Effect of powdery mildew on yield of the common bean crop

Abstract

Presently the common bean crop has been intensified during the Autumn-Winter season, with the purpose of exploring the growing areas for a longer period of time. In this planting time the occurrence of powdery mildew (Erysiphe polygoni) should increase due to the favorable environmental conditions. This study was carried out aiming at verify the effect of this pathogen on yield of common bean (Phaseolus vulgaris). For each cultivar a separate experiment was conducted, with and without chemical treatment, during two sowing times, April and August. In each experiment three treatments were evaluated: inoculation at 20, 30, and 40 days after sowing, with seven replications. The effect of the pathogen was more conspicuous as earlier was its occurrence, with average reduction on yield of 50% and 40% in cultivars Eriparza and Rio Vermelho, respectively, independently of the time the experiment was done. Results show that, to continue common bean sowing during this time, powdery mildew could become a pathogen of great nocivity to the economy.