Suscetibilidade e resposta comportamental de Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) à lambda-cialotrina

Abstract

The lacewing species, Chrysoperla externa (Hagen), exhibits natural occurrence in various crop ecosystems in Brazil preying upon sucking sap pest species such as aphids, scales, psyllids, and eggs and small larvae. Likewise, pyrethroid insecticides are widely recommended to control lepidopteran and coleopteran pest species in these ecosystems, but usually lacking efficacy against sucking sap pest species attacked by lacewings. Thus, in this study, two populations of the green lacewing C. externa were investigated regarding its susceptibility to lambda-cyhalothrin under selection (Ce-Sel) and non-selection (Ce-NSel) through topical application by determining dose-mortality curves. In addition, influence of the insecticide residues on oviposition, walking and predatory behaviors was studied. Significant variation in the susceptibility to lambda-cyhalothrin was found between the populations. At 1st-tested generation the resistance ratios (RRs) considering the LD50s and LD90s were 4.16 and 2.60-fold for larvae and 1.02 and 1.43-fold for adults. After seven generations of larval selection the RR based on the LD50s and LD90s became 5.85 and 9.37-fold for larvae, and 3.38 and 2.75-fold for adults, respectively. Females of the population Ce-Sel subjected to partially treated arenas laid similar number of eggs on both surfaces, while female Ce-NSel laid lower number of eggs on treated surfaces. Based on behavioral parameters, larvae of both populations did not exhibit repellence when observed on partially insecticide-treated arena, although irritability was observed for larvae of Ce-NSel. Larvae of Ce-Sel population confined on fully treated arena exhibited greater walking distance, time and speed compared to larvae of Ce-NSel. Predation rate was reduced for larvae of both populations, but larvae of Ce-NSel exhibited prey consumption ~1.6x lower compared to larvae of Ce-Sel. The results indicated alterations on susceptibility of C. externa when subjected to selection with lambda-cyhalothrin and, hence, changes on behavior and predation rate.