Abstract

Historically, cowpea farming has been concentrated to the north and northeast of Brazil, and is usually cultivated with low level of technology. However, in recent years, there has been an increase in the area planted with the crop in the central west, using technology, and there is therefore now a need to study, among other factors, the chemical control of weeds. Two experiments were carried out with the aim of making a preliminary study during the vegetative phase of the cowpea, the first using pre-emergent herbicides and the second with post-emergent herbicides, in a greenhouse at the Federal University of Paraíba, in Areia, state of Paraiba, Brazil. The experimental design was completely randomized with four replications. The Relative Chlorophyll Content (SPAD index) was evaluated together with a visual evaluation of phytotoxicity. Promising results for selectivity in the cowpea were seen in relation to the herbicides under evaluation, whether applied prior to or after emergence of the crop. For weed control prior to crop emergence, the herbicides Diuron, S-metolachlor, Metribuzin, Diquat dibromide and Sulfentrazone gave promising results. In addition to these products, Clethodim and Haloxyfop-p-methyl should be noted as potential post-emergent herbicides.

Key words: Chemical control, phytotoxicity, tolerance, Vigna unguiculata, weed management.