Importance of the Husk Covering on the Susceptibility of Corn Hybrids to Fusarium Ear Rot

Abstract

The role of the husk covering and the influence of intra-ear thrips infestation on severity of Fusarium ear rot (Fusarium moniliforme) were evaluated in 1990, 1991, and 1992 among corn (Zea mays) hybrids previously rated as susceptible, intermediate, or resistant to Fusarium ear rot. For the three treatments imposed on individual corn ears in 1990, ears were either left untreated, wrapped with a strip of parafilm at the ear tip to maintain a tight seal, or husk layers were split open along one side of the ear I to 2 weeks after pollination to partially expose the developing kernels. In 1991 and 1992, two additional treatments, split husks followed by acephate insecticide application and insecticide application to ears with intact husks, were added. Split husks compromised the natural barrier to insects and fungi and significantly increased Fusarium ear rot severity among all corn hybrids in 1990 and 1991. In 1992, a year with naturally high levels of disease, split husks significantly increased disease severity among the resistant hybrids, but did not affect the susceptible hybrids. Acephate applied to ears with split husks reduced ear rot among all hybrids. Grain yields were significantly less in ears with split husks for all hybrids in 1990 and 1991, and for the resistant hybrids in 1992. Grain yields were higher for all insecticide-treated hybrids each year. These results demonstrate that susceptibility to Fusarium ear rot is influenced by both husk morphology and intra-ear thrips infestation.