Epidemiology and Control of Cowpea Rust Uromyces phaseoli var Vignae in Kenya

Abstract

Cowpea rust caused by Urornyces phaseoli var Vignae is a major factor limiting cowpea production in Kenya. Epidemiology and control measure studies were carried out on this disease. Investigations included studies on symptomatology, factors affecting uredospor.e germination, disease development, histopathology, disease progress in the field, spread and survival of the pathogen, host range of the fungus, varietal reaction of the different cowpea cultivars and chemical control. Germination of uredospores occurred within a wide range of temperatures, relative humiditY9 liquid media, and pH. However, the optimum conditions for germination were when the spores were mounted in sterile tap water dried and incubated at 200C and 100 percent relative humidity. Plant and leaf age affected disease development. The older the plant and the leaf, the Iess susceptible it was to cowpea rust. Uredosori developed within six to eight days after inoculation. Uredospores formed on the leaf pustules were spread to higher leaves on the same plant and to other plants through wind ·and probably by

contact. The pathogen survived only on infected

debris. Besides cowpea, the pathogen attapked ,Phaseolus aureus, MacroRtilium atropurpureum and Vigna parviflora. Varieties of cowpea differed significantly in their reaction to this rust and could therefore, be incorporated in breeding for disease resistance. Baycor and bayleton proved to be the best·fungicides in controlling cowpea rust in laboratory, glasshouse and in the field.