Associação de variedades resistentes de milho e fungos entomopatogênicos para o controle de Sitophilus spp.

Abstract

This work s objective was to associate strategies and control methods, aiming to minimize the damage caused by Sitophilus spp., in as much as it is considered the main pest insect in stored corn. Thus, corn cultivars resistant and susceptible to Sitophilus spp. attack were chosen through tests with chance of choice, to verify the feeding preference, and without chance of choice (confinement), where the insect s biology was analyzed, as well as the damage caused to the grains and the weight loss. Isolates of entomopathogenic fungi were selected through pathogenicity evaluations and lethal concentration, vegetative growth, conidia production in petri dishes, rice and in corpses. The susceptible and resistant C were associated to the selected isolates, and these were inoculated in the cultivars before and after the Sitophilus spp. infestation. It was verified that the cultivars CD 3121 presented resistence, increasing the duration of the egg-adult cicle, diminishing the number of emerged insects and diminishing the weight loss of the grains, and showed non-preference to feeding by Sitophilus spp., while cultivar CD 307 presented susceptibility and feeding preference to this insect. It was verified that all tested isolates were pathogenic to Sitophilus spp. Nevertheless, they differed about virulence, when 7 isolates caused at least 80% of confirmed mortality of this insect. Among these, the 3 that presented higher accumulated mortality at the 5th day after inoculation were selected: Unioeste 4, Unioeste 39 and Esalq 643. However, just isolates Unioeste 4 and Esalq 643 were selected to be associated to the cultivars, because they presented the best results on the realized tests. Analising the association between the isolates and the cultivars, higher control of Sitophilus spp. was verified, independent of the grain treatment strategy. The association caused an increase in the duration of the duration of the egg-adult duration, decrease of the number of emerged insects, decrese of damaged grains percentage and decrese of weight loss, for both cultivars CD 3121 and CD 307, and for both isolates. On the other hand, the isolates association with cultivars CD 3121 standed out for the control of Sitophilus spp., and the averages presented by this cultivar were more expressive