Incidência de podridão de colmo e grãos ardidos em híbridos de milho cultivados sob diferentes densidades de plantas e épocas de colheita

Abstract

Corn is a cereal of great importance worldwide and its use goes from the feed to hightech industries. Brazil is the third largest producer of grain, but the average yield is still considered low, about 4500 kg ha?¹. Among the factors that can limit the production of corn are diseases, which has caused huge losses to producers due to different production systems, together with the continuous cultivation, expansion of cropping seasons, use of susceptible cultivars, tillage, increased plant population, indiscriminate use of pesticides, among others, and the lack of crop rotation and planting of second crop contribute to the increased survival of pathogens in the field. Besides foliar diseases stand out also stalk rot and ear rot, the latter responsible for the production of damaged kernels. As control methods damaged kernels can be used genetic resistance, considered an efficient method, plant density and harvest time. The objective of this study was to evaluate the incidence of damaged kernels, stalk rot and yield of three maize hybrids grown at three plant densities, with two harvest seasons. The experiments were conducted in Guarapuava - PR and Sete Lagoas - MG in crop 2011/2012. The experimental design was a randomized block design with three replications in a factorial arrangement of three 3 x 3 x 2 (hybrids x plant densities x harvest season). Evaluated the incidence of stalk rot (%) and damaged kernels (%), grain sanity by Blotter test with freezing, grain yield (kg ha?¹) and 1000 grain weight (g). The highest yielding hybrids in experiments in Guarapuava and Sete Lagoas were the DKB 390YG and Status TL, respectively. In both experiments the incidence of damaged kernels was lower when the harvest was anticipated. The plant density did not influence the incidence of damaged kernels in either experiment, but increased the incidence of stalk rot. The fungus was prevalent in asymptomatic grains Fusarium spp.