Enhanced Fusarium solani f. sp. phaseoli Infection by Bean Fly in Malawi. D. K. Letourneau, Environmental Studies, College Eight Academic Building, University of California, Santa Cruz 95064. W. A. B. Msuku, Crop Production, Bunda College of Agriculture, University of Malawi, P.O. Box 219, Lilongwe, Malawi. Plant Dis. 76:1253-1255. Accepted for publication 3 August 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-1253.

Field samples of beans on subsistence farms in Ntchisi, central Malawi, showed a correlation between the incidence of Fusarium solani f. sp. phaseoli and the presence of bean fly (Ophiomyia complex) puparia. Exclusion experiments in the field and greenhouse measured the rate of F. s. phaseoli infection in beans subjected to and protected from bean fly attack. Results indicated that F. s. phaseoli infection was significantly higher in plants exposed to bean fly attack than in those protected from bean flies. Malawian farmers may need to alter nitrogen fertilizer practices to keep bean fly and F. s. phaseoli levels low.