Crop Sensitivity to Dicamba and 2,4-D Applied at Commercial and Subdose Levels

Abstract

The development of dicamba and 2,4-D resistant crops may result in the widespread use of these herbicides in agricultural areas, potentially affecting nearby susceptible crops. This study aimed to evaluate the sensitivity of bean, peanut, and cotton to different doses of Dicamba and 2,4-D. To do so, separate experiments were conducted for each crop and herbicide in a greenhouse, using a completely randomized design with four replications. Both herbicides were applied at different doses to plants with the second pair of true leaves. Phytotoxicity and dry biomass were evaluated. For cotton, 2,4-D showed high phytotoxicity at doses of up to 83.75 g ai ha−1, with a reduction in suppressive effect observed at 20.93 g ai ha−1. Dicamba exhibited a pronounced reduction in crop biomass up to a dose of 70 g ai ha−1, with 94 % phytotoxicity. For beans, the evolution of symptoms using 2,4-D occurred more slowly, but the highest doses resulted in phytotoxicity of up to 95 % and a 30 % reduction in biomass at 167.5 g ai ha−1, indicating a significant impact on the crop. Dicamba also had a high negative impact, with a 100 % reduction in biomass at 70 g ai ha−1. The peanut crop was more tolerant to herbicides, with 2,4-D doses of 670, 335, and 167.5 g ai ha−1 resulting in phytotoxicities of 69.5, 37.49, and 14.37 %, respectively. Dicamba significantly reduced dry biomass at doses of up to 70 g ai ha−1. The results show that, despite the differences in sensitivity of cotton, bean, and peanut to 2,4-D and Dicamba, even low doses of these herbicides applied early in development had a significant negative impact on these crops.