Response of Soybean, Cotton, and Tobacco to Volatility of 2,4-D and Dicamba Formulations in Humidome

Abstract

2,4-D and dicamba are postemergence herbicides widely used to control broadleaf weed species in crop and non-crop areas in the United States. Currently, there are multiple formulations of 2,4-D and dicamba available in the market. Even though the active ingredient is the same, the chemical form may vary by formulation, which can influence the volatility potential of these herbicides. Therefore, the objective of this study was to evaluate the response of soybean, cotton, and tobacco plants exposed to vapor of 2,4-D and dicamba formulations alone or mixed in humidomes for 24 h. Humidome studies were conducted in an open pavilion at the Lake Wheeler Turfgrass Field Lab of the North Carolina State University in Raleigh, NC. Dicamba and mixture treatments injured and affected height of soybean. Injury varied from 55% to 70%, and average plant height was 8.8 cm lower when compared to the untreated control. 2,4-D treatments caused the lowest injury in soybean (≤ 21%), and differences among formulations were identified (dimethylamine > choline > dimethylamine-monomethylamine). However, soybean height was not affected by 2,4-D treatments. No differences between herbicide treatments were observed for cotton. The highest injury in tobacco was caused by dicamba dimethylamine (23.3%). Overall, the effect of 2,4-D and dicamba vapor was species-specific and formulation-dependent. Additionally, weather conditions in the humidomes possibly played a major role on the outcome of this study.