Efeito dos extratos orgânicos de Annona muricata L. e Annona squamosa L. (Annonaceae) sobre o pulgão Aphis gossypii (Glover, 1887) (Hemiptera:Aphididae) e seletividade ao predador Eriopis connexa (Germar, 1824) (Coleoptera: Coccinellidae)

Abstract

The use of botanical extracts has been reported as an alternative to control insect pests in agricultural crops, but the harmful effects of these natural products on the beneficial insect fauna of agricultural ecosystems have to be assessed. The aim of this study was to evaluate the efficiency of seed extracts of sugar apple (Annona squamosa L.) and soursop (Annona muricata L.) on Aphis gossypii (Glover, 1887) (Hemiptera: Aphididae) and its natural enemy, the ladybug Eriopis connexa (Germar, 1824) (Coleoptera: Coccinellidae). Therefore, bioassays were performed with hexane and ethanol extracts at concentrations of 0.125; 0.25; 0.3; 0.4; 0.5; 1.0; 1.5 and 2.0%, to estimate by Probit analysis their lethal concentrations. For the ladybird, it was tested the action by contact, residual effect and ingestion to evaluate survival, oviposition and viability of the eggs. The CL50 and CL99 estimated for A. gossypii were, respectively, 0.39 and 5.47% for the ethanolic extract of sugar apple (EEP); 0.23 and 1.19% for the ethanolic extract of soursop (EEG); 0.47 and 4.39% for the hexanic extract of sugar apple (EHP); 0.42 and 6.38% for the hexanic extract of soursop (EHG). Considering the action of the extracts by contact, the EEG (0.23%) was considered innocuous, on the other hand, the EHG (0.42%) promoted mortality of 30% of insects and is classified as slightly harmful for 1st instar larvae; for adults, only EEP (5.47%) was classified as slightly harmful and the other treatments were classified as harmless, including for the residual effect. Regarding the selectivity of the extracts, the LC50 of EEG and EHG did not affect the survival rate of the ladybirds. By contrast, the EEP in both tested concentrations (0.39 and 5.47%) reduced the rate of survival to zero in less than 7 days, resembling the chemical treatment with Decis®. All treatments reduced the consumption of Anagasta kuehniella eggs, alternative prey, treated with the extracts, reducing the predation and causing as a consequence, oviposition to a decrease in lower concentrations and no egg laid for higher concentrations, affecting fertility and predator the viability of the eggs. The EEG in the concentration of 0.23% was effective in controlling A. gossypii, and its selective natural enemy E. connexa, not interfering with the survival rate of these.