extension educator at Penn State (Growth Regulator Herbicides and Grapes Don’t Mix).
Due to the increase in reports of herbicide drift damage in Pennsylvania vineyards it seems appropriate to discuss some key points surrounding this issue. This article will review how to identify herbicide drift symptoms, what measures grape growers and pesticide applicators can take to prevent herbicide drift, and what steps to take if the drift occurs.
Plant growth regulators (PGR) herbicides are those most likely to injure grapevines, mainly through drift.
I will only focus on the herbicides which belong to the plant growth regulators (PGR) mode of action group. Common active ingredients of PGR herbicides are 2,4-D (2,4-Dichlorophenoxyacetic acid; phenoxy family), dicamba (benzoic acid), tricolopyr or picloram (pyridine family). A partial list of common PGR herbicides as well as other herbicides that may injure grapevines can be found at Preventing Herbicide Drift and Injury to Grapes, Table 1.
PGR herbicides are widely used for controlling broadleaf weeds in many crops, such as wheat, corn, soybean, pasture, rangeland, etc. They are also frequently utilized to control unwanted broadleaf vegetation in turf, by railroads, road ditches, fence lines, and rights-of-way. These herbicides are not registered for use with grapes. However, when applied to a nearby field, they can drift into the vineyard and cause significant injury to grapevines.
Most of the herbicide drift damage reported this season by Pennsylvania grape growers were caused by drift of PGR herbicides (Figure 1). Physiological symptoms to PGR exposure is not too surprising because grapevines are extremely sensitive to PGR herbicides, including the phenoxy, benzoic, and pyridine classes of compounds . For example, herbicides containing 2,4-D can damage grapes at a concentration 100 times lower than the recommended label rate. Moreover, drift from PGR herbicides can injure grapevines located half a mile or more from the application site.
What is “drift”?
Drift is defined as “the movement of herbicides off the site where they were applied” . Non-target drift can occur either as spray drift or vapor drift. Spray drift occurs during herbicide application when small droplets move off the application site under unfavorable wind conditions. Vapor drift occurs after herbicide application as the spray material volatizes or evaporates and is carried away from the application site by wind or temperature inversions. Some PGR herbicides, such as ester formulations of 2,4-D, readily volatilize, especially when used under high temperatures and low humidity conditions (high vapor pressure) .
How PGR damage occurs in grapevines
PGR herbicides mimic auxins, plant hormones that regulate growth and development. Applications of PGR herbicides disrupt plant hormone balance causing growth abnormalities. PGR herbicides can be absorbed by both roots and leaves, however grapevines are usually injured through foliar absorption.
How to tell if the vines have been damaged by PGR herbicide drift
Damage from PGR herbicides typically appears within 2 days of the drift occurrence. Herbicide drift can damage leaves, shoots, flowers, and fruit. Leaf symptoms are often easy to recognize, but sometimes can be mistaken with those of fanleaf degeneration, a viral disease . Growers can send pictures of damaged vines to a local extension specialist for confirmation.
Typical symptoms include:
- Distorted leaf appearance: Symptoms are typically more severe on the youngest leaves and shoot tips. Affected leaves are “smaller, narrow, deformed, and they have closely packed, thick veins that lack of chlorophyll” . They may also have a distinct fan-shape appearance, and depending on the herbicide’s active ingredient, they can bend downward or cup upward (Figures 2, 3). Leaves may or may not outgrow the symptoms, it largely depends on the severity of the injury and other factors listed in the following section (“Factors affecting the severity of injury”). It is also common to see regrowth of deformed leaves after drift exposure .
- Shoot growth: Damaged shoot tips rarely resume growth, but lateral shoots can keep growing giving in some cases a “bushy” appearance to the vine resulting in a highly shaded canopy and poor fruit sun exposure.
- Flower clusters (inflorescences): symptoms can include aborted or failed flowers, and poor fruit set (Figure 4). If the injury is severe enough it can cause reduced yield at harvest and poor fruit quality, in addition to potentially illegal residues of herbicide on the exposed crop.
In some cases, depending on the timing and level of drift exposure, floral symptoms may be much more pronounced than those on the leaves making the diagnosis more difficult (i.e., growers may relate poor fruit set or dead flowers to other causes rather than herbicide drift) (Figure 5).
If the damage occurs early in the season, between bud burst and bloom, as it usually does, a significant reduction in healthy leaf area during the period of rapid shoot growth may affect vine photosynthetic capacity, lowering vine ability to fully ripen the crop and possibly its ability to survive cold winters.
Unfortunately there is no guarantee that the vines will fully and rapidly recover from herbicide drift damage. Carry-over effects into the following years, such as reduction in vine vigor, yield, fruit quality, and increased susceptibility to diseases, are common if the damage is extensive and/or the vines have been repeatedly exposed to PGR-herbicide drift. Finally, vines may die as a consequence of their weakened condition .
What factors affect the severity of PGR-herbicide drift damage?
Some of the most important factors affecting the severity of drift damage are:
- Vine growth stage at the time of exposure. Grapevines are always sensitive to PGR herbicides, but they are most susceptible during the early part of the growing season, from bud burst through bloom. While dependent on the growing season and site, in Pennsylvania this usually occurs around April through June. Early in the growing season shoots are rapidly growing and PGR herbicides are quickly translocated to the shoot tip, where the natural concentration of auxins is greatest inside the grapevine. If exposure occurs later in the season, vines typically outgrow the damage and still produce good yield .
- Vine age: Younger plants are more vulnerable and they have a lower ability to recover from the PGR herbicide damage than mature vines. Young vines may be killed even at low exposures .
- Level of exposure: Higher concentration and/or repeated exposures will result in higher disruption of the vine’s physiology and lower ability of the vines to rapidly and fully recover from the damage .
- Grapevine variety. All grapevine varieties are sensitive to PGR herbicides, but some may show more visual and physiological symptoms than others (see for example Table 1, Questions and Answers about Vineyard Injury from Herbicide Drift)
- Other factors include herbicide concentration and formulation (for example ester formulations of 2,4-D are more volatile than amine formulations, thus ester formulations of 2,4-D are more prone to move off-target as vapor), weather conditions (temperature, humidity, and most importantly wind speed) at the time of herbicide application.
What is the best strategy to protect vines from herbicide drift injury?
Prevention is undoubtedly the best strategy for grapevine growers to avoid herbicide damage. To reduce the risk of herbicide drifting into their vineyard, vineyard managers and/or owners should be proactive. Some prevention steps both grape growers and nearby growers of other crops can take are listed below:
- Maintain good relations with neighbors. Vineyard owners and managers should make sure their neighbors within approximately a half-mile to 1 mile radius, are aware that vines are extremely sensitive to PGR herbicides . It is also recommended to encourage neighbors to “use drift-reduction spray nozzles (nozzles that produce large droplets) and to select herbicides that are less likely to injure grapes” . If growers of other crops are unaware of damage to grapevines, collecting information such as this blog post, may be an important educational tool to share. Mike White, viticulture extension specialist at Iowa State University, suggests to share an aerial map of the property showing the vineyard location with neighbors and commercial pesticide applicators to increase their awareness. It is also recommended to communicate the presence of the vineyard to state and county highway departments.
- Windbreak (shrubs, trees, physical barriers) and a buffer area between the vineyard and the edge of the field being sprayed are always a good idea. Penn State offers a free publication or pdf print-out regarding windbreaks: http://extension.psu.edu/publications/uh172/view
- For those states where the service is available, growers can register the location of their vineyard on https://driftwatch.org/. This online service is not available in Pennsylvania, but in many Midwestern states growers and pesticide applicators can use this web resource free of charge to report (growers) and locate (applicators) potential drift hazards.
Taking all these steps may not guarantee that herbicide drift will not occur in your vineyard, but increasing pesticide applicators awareness of grape sensitivity to PGR herbicides, the resulting economic loss, and potential litigation risks may very well serve the purpose.
Applicators should always follow all the measures available to minimize the risk of herbicide drift into a nearby vineyard or to other sensitive crops. Legal complaints may result in expensive settlements. In an extreme example, an owner of a 150-acre vineyard in Australia was awarded AUS$ 7M in damages over pesticide drift (Grape grower Awarded $7M in damages over spraying) that occurred from 2013 to 2015.
If PGR herbicides are applied after vine bud burst, applicators should consider eliminating volatile compounds and apply only non-volatile products.
Extension personnel could also facilitate communication between grape and crop field growers as it happens in Long Island, NY. Extension personnel from Cornell University-Long Island, including Alice Wise and Andy Senesac, organized a meeting with local grape and sod growers to tackle the herbicide drift issue which was affecting local grape growers without having to resort to regulatory restrictions. The result of that meeting was a ‘gentleman’s agreement’ not to spray herbicides containing 2,4-D after April 15, around bud burst for the earliest grapevine varieties in Long Island. To keep all parties informed, extension sends out a weekly reminder about this issue.
What to do if the drift occur
Here some key steps Mike White put together on what to do right after a drift incident :
- Identify area affected.
- Document the date, time and growth stage of the grapes.
- If possible, identify the source of the drift and make a determination if you want to settle the problem amongst your neighbors.
- Contact your state department of agriculture (Pennsylvania Department of Agriculture, PDA) as soon as possible if you cannot determine the source of the drift and/or you want to formalize the complaint (30 – 45 day deadline in many states).
- Flag both affected and unaffected plants, take high resolution pictures weekly until symptoms subside and measure final yields per plant.
- Severe injury settlements should be delayed until after next season’s harvest. Photo and yield documentation should be continued. Unless the settlement offered seems exceptionally lucrative, I would suggest delaying any settlements until after next season’s harvest to assess for potential carry-over vine damage.
For information on where to find a drift consultant please refer to Need Help? Pesticide Drift Consultants
How to estimate the loss in revenue
Tim Martinson, viticulture extension specialist at Cornell University, provided useful examples on how to estimate the economic loss associated with herbicide drift damage under different scenarios. Scenarios include vine recovery across multiple years, with and without the need of vines replacement. Please refer to: Diagnosis, Economics, Management of Grape Injury from 2,4D and other Growth Regulator Herbicides.
How to manage damaged vines
There is limited information available on best management practices for vines affected by herbicide drift damage. To favor a full and a rapid recovery it is recommended to still implement good management practices and avoid further stress to damaged vines, as for example over cropping (assuming damaged vines have fruit). Fungicide applications made to protect the fruit should not be necessary if the fruit has been removed . It is also recommended to adjust pruning strategies to smaller vines, with the intent of regaining full vine size .
- Growth regulator herbicides and grapes don’t mix. Penn State. https://psuwineandgrapes.wordpress.com/2015/10/16/growth-regulator-herbicides-and-grapes-dont-mix/
- Watch out for: Grapes. Purdue University. DW-10-W. https://www.extension.purdue.edu/extmedia/ho/dw-10-w.pdf
- Preventing herbicide drift and injury to grapes. Oregon State University. EM 8860. http://extension.oregonstate.edu/yamhill/sites/default/files/spray_drift/documents/3-preventing_herbicide_drift_to_grapes_osu_8660.pdf
- Avoid phenoxy herbicide damage to grapevines. Texas Cooperative Extension. http://winegrapes.tamu.edu/files/2015/11/phenoxy1.pdf
- Avoiding 2,4-D injury to grapevines. Colorado State University. http://webdoc.agsci.colostate.edu/cepep/FactSheets/Avoiding%202,4-D%20Injury%20to%20Grapevines.pdf
- Questions and answers about vineyard injury from herbicide drift. Kansas State University. MF-2588. https://www.bookstore.ksre.ksu.edu/pubs/MF2588.pdf
- Need Help? Pesticide drift consultant. Northern Grapes Project. http://northerngrapesproject.org/wp-content/uploads/2013/01/11-3-NE-Find-Drift-Consultant.pdf
- Top 10 questions about herbicide drift into vineyards. Iowa State University. https://www.extension.iastate.edu/wine/growersnews/243-may-29-2013#Top
- The view from New York: Diagnosis, economics, management of grape injury from2,4‐D and other growth regulator herbicides. Northern Grapes Project. http://northerngrapesproject.org/wp-content/uploads/2013/01/Martinson-2-4D-Presentation.pdf
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: 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.
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.
- 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.
- 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.
- 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.
- 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.
- 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.
Insect and Disease Resources – 2016 articles
Articles from the 2016 season that should be reviewed include:
- 2016 Pre-Bloom Disease Management Review by Bryan Hed, Penn State University
- 2016 Post Bloom Disease Management Review by Bryan Hed, Penn State University
- Late summer/early fall grape disease control; 2016 by Bryan Hed, Penn State University
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.
By: Dr. Michela Centinari
In cool climate vineyards labor (hours/acre) employed for canopy management operations (e.g., shoot positioning and thinning, cluster thinning, leaf removal, hedging) is estimated to be much higher than for floor management practices (approximately 32% vs. 11% of total labor hours, excluding harvest) . Canopy management practices are critical for optimizing crop load, improving microclimate conditions in the fruiting zone and reducing disease pressure on the leaves and fruit. However, we tend to forget that floor management also has profound implications for the vineyard ecosystem, productivity and indirectly wine quality . The main goals of vineyard floor management span from weed control, soil conservation, soil nutrient and water management, and biodiversity improvement . Among many factors, the best floor management strategy for a given vineyard site depends on the age of the vine, growing region, soil type, and production goals of the grower . Environmental regulations and public perceptions may also influence growers’ choices toward a specific floor management practice .
The conventional floor management practice for mature vineyards in the eastern U.S. and other temperate regions around the world is a cover cropped inter-row combined with a vegetation-free area directly beneath the vines to reduce competition for soil resources (i.e., water and nutrients). The under-trellis area is kept bare using herbicides and in some cases by soil cultivation (Figure 1).
Why explore alternative under-trellis management options?
- Seeking environmentally responsible and (potentially) affordable alternatives to the use of herbicides
Herbicides are the most widely used pesticides in the U.S.; they are commonly used in vineyards because they effectively suppress weed growth and are easy to apply . However, repeated herbicide use increases the risks of resistance development . Also, bare soil left exposed after herbicide use or tilling is susceptible to erosion, soil structure degradation and crusting as well as increased water runoff and leaching of nitrates and pesticides .
- Reducing excessive vine growth and the need for expensive canopy management practices
Despite the presence of cover crops between the rows (inter-row area), grapevines can still exhibit excessive vegetative growth in regions with deep,fertile soils and ample precipitation during the growing season (Figure 2). Large and dense canopies with heavily shaded fruit may contribute to reduced fruit and wine quality as well as an increase in disease pressure . In addition, excessively vigorous grapevines are more expensive to train and manage: main and later shoot thinning, multiple passes of fruit-zone leaf removal and hedging are costly management practices  often required to improve clusters light environment.
What are the alternative under-trellis options?
One alternative option to the under-trellis herbicide-treated strip is to establish cover crops directly beneath the vines (intra-row) in addition to between the rows (inter-row) (i.e., complete floor cover) (Figure 3). Under-trellis cover crops could serve multiple purposes depending on grower’s needs and the cover crops species used. Cover crops species have different degrees of competition with vines for soil resources (e.g., water and nutrients). For example, annual cover crops tend to be less competitive for soil nitrogen resources than perennial plants because of their shorter growth cycle and less root development . Furthermore, fine fescues (e.g., Festuca ovina) tend to be less competitive than other perennial grasses such as tall fescues (Festuca arundinacea Shreb) .
Several studies have been conducted in the eastern U.S. over the last 10 years to test if and which under-trellis cover crops species could be used as an environmentally responsible means to suppress the use of herbicide and as a proactive measure to reduce excessive vine grow through competition with the grapevine root system for soil resources.
Do under-trellis management strategies impact leaching of nutrients and pesticide?
Yes, under-trellis management strategies can impact leachate composition [4;9]. For example dissolved organic carbon (DOC) leaching was reduced by maintaining a green cover under the trellis (white clover or native vegetation) as compared to conventional under-trellis strategies, as herbicide (glyphosate) application or soil cultivation . Thus, not only herbicide application but also soil cultivation can increase carbon loss from the soil in addition to increasing its erosivity. Also, total nitrogen (N) concentration was higher in leachate samples collected from under-trellis glyphosate and white clover plots as compared to those from native vegetation or cultivation plots.
What cover crops can growers use to suppress excessive vine growth and increase crop load?
Cool season perennial grasses have been planted under the trellis in vineyard located in Virginia, North Carolina (Dr. Tony Wolf lab, Virginia Tech University) and in Long Island (NY) (Alice Wise, Cornell Cooperative Extension) to impose competition for moisture and nutrients early during the growing season, when grapevines grow vigorously (at least in the Eastern U.S.) [8;9;10].
Compared to an herbicide-treated soil strip, complete vineyard floor cover cropping reduced excessive vigor of Cabernet Sauvignon vines in a wet and humid region (NC) over a six-year-period . Among the perennial grasses tested Festuca arundinacea cv. Elite II, a turf-type tall fescue, and cv. KY-31, a forage-type tall fescue, were the most effective in reducing vine vigor and increasing light available to the fruit with minimum impact on crop yield .
Creeping red fescue (Festuca rubra) planted under Cabernet Sauvignon vines in the fall of the second year of vineyard establishment reduced vine size in a favorable way (average of 26%) and increased sunlight fruit exposure by 35% over a 7-year-period as compared to herbicide-treated strip .
(Note: This study was conducted at the Virginia Tech’s AHS, Jr. Agricultural Research and Extension Center, in a ‘research’ vineyard with high vigor potential. We don’t suggest using under-vine cover crop in young vineyards without knowing the history and vigor potential of the site.)
Interestingly, the growth suppressive effect of the under-trellis fescue decreases over the years suggesting that the vines may be able to adapt to the presence of under-trellis cover crops by, for example, relocating absorptive roots to a deeper soil profile .
Chicory (Chicorium intybus) annually planted under the trellis of mature, vigorous vineyards in the Finger Lakes region of NY resulted in considerably diminished vine size, up to 35 % (Figure 3) [Dr. Justine Vanden Heuvel lab, Cornell University; 12; 13]. Furthermore, chicory effectively suppressed weed pressure underneath the grapevine canopy.
When vine growth is vigorous, the balance between vegetative and reproductive growth tend to be below the recommended Ravaz index (yield /pruning weight) ratio ranging from 4 to 10 for high-quality wine production . The devigorating effect of the under-trellis cover crops often translated to an increase in crop load (i.e., Ravaz index) toward the ‘optimal’ values. Although the reduction in vegetative growth/vine size is usually greater than that of crop yield, growers should take into consideration a potential yield penalty associated with the use of under-trellis cover crops .
Can under-trellis cover crops impact fruit composition?
In several studies the use of under-trellis cover crops did not significantly impact, either positively or negatively, juice chemistry [total soluble sugar (°Brix), pH, titratable acidity (TA)] [4;9;15;16;17] or total phenolics or anthocyanins . In other cases an increase in juice °Brix or reduction in TA (1 g/L) was attributed to the devigorating effect and increased fruit sunlight exposure brought on by the presence of under-trellis cover crops [ 10;12].
What causes the reduction in vine size associated with the use of under-trellis cover crops?
It depends on, among other factors, the seasonal weather conditions, soil resources available and nutritional requirements of the cover crop. Vines can also compete with cover crops for multiple resources at the same time making it in some situations very difficult to separate the effect of moisture vs nutrient competition. In most of the studies conducted in upstate NY, NC and VA vine water status (stem, pre-dawn water potential) never reached what we define a ‘stressful’ value indicating that under-trellis cover crops were not overly competitive with grapevines for soil moisture under the specific weather conditions of those regions and during the years studied [4;10;12;13]. However, during consecutive seasons of summer drought in Long Island, vines with under vine green growth exhibited more symptoms of water stress than those with an herbicide-treated strip 
At several sites, cool-season grasses depressed grapevine nitrogen [4, 10; 12] levels relative to the under-trellis herbicide strip suggesting that under-trellis cover crops can affect vine nitrogen status and thus vine capacity .
What about leaving native vegetation growing under the trellis instead of planting cover crops?
At several research sites in upstate NY, native vegetation was allowed to grow under the vines (Dr. Vanden Heuvel lab, Cornell University). Compared to an herbicide-treated strip, native vegetation had a variable impact on vine size across sites, from nil effect at one site  up to 57% reduction in pruning weight in a young vineyard . Site characteristics, plant material and age in addition to diverse weed populations at the research sites may explain the variable impact of native vegetation on reducing vine size.
Growers in Long Island (NY) have been experimenting with under-trellis mowing (i.e., native vegetation mowed several times throughout the season). Costs of under-trellis mowing compare well to the herbicide regime (approximately $120/acre) . A. Wise pointed out that, while more growers are interested in under-trellis mowing, a deterrent for its adoption may be “the price of suitable mowers, which go from $3,500 for a single head to over $15,000 for two mowing heads with a row middle mower” (Figure 5). Wise also noted that “under vine mowing is a viable option for under vine management though it is best suited to mature, laser planted vineyards because of the risk of trunk damage to young vines and crooked trunks”.
Can under-trellis cover crops be used to eliminate the use of herbicide while maintaining vine size?
Planting annual cover crops, such buckwheat (Fagopyrum esculentum) or annual ryegrass (Lolium multiflorum) under the vines may eliminate the need for herbicide with little impact on vine size or fruit composition. Most of the work on under-trellis annual cover crops has been conducted in the cool and humid Finger Lakes region, upstate NY, at Cornel University by Dr. Vanden Heuvel lab [4; 15; 16; 17]. In the Northeastern U.S. perennial cover crop species are not suitable for the under-trellis area due to the need to mound soil from the under-vine row around the graft union for insulation to protect scion budwood from low winter temperature. For example, buckwheat planted in late-May in in mature vineyards in upstate NY (seeding rate is approximately equal to 350 lbs/acre) was found to compete extremely well with weeds pressure without compromising vine size [13; 16] or fruit composition  (Figure 6).
How much will establishing and maintaining under trellis cover crops cost?
A partial budget analysis was developed for one of the studies on under-trellis cover crops using information gained from the research trial and grower cost estimates (Table 1). In this study establishing and maintaining white clover or native vegetation was a cheaper under-trellis groundcover options than repeated soil cultivation or glyphosate applications. However, vines maintained with herbicide (glyphosate) generated the highest revenue because of their higher yield. Thus, yield penalty associated with vines growing with under-trellis cover crops was the cause of reduced grower’s income. Outcomes could definitely change if crop yield is maintained or only slightly reduced, or if other cover crops are used. Compared to white clover (seeding rate: 5 lbs/acre), creeping red fescue can be more expensive to establish because of its higher seeding rates, as much as 220 lbs/acre . However, fescue can persist for more than four years, while white clover would need to be reseeded every 2-3 years .These figures should be used only as an example because there are many variables that could change the outcomes and growers interested in experimenting with under-trellis cover crops should develop their own cost analysis . Also, vigor suppression associated with under-trellis cover crops may result in reduction of costly canopy management operations.
For grape growers managing vigorous vineyards and interested in reducing pesticide input, complete vineyard floor cover could be a viable option. However, to avoid an undesirable decline in pruning weight, vine nutrient deficiency or water stress it is recommended to monitor pruning weight and Ravaz index on sentinel vines. It is also important to annually assess vine nutrient status and be prepared to efficiently apply fertilizer if needed. In a dry season growers should look closely for visual symptoms of vine water stress. To avoid over-devigorating the vines it may be possible to start with an ‘aggressive’ cover crop and switch after a few years, when vine balance is achieved, to a less competitive cover crops species.
- Yeh AD, Gomez MI, White GB. 2014. Cost of Establishment and production of vinifera grapes in the Finger Lakes region of New York-2013. Cornell University Department of Applied Economics, 716 Ithaca, NY. 717.
- Guerra B, Steenwerth K. 2012. Influence of floor management technique on grapevine growth, disease pressure, and juice and wine composition: a review. Am J Enol Vitic 63:149–
- Skinkis P. Overview of Vineyard Floor Management. eXtension.org.
- Karl A. 2015. Impact of under-vine management in a Finger Lakes Cabernet Franc vineyard. MS thesis, Cornell University, Ithaca, NY.
- Holt JS. 1992. History of the identification of herbicide-resistant weeds. Weed Technol. 6:615–620.
- Landry D, Dousset S, Andreux F. 2006. Leaching of oryzalin and diuron thorugh undisturbed vineyard soil columns under outdoor conditions. Chemosphere 62:1736–1747.
- Austin CG, Grove GG, Meyers JM, Wilcox WF. 2011. Powdery mildew severity as a function of canopy density: associated impacts on sunlight penetration and spray coverage. Am J Enol Vitic 62: 23–31.
- Giese G, Velasco-Cruz C, Roberts L, Heitman J, Wolf TK. 2014. Complete vineyard floor cover crops favorably limit grapevine vegetative growth. Scientia Hortic. 170:256-266.
- Wise A. 2015. Innovative undertrellis management for vineyards. Available at: http://mysare.sare.org/sare_project/lne12-322/?page=final.
- Hickey CC, Hatch TA, Stallings J, Wolf TK. 2016 Under-Trellis Cover Crop and Rootstock Alter Growth, Components of Yield, and Fruit Composition of Cabernet Sauvignon. Am J Enol Vitic. doi: 10.5344/ajev.2016.15079.
- Klodd AE, Eissenstat DM, Wolf TK, Centinari M. 2016. Coping with cover crop competition in mature grapevines. Plant and Soil 4:391–400.
- Jordan LM. 2014. Evaluating the effects of using annually established under-vine cover crops in northeastern Riesling vineyards. MS Thesis, Cornell Univ., Ithaca, NY.
- Karl A, Jordan L, Vanden Heuvel JE. 2015. Investigating annual under-vine cover crops as an enviromentally sustainable alternative to herbicides in northeastern vineyards. SARE Final report.
- Kliewer WM, Dokoozlian NK. 2005. Leaf area/crop weight ratios of grapevines: Influence on fruit composition and wine quality. Amer. J. Enol. Vitic. 56:170–181.
- Centinari M, Vanden Heuvel JE, Goebel M, Smith MS, Bauerle TL. 2016. Root-zone management practices impact above and belowground growth in cabernet franc grapevines. Aust J Grape Wine Res. 1: 137–
- Jordan LM, Björkman T, Vanden Heuvel 2016. Annual under-vine cover crops did not impact vine growth or fruit composition of mature cool-climate ‘Riesling’ grapevines. HortTech 26: 36–45.
- Karl A, Merwin IA, Brown MG, Hervieux RA, Vanden Heuvel JE. 2016. Impact of undervine management on vine growth, yield, fruit composition, and wine sensory analyses of Cabernet franc. Am J Enol Vitic. doi: 10.5344/ajev.2016.1506.
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: Bryan Hed, PSU Research Technologist
The past two winters have ramped up concerns about crown gall in Pennsylvania and other parts of the Northeast. Wine grape growers are discovering, many for the first time, the horrors of this disease and the extent of the damage it can cause in their vineyards. While there is reason for great concern, I would like to start out by saying that research efforts are generating extensive information on management of this disease, and there are new solutions from research in the pipeline.
CROWN GALL AND INCREASE SUSCEPTIBILITY TO WINTER INJURY
After the past couple of harsh winters vines have been collapsing in your once “healthy” and productive vineyard. What’s going on?
In some cases, brutal winter cold has simply damaged or killed a vine that was not suitable for its site. It is well known that the many varieties of Vitis vinifera that vintners prefer are simply less cold hardy than many of the French hybrid varieties. The crown gall bacterium, Agrobacterium vitis, can also play a large role by rendering infected vines incapable of properly repairing the cold damage to their trunks. The most obvious symptom of crown gall infection is gall formation at the base of infected vines. These tumor-like growths eventually choke out the vascular connection between roots and canopy, and the vine collapses (Figures 1 and 2).
How did vines get contaminated with the crown gall bacterium in the first place and why is it now causing problems?
There are many sources of the crown gall bacterium and probably many ways in which vines can acquire it. It is now known that the bacterium exists in populations of wild grapevines and can be found on plant surfaces in the vineyard. The most likely or common source, however, is through contaminated nursery stock. Since the bacterium can live systemically as an endophyte inside vines used for propagation material, cuttings from that material will carry the bacterium as well. The bacterium that causes crown gall can probably live inside vines without ever causing any disease, without causing the growth of tumors at the base of the trunk, without bringing about the collapse of vine trunks. Cuttings, produced from symptomless, contaminated mother vines, may be contaminated with the bacterium from “day one,” but may never develop crown gall. This is probably the case in California and other Mediterranean climates where many of the world’s wine grapes are grown.
So why is crown gall such a problem here in the Northeast, and not in California?
The crown gall bacterium shifts from benign coexistence, as an endophyte inside vines, into a tumor-inducing organism when there is damage or injury to grapevine vascular tissue. When injury occurs to the cambium, the bacterium attaches to plant cells at the wound site and literally inserts a copy of a self-replicating DNA strand (called a plasmid) into the plant cells (infection). The plasmid contains genes that code for hormone production that leads to the growth of tumors. These genetically modified grapevine cambium cells begin to grow tumor tissues with poorly organized vascular structure (that is, not capable of adequately conducting resources needed by the vine) at the wound site instead of organized vascular tissues. The injured trunk areas are never properly repaired by functional vascular tissue and as the tumor tissues grow, the trunk becomes more and more non-functional and eventually the vine collapses. And what is the most common cause of widespread grapevine trunk damage in the Northeast? Severe winter cold—which does not occur in most parts of California and similar warm, wine grape production climates.
All is not lost—tips on vineyard renovation
A collapsed vine with healthy roots will throw new shoots from the base of the plant, and these can be used to make new trunks and restore the vine to productive status. Here in the “Great White North” of Erie County, we renovate vines almost every year (Figure 3). Vines “laid low” by crown gall are often capable of being completely restored to productive life. Rather than ripping out your 7 or 10-year-old vineyard and replacing it, it can be more cost-effective to train up new trunks with the potential for a partial crop this year and a full crop in Year 2. An exception to this remedy is when trunks of grafted vines were not hilled with soil in the fall and the base of scions experienced the full force of the severe cold. This can completely kill the scion and leave growers with nothing but the rootstock. In this case, growers may have to start over with new vines, unless there is potential for field grafting of new scion wood. Also, when very young or newly planted vines develop crown gall, it is best to remove the plants, and replace them. The bacterium can be found in roots as well as trunks and can survive for long periods of time (years) in the soil, and it is important to remove all parts of infected plants.
All of us would love to be able to train up one original trunk and rely on that single trunk for every vine, every year. Unfortunately for many in the Northeast, that’s a pipe dream. Now that you know about crown gall in your vineyard, you can assume that more vines are contaminated than you previously thought. For example, we have a Chambourcin vineyard at the North East lab in which just about every vine is host to the crown gall bacterium. I had no idea this was the case until the winter of 2003-2004, when brutal cold caused nearly every vine trunk to explode with crown gall the following spring (Figures 4 and 5). Apparently, nearly every vine was contaminated with the bacterium and the vineyard collapsed! After discussing my conundrum with Dr. Tom Burr at Cornell University, an expert in crown gall biology/pathology, we spent the 2004 season training up new trunks for every vine, using only shoots that originated from below the galls. From 2005 on, the vineyard was enormously productive for almost ten years. Then came the polar vortex of January 2014, followed by the severe winter cold of February 2015, and with it more devastating bouts with crown gall.
Improving your odds that a winter cold event will not lead to complete loss
Growers of V. vinifera in Erie County, PA have pretty much resigned themselves to losses from winter cold and crown gall every few years, and they deal with it in a number of ways. The first way is by growing vines on multiple (2 to 3) trunks. The logic follows that if one or two trunks collapse from crown gall there may still be one trunk that produces a crop and provides some income until new trunks can be groomed to replace the galled/damaged ones. Trunks do not need to be replaced as a matter of regular maintenance, but rather when they become injured and/or diseased. The maintenance of more than one trunk can greatly improve your odds that a winter cold event will not lead to complete loss.
Growers of the hardier French hybrids generally suffer fewer economic down times from winter cold-induced crown gall than growers of V. vinifera. We cannot escape bouts of brutally cold winter weather, but we can (and should) plan for the worst and try to wisely match variety with site in order to minimize or eliminate losses to winter trunk damage and crown gall. Simply put, cultivars of V. vinifera and cold-sensitive hybrids should be planted only on the best sites in Pennsylvania—sites that ensure good cold air drainage during the worst bouts of winter weather. Where a vineyard is already established, vine management that maximizes vine cold hardiness (balanced timely nutrition, effective disease control, proper balance between growth and yield, good weed and water management) is absolutely essential for minimizing trunk damage and the onset of crown gall after a severe winter cold event.
For grafted vines, hilling soil around the graft union in late fall will protect the base of the scion and may ensure that scion bud wood will survive to throw shoots for replacement trunks the following spring. During the following spring, hilled soil should be removed from around the graft to prevent rooting of the scion, which would otherwise defeat the purpose of the rootstock. Although an added expense, this practice is commonplace in many wine growing regions of the Northeast. Farther south and especially in the mid-Atlantic region, many growers have been avoiding this management practice because it represents a substantial added expense, can contribute to erosion on steep sites, and can increase the odds that vines may become mechanically damaged. Unfortunately, severe cold during the past two winters caused heavy damage to the less favorable variety/site combinations even in parts of southern PA and the mid-Atlantic. Where grafts were not protected, the supply of scion buds that would have provided for new trunks was killed. In such cases, all but the rootstock dies and the vine must be replaced—a much more expensive operation than trunk renewal. So in these more southerly regions, the decision to hill or not, may be less clear. In southern PA, proper variety matched to the site along with multiple trunk maintenance may be sufficient for sustainability. However, on poorer sites that suffer more frequently from a severe winter cold event, annual hilling of grafts may be necessary or a grower may need to rethink his/her established variety/site combination. As in all matters of farming, growers must weigh the expense of a practice against the magnitude of the consequences for not doing so as well as the odds that he or she will get hit with another severe cold event. The prudent integration of these management practices will help to guarantee that farms can remain sustainable and profitable in the Northeast.
Research in the pipeline
Once contaminated, there is no practical way to rid a vine of the crown gall bacterium. The best long term solution rests with the production of crown gall-free planting stock so that growers can at least start with a clean vine/clean vineyard. To that end, through funding from the National Clean Plant Network, Dr. Tom Burr’s grape research program and others are devoted to the generation of mother vines free of crown gall that can be used to start clean sources of grapevine nursery material. The emphasis in this effort is the development, and ongoing refinement, of extremely sensitive tests used to detect the presence of the pathogen, in order to determine whether a vine that might be used for propagation is “clean” or contaminated. Clean vine material can then be confidently used to establish grapevine mother blocks that will serve as the foundation of nursery propagation stocks. In turn, the mother blocks and nursery stocks can be continuously monitored for the presence of the bacterium using these same tests. The latest research has indicated that plants free of the crown gall pathogen can be generated but they will need to be assayed periodically to ensure they remain clean. Remember, however, that the crown gall pathogen, once introduced into a vineyard through contaminated plants, can live in the soil for many years. Therefore, the availability of crown gall free planting stock is not going to end our encounters with this pathogen. Clean planting stock will reduce or help to eliminate the incidence of crown gall in new plantings, but the pathogen will likely always remain present and northeastern growers will still have to manage their vineyards with a view toward minimizing the incidence of crown gall.
Extension Support for the Upcoming Season:
- This blog post and others will continue to be made available at Wine and Grapes U. to assist growers with the latest information. We hope you find this useful for managing crown gall and we encourage feedback.
- You can sign up for the Penn State Extension V&E News listserv by email Denise Gardner at firstname.lastname@example.org. This will keep you current when we release crown gall related information.
- Bring your crown gall questions and concerns to the upcoming Mid-Atlantic Fruit and Vegetable Convention in Hershey PA (February 3, 2016); let’s discuss them.
- Bryan will discuss current disease updates at the 2016 PA Wine Marketing & Research Board Symposium at the Nittany Lion Inn (University Park, PA) on March 30, 2016.
- Participate in a series of webinars being organized by Tim Martinson, Cornell University, that will enable growers to tap into Tom Burr’s long standing research program on managing crown gall and what we have to look forward to in the future. Stay tuned for more details later this winter.
- Check out this recent presentation by Dr. Burr at this link.
Information used in composing this article was from personal communication with Dr. Tom Burr and:
Compendium of grape diseases, disorders, and pests. Second edition. 2015. Wayne F. Wilcox, Walter D. Gubler, and Jerry K. Uyemoto, eds. American Phytopathological Society Press. Pages 95-98.
Tim Martinson and Thomas Burr. How Close are We to Crown Gall-Free Nursery Stock? Appellation Cornell; Research Focus 2012-1. http://nationalcleanplantnetwork.org/files/144948.pdf
Wine Grape Production Guide for Eastern North America. 2008. Tony Wolf, ed. Natural Resource, Agriculture, and Engineering Service. Cornell Cooperative Extension.