Seletividade e eficiência de herbicidas no controle de plantas daninhas na cultura do feijão-caupi

A lack of knowledge about herbicides for chemical weed control is one of the major difficulties for the expansion of the cowpea crop in the mid-south region of Brazil. Aiming to evaluate the selectivity and efficiency of herbicides for cowpea crop, two field experiments, one of them with BRS Guariba and the other with BRS Novaera, were carried out in Botucatu, São Paulo, Brazil. In both experiments, the experimental design was a randomized block, in a 3 x 2 + 2 factorial scheme, with four replications. The treatments were a combination of three herbicides (bentazon, fomesafen, and diclosulam) and two application times (early and late), besides a weeded control and a non-weeded control. The herbicide diclosulan provided high phytotoxicity and reduced plant population, while bentazon provided the lowest levels of phytointoxication in both cowpea cultivars. The fomesafen, especially when applied in the initial phase, was the most effective in controlling weeds and even causing phytotoxicity to cowpea crop, provided adequate population of plants and grain yield similar to those obtained in the weeded control. Thus, it is concluded that the herbicide fomesafen is the most efficient to both cowpea cultivars.