RESUMO
The efficacy of the fungus Metarhizium rileyi (Farlow) Kepler, S. A. Rehner & Humber (Hypocreales: Clavicipitaceae) against the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) and the impact on the community of epigeans predators as well as the natural occurrence of native fungal strains were evaluated after sequential sprays in maize. In the first season, the infestation was lower than 0.2 larvae per plant throughout the three fungal sprays and no significant difference was observed in the number of infected larvae among treatments. In the second season, insect population reached an average of 0.8 larvae per plant between the second and third sprays and the number of larvae succumbed by M. rileyi was higher in fungal-treated plots in the following weeks. Molecular characterization of the collected isolates on mummified larvae revealed the introduction of a new isolate did not eliminate the native strain on the fungal-treated plots. In both seasons, the diversity and abundance of predator species in the plots were not affected by any of the treatments. We showed that applications of selected strains of M. rileyi early in the season have no significant impact on the occurrence of natural enemies in maize.
Assuntos
Metarhizium , Mariposas , Animais , Larva , Spodoptera , Zea maysRESUMO
O uso de plantas inseticidas é uma importante ferramenta para o manejo de insetos-praga. Visando ao controle de Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), nanoformulações de nim foram avaliadas. Após a estimativa de uma CL50 para uma formulação de óleo comercial de nim, bioensaios de seleção foram realizados com 22 nanoformulações. Para isso, lagartas neonatas foram alimentadas sobre folíolos tratados com soluções das nanoformulações durante 10 dias. Com as duas nanoformulações mais promissoras, NC40 aquoso e NC40 pó (NC 40=nanocápsulas de Poli- β-hidroxibutirato), foi avaliado o efeito sobre o desenvolvimento e a longevidade do inseto. A CL50 para o óleo de nim foi estimada em 0,20% ou 1,31mgL-1 de azadiractina. As nanoformulações NC40 aquoso e NC40 pó afetaram o desenvolvimento do inseto.
The use of insecticide plants is an important tool in the management of insect pests. Aiming to control Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), neem nanoformulations were evaluated. After estimating the LC50 for a commercial neem oil formulation, selection bioassays were performed with 22 nanoformulations. In order to do that, newly emerged caterpillars were fed on leaflets treated with nanoformulation solutions for 10 days. The effect on the development and longevity of the insect was evaluated with the two most promising nanoformulations, aqueous NC40 and powdered NC40 (NC 40 = Poly-β-hydroxibutirate nanocapsules). The LC50 for neem oil was estimated in 0.20% or 1.31mgL-1 of azadiractin. The nanoformulations aqueous NC40 and powdered NC40 affected the insect development.