Most vegetable and fruit farmers have probably experienced crop injury from glyphosate spray drift at one time or another. The most recognizable name in this class is Roundup along with several other glyphosate products such as Acquire, Glystar Plus, Rodeo and Touchdown.
The glyphosate group provides good control to a wide variety of broadleaves and grasses with no residual effects to the soil. The low doses of glyphosate involved in drift may cause little or no injury and often go undetected. Depending on the crop species, glyphosate can be much less toxic than 2,4-D or dicamba, herbicides that are becoming much more important in agronomic crop weed management.
During spring 2013, grapevines in nearly every vineyard we have visited show symptoms of 2,4-D injury. Isolated vineyards, that are not anywhere near corn or soybean fields are in the minority without herbicide injury symptoms.
In at least one vineyard, drift from a nearby soybean field resulted in a complete crop loss. 2,4-D use in burn downs to kill marestail in nearby grains fields was a common factor across most of the vineyards with drift-injury symptoms.
Despite the windy and wet weather this spring, it is unlikely that environmental conditions were the major role in the high incidence of drift detection in vineyards. Rather it is the extreme sensitivity of grapevine leaves and bloom to 2,4-D, compared to the species relative tolerance to glyphosate, that is at play.
Depending somewhat on the species, broadleaf plants are 100 times or more sensitive to 2,4-Dthan to glyphosate.
Crop field burn downswith herbicides are mostly completed before the transplanting of sensitive crops like field grown tomatoes which usually occurs at the end of May. However with the imminent introduction of 2,4-D- and dicamba tolerant soybeans, the time of herbicide use will extend through June and into July. This coincides with a period of intensive vegetable crop establishment and growth.
The days of escaping the impact of occasional herbicide drift are likely to be over soon and it is important to become informed, and to inform your grain farming neighbors and commercial applicators who will be using this new herbicide combinations.
The injury from the combination of these herbicides will also have more severe effects on sensitive crops such as vineyards, field and greenhouse tomatoes. Look at the surrounding trees and landscape bordering a field that has been burned down with herbicides for herbicide injury symptoms
Know the symptoms of 2,4-D and dicamba injury on your crops and plan on scouting regularly during the time when grain growers are spraying. Early symptom detection within a few days of drift is important if you hope to detect residues of the causal agent – a data point of great value in obtaining compensation.
Inform your neighbors about the high dollar value per acre of the crops you grow and of their extreme sensitivity to trace amounts of 2,4-D and dicamba. Herbicide concentrations as little as 1/1000th of a field rate can cause symptom development.
Help them to understand that you will be financially forced to seek compensation should drift symptoms occur in your fields.
Starting in 2014, Pesticide Education Programs we will be conducted with sessions on Crop Sensitivity and Herbicide Drift aimed primarily at grain growers, their advisors, elevator operators, and custom applicators. Help us spread the word and let’s get ready to keep drift from happening.
Comments and questions regarding this article are welcome. Please email Doug at Doohan1@osu.edu
Reprinted with permission of The Ohio State University. To see the original story by Dr. Doug Doohan,OSU/OARDC Horticulture Dept. and Dave Scurlock, OSU/OARDCViticulture Outreach Specialist, which contains excellent photos of herbicide drift damage, see: www.oardc.ohio-state.edu/grapeweb/ This story was in the July 31, 2013 edition of the Ohio Grape-Wine Electronic Newsletter. (The publication date is necessary to find the article on the OSU website.)