Resistência de genótipos de milho a densidades de Sitophilus zeamais (Coleoptera: Curculionidae)

Abstract

Sitophilus zeamais is the main pest of stored corn grains, causing millions of economic losses annually. As it is difficult to control, an alternative that has been studied is the resistance of plants, which affects the behavior and biology of the insect, which can lead to death. The objective of this work was to identify the resistance of varieties of Creole corn to densities of S. zeamais. Densities of 15, 20, 25, 30 and 35 adult insects were used for infestation in samples of four varieties of corn: Nutricional Embrapa, Milho Roxo, 8 Carreiras and Palha Roxa, for ten days for copulation and oviposition and were removed after thirty days. The following evaluations were carried out: number of emerged insects, loss of grain weight, insect weight, longevity and sex ratio. The corn varieties Milho Roxo and 8 Carreiras were resistant to the attack of S. zeamais, as they presented the least number of emerged insects and the smallest loss of grain mass. Purple corn still showed an elongation in larval development. The Nutricional Embrapa varieties and Palha Roxa are susceptible. The lowest insect weight was found for 8 Carreiras, a result that may have occurred due to the action of amylase inhibitors present in the grains. Longevity was observed only for Milho Roxo and Nutricional Embrapa corn. Milho Roxo Corn had higher averages for longevity in the density of 15 and 20 insects, decreasing from 25 insects, thus suggesting that longevity is affected by the number of insects during infestation. The sex ratio had no interaction between insect densities and maize varieties, but in isolated factors, increasing densities increased sex ratio. The varieties that had the highest sex ratio were Milho Roxo corn and Embrapa Nutricional, thus showing that the sex ratio is not affected by resistance. The corn varieties Milho Roxo and 8 Carreiras show resistance by antibiosis, so they can be used for future studies for genetic improvement and obtaining new efficient cultivars in the control of S. zeamais.