The Fungus Causing Zonate Leafspot of Cowpea

Abstract

A disease of cowpea (Vigna sinensis (L.) Endl.), which has been designated here as the zonate leafspot (FIG. 1, A-B), was much in evidence, particularly in the Southern States during the 1943 growing season. The disease has been known for many years as a minor trouble of cowpea and the causal organism has been called Amerosporium oeconomicum Ellis & Tracy. One finds, however, that the fungus causing this leafspot has septate conidia, hence it does not agree with the description given by Ellis and Tracy (9, p. 102), and should not be referred to the genus Amerosporium. Because this leafspot of cowpea is so striking, many collectors have referred their specimens to Amerosporium, however, probably without a microscopic examination of the causal fungus. Since the leafspot is common, apparently wherever cowpeas are grown, and since so many have either wrongly identified the causal fungus or left their specimens undetermined, as indicated by the number being sent in for identification, both the disease and the causal organism appear to warrant further study.