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Off-Target Herbicide Drift Threatens Vineyards Across U.S.

by Michelle Williams
January 12, 2021

In 2018-19, Joe Juniper, owner of Vermilion Valley Vineyards and Ohio Vineyard Management, lost 5 acres of vines due to off-target drift. That’s because grapevines — from canopy to cluster — are readily affected by drift from the herbicides commonly used on their neighbors’ field crops.

Three of those lost acres were planted with Moscato Giallo, a grape so rare he has to wait until 2022 to get replacement wood. “The biggest issue was the way we were hit, leaving a patchwork of living and dead vines: living, dead, living, living, dead, dead, dead,” he said. It will take a decade for the fully replanted block to mature, with lost revenue extending years into the future. 

It’s not just a problem in Ohio. Off-target drift from Plant Growth Regulator (PGR) herbicides threaten vineyards across the United States. Despite years of complaints and court rulings restricting use, the Environmental Protection Agency (EPA) issued a decision on October 27, 2020, approving the use of dicamba, a PGR, through 2025, with some modifications. But an ongoing lack of EPA oversight, vague regulatory language, and loose controls on chemical manufacturers have led to confusion over use and tension in agricultural communities, pitting farmer against farmer. 

Decades of widespread farm use of Roundup, an amino acid inhibitor herbicide, led to resistant weeds, which prompted chemical companies to adopt PGR herbicides. This new class of chemicals mimics a plant’s natural hormones, resulting in abnormal growth and, eventually, death. They're now commonly used to control broadleaf weeds among genetically modified resistant row crops like corn, soybean, and cotton, as well as peanuts, turfgrass, rights-of-way, golf courses, rail lines, and even residential lawns.

Systemic in nature, the chemicals move from the absorption site to areas of rapid plant growth: the shoots. Two compounds commonly found in unison in PGRs are 2,4-Dichlorophenoxyacetic acid (2,4-D) and dicamba. While treated differently by the EPA and some court rulings, both chemicals are highly susceptible to volatilization, readily converting from a liquid into vapor. The volatilized chemicals can potentially drift for miles from their intended target. A salient point: Conscientious applications by farmers who follow the label explicitly, monitor weather and wind conditions, and communicate to the neighboring vineyards often still unintentionally cause off-target drift damage. 

Off-target drift from volatilization is devastating to neighboring broadleaf plantings: think grapevines. In 2018, Mike and Rosann Mitrione began to pursue their dream to make premium Texas wine, planting 37 total vineyard acres in the Texas High Plains AVA. They selected an elevated location, deep-ripped the soil, planted Sangiovese, Malbec, and Tempranillo and installed a vertical shoot positioning trellis system. But the vineyard immediately faced an invisible threat. 

Even after some trellising adaptation, off-target drift damage still cost the Mitriones 25 percent of the 37 acres they planted. “I must be prepared for off-target drift every vintage. And when it comes, it’s going to negatively impact my vines,” he shares. 

Larry Shrawder, proprietor of Stony Run Winery in Pennsylvania, vineyards have experienced a range of drift-induced symptoms, from leaves shriveling and curling up on the ends, which takes about four to six weeks to recover, to complete destruction of primary buds for next year’s crop. “Using 2,4-D and dicamba to kill weeds is like burning your trash with a thermo-nuclear weapon. It produces a lot of collateral damage,” he shares. Impacted by drift five years in a row, he has lost $1.4 million in revenue in 3 of those years alone.  

In response, Shrawder has modified his canopy management, limited dropped fruit, and modified bud cultivation. “We would like to be fine-tuning our vineyards and working on the finer points of sustainability, but instead we are constantly in survival mode from drift. Its doubling the amount of handwork, which doubles our costs, and we can’t be competitive if we have herbicide damage and our competitors don’t.”

In Iowa, a state largely associated with corn, there’s also a long tradition of growing wine and table grapes, but an Iowa State University study cites 2,4-D as a key cause in overall decline of grape production. Both ISU and Texas A&M Extension work with their states’ winegrowers on drift damage, offering voluntary survey programs noting location, varieties, rootstock, and extent of damage. They also seek to educate non-viticulture farmers about proper spraying techniques and crop sensitivity. 

In the Texas High Plains AVA, home to 80% of the grapes grown in Texas, cotton outnumbers vineyards three to one. In 2019, 99% of drift damage recorded throughout the state happened in that region. “In Texas, we want to be able to farm grapes and make wine from healthy grape vines without being constantly drifted on,” said Chris Brundrett, co-proprietor of William Chris Vineyards. “Row crop farmers are angry with grape farmers because they feel their livelihood is being threatened.” 

The recommendations in the EPA’s October 2020 memo offered little solace for vine growers. For example, the recommended expansion from a 240-foot downwind buffer to 310 feet seems inconsequential to the growers, even with pH-buffering to reduce volatility. 

Many growers have scoured the EPA website in search of the new but vaguely-cited scientific assessments. They came up empty-handed. “Unless the EPA can be clear to the public and non-targeted growers like myself how they came to their ruling, I am going to hold a grudge,” said Juniper, the grower in Ohio.

“I’m not enthused about EPA decision from a specialty crop perspective,” shares Joe Hannan, Commercial Horticulture Field Specialist for Iowa State University Extension and Outreach. “They have said many times the new iteration of the product will solve the problem. So far that hasn’t happened. The products seem to be volatile by nature.” 

Reporting every instance of damage, no matter how small, to a state’s Department of Agriculture aids in awareness and long-term impact. Research must be conducted on how PGRs impact grapevines—it cannot begin without data. 

Of the 170 cases reported to Texas A&M AgriLife Extension, 165 were in the Texas High Plains AVA. Questions of drift damage on a vine’s cold hardiness, impact on drought stress, variety, rootstock, and below-ground symptoms are a few unknowns. “There is no definitive handle on this in Texas,” said Justin Scheiner, Ph.D., Assistant Professor and Extension Viticulture Specialist for Texas A&M AgriLife Extension Service. “It was not a compelling research topic prior to the widespread damage. Now we are trying to catch up, and research moves relatively slow.” 

In Ohio, all 137 acres of Vermillion Valley’s vineyards have some degree of drift damage. Yet the Ohio Department of Agriculture, which does not currently record monetary loss or number of acres damaged by herbicide drift, has issued only three warnings and one civil penalty across the entire state for off-target drift damage since 2015. 

Karl Mohr, of Atlas Vine Management in Willamette Valley, believes the metrics are partly to blame. In 2015, their company lost 7.4 tons of grapes to drift damage, yet the Oregon Department of Agriculture reported no detection. Sending the same samples to a third-party lab confirmed the total loss using vine detection measurements. Whereas the State determines damage at 0.1 parts per million — the threshold for human harm — the grapes were clearly destroyed at merely 0.0039 parts per million. 

Grape growers are now issuing a resounding call to improve labeling on such products, and to educate row crop farmers — and even consumers — about how they’re affected by wind direction, temperature, and humidity. “People think these products are safe because they bought them at Walmart,” said Mohr. Yet each spring brings a new game of “Russian Roulette doling out PGR drift.” He wants winegrowers to stay noisy, keep in contact with neighbors, and crowd-share recommendations of non-volatizing chemicals where appropriate. Most importantly: “Hold the EPA accountable.” 

Larry Shrawder, the grower in Pennsylvania, said, “It’s a matter of everyone sitting down and deciding where we can and cannot use these products,” because they’re not appropriate everywhere. “You don’t let children play with guns,” he concluded. “You shouldn’t let farmers play with dicamba.” 



Editor's Note: The headline has been corrected to "Herbicide". Article has been edited for clarification and to include reference links.

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