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Ohio State University Extension

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Herbicide Injury and the Problem of Spray Drift

ANR-0137
Agriculture and Natural Resources
Date: 
06/12/2023
Doug Doohan, Department of Horticulture and Crop Science, The Ohio State University
Imed Dami, Department of Horticulture and Crop Science, The Ohio State University
Bruce Bordelon, Department of Horticulture and Landscape Architecture, Purdue University

Herbicides recommended for use in the vineyard are usually very safe if the user follows the product label directions. When slight injury does occur, yield and fruit quality are rarely jeopardized. Vine injury resulting from ordinary weed control operations can largely be prevented by following simple guidelines:

  • Review and familiarize yourself with the principles, general practices, and programs of weed control.
  • Read and adhere to the label instructions for the use of registered herbicides in the vineyard. Labels are available at cdms.net/LabelsSDS/home and at greenbook.net/.
  • Apply herbicides with high-volume nozzles that produce coarse droplets with a spray pressure at or less than 30 psi.
  • Use a shielded sprayer to direct sprays to the base of vines and prevent herbicide spray contact with green bark and foliage. Avoid applying herbicides when shoots begin to trail, especially with downward shoot training systems such as single high wire, Geneva Double Curtain, Smart-Dyson, and Scott Henry. Grow tubes can be used on newly planted vines to enable the use of foliar-active herbicides under the trellis.

In instances when herbicide injury from ordinary weed control operations occurs, it can usually be traced back to sprays that contacted the foliage or green bark, a high spray rate, or vine predisposition resulting from environmental stresses that weakened the plant. The latter is usually indicative of other, more serious problems. In contrast, drift from herbicides used on neighboring corn, soybean, pasture, and cotton fields poses a major threat to commercial grape crops. Herbicide drift can injure the shoots, fruits, and roots. Reduced yield, poor fruit quality, problems with overwintering, and sometimes vine death are all potential outcomes of a drift event. Damages inflicted by drift have resulted in substantial losses for vineyard owners, winemakers, communities, and consumers.

Why is Herbicide Drift Such a Problem for the Grape Industry?

At the time of this writing in summer of 2022, herbicide drift might have been the single greatest threat to the prosperity of the Midwest grape industry. While vine damage from drift is not a new phenomenon, its occurrence and the severity of its impact have increased due to the resurgence of 2,4-D and dicamba use. Until recently, these herbicides had been relegated to spring pasture and cereal grain weed control, and autumn grape weed control. For grape plants, autumn spraying ensured they were in growth stages less susceptible to injury, which allowed the use of low-cost options for controlling weed biotypes that have developed resistance to glyphosate, the herbicide in Roundup and other glyphosate-based products.

In previous years, 2,4-D and dicamba were used to burn down hard-to-kill broadleaf weeds before planting no-till corn and soybean. That use eventually extended to millions of acres of row crops, was coincident with budbreak and later stages of grapevine development including bloom to early fruit set. Reports of grapevine injury from growth-regulator herbicides increased rapidly after 2005 as burndowns became standard practice in row-crop production. Drift incidents also increased recently with the release of dicamba- (Xtend) and 2,4-D- (Enlist) resistant soybean and cotton. Today, 2,4-D and dicamba are used to control glyphosate-resistant weeds on tens of millions of acres of soybean and cotton in the central United States. Applications extend through May, June, and July, which are months when grapevines are sensitive to the injurious effects of drift. Also, the past five years has shown that the formulations of these herbicides makes them susceptible to off-target movement when used in commercial farming.

Many grape growers, as well as row crop and other farmers, hold a number of misconceptions about drift. For the vineyard owner, it is important to take steps to prevent the occurrence of occasional drift damage from weed control operations. Prevention is straightforward. When applying foliar-active herbicides, use only carefully directed, low-pressure sprays that produce large droplets. This is especially important when controlling weeds in lawn areas that are close to the vineyard (e.g., an estate winery). However, grape growers should be aware that drift from a neighboring row-crop field is usually of far greater impact than drift originating within the vineyard. This is because large volumes of herbicides highly toxic to grapes may be used on those fields, and because applications are often done under less-than-ideal environmental conditions.

Understanding Drift

Drift is the movement of minute quantities of pesticide, usually from an adjacent or nearby field onto foliage that was not intended to be sprayed. Drift can occur with any pesticide application. Drifting insecticide or fungicide sprays may go unnoticed, but the negative impacts to beneficial organisms in the vineyard and the environment can still occur. In most cases, herbicide drift into a vineyard is almost always obvious and often has devastating effects on the vines. Drift may occur as droplet drift, volatility drift, or both.

Droplet drift is also called physical, primary, or particle drift. It is the movement of spray droplets downwind during an application. Minimize droplet drift by applying herbicides through coarse nozzles, at a low pressure that produces large droplets, and by following all label recommendations regarding prohibited weather conditions. Wind speeds up to 10 and sometimes 15 mph are permitted by most herbicide product labels, but can result in drift into the vineyard particularly if the sprayer produces small droplets. Some labels (e.g., Enlist Duo) prohibit spraying if the wind is moving toward a grape or other sensitive crop. The vineyard owner should be aware of any prohibitions. Droplet drift usually results in a visible pattern in the affected crop. Plants that are closer to the source field will exhibit more injury. Symptoms will decline as the distance from the source field increases. Droplet drift does not usually extend over large distances downwind.

Volatility drift is associated with a small number of pesticides that have high vapor pressure (i.e., the characteristic to change from a liquid or solid to a gas form). Volatilization occurs under normal conditions of temperature and humidity but is most likely to occur when temperatures are high and humidity is low. A spike in air temperature on an afternoon in May or June can cause a volatile herbicide to turn into a gas even after having been successfully applied to target surfaces. Labels of most volatile herbicides include language prohibiting their use when air temperatures are high. Drift occurring as a result of volatilization is sometimes referred to as secondary drift. The most well-known volatile herbicides are 2,4-D and dicamba. They are highly associated with vineyards damaged by drift. Dicamba is inherently more volatile than 2,4-D, but both herbicides have been implicated repeatedly in volatility drift to grape and many other nontarget crops. Keep in mind that a volatile herbicide, such as 2,4-D, can drift because of droplet drift and volatilization. When volatilization is the main factor, entire fields may be affected, and a drift-pattern is less likely to be observed.

Spraying when there is no wind may seem like a good idea; it is not. This is because temperature inversions—common in the spring and summer—have an amplifying effect on drift. Inversions typically form in the late afternoon or evening and persist for 1–3 hours after sunrise. Calm conditions or wind less than 3 mph are an indication that inversion conditions exist (Figure 1). Labels of many herbicides include specific warnings to not spray during inversion conditions. A temperature inversion occurs when cold air near the ground is trapped by warmer air above, and there is little vertical air movement. This can result in very small spray droplets becoming suspended near the ground in the colder, denser air. This colder surface layer of air can then move horizontally like a fog onto neighboring fields, carrying suspended herbicide spray droplets along. Morning sunlight or stronger winds eventually mix the air layers and bring an end to inversion conditions, but applications made during an inversion late in the day may have until midmorning the following day to drift off target.

Tractor pulling a sprayer. Arrows show spray droplets moving up into the air. tTractor and sprayer with arrows showing how spray droplets are unable to rise above an inversion line between the warm air higher in the atmosphere and cooler air below.
Figure 1. Understanding inversions. Increasing temperature results in rising and falling air columns, and slight wind (>3 mph) that mixes the air, resulting in droplets contacting target surfaces or dissipating harmlessly into the atmosphere (left). During inversions spray droplets are trapped in cold air near the ground and can subsequently travel horizontally along the ground surface to cause damage to off-target plants (right). Inversions regularly occur in early morning and in evenings of days with clear skies because of rapid cooling of the ground surface through irradiation. Graphic by Gretchen Wieshuber.

Types of Herbicides Known to Cause Drift Injury of Grape

Herbicides are plant toxins. Virtually any herbicide can damage a vine that is exposed to a sufficiently high dose. Herbicides that cause vine damage as a result of droplet or volatilization movement from target-fields to the vineyard affect the vine at extremely low doses. The complete and rapid death of young vines, however, has been observed in commercial settings. Injury is usually much more severe if exposure occurs during rapid shoot growth in early spring, or at any point during the bloom phase. Herbicide exposure to developing berries may greatly delay or even prevent veraison. Herbicides most likely to be involved in drift include growth regulators (e.g., 2-4, D, dicamba), amino acid synthesis inhibitors (e.g., glyphosate), and acetolactate synthase (ALS) inhibitors (e.g., sulfonylureas and imidazolinone).

Growth regulators are the herbicides most likely to injure grapevines. Grapevines are extremely sensitive to growth regulators—by one estimate, a million times more sensitive than corn or wheat. Symptoms of injury are primarily a function of the herbicide, the quantity of herbicide delivered to the vine, the vine age, and the vine’s stage of development at the time drift occurred. Growth regulators are quickly translocated in the plant from expanded leaves that intercept drift to areas of rapidly expanding new plant growth. Symptoms are obvious within a couple of days and sometimes within hours, consisting of twisting shoots, tendrils, and leaf petioles; and leaf blades that are grossly deformed (Figures 2 and 3).

View down grapevine rows with blue sky above. Medium close -up of end of new grapevine growth, showing tendrils and leaves.
Figure 2a. Uncontrolled growth following exposure to 2,4-D. Photo by Doug Doohan. 2b. Distorted shoot growth, feathering, chlorosis, following exposure to 2,4-D. Photo by Doug Doohan.
Leaf on grapevine appearing shriveled and drooping from the vine. Green foliage with section growing a cluster of young, green, round fruit.
Figure 2c. Fan-shaped, deep sinuses, leaf-blade puckering and constricted veins following exposure to 2,4-D. Photo by Doug Doohan. Figure 2d. Millerandage (chicken and eggs) following exposure during flowering/early fruit set. Photo by Imed Dami.

Growth regulators mimic auxins, the naturally occurring hormones that regulate plant growth and development. Of the growth regulator herbicides, 2,4-D and dicamba are by far the most common and well known. Dozens of branded products containing 2,4-D or dicamba—alone, in combination with each other, or in combination with different herbicides—are readily available for purchase. As volatile herbicides, 2,4-D and dicamba, can gas off at normal spring and summertime temperatures and humidity, causing drift damage to plants in nontarget fields.

The herbicide 2,4-D can be formulated as an ester, or as an amine, with ester forms more volatile and less expensive than amine forms. Both 2,4-D and dicamba are relatively inexpensive, which makes them popular with crop farmers. The least expensive brands often contain volatile forms of the herbicides that are most prone to off-target movement. Ester formulations of 2,4-D are preferred by soybean farmers for preplant weed burndown because the interval from application to safe-seeding is shorter than it is for amine formulations. Several brands of 2,4-D formulated as a choline salt are now available. These brands are considered to be less volatile, according to the manufacturer’s data, and 2,4-D choline is the only form registered for use on Enlist soybean and cotton. The most well-known 2,4-D choline product is sold under the name Enlist.

Formulations of dicamba that have been commercially available for decades include dimethyl amine salts, diglycolamine salts, and isopropylamine salts. While they vary in vapor pressure, all are considered to be highly volatile. Following the release of dicamba-tolerant soybean and cotton, several manufacturers registered formulations of dicamba that were reputed to be nonvolatile. These include Engenia, based on BASF’s proprietary BAPMA salt, and XtendiMax and Tavium that both use a diglycolamine salt and VaporGrip Technology. Most drift injury resulting from dicamba use on dicamba-tolerant soybean and cotton has almost certainly arisen from the use of these new formulations.

Symptoms of 2,4-D injury are easily recognized and include characteristic fan-shaped leaves with sharp points at leaf margins, epinasty (downward bending of leaves), leaf strapping with deep sinuses, and leaf puckering with constricted veins that may be slightly chlorotic (Figure 2c). The youngest terminal growth is most severely affected. Vines and leaf petioles are severely twisted. Leaf blades may be stunted and misshapen with closely packed, thick veins. Terminal growth may cease for a time following the initial effects. Severe injury will retard growth for several weeks. Vines with these symptoms rarely produce new normal growth for the remainder of the season. Normal growth usually resumes the following spring, but injury symptoms may resume if the drift dose was high, or if more than one drift event occurred early in the vine’s annual growth cycle. Severely injured vines may die or not recover for two or more years. Vines injured by 2,4-D also may have delayed fruit ripening and fruit clusters that display millerandage, also known as the hens and chickens appearance. If vines are severely injured, fruits may never mature, regardless of the season’s length. These delayed-maturity effects may persist for 1–3 years before normal ripening returns.

Dicamba injuries are similar in appearance to those described for 2,4-D. However, leaf cupping and a distinct marginal band of restricted growth are much more common than with 2,4-D, and are relatively diagnostic for the herbicide (Figure 3a and 3b). Round-leaf varieties are more likely to develop strongly cupped leaves. Varieties with deeply lobed leaves are more likely to develop symptoms that overlap with those caused by 2,4-D (Figure 3d). It is important to note that a maximum residue level (MRL) has not been established for dicamba in fruit crops. Any detected residue at harvest means the crop cannot be sold.

Overhead view of leaves with edges that are curling in, resulting in a “cupped” appearance. Overhead view of leaves with edges that are curling downward.
Figure 3a. Typical strong upward leaf cupping response following exposure to dicamba. Photo by Doug Doohan.

Figure 3b. Downward leaf cupping in response to exposure to dicamba. Photo by Imed Dami.

View of multiple green leaves, with some that have curled and twisted, resulting in a fluted appearance. Hand holding a leaf among a bunch of puckered leaves.

Figure 3c. Fluted leaf shape after exposure to dicamba. Photo by Imed Dami.

Figure 3d. Fan-shaped distortion with deep sinuses and leaf blade puckering on a deeply lobed variety following exposure to dicamba. Photo by Imed Dami.

Other growth regulator herbicides that may cause drift-related injury to vines are triclopyr, clopyralid, aminopyralid, picloram, and aminocyclopyrachlor. Triclopyr, commonly used to kill brush, is highly volatile and can be expected to move away from the target even when there is no droplet drift. Clopyralid (Stinger) is an effective control for Canada thistle, but it has a high degree of uptake from the soil and is very persistent. Grape injury has been observed from direct droplet drift and from root uptake. Overall, little is known about the potential impact on grape when these herbicides drift. Effects may be delayed and/or manifested only at bloom or fruit set with little or no effects on foliage at the time of impact. Because their use is limited, risk of damage to vineyards is probably low. Clopyralid, aminopyralid, picloram, and aminocyclopyrachlor are highly persistent in the environment and have injured crops grown in, or amended with, contaminated composts and yard wastes.

Amino acid synthesis inhibitor herbicides include the active ingredient glyphosate and the broad category of herbicides known as acetolactate synthase (ALS) inhibitors. They injure and kill plants by inhibiting a step in the biosynthetic pathways for formation of certain amino acids, the building blocks of proteins. Because glyphosate and ALS inhibitors do not volatilize under normal atmospheric conditions, grapevine injury resulting from their misuse usually occurs only from nearby applications and as a result of droplet drift.

Glyphosate is the active ingredient in Roundup herbicides and many similar products. Glyphosate can drift and injure grapes but is generally less of a problem because, unlike the growth regulators, it is not volatile, and grapes are less sensitive to the low doses associated with droplet drift. Nevertheless, glyphosate sprays can move off-target in windy conditions or during atmospheric inversions. Since glyphosate is systemic, it can translocate to and kill the growing points of plants, and injure root systems. Glyphosate is applied, usually in combination with 2,4-D or dicamba, prior to planting no-till soybean or corn. It is widely used on Roundup Ready crops and is also mixed with formulations of dicamba and 2,4-D for use on Xtend and Enlist soybean and cotton. Effects on the vine are often more severe when glyphosate is mixed with either 2,4-D or dicamba than when either is used alone. Glyphosate is labeled for use in vineyards and is one of the most commonly used grape herbicides. Therefore, injury resulting from accidental spraying of green vine tissue, or particle drift resulting from high-pressure application through a small orifice nozzle, is common.

ALS inhibitors are systemic and may cause injury similar to glyphosate. The ALS inhibitors include the sulfonylureas (trade names: Accent, Classic, Harmony, Permit) and the imidazolinones (trade names: Pursuit, Raptor, Scepter). ALS inhibitor herbicides were once widely used in corn, soybean, and wheat, and while their use is no longer dominant, they are still important components of weed control programs for those crops. At least one ALS inhibitor, rimsulfuron, is the active ingredient in Matrix (among other brands) which is registered for use in vineyards. ALS herbicides are applied before and after crop seeding/emergence at extremely low rates. 

Symptoms caused by glyphosate and ALS inhibitors develop slowly and may not be easy to detect for up to two weeks after a drift event. Because glyphosate and ALS inhibitors translocate to the growing points, symptoms develop most noticeably on new leaves. Stunted growth and leaf blade chlorosis are the primary symptoms of glyphosate injury. Leaf shape distortion and leaf blade puckering are also common (Figures 4a–4c). Cupped leaves, upward curled leaves, and shortened internodes are common. Terminal growth may die and slough off. In severe instances, vines may be killed or experience severely stunted growth. Glyphosate drift during active vegetative growth may break apical dominance in shoots, resulting in the growth of numerous lateral shoots, giving the vine a bushy appearance. When vines are exposed to glyphosate prior to dormancy in late summer or early fall, symptoms may not be expressed until regrowth starts the following spring. Symptoms include short internodes, stunted growth with abundant lateral shoots, leaf shape distortion (often arrow-shaped), chlorosis, and aborted flowers. Recovery from severe glyphosate injury may be slow, and symptoms can be expected to decline slowly over two or more years. Early-spring symptoms of glyphosate injury may be confused with viral or fungal diseases such as Eutypa dieback. Leaf blade chlorosis is the primary symptom of ALS herbicide drift (Figures 5a and 5b). Affected leaves may take on a mosaic appearance that could easily be confused with the effects of a virus. Because the photosynthetic apparatus is impaired, reduction in growth is certain. It is unknown if ALS herbicide drift kills vines or causes symptoms that extend beyond the growing season.

Two photos, with one showing overhead view of plant, and another showing a close up of the plant’s leaves, which are puckered.
Plant growing from a pot, with some large green leaves, and some that are small, yellowed, and have green veins.
Overhead view of puckered, withered appearing leaves growing from vines.
Figure 4a. Leaf blade puckering following exposure to glyphosate. Photos by Doug Doohan and Imed Dami. Figure 4b. Severe chlorosis on newly forming leaves following exposure to glyphosate. Photo by Doug Doohan.

Figures 4c. Lateral shoot growth, fan-shaped leaf blade including puckering and formation of deep sinuses. Photo by Imed Dami.

Overhead view of leaves with wrinkled appearance growing off a vine on the ground. Overhead view of leaf with crinkled appearance and light green veins.

Figure 5a. Injury by Permit causing short internode and leaf puckering. Photo by Imed Dami.

Figure 5b. Injury by Permit causing crinkle appearance and vein chlorosis of leaves. Photo by Imed Dami.

Other herbicides are occasionally implicated in drift-related injury and include photosynthesis inhibitors, such as paraquat (Gramoxone), glufosinate (Rely); and protoporphyrinogen oxidase (PPO) inhibitors such as carfentrazone (Aim), and flumioxazin (Chateau). Symptoms of drift (internal or external to the vineyard) consists of chlorotic and necrotic spots on leaves and berries (Figures 6 and 7). Likewise, photosynthesis (Photosystem II) inhibitors like diuron (Karmex) and simazine (Princep) may cause chlorosis of leaf tissue (Figures 8a and 8b). Both are registered for use in the vineyard. Injury, however, may occur if the spray rate is too high when these herbicides are applied to soil under the trellis, or droplet drift lands directly on tender foliage. Because these herbicides do not move systemically throughout the plant, long-term effects from a drift event are unlikely. Each is registered for use in the vineyard but also used extensively in row-crop agriculture or vegetation management (diuron).

Hand behind leaf with brown spots. Close-up of leaf with yellow spots outlined in brown.

Figure 6. Chlorotic and necrotic spotting of leaf blade caused by droplet drift of glufosinate applied under the trellis. Photo by Doug Doohan.

Figure 7. Paraquat damage to leaves with yellow then brown spots. Photo by Imed Dami.

Close -up of leaf with yellow veins. Multiple leaves, with some having a yellowish appearance with green veins.

Figure 8a. Leaf vein chlorosis caused by diuron (Karmex). Photo by Imed Dami.

Figure 8b. Leaf blade chlorosis caused by simazine (Princep). Veins remain green. Photo by Doug Doohan.

Long-term Impacts of Herbicide Injury

Once absorbed, growth regulator and amino acid synthesis inhibitor herbicides move throughout the plant and accumulate in rapidly growing tissues, including the root system. Young vines are more likely to be severely impacted by drift and may take years to recover or should simply be replaced. Other effects are a reduction in total leaf area, decreased biomass accumulation, and the stunting of plants. The effect on an impacted vine’s overwintering capacity has not been adequately studied. But evidence from drift events in commercial vineyards indicates an overall reduction in environmental stress tolerance and symptom reappearance on new growth in early spring. Recent research from Australia indicated that less total soluble carbohydrate storage is available in the roots of growth-regulator injured vines, and showed an increased incidence of primary bud necrosis following dicamba exposure.

Generally, injury symptoms resulting from herbicide drift in the other category, which includes photosynthesis and protoporphyrinogen oxidase (PPO) inhibitors, are unlikely to cause long-term impacts on vine growth and productivity. Damage is localized to tissues in direct contact with herbicide drift. An exception would be if vines are very young and not yet well rooted. In this situation herbicides such as paraquat, glufosinate, or atrazine may completely defoliate the vine and cause death.

The sensitivity of grapevines to herbicide drift varies depending on the grape cultivar. Table 1 shows the sensitivity of different cultivars to 2,4-D and dicamba exposure. With severe and repeated exposure, all cultivars are vulnerable.

Table 1. Wine Grape Cultivars Sensitivity to 2,4-D and dicamba in the Midwest.
Variety Dicamba sensitivity 2,4-D sensitivity
Brianna + ++
Cabernet franc +++ +
Cabernet Sauvignon ++ +
Catawba ++ ++
Cayuga White +++ +
Chambourcin ++ +++
Chancellor ? ++
Chardonet +++ ++
Chardonnay +++ ++
Concord ++ +++
Corot noir +++ ++
Dechaunac ++ +
Delaware ? +++
Edelweiss ? ++
Foch +++ +++
Fredonia ++ ++
Frotenac +++ +
Frotenac gris + +
Geneva Red +++ +
Horizon ? None
LaCrescent +++ +++
LaCrosse +++ +++
Leon Millot ? +
Marquette + +++
Melody ? +
Niagara ++ +++
Noiret +++ ++
Petite Pearl ? +
Petite Syrah (Durif) ++ ++
Pinot gris +++ +++
Ravat 34 ? ++
Riesling ++ ++
Sauvignon blanc + +
Sangiovese + +
Seyval +++ ++
Siegfried ? +++
Traminette ++ ++
Valvin Muscat + +++
Vidal blanc +++ ++
Vignoles +++ ++
Villard blanc ? None

Sensitivity rating
None: No evidence of response to 2,4-D and dicamba exposure.
+: Slightly sensitive. Mild curling or feathering of leaves, twisted leaf petioles.
++: Moderately sensitive. Readily apparent leaf blade, petiole, and tendril deformation and occasional shoot tip curling. Temporary stunting followed by normal regrowth.
+++: Extremely sensitive. Extreme symptoms, including deformation of leaves on most shoots, severe stunting of new shoot growth, and symptoms on regrowth.
?: Susceptibility unknown or not established.

Prevention and Preparing for Drift Damage

For most of those growing grapes in the Midwest, herbicide drift is not a matter of if, but of when. Taking deliberate steps to minimize the occurrence and severity of drift is an essential part of the vineyard management plan.

Avoid establishing vineyards in areas with high drift hazards. Considering the current weed control practices for corn, soybean, and cotton reviewed here, growers should consider the wisdom of planting new vineyards in areas that are dominated by row-crop agriculture. Such areas pose the highest risk to the vineyard owner.

Establish wind breaks and buffer zones to minimize droplet drift. When considering where to establish grape plantings, select a site that is protected from surrounding fields and unlikely to experience cold-air drainage from surrounding row-crop fields. Maintain buffers of at least 250 feet around your vineyard and plant evergreens and shrub windrows between your vineyard and your neighbors’ fields. The buffer and the windrows will slow the wind and may reduce the distance that droplet drift will travel.

Evaluate your risk factors and communicate with owners and operators of surrounding properties. Discuss your vineyard operation with the neighbors so they are aware you are growing grapes and that your vines are sensitive to drift from many different herbicides. Make sure that your neighbors, and any custom applicators spraying their property, avoid spraying when inversion conditions are likely (still conditions in early a.m. or late p.m.) and use application methods that produce large droplets. A positive personal relationship with your neighbors will help. Explain the high sensitivity of your crop to herbicide drift, the high cost of production, and the per-acre cash value. Your neighbors may not know there is no established maximum residue tolerance (MRL) for dicamba residue on grapes. This means that a drift event may result in a complete loss of your crop even if yields are not negatively impacted. If neighbors are planning preplant burndowns using 2,4-D for control of glyphosate-resistant weeds, encourage the use of a non-(or very low-) volatile choline formulation such as Enlist and discourage the use of ester formulations that are highly volatile. Remind neighbors about alternatives to spraying dicamba or 2,4-D that can be used postemergence on row crops growing close to the vineyard. For example, many vineyard owners who also grow row crops on their farm have adopted the LibertyLink cropping system available for corn, soybean, and cotton. Weeds are controlled postemergence by spraying a glufosinate herbicide such as Liberty or Ignite. Because glufosinate is nonvolatile and does not translocate significantly within the plant, if droplet drift occurs, it would only cause localized damage. For some fields next to the vineyard, legacy weed control products such as metribuzin or linuron (broadleaf weed control in soybean), S-metoloachlor or dimethenamid-P (grass control in soybean and corn), and atrazine and bentazon (broadleaf weed control in corn) may provide an acceptable level of weed control while minimizing the risk of severe grape injury as a result of drift. Postemergence grass killer herbicides such as sethoxydim and fluazifop are not toxic to grape and their use does not pose a risk of grape injury. Communicate the presence of your vineyard to township highway departments, utilities, and other agencies that might be spraying rights of way or roadsides. If these areas run through your property, keep them free of weeds so they are less likely to be sprayed.

Register with your state’s sensitive crop registry. This list is managed by Driftwatch (driftwatch.org) or your state agricultural agency. Commercial pesticide applicators are required to check these registries before spraying. You can also mark your property with signage available from Fieldwatch/Driftwatch and other associations.

Know the rules and regulations that govern application of drift-prone herbicides. You can look up specific product labels at CDMS (cdms.net) or Greenbook (greenbook.net). Label instructions are part of pesticide regulations. Applicators who do not follow them can face fines or lose their applicator’s license. In addition to the national label, your state pesticide regulatory agency may have additional restrictions, such as cut-off dates for spraying dicamba or other herbicides.

Maintain financial and production records. If a drift event occurs, good records will prepare you to document financial losses for reduced or lost yield, reduced quality, and the inability to recoup production costs. Historical yield data can be used to approximate yield losses associated with drift injury. Production budgets documenting costs of inputs, labor, and equipment depreciation will document production-related financial losses.

Prepare a detailed set of maps, including landscape features (wooded areas, wind breaks, buildings, farm ponds, adjacent property). These maps can be a handy way to track where damage occurred and where samples were collected. Since these may be used as evidence for a loss claim, make sure the maps are accurate. To-scale, hand-drawn maps may be acceptable. Alternatively outlining the farm and fields on a series of aerial photographs or satellite images (such as Google Earth) is also acceptable.

Familiarize yourself with analytical laboratories that will analyze crop samples for herbicide residues. Research their requirements regarding sample size, labeling, storage, and shipping since these may vary. Also find out what pesticides they provide testing for and how low their detection levels go.

Do not rely on your crop insurance. Insurance companies typically do not consider herbicide drift an “act of God” and therefore do not provide coverage for drift damage. Check with your insurance provider before drift happens and know where you stand.

Consider investing in a weather station and surveillance video cameras. A weather station with data logging can track wind data and provide other useful information for your operation, such as rainfall and air temperature. Weather data is often a key factor in determining applicator negligence. Video that records spraying activity in nearby fields in combination with weather data and scouting records may help pinpoint the source of drift.

Learn the typical symptoms of injury caused by herbicide drift and how to distinguish them from other similar symptoms. Keep in mind that other factors, such as nutrient deficiencies and spring frosts, may cause symptoms easily mistaken for those caused by herbicide drift. Final diagnosis is best when accompanied by an analysis of grape tissues for herbicide residues. Professional assistance is likely to be needed and may be obtained through the state land-grant university.

Talk to other growers. Conferences and grower support organizations can help growers share regional information and resources, including available experts or lawyers. Consider establishing a relationship with a lawyer before a problem arises or discussing the issue preemptively with a current legal advisor.

Reporting Drift

If you are convinced that herbicide drift injured your grapes, contact the applicator and try to work out a settlement. To conclusively demonstrate that a particular herbicide is present, it is necessary to analyze samples of the injured grape plants for the herbicide. Ensure that residue analysis samples are obtained as soon as possible and are handled in a manner that will preserve the sample integrity and chain of evidence/custody. Your analytical lab of choice can provide advice on how to take and handle samples. If a drift pattern is apparent in your vineyard, consider taking separate samples of sections showing extreme symptoms, mild symptoms, and no symptoms. Doing so may demonstrate a gradient of herbicide residue levels corresponding to symptom expression, while also linking your vineyard directly to the source field. Keep in mind that chemical analysis can quickly become expensive unless you know the herbicide that caused the injury.

You may contact the state regulatory agency (usually the Department of Agriculture). Typically, a completed complaint form must be filed with the state Department of Agriculture within 30 days of when the drift occurred, or when the injury was first observed. The state Department of Agriculture will send out an investigator to collect evidence, including samples for residue analysis. The collection of samples, however, may not occur in a timely manner. If the regulator takes samples, the levels found in those may be given preferential standing in court. Based on the findings of the investigation, the department might assess penalties against the applicator. Keep in mind that the regulator cannot help you recover your losses from herbicide drift. It is up to you to reach a settlement with the applicator or initiate a civil lawsuit. If you choose to pursue legal action, you will probably need professional assistance.

Additional Resources

Many excellent education resources are available through land-grant university extension programs, grower organizations, and the internet to assist the vineyard manager. Because each manager is likely to experience damage from herbicide drift at some point, preparation is key.

DriftWatch

Provides a directory of state sensitive crop registries that is used by commercial and private applicators. DriftWatch also sells field signs. Registering your vineyard may be the most useful few moments you will ever spend on the internet.

For more information, check out driftwatch.org.

North Central IPM Center FACT SHEET SERIES on Herbicide Drift

An overview of dicamba and 2,4-D drift issues. ipm-drift.cfaes.ohio-state.edu/dicamba-and-24-d-fact-sheet-series/overview-dicamba-and-24-d-drift-issues

Preparing for drift damage. ipm-drift.cfaes.ohio-state.edu/dicamba-and-24-d-fact-sheet-series/preparing-drift-damage

Responding to drift damage. ipm-drift.cfaes.ohio-state.edu/dicamba-and-24-d-fact-sheet-series/responding-drift-damage

Frequently asked questions. ipm-drift.cfaes.ohio-state.edu/dicamba-and-24-d-fact-sheet-series/frequently-asked-questions

Herbicide Injury Symptom Identification

University of Missouri Herbicide Injury ID App
The Herbicide Injury ID app helps you diagnose plant damage that may have been caused by herbicides and links to herbicide information and other resources. This app is available for Android smartphones. herbicideinjuryid.missouri.edu/Support/

University of Missouri Herbicide Damage Trials
Excellent photos of drift damage at various levels of severity

IPM Herbicide Symptoms database
University of California Division of Agriculture and Natural Resources
ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=16456

Other

Air Temperature Inversions Causes, Characteristics and Potential Effects on Pesticide Spray Drift
North Dakota State Online Publication AE1705 (Revised Oct. 2019)
ag.ndsu.edu/publications/crops/air-temperature-inversions-causes-characteristics-and-potential-effects-on-pesticide-spray-drift

Five Things We’ve Learned about Dicamba
University of Missouri
Recent findings on temperature inversions, pH effects on volatilization, and plant drift injury.
ipm.missouri.edu/IPCM/2019/4/dicamba/

Best Practices for Spraying
Check your state Extension service for state-specific resources. Below are some excellent and recently updated resources from Ohio State.

Buckeye Appellation. Website maintained by the College of Food, Agricultural, and Environmental Sciences, The Ohio State University, including access to regular newsletter content. ohiograpeweb.cfaes.ohio-state.edu

Disclaimer: Products and brands mentioned in this publication are listed for information purposes only. The Ohio State University does not endorse the products listed, nor does it intend to discriminate against other products not mentioned.

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Originally posted Jun 12, 2023.
Ohioline https://ohioline.osu.edu