Chemical Control of Cowpea Powdery Mildew and Foliar Spots

Abstract

The fungicides chlorothalonil, mancozeb, dinocap, benomyl and Macuprax controlled foliar diseases of cowpea, such as powdery mildew (Erysiphe polygoni DC) and leaf spots (Corynespora cassiicola (Berk. & Curt.) Wei, and Cercospora spp.). Dinocap was very effective against powdery mildew during the dry season, but failed to protect the plants during rainy weather. Low dosages (0.28 kg/ha) of benomyl applied biweekly were enough to prevent infection by E. polygoni, C. cassiicola and Cercospora spp. It is suspected that a new race of E. polygoni, capable of thriving under high relative humidity and heavy rains, is present in the field. In addition, the erratic performance of benomyl in controlling powdery mildew suggests the existence of field races of the pathogen resistant to this fungicide.