The Grapevine Newsletter - PSU Wine Grape Network

2-4D
Herbicide Drift Into Vineyards

Mark Chien

Wine Grape Extension Agent, Penn State Cooperative Extension

Damaged vines

Controlling the Drift

Timing of applications is important

Possible Alternatives

Communicate with your neighbors

PA has no tolorance for drift

Who to call

One problem that is raised more than any other to me during the growing season is the problem of herbicide drift into vineyards from neighboring fields. Wine grapes are still a small crop in Pennsylvania and vineyards are often surrounded by field or turf crops. Many farmers don't realize the hazard that herbicides present to grapes. Some simple measures of cooperation and consideration between neighbors can help control the damage without economical or plant harm to either farmer. Controlling chemical drift has many benefits for all growers. It reduces the amount of herbicide waste and increases efficacy. It will help to preserve the availability of existing pesticides. It reduces liability problems and losses due to lawsuits and fines. It reduces insurance costs for all farmers. It will help prevent the creation of more regulatory legislation restricting the use of chemicals.

Damaged vines

Damage is often caused by Phenoxy herbicides include 2,4-D based products, MCPA, Crossbow, Banvel, Garlon, Brush Killer. The active ingredient is 2,4-dichlorophenoxy-acetic acid. Grapes are extremely sensitive to phenoxy-type herbicides. While most sensitive during the early growing season, vines can be damaged anytime there is exposed green tissue. During the active growing season, exposure can cause growth to stop temporarily. Damage to young leaves is dramatic and obvious, characterized by the curling or cupping of leaves, a wide open leaf sinus and spiky leaf margins. Damage usually does not cause long- term harm to the plant but it can delay the ripening of grapes and compromise the proper hardening off of vines during the season that vines are affected. However, severely affected vines may not recover for two or more years. Flower clusters are very sensitive and poor fruit set can result from exposure to 2,4-D.

Damage to vines happens when herbicide drift and/or volatilization occurs. 2,4-D is produced in two basic chemical formulations - amine salts and esters. The amine form is generally considered safer since they are not as volatile as the esters, but they are still potentially dangerous to vines. The ester forms have variable volatility according to their chemistry, but can be assumed to be highly dangerous to vines. Warm days make volatilization a much greater concern.

There are other herbicides that may be causing foliar damage to vines that look similar to 2,4-D. Dicamba products are often used in June when vines are in bloom. Dicamba is very volatile and needs to be watered in to prevent unwanted movement. It is uncommon for farmers to do this by artificial means.

Controlling the Drift

Particle drift can also carry herbicides to non-target crops. Wind, shifting air currents, inversions or spraying at high pressure (reduced droplet size) can all exacerbate drift problems. Applicator care can usually help to avoid this problem. Spray early in the morning when humidity is high and wind is low (except under inversion conditions). Many farmers boom spray at 40+ psi, which can result in over 25% material drift. 20-30 psi is an ideal range for herbicide applications. Lower pressures increase droplet size which reduces the chance of drift. Using new nozzle technology can help to greatly reduce the pressure needed to spray effectively. Turbo T-Jet, Driftguard and Turbo floodjet nozzles are designed to be sprayed at normal pressures but have drastically reduced drift potential. They also maintain a high percentage of larger droplet sizes. Drop down boom nozzles are also very helpful in delivering chemical where it belongs. Otherwise, set the boom height at no greater than 22 inches. The use of shielded sprayers, electrostatic sprayers and air assisted sprayer can all help to reduce drift problems.

Make absolutely sure you know the source of the drift or volatile hazard before making any assumptions as to its source. Monitor your own practices as well as observing those of your neighbors. Make every attempt to document the source of damage and not to falsely accuse anyone. First, take a close look at your own herbicide application practices. Know the chemical composition of all your herbicides. Were you spraying Crossbow on blackberry? How do you use your sprayers? Do NOT use the same spray applicator for both fungicides and herbicides. Especially 2,4-D, which tends to bind with rubber and plastic materials in spray systems. This is a no-no. The more you fully understand the safe and recommended use of pesticides, the less chance any problems will occur.

Timing of applications is important

Grapes break bud in SE PA in April and from that point on are susceptible to damage, especially through bloom when plant tissues are most delicate. Corn farmers are often spraying by the end of April and sometimes into July for late corn, which poses a hazard to grapes. Bob Anderson, our extension agronomist in Lancaster suggests that knowing the crop and the weed complex is essential to formulating a spray strategy that will accommodate both field crops and grapes. The main weed problem for field crop growers are perennial weeds such as Bindweed and thistles. Annuals like Lambsquarter, Pigweed and Velvet Leaf are not as difficult to control but still a problem. Most farmers use a pre-emergent for early control in the spring, but the perennials grow past this and need additional control going into the summer. It is possible to use Atrazine in heavy doses but this can be damaging to vineyards if any residual finds its way to grapevine roots. Atrazine, as well as many other herbicides used on field crops, are not registered for use on grapes.

Possible Alternatives

The following are some possible alternative herbicide programs for field crop farmers. You can use these suggestions as a foundation for a civilized discussion with your neighbor.

While Dicamba products (Banvel) are generally considered harmful to vines, there is an alternative formulation that you can suggest to your neighbor called Clarity. It has 16x less drift potential than Banvel but still is not recommended for use near vineyards.
Other postemergence chemical alternatives include Buctril, a broadleaf herbicide that is used on corn and turf. It has limited success on broadleaves, slightly better on annuals. Hornet is a post-emergent that gives excellent control of thistles but is not as good on bind weed. Hornet contains some Stinger - which is another chemical alternative for broadleaves. All of these herbicides are more expensive than the widely used 2,4-D products.
Another possible alternative control program is to use a mixture of herbicides such a single application of Exceed plus Buctril. This is a very good program, in fact, better than the standard 2,4-D program for controlling perennials. Its expensive, however, at about $16 per acre compared to $4-5 per acre for Banvel. If cost is an issue, you might consider negotiating a cost share program with your neighbor. Its worth it to protect your grapes.
Another possible solution is to ask your neighbor to plant Round Up Ready corn or soybean in fields that are adjacent to your vineyard, instead of the conventional seed products. Roundup is much less subject to drift and volatilization and can be safely applied on calm days, preferably during the cool and damp morning hours. Roundup Ready corn products are licensed through Monsanto and widely available under other names such as Dekalb, Mid Atlantic, Chem Gro, Garst and others. Roundup Ready soybean is even more readily available. And, a Roundup herbicide program is comparable in cost to the conventional program, however, the seed may be more expensive. This may be the safest alternative strategy as it avoids the use of 2,4-D completely.

Communicate with your neighbors

I encourage vineyard owners to make every effort to cooperate with your neighbors. During the winter, meet with them for lunch or over a cup of coffee and educate them about the damage that drift causes, both economic and to the plant. Be explicit about the potential economic loss, all farmers understand these numbers. Make a plan. Decide what materials might be less harmful to grapes and when to apply them with the least risk to the vineyard, not only the time of season but the time of day. Set specific weather condition parameters within which it is safe to spray. Use nozzle technology that will reduce drift.

Consider alternative crops or Roundup Ready products. And, above all, keep in contact. Ask the farmer to call you the day before he or she plans to use a 2,4-D or Dicamba product. If there is a significant cost difference in the alternative materials you have agreed to use, you might offer to help offset the additional cost. Remember, its your crop that is at risk. If damage occurs, before you call PDA, invite your neighbor to come see the damage.

The grotesque appearance of 2,4-D damage on vines is often very persuasive when trying to convince a neighbor to cooperate. Keep good records of all observations and spray schedules, including your own. Many farmers hire contract applicators to spray their fields. It is the applicator who is ultimately responsible for the final destination of the applied pesticide.

PA has no tolorance for drift

Pennsylvania has very strict laws governing the distribution and use of pesticides. There is a ZERO tolerance for drift. You can look at all the statutes governing pesticide use on line at www.pacode.com. Look under Title 7, Chapter 128.103 g) A person may not use a pesticide in a manner which results in unwanted residues on the property of another, except in the case of easements or right-of-ways or when done under the direction of a governmental entity to protect the health and welfare of the public.

The Grape Herbicide Act of 1964 allows the secretary of agriculture to designate a region as pesticide free - the only example to date regulates the use of certain pesticides in Erie County.

Who to call

If a vineyard is affected by herbicide drift, contact your regional office of the Bureau of Plant Industry, which is part of the Department of Agriculture.

An agronomic inspector will come out to look at the damage and take tissue samples to determine what chemical caused the damage. An attempt will be made to locate the source of the offending drift and a warning or civil penalty may be issued.

It is crucial that you contact PDA as soon as you suspect a problem as possible. Chemical evidence begins to degrade as soon as the product is applied. Records and witnesses are very helpful. Punishment can be based on violation of label instructions or just poor judgment. The PDA will handle this process in its entirety. Contact Joe Uram at PDA for more details at 717 772-5212.

This is one situation where preventative measures are by far the best strategy for control. Once you sustain herbicide damage, there are no remedies. It is possible to grow grapes without suffering damage from herbicides. Care and cooperation is necessary.

I'd like to thank Jan Waltz, Dwayne Weaver, Bob Anderson, Ed Hellman, Tim Elkner, Bill Hoffman, Barb Bowlingt, Joe Uram, John Lake and Ron Serfass for their help on this article.