Factors affecting oviposition, development, and behavior of the maize weevil Sitophilus zeamais Motschulsky in Peruvian maize accessions

The performance of 114 accessions of Zea mays L. from the Peruvian maize germplasm bank against the maize weevil Sitophilus zeamais Motsch. infestation, was evaluated in a free-choice test of susceptibility. After rating as resistant or susceptible, 35 accessions were re-evaluated in a no-choice test. Several accessions were found resistant. Resistance was associated with the flint character and susceptibility to the floury character. The females oviposited more eggs in the endosperm than in the germ or germ-interface. During the search for oviposition sites, the females avoided more kernels of resistant than of susceptible types. Developmental success of the progeny was linked to oviposition site. Development was delayed when the first instar larva was placed in the endosperm of the crown area. In both, natural and artificial infestation, morality in the germ was higher than in the endosperm or interface, especially in the resistant SMTI-057. The number of larval instars was 4. The pre-imaginal adult stage was longer in resistant than in susceptible types. Adult survival, egg distribution, choice of emergence site, surface feeding of the larvae, growth, and development were significantly affected by type of maize and relative humidity (RH). Kernel epicuticular waxes had less influence. At all RH's, the predominant frequency of weevils which completed development was one/kernel, but at higher RH 2, 3, and 4 weevils completed development in one kernel. The weight of the weevils decreased with increasing RH. The relationship of average weight per weevil to the number of weevils emerged per sample of grain was negative and exponential. There was a wide array of influences among kernel characteristics, maize weevil developmental parameters, and between the two sets of variables. Susceptibility of maize genotypes could be predicted by using maize kernel characteristics or maize weevil developmental parameters. A modification to the Dobie index for determining the inherent susceptibility of maize to the maize weevil is proposed.