Changes in leaf structure and control of Conyza spp. by herbicides applied in the presowing desiccation of soybean

Abstract

Abstract The presowing desiccation of Conyza spp. is an important practice to reduce weed competition with soybean, and the applications of post-emergent herbicides, as an alternative to 2,4 D, promote changes in the leaf anatomy of horseweed. The objective of the present study was to evaluate the effect of post-emergent herbicides on the leaf structure and chemical control of Conyza spp. with heights greater than 10 cm in soybean presowing desiccation. A field experiment was conducted following a randomized block design, with seven treatments and four replicates. For the control data, only mesotrione + atrazine and chlorimuron resulted in control percentages lower than 80%. Regarding scanning electron microscopy (SEM), trichomes showed higher density in the adaxial part and stomata in the abaxial part, although they were present on both sides. Both trichomes and stomata showed clustering and random distribution tendencies. The control and halauxifen + diclosulam showed greater intensity of trichomes and less damage to these structures, while fluroxypyr + clethodim, dicamba and tryclopyr showed lower intensity. Therefore, fluroxypyr + clethodim and tryclopyr, dicamba and halluxifen + diclosulam were effective in the desiccation of Conyza spp., and the first two caused disruption of the trichomes due to plasmolysis.