Competição e sucesso reprodutivo de carunchos do feijão

• Autor(a) principal: Mallqui, Karina Soledad Vilca
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/918
• topic: Bruchineos; Phaseolus vulgaris; Competição interespecífica; Bruchineos; Phaseolus vulgaris; Interspecific competition; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::ENTOMOLOGIA AGRICOLA

Beeltes of the subfamily Bruchinae (Coleoptera: Chrysomelidae), also commonly known as bruchids, are insects specialized in feeding on the inner part of legume seeds. Among them, Acanthoscelides obtectus (Say) e Zabrotes subfasciatus (Boheman) are considered the main bests of stored common beans occurring in all regions were this legume is cultivated and they frequently co-occur. In Brazil, the losses caused by Z. subfasciatus range from 7 to 40%, while losses caused by A. obtectus range between 20 and 30% of the total common bean production in the country. Despite of well-known and of recognized importance of both bruchid species, the impact of their co-occurrence in their mutual development and colonization was not investigated. Although both species exhibit similar development, size and sex ratio (1:1), the females of A. obtectus lay their eggs loosely and the 1st instar larva burrows into the bean kernek, while females of Z. subfasciatus glue their eggs in the surface of the bean kernel and the larva burrows into the kernel from within the egg without external exposure. Direct competition experiments were carried out with both species using an additive series expecting a co-occurrence without food limitation as usually takes place in grain storage units. The lack of influence or even positive influence of one bruchid species over the other was the most likely expectation. The competition capacity of each species in the presence of its heterospecific competitor was assessed using (adult) mixed infestations in common bean seeds. The results indicate that the co-occurring species did not exhibit negative interaction and the presence of A. obtectus may even favor Z. subfasciatus. Botanical insecticides have been receiving attention for pest management and among them neem, Azadirachta indica has beem tested in different formulation including water extract, oil, seed powder and commercial insecticide formulations based on them. However, few studies are available exploring the effects of botanical insecticides in the reproduction of stored grain insect pests. Here we explored the hypothesis that azadirachtin, the active ingredient obtained from neem extracts, may negatively impact the reproductive capacity of Z. subfasciatus. Furthermore, we also investigated if the adults are able to compensate the sublethal effects of this botanical insecticide adjusting their reproductive efforts. The results obtained showed that females of Z. subfasciatus increase their daily fecundity to compensate a reduction in longevity caused by azadirachtin exposure. Furthermore, the structure matrix by developmental phases of the insect revealed that the populations of Z. subfasciatus engendered from females exposed to azadirachtin exhibited higher population growth rate (r) and net reproductive rate (Ro) and finally, an analysis of the projection matrix showed densities notably higher through subsequent generation for populations of Z. subfasciatus exposed to azadirachtin.