Interference of post-emergent herbicides with wheat (Triticum aestivum L.) productivity parameters/ Interferência de herbicidas pós-emergentes sobre parâmetros produtivos do trigo (Triticum aestivum L.)

Wheat is the most important income-generating crop in southern Brazil during the cold season. It also contributes to the crop rotation system and increases the yield of successive crops. During its growth cycle, herbicides are used to control weeds, which are the main factor limiting wheat productivity. Further, high costs of weed control directly affect crop economic returns. The objective of this study was to evaluate the effect of the application of two herbicides, namely, 2,4-D and iodosulfuron-methyl, on the productivity of two wheat cultivars during the nine different stages of crop development. The most suitable crop stage for herbicide application, as described in the corresponding label on the package, is at the beginning of tillering. 2,4-D had a significant impact on productivity parameters, reducing the number of tillers, the number of ears, and the number of tillers without grains, while increasing the number of tillers without ears and ears without grains, indicating greater phytotoxicity and, ultimately, reducing crop productivity. Conversely, iodosulfuron-methyl showed greater selectivity to the wheat cultivars tested and caused a much lesser impact on the productivity parameters measured.