EFFECTS OF REDUCING INTERPLANT COMPETITION AT DIFFERENT STAGES OF GROWTH ON STALK ROT AND YIELD COMPONENTS OF CORN

Abstract

Stress effects on stalk rot and yield components of corn (Zea mays L.), arising from interplant competition, were, studied by removing at various times either the competing plants or the developing ears. The number of ears per plant and the number of kernels per ear at harvest were greater when plants were thinned before mid-silk, but the only yield component associated with stalk rot was 1000-kernel weight.Removal of alternate plants at any time up to 4 weeks after mid-silk greatly reduced the proportion of plants developing stalk rot. In plots thinned less than 4 weeks before physiological maturity, the incidence of stalk rot increased progressively as thinning was delayed. Similarly, up to 1 month before physiological maturity, stress had little effect on weight of individual kernels but when the stress was continued into the month which preceded physiological maturity, individual kernel weights were substantially decreased. Ear removal 3 weeks or more before maturity practically eliminated stalk rot whereas later removal had progressively less effect. Thus, the deleterious effects of stress from interplant competition and ear development had their maximum effect on stalk rot susceptibility and kernel weight during the month before physiological maturity.