Grapevine leafroll associated virus; A brief introduction to an old disease. Should Pennsylvania grape growers be concerned?
By: Bryan Hed, Michela Centinari, and Cristina Rosa
As if wine grape growers don’t have enough challenges in this day and age, the effects of grapevine viruses have been taking on greater importance in eastern vineyards over the past several years. Studies examining grapevine leafroll-associated viruses are developing a growing body of information that will be essential for vineyard managers to continue moving the eastern wine grape industry forward. Grape growers in the eastern United States need not feel they are the only ones with this disease management challenge (as is the case with many fungal diseases of grapes); grapevine leafroll-associated viruses (GLRaVs) are found in vineyards all over the world (Compendium of Grape Diseases). This group of viruses causes a disease known as grapevine leafroll disease, and the association of symptoms with grapevine leafroll viruses was recognized over 80 years ago. As is the case with so many plant pathogens, the worldwide distribution of these viruses occurred as a result of increased movement of plant material/goods across the globe; the ever widening dissemination of infected planting stock (Compendium of grape diseases). The effects of these leafroll viruses is most severe on – you guessed it – cultivars of V. vinifera, where the disease is known to greatly reduce yield, vine vegetative growth or vigor, and cold hardiness; a factor of critical importance for these cultivars grown in the northeastern United States. Grapevine leafroll disease can also delay fruit maturity, reduce color development in red grapes, and fruit quality (decreased soluble solids, increased titratable acidity) of V. vinifera grapes (Fuchs et al. 2009), which can negatively impact perceived wine quality. The severity of the effects of leafroll viruses is dependent on a great number of factors such as grapevine cultivar, virus strain, climate, soil, cultural practices, stress factors, etc. So naturally, the severity of symptoms can vary from one season to the next (Compendium of Grape Diseases). With respect to cultivar, the effects of these viruses on Vitis interspecific hybrids and Vitis labrusca are generally considered to be less serious, but are also less well defined and studied.
Infection by leafroll viruses results in the degeneration of primary phloem tissues in grapevine shoots, leaves and clusters (Compendium of Grape Diseases). As one can imagine, this can have profound effects on all parts of the vine. Symptoms of the disease, which are generally most observable on V. vinifera, consist of cupping and discoloration of older leaves in late summer and fall. On red fruited varieties, leaves of infected vines can display a distinct red coloration of the interveinal tissue, while veins remain green (Figure 1). On white fruited varieties of V. vinifera, symptoms are less striking and leaves tend to look yellowish (chlorotic) and cupped (Figure 2). Leaf discoloration generally affects older leaves first, but these symptoms are not diagnostic of the disease, as they may be due to other causes such as nutrient deficiencies, water stress, and even crown gall. Analysis of grapevine tissues in the laboratory is the only way to confirm the presence (or absence) of these viruses.
Currently, there are about seven GLRaVs found in cultivated grapes, the most common being GLRaV-3. These viruses are easily spread over long distances through the movement of infected nursery stock, but can be spread (vectored) within the vineyard by mealybugs (Compendium of Grape Diseases). Unfortunately, there are no known sources of resistance to GLRaVs among Vitis species and they have been found in many cultivated grape varieties, including V. labrusca, Vitis interspecific hybrids, and V. vinifera. Interest in grapevine leafroll disease and the extent of its effects has been growing in the eastern United States over the past ten years or so. Surveys conducted in New York, Ohio, and Virginia (Fuchs et al. 2009, Jones et al. 2015, Han et al. 2014), have provided confirmation of the presence of GLRaVs in commercial vineyards and have yielded important information necessary to the management of grapevine leafroll disease. For example, infection by GLRaVs is permanent and infected vines must be destroyed to reduce the incidence of grapevine leafroll disease. Therefore, management of the disease would naturally include planting only stock that is free of GLRaVs. Insecticides that target mealybugs and soft scales can prevent vine to vine spread (within the vineyard) of GLRaVs that are known to be vectored by these insects (Compendium of Grape Diseases). Indeed, studies have shown that applications of insecticides like dinotefuran (Scorpion) and spirotetramat (Movento) can significantly reduce mealybug counts and result in a slowing of the progress of the disease in vineyards. One study from New York (Fuchs et al. 2015) showed that insecticide applications should target overwintered and second instar mealybug crawlers from bud swell to bloom and summer generation crawlers later in mid-summer. A study with grape phylloxera as a potential vector of these viruses showed that phylloxera can acquire the virus through phloem feeding on infected vines, but there was no evidence that phylloxera can transmit it (Wistrom et al. 2017).
As was mentioned earlier, cultivars of Vitis labrusca (Concord, Niagara) can also become infected with GLRaVs, but the infections appear to remain latent or dormant (Bahder et al. 2012) and have not been shown to result in visual symptoms of the disease (Wilcox et al. 1998). On the other hand, cultivars of V. vinifera are severely affected by GLRaVs and make up a very important and growing sector of the PA wine grape industry. Surveys conducted in New York, Ohio, and Virginia (Fuchs et al. 2009, Jones et al. 2015, Han et al. 2014) have revealed the presence of GLRaVs in commercial vineyards to the north, west, and south of Pennsylvania and have led to the development of some important guidelines for management of grapevine leafroll disease.
Given the fact that grapevine leafroll disease is common worldwide and that grapevine leafroll disease can profoundly impact wine quality and grapevine health, researchers at Penn State University are initiating a project to look for GLRaVs in Pennsylvania vineyards. As in other states, the study is targeted to help growers recognize the impact that the disease may be having on the Pennsylvania wine industry and help them to address the effects of these viruses on productivity and fruit quality, reduce their spread and impact, and thereby grow and improve the wine grape industry in Pennsylvania.
The short term, initial objectives of this project will focus on the development of an online survey to collect information from growers with regard to the presence of symptoms of grapevine leafroll disease in Pennsylvania vineyards and their interest in participating in the project. The project will then follow up with tissue sampling from participating, symptomatic and non-symptomatic vineyards throughout the state and serological analysis to determine the presence of Grapevine leafroll virus-1 and Grapevine leafroll virus-3 – the most common of the leafroll viruses – in commercial vineyards in Pennsylvania. The collection of vineyard samples across the state will map the incidence and geographical distribution of these viruses on cultivars of Vitis vinifera and Vitis interspecific hybrid grapevines. The project will also determine and compare the impact of grapevine cultivar and age on infection by Grapevine leafroll virus-1 and -3 in Pennsylvania. Once infected vines have been identified in Pennsylvania vineyards, future objectives will focus on studying the impacts of grapevine leafroll disease on grape quality and productivity in Pennsylvania, and management techniques to mitigate the economic impact of the disease on the Pennsylvania wine industry.
Vineyards will be selected from all parts of Pennsylvania, but the number of locations will favor northwestern and southeastern PA, where the majority of vineyards are located. The study will be expanded as new findings are made and the results will be made available to growers at various meetings throughout the next several years.
Bahder, B., Alabi, O., Poojari, S., Walsh, D., and Naidu, R. 2013. A Survey for Grapevine Viruses in Washington State ‘Concord’ (Vitis x labruscana L.) Vineyards. Plant Health Progress, August 5, 2013. American Phytopathological Society (online).
Compendium of Grape Diseases, Disorders, and Pests. 2nd edition, 2015. Editors Wayne F. Wilcox, Walter D. Gubler, and Jerry K. Uyemoto. The American Phytopathological Society. Pp. 118-119.
Fuchs, M.; Marsella-Herrick, P.; Hesler, S.; Martinson, T.; Loeb, G. M. 2015. Seasonal pattern of virus acquisition by the grape mealybug, Pseudococcus maritimus, in a leafroll-diseased vineyard. Journal of Plant Pathology Vol.97 No.3 pp.503-510
Jones, T. J., Rayapati, N. A., Nita, M. 2015. Occurrence of Grapevine leafroll associated virus-2, -3 and Grapevine fleck virus in Virginia, U.S.A., and factors affecting virus infected vines. European Journal of Plant Pathology 142:209-222.
Wistrom, C. M., G. K. Blaisdell, L. R. Wunderlich, M. Botton, Rodrigo P. P. Almeida & K. M. Daane. 2017. No evidence of transmission of grapevine leafroll-associated viruses by phylloxera (Daktulosphaira vitifoliae). European Journal of Plant Pathology. Volume 147, issue 4. pp 937–941.
By: Denise M. Gardner
The eastern U.S. growing seasons can be somewhat unpredictable. Late season rains or untimely hurricane events can be a recipe for disaster for local grape growers (http://www.pawinegrape.com/uploads/PDF%20files/Documents/Viticulture/Harvest/Rain%20at%20Harvest.pdf), and a few have been unprepared for such events in the past. These weather events can lead to higher incidences of the grey-rot form of Botrytis in addition to other rots, which may also be related to pest damage. Furthermore, these weather incidences and pest damage can ultimately impact picking decisions for growers and wineries (Osborne, 2017).
It is almost inevitable that wineries need to be prepared for end-of-season weather flops, and plan for the best possible ways to manage or maintain wine quality in light of above-average disease pressure.
One disease that winemakers can prepare for prior to harvest is Botrytis. For the purpose of this article, we’ll be using the term Botrytis to indicate the grey-mold or grey-rot form of the disease. Grey-mold, the form of Botrytis more commonly noticed in humid regions or during heavy-precipitation seasons, can ultimately affect wine quality. Peynaud (1984) has defined 4 ways in which the grey-mold can negatively affect wine quality:
- Deplete wine color (especially important in red varieties),
- Increase the risk of premature browning (through oxidative enzymes),
- Deplete varietal character (through degradation of grape skins), and
- Contribution to off-flavors developed by the mold’s presence on the fruit.
Based on a 1977 study by Loinger et al., guidelines pertaining to wine quality were developed with regards to a visual assessment of Botrytis incidence on incoming fruit:
- 5-10% Botrytis rot on clusters: noticeable reduction in wine quality; wine quality is still “good” (as opposed to very good with 0% rot on clusters)
- 20-40% Botrytis rot on clusters: marked reduction in wine quality; wine quality is “low”
- >80% Botrytis rot on clusters: wine is commercially unacceptable
With a noticeable sensory and chemical difference in Botrytis-infected clusters, it is best for wineries to develop a standard operating procedure (SOP) for assessing rot-infected fruit, as well as how the grapes should be handled and processed during production. While there is no one correct way to work with the wine, below are some suggestions or options that wineries can integrate when dealing with Botrytis-infected grapes. For a full list of possibilities, please visit: http://extension.psu.edu/food/enology/wine-production/producing-wine-with-sub-optimal-fruit/fermenting-with-botrytis-101
Some wineries will sort through all incoming grape clusters prior to the crushing/destemming process to assess for any cluster damage or presence of unwanted material. If your operation is not set up with this equipment, sorting can also take place in the vineyard. Depending on the concentration of disease and on the projected wine style or quality parameter the fruit will go towards, disease portions of clusters can be cut out in the vineyard. Or diseased fruit can be left in the vineyard to deal with after the harvest is complete. Sorting out diseased fruit from that of decent quality will reduce the impact of the mold on the wine’s aroma, flavor, and quality.
Limit Contact Time with Skins
Depending on the resource, there are various recommendations for how to handle diseased fruit. In whites, some recommend whole cluster pressing and tossing the first 10+ gallons, which are rich in Botrytis metabolites (Fugelsang and Edwards, 2007). Many recommend separating juice press fractions for white and rosé wines, as this will give the vintner more control over the chemical constituents (e.g., phenolics, enzymes, and disease-related off-flavors) in the final wine.
Depending on the desired outcome for a red wine, treating or limiting skin contact with diseased fruit may be ideal post -primary fermentation. This would include avoiding extended maceration processes. Due to the fact that the presence of Botrytis on red varieties reduces anthocyanin and phenolic extraction (Razungles, 2010) in addition to the varietal aromatics, excessive skin contact may not be ideal during primary fermentation. Whole berry fermentations, as opposed to a more aggressive crush and destem process, may help minimize extraction of Botrytis metabolites, which can also contribute to mouthfeel variations or off-flavors.
Tannin additions pre-fermentation may also be good considerations to compensate for phenolic losses associated with Botrytis infection. Pre-fermentation and post-fermentation additions may help rebuild the wine’s structure or provide constituents for color stabilization.
Flash pasteurization (i.e., flash détente) has been previously recommended for Botrysized fruit to inactive the laccase enzyme associated with Botrytis, enhance color stability in reds, as well as improve the aromatics and flavors associated with the final wine. Wines that undergo a thermovinification step tend to extract more anthocyanins and phenolics compared to traditionally fermented wines (Razungles, 2010). Additionally, this heat step helps to inactivate laccase, which can contribute to early browning or oxidation of young wines. However, commercial producers may not find this technological application easily accessible.
Therefore, in addition to minimizing skin contact time, winemakers will want to reduce contact time with the gross lees, and may also remove the wine from fine lees associated with the mold-infected fruit quickly. The integration and use of clean, fresh lees, however, is still encouraged. Removing the lees associated with mold-infected fruit can help reduce additional contact time with rot metabolites that have settled out with the lees. This inhibits further integration of those metabolites into the wine.
Inoculate with a Commercial Yeast Strain
The presence of rot is one incidence in which processing techniques (e.g., cold soak) that encourage native microflora to dominate the fermentation are probably not desired. Things like cold soak and native ferments allow ample opportunity for the mold to progress and contribute to the wine’s flavor.
Fruit that has rot or microflora issues is best inoculated with commercial yeast and malolactic bacteria strains to outcompete the native microflora (including those microorganisms that contribute to the rot), and to give the fermentation its best chance at completing the fermentation cleanly. Remember that proper yeast nutrition is important to support the yeasts’ growth and to reduce the risk of hydrogen sulfide development. For more information on determining the starting nitrogen concentrations (YAN) and how to properly treat your fermentation with added nutrients, please refer to:
Penn State Extension’s Wine Made Easy Fact Sheet: Nutrient Management During Fermentation
With high Botrytis concentrations, a more robust yeast strain may be preferred in order to quickly get through primary fermentation. A quicker fermentation may simplify the aromatics associated with the wine, but it will also ensure little opportunity for additional spoilage. Saccharomyces bayanus strains are often selected as more robust yeast strains.
Use of Sulfur Dioxide
Sulfur dioxide additions at crush will be determined based on the style of wine in which you are producing (e.g., white, rosé, red, etc.), but in general, the use of sulfur dioxide can help inhibit further spoilage of your product and retain antioxidant capacity. Sulfur dioxide additions in the juice stage will help minimize early browning, but primarily inactivate PPO.
In general, botrysized wines tend to require more sulfur dioxide as Botrytis metabolites bind with free sulfur dioxide (Goode, 2014). This is true even when processing wines with the noble rot version of Botrytis.
When primary fermentation, and malolactic fermentation (dependent on style), is complete it is a good idea to ensure that the wine has an adequate free sulfur dioxide content in order to retain its antimicrobial protection.
Some fining agents may also be applicable in the juice stage. For example, some producers find it helpful to fine juice with bentonite in order to reduce protein content, as well as help minimize rot-associated off-flavors or partially reduce laccase concentrations.
PVPP can be added to the juice to reduce potential browning pigments or their precursor forms (Van de Water, 1985).
In both of these scenarios, neither bentonite or PVPP is specific for rot-related constituents, but each could be helpful to avoid potential challenges later on in the production process.
The presence of Botrytis can also contribute glucans to the must/wine, which can cause filterability problems for heavily-infected wines. In this situation, many suppliers have beta-glucanase enzymes that can be applied either to the juice, wine, or both, to help breakdown the glucans and enhance ease of filterability.
A Word about Laccase
Both polyphenol oxidase (PPO) and laccase can cause early browning in grapes and wine. However, PPO is inhibited by the alcohol content that is developed during primary fermentation. Laccase, however, is not inhibited by the presence of alcohol, and can only be inactivated by a pasteurization step, heated to at least 60°C (140°F) (Wilker, 2010).
Grapes tend to be higher in laccase concentration when infected with Botrytis, and, thus, wines produced from grapes that had a high incidence rate of Botrytis can develop a brown hue post-primary fermentation. This oxidative activity can occur even in young wines.
If you are concerned about the prevalence of laccase in diseased-fruit, wineries can submit wine samples to a wine lab for a laccase test. Or, if you own a copy of “Monitoring the Winemaking Process from Grapes to Wine: Techniques and Concepts” by Patrick Iland et al., pg. 90 and 94 have 2 laccase test protocols that outline how wineries can assess oxidation by laccase. The results of these test will indicate if extreme treatments are required during production to avoid the rapid and early oxidation caused by laccase.
- Fermenting with Botrytis 101
- Management of Botrytis Infected Fruit
- Managing Botrytis Infected Fruit Fact Sheet
Goode, J. 2014. The Science of Wine: From Vine to Glass. (2nd Ed.) University of California Press: Berkley, California. 216 pg.
Fugelsang, K.C. and C.G. Edwards. 2007. Wine Microbiology: Practical Applications and Proceedings. (2nd Ed.) Springer: New York, NY. 393 pg.
Loinger, C., S. Cohen, N. Dror, and M.J. Berlinger. 1977. Effect of grape cluster rot on wine quality. AJEV. 28(4): 196-199.
Peynaud, E. 1984. Knowing and Making Wine. Wiley-Interscience: New York, NY. 391 pg.
Razungles, A. 2010. Extraction technologies and wine quality. In Managing Wine Quality, Vol. 2 Oenology and Wine Quality. Andrew G. Reynolds, Ed. Woodhead Publishing: Philadelphia, PA. 651 pg.
Van de Water, L. 1985. Fining Agents for Use in Wine. The Wine Lab.
Wilker, K.L. 2010. How should I treat a must from white grapes containing laccase? In Winemaking Problems Solved. CRC Press: Boca Raton, Florida. 398 pg.
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: Denise M. Gardner
If you are a wine producer in the northern hemisphere, harvest may feel quite far away. However, given that it is now the month of July, it will be here before we all know it.
The month of July is a great time to start preparing a few essential pre-harvest tasks including getting a bottling schedule ready, especially if bottling operations have not yet begun, and ordering harvest supplies. This blog post will focus on these two tasks.
Prepare and Enact a Bottling Schedule
New grapes are about to flood your winery with juice and future wine. Now is the time to review inventory within the cellar and determine what has to be moved and what has to be bottled before harvest begins.
Freeing up previous years’ inventory by moving it into bottle will free up tank, barrel and storage space for this year’s incoming fruit. It makes for a much easier transition if all of the wines that need bottling are bottled before harvest season starts. Bottling during harvest is not only chaotic, but it tires employees, pulls resources from the incoming product, and may lead to harvest decisions that may be regretted later.
Always make sure to get bottled wines properly stored and away from any “wet areas” on the production floor. If possible, bottled wines should have a separated storage area within an ideal environment that is physically separated from production. From there, stored wines can be moved into retail space when needed.
For more information on how to get wines prepared for bottling, please visit our previous posts:
Ordering Fermentation and Lab Supplies
Many suppliers and wine labs offer free shipping in July, which can especially be useful for wineries that are not geographically close to a winery supply store-front. Planning ahead and determining what fermentation supplies will be needed in August, could save extra money. Not to mention, having supplies on hand during the busy processing season can be a big stress relief.
Winemakers should also take the time to look at new fermentation products and assess the previous year’s needs in order to adequately supply for the up-and-coming harvest. Keeping an annual inventory of purchases can be helpful to isolate regular needs.
Things to consider purchasing include:
- Fermentation Nutrients
- Malolactic Bacteria
- Yeast Hulls
- Salts for Acid Adjustments
- Pectic Gums and/or Inactivated Yeast Products
- Fining Agents
- Oak Alternatives or Barrels
- Sanitizing Agents
While new yeasts are released frequently, being constructive about the production’s fermentation needs can help isolate what yeasts are needed for the upcoming harvest. I typically recommend that all vintners have at least 5 strains on hand for harvest: 2 reliable strains that will get through primary fermentation with little hassle, 1 strain that can be relied upon for sluggish or stuck fermentations, and 2 strains for specialty needs (e.g., sparkling or fruit wine/hard cider production) or experimental use.
Fermentation nutrients should be a must-have for all wineries to help minimize the risk of hydrogen sulfide. Always double check nutrient requirements for yeast strains purchased. In general, wineries will need hydration nutrients (e.g., GoFerm), complex nutrients (e.g., Fermaid K), and diammonium phosphate (DAP).
For more information on why YAN is important and how yeasts utilize nitrogen during primary fermentation, please visit the following blog posts:
- Reviewing YAN and Hydrogen Sulfide Part 1
- Reviewing YAN and Hydrogen Sulfide Part 2
- Yeast Selection and Hydrogen Sulfide
If you need further step-by-step instructions on how to determine adequate nutrient additions during primary fermentation, please visit our Penn State Extension fact sheet: Wine Made Easy Nutrient Management during Fermentation
Sometimes hydrogen sulfide will arise in a wine by the time primary fermentation ends despite all preventative care. Making sure there are adequate supplies on hand, such as copper sulfate and PVI/PVP can save time in the future. Also make plans for ways that the production can reserve fresh lees. PVI/PVP is a fining agent that can help reduce metals like residual copper, but fresh lees will also help reduce the perception of hydrogen sulfide aroma/flavor and residual copper in the wine. Having a plan for retaining and storing lees during harvest season can save time during challenging situations that develop through the end of harvest and into the winter’s storage season. A fact sheet on copper screens and addition trials can be found at the Penn State Extension fact sheet: Wine Made Easy Sulfur-Based Off-Odors in Wine.
I also like to make sure we have supplies on hand in case of heavy disease pressure come harvest. This includes things like Lysozyme, beta-gluconase, pectinase or other clarification enzymes, and fermentation tannins. Lysozyme can help reduce lactic acid bacteria levels while beta-gluconase can assist clarification problems associated with Botrysized wines. For further information on how to manage high-disease pressured fruit, please visit the Penn State Extension website on Fermenting with Botrytis or Managing Sour Rot in the Cellar.
Double check the storage requirements for all materials purchased before and after the product is opened. It’s important to store all of those supplies in the winery properly as it will ensure their efficacy by the time the product is needed.