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Justin Keay
University of Missouri
(636) 970-3000

Herbicide Drift and Specialty Crops

Justin Keay
University of Missouri
(636) 970-3000

July 10, 2023

minute read

A statewide interview of Missouri specialty crop growers occurred in 2019, as part of a research project titled The Economic Viability of Expanding Fresh and Processed Fruit and Vegetable Production in Missouri1. Growers indicated that herbicide drift is a serious barrier to fruit and vegetable production expansion in Missouri and emphasized the investment risk associated with high-value specialty crop acreage. Some growers mentioned losing markets for their specialty crops because they couldn't guarantee their clients that their produce was free of herbicide drift.

MU Extension Horticulture Specialists receive calls from across Missouri every year related to suspected herbicide damage in home gardens and fruit and vegetable farms. The cost of an herbicide drift event can be substantial even on small plots of high-value specialty crops.

Protecting Crops from Drift

Communicating with neighbors is a key step in preventing herbicide drift. Inform neighbors of the presence of sensitive high-value crops, and that crop damage or total loss can occur from drift events.

Specialty crop growers are encouraged to use the website driftwatch https://driftwatch.org/, to register the location of their specialty crop fields. Pesticide applicators are encouraged to view the driftwatch website prior to application of pesticides, to locate sensitive sites that may be impacted by their application. However, pesticide applicators are only required to consult with driftwatch if using approved over the top herbicides containing dicamba, including Engenia, Xtendimax, and Tavium. The driftwatch website also sells signage to put at field borders to alert neighbors and applicators of the presence of sensitive crops. The high-contrast signage contains language such as "Specialty Crop DO NOT DRIFT". If assistance is needed in registering specialty crop fields on driftwatch, contact the local MU Extension office.

Windbreaks may be planted at field borders to reduce wind speeds across the landscape. It is possible that windbreaks may offer some protection from herbicide drift, however best management practices related to species selection and windbreak design for herbicide risk mitigation have not been extensively studied. The USDA Natural Resource Conservation Service offers technical resources related to windbreak design, as well as cost-share practices for windbreak plantings that protect soils and crops from wind effects. Contact the local USDA office for more details.

Identifying Signs of Drift

When a drift event occurs, it is common to see an abrupt change in crop appearance across an entire planting of a crop, and possibly across several or all crops. The two most common culprits are the broadleaf herbicides Dicamba and 2-4,D. An occurrence of a drift event on a specialty crop farm can cause a major loss of investment and income, especially when considering perennial fruit crops.

Some of the crops that are most sensitive to common broadleaf herbicides include tomatoes, as well as legumes such as green beans and peas. Growers might notice that leaves of plants begin cupping upward and appear distorted in shape. Plants may die, and surviving plants are likely to have decreased yields. Following an herbicide drift event, leaves on a tomato plant may be curled upward, and new growth may show leaf elongation and parallel veination.

The source of Dicamba and/or 2-4,D may include drift from neighboring crop fields, pastures, utility right-of-ways, ditch/shoulder maintenance on highways and roads, as well as lawns and turf.

There are 2 ways that Dicamba and/or 2-4,D can move off-site and damage neighboring crops. One way is known as particle drift, where spray-droplets are moved across the landscape in wind, this happens at the time of application. The 2nd way is what is known as volatilization, where herbicide residue turns into a gaseous vapor that moves across the landscape. This occurs most commonly during inversion events. Inversion occurs when air near the soil surface is cooler than air higher in the atmosphere. As the vapor rises from the foliage or plant residue it is trapped in cooler and denser air near the soil surface. The vapor then travels across the landscape where it can damage sensitive crops and plants. This contrasts with non-inversion conditions, where vapor travels upwards into the atmosphere. Herbicide drift is most likely to come from adjacent/neighboring fields, while volatilized herbicide can travel much farther offsite.

If it suspected that crops might have been impacted by herbicide drift, reach out to the local MU Extension office to connect with the Horticulture Specialist. The Horticulture Specialist will assist in ruling out other potential causes affecting plant appearance, such as physiological leaf roll, an environmental disorder caused by high winds that can cause tomato leaves to curl upward.

Documentation and Recordkeeping

When suspected drift occurs, it is recommended that several actions be taken as soon as possible to record information related to the event. Gathering information is important whether seeking to only discuss with a neighbor, the incident is reported to the Missouri Department of Agriculture and/or pursuit of civil action is taken. Information recommended for records includes the date of application (if known), weather conditions at the time of application, and the date symptoms of drift were identified. It is suggested to take time-stamped and geo-tagged photographs of affected crops. Consider record the quantity of crops affected, as well as expected yields and sales revenue. Gather historical data from the affected farm related to yields and sales prices. Broadleaf herbicides can degrade in the environment within several weeks and may become undetectable when analyzed. Samples of plants damaged by drift need to be taken as soon as possible and placed in a zipper storage bag in the freezer.

Talk to Neighboring Farmer(s)

Prior to filing a pesticide incident with the Missouri Department of Agriculture, or pursuing civil action, growers may choose to talk to neighboring farms that they suspect may have been the source of a drift event. In some cases, identifying the site where pesticide drift has occurred can be challenging. Talk openly with neighbors about concerns and inquire what herbicides were applied to neighboring fields, and when they were applied. These conversations will allow for a better understanding of the possible sources of a drift event, prior to laying blame on a neighboring farmer. Affected growers may work with neighbors to resolve the situation through financial compensation related to the loss of investment and income from affected crops. Working with neighbors can lead to a resolution both parties are satisfied with, and lead to better communication in the future about application events. Resolving issues with neighbors negates the need to hire an attorney, saving legal costs that may surpass the value of the lost or damaged crop.

Reporting Drift Events to the Missouri Department of Agriculture

To file an Pesticide Incident Report with the Missouri Department of Agriculture, visit https://agriculture.mo.gov/plants/pesticides/incidentreport.php for an electronic submission portal, or call (573) 751-5504 to request that a form be mailed. If it is suspected that 2-4,D or Dicamba is the culprit, communicate this specific information to the Missouri Department of Agriculture within the report submission. Pesticide incidents must be reported within 30 days of the suspected drift event. If through investigation Missouri Department of Agriculture staff determine that herbicide drift is likely to have occurred, plant samples will be taken for laboratory analysis of suspected pesticides. If a pesticide applicator is found to be in violation of the Pesticide Use Act2, warnings or fines may be issued. Missouri Department of Agriculture does not work with affected parties to obtain restitution for damages and/or losses.

Pursuing Civil Action

If a resolution cannot be made with a farm that is the source of a drift event, growers may choose to pursue civil action. The costs and benefits of pursuing civil action against a neighboring farm for crop losses related to drift, need to be weighed prior to taking action. Considerations related to the value of the crop loss and the cost of attorney fees are part of this decision process. If a decision is made to pursue civil action, it is recommended that consultation with an attorney proceed as soon as possible. An attorney may request that collected samples from affected plants be sent to a private lab for analysis, contact the lab prior to shipment to determine costs and best practices for shipping plant samples. If assistance is needed in identifying a lab, contact the local MU Extension office.


1The Economic Viability of Expanding Fresh and Processed Fruit and Vegetable Production in Missouri - Interview Summaries, Marketing, Outlook, and Next Steps - John Kruse and Peter Zimmel University of Missouri - Columbia https://fapri.missouri.edu/wp-content/uploads/2023/05/Part-1-The-Economic-Viability-of-Expanding-Fresh-and-Processed-Fruit-and-Vegetable-Production-in-Missouri.pdf

2Missouri Pesticide Use Act - https://agriculture.mo.gov/plants/pdf/pesticideuseact.pdf

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REVISED: July 11, 2023