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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #294763
Title: A meta-analysis on the effects of 2,4-D and dicamba drift on soybean and cotton

Author
item Egan Jr, John
item BARLOW, KATHRYN - Pennsylvania State University
item MORTENSEN, DAVID - Pennsylvania State University

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2013
Publication Date: 1/20/2014
Citation: Egan Jr, J.F., Barlow, K.M., Mortensen, D.A. 2014. A meta-analysis on the effects of 2,4-D and dicamba drift on soybean and cotton. Weed Science. 62(1):193–206. doi:10.1614/WS-D-13-00025.1.

Interpretive Summary: New types of genetically-modified crops with resistance to the herbicides dicamba and 2,4-D will allow farmers to use these compounds with greater flexibility to control weeds without harming their crops. Expanded use of dicamba and 2,4-D could lead to an increase in herbicide drift, where herbicides move off of the crop fields they are applied to and damage sensitive crops including soybean and cotton. In this analysis of many previously published experiments, we found that substantial yield losses can occur especially when soybean and cotton are exposed to these herbicides during critical growth stages. Farmers and applicators using dicamba and 2,4-D need to be cautious of susceptible crops in nearby fields, apply herbicides only under appropriate, low-wind weather conditions, and use coarse droplet nozzles and other drift-reducing application technologies.

Technical Abstract: Commercial introduction of cultivars of soybean and cotton genetically modified with resistance to the synthetic-auxin herbicides dicamba and 2,4-D will allow these compounds to be used with greater flexibility but may expose susceptible soybean and cotton cultivars to non-target herbicide drift. From past experience, it is well known that soybean and cotton are both highly sensitive to low-dose exposures of dicamba and 2,4-D. In this study, a meta-analysis approach was used to synthesize data from over seven decades of simulated drift experiments in which investigators treated soybean and cotton with low doses of dicamba and 2,4-D and measured the resulting yields. These data were used to produce global dose-response curves for each crop and herbicide that plot crop yield against herbicide dose. The meta-analysis showed that soybean is more susceptible to dicamba in the flowering stage and relatively tolerant to 2,4-D at all growth stages. Conversely, cotton is tolerant to dicamba but extremely sensitive to 2,4-D, especially in the vegetative and the pre-flowering squaring stage. Both crops are highly variable in their responses to synthetic auxin herbicide exposure, with soil moisture and air temperature at the time of exposure identified as key factors. Visual injury symptoms, especially during vegetative stages, are not predictive of final yield loss. Global dose-response curves generated by this meta-analysis can inform guidelines for herbicide applications and provide producers and agricultural professionals with a benchmark of the mean and range of crop yield loss that can be expected from drift or other non-target exposures to 2,4-D or dicamba.