Future Herbicide Injury Concerns Winegrape Growers
January 30, 2017 
Dicamba injury is seen on a secondnd-leaf grapevine in the Texas High Plains in 2016. (Photo credit: Ed Hellman)
Spray drift is something growers worry about constantly, especially on smaller parcels of land which are near other farmland. As herbicide resistance becomes a greater concern, newer formulas of herbicides are released to offer growers another option to combat resistant broadleaf weeds.
These new dicamba formulations, such as a Monsanto product called Xtendimax with VaporGrip, are said to offer lower drift potential. Another is Dow’s Enlist Duo with 2,4-D and glyphosate with Colex-D technology to also reduce drift. EPA recently amended the current registration for Enlist Duo to make it available in 19 additional states for use on treated corn, soybean, and cotton crops.
“If cotton farmers use Xtendimax according to label directions for use, and are especially cautious near sensitive crops like grapevines, there is will be a low risk of injury to vineyards,” says Ed Hellman, Professor of Viticulture with Texas Tech University.
However, with the release of dicamba-resistant cotton and soybean varieties, specialty crops growers fear cotton and soybean growers will opt for older dicamba products on the market instead of newer dicamba formulations. These new crop varieties require the use of new formulations, but they will likely be more expensive than older formulations.
“The current concern is that row crop use of both 2,4-D and dicamba is expected to increase dramatically in 2017 now that cotton varieties tolerant to these herbicides have been approved for use by EPA,” he says. “This enables cotton farmers to spray either 2,4-D or dicamba, depending on which herbicide-tolerant variety they grow, during most of the growing season rather than only before planting as has been the case previously. From strictly a probability standpoint, it seems likely that increased usage of these herbicides is likely to result in more incidences of off-target spray drift damage to vineyards.”
In fact in 2016, EPA received 117 complaints of dicamba injury in Alabama, Arkansas, Illinois, Kentucky, Minnesota, Mississippi, North Carolina, Tennessee, and Texas. In Missouri alone, EPA reports damage from dicamba misuse was reported on more than 42,000 acres of crops including peaches, tomatoes, cantaloupes, watermelon, peas, and other row crops. Hellman says there were several suspicious incidents of dicamba injury to vineyards in the Texas High Plains last year.
In light of these reports, EPA released a compliance advisory which stated “The EPA has not registered any dicamba herbicides for application at planting or over the top of growing cotton or soybean plants, including crops genetically modified to tolerate dicamba.”
Herbicide-Exposed Vines
Although the severity of dicamba damage to exposed vines varies, grape leaves can be stunted or malformed, which Hellman characterizes as an “upward cupping.” He says shoot growth is stunted and shoot tips can be killed, too.
“If 2,4-D or dicamba exposure occurs during grapevine bloom, fruit set can be reduced. Damaged vines are less able to fully ripen fruit, and a weakened condition may make them more susceptible to other stresses,” he says.
As damaging as 2,4-D and dicamba exposure is, Hellman says this is nothing new to Texas winegrape growers — spray drift is an issue they’re very aware of. In fact, Hellman is a member of the Texas Wine and Grape Growers Association’s 2,4-D Committee.
“2,4-D has commonly been used by row crop farmers practicing no-till or minimum tillage practices and spray drift damage to vineyards has sometimes occurred,” he says. “Reduced tillage row crop farmers use 2,4-D to clean up winter weeds before planting crop seeds. If the row crop farm is near a vineyard and herbicide spraying is done carelessly after grapevines have broken bud, there is the potential for vine injury.”
What Can a Grower do?
A recent story from the Fort Worth Star-Telegram paints a bleak future of the Texas winegrape industry in light of these new formulations. However, researchers and industry groups say the purported demise of the winegrape industry is premature. That’s not to say growers aren’t concerned. But no winegrapes in Texas? That’s a gross overstatement.
These industry groups and researchers say outreach to row crop growers is necessary, and it’s been something Texas grape growers have been working toward, Hellman says.
“Grape producers have worked hard, and mostly successfully, at developing good relations with their neighbors to prevent such accidental off-target spray damage,” he says.
In fact, Andy Timmons, president of the High Plains Wine Growers Association, cites an old proverb of “being a good neighbor increases the value of your property,” when responding to the Star-Telegram’s story on the High Plains Wine Growers Association’s Facebook page. It’s that exact outreach that Timmons says the winegrape industry needs to understand — unlike in other major American Viticultural Areas (AVAs), in the High Plains AVA, row crop and winegrape growers are often one in the same. Singling out a commodity won’t help the end return, he says.
“Many of our largest grape growers are also large scale row crop producers as well,” he says. “We share school boards and church pews as well as the sky above and the dirt below. Each instance is site- and circumstance-specific and that can seem formidable. Together we are responsible and through transparency, communication, and advocacy we’ll go forth.”
Hellman says concerned growers “can also appeal to local retailers of pesticides to be more cautious about selling old, more volatile formulations of dicamba.”
Moving Forward
Hellman says the Texas Wine and Grape Growers Association and its 2,4-D Committee is considering the introduction of legislation to help specialty crop growers.
“The Texas Wine and Grape Growers Association is considering proposing state legislation to restrict the use of these herbicides near sensitive crops. This approach is still under discussion,” he says. “Texas Wine and Grape Growers Association will continue to educate grape producers and the general public about the issue of herbicide spray drift damage.”
Timmons says working together is vital to the Texas agriculture industry.
“It’s important that [consumers] see our two ag sectors coexisting together — versus at opposition. Row crop commodities have made much larger and longer term financial contributions than our new specialty crop.”
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