Efeitos de extratos de fumo e nim sobre Myzus persicae (Sulzer) (Hemiptera: Aphididae) e Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae)

Abstract

In the quest for sustainable agriculture, concern about its impact on the environment and the contamination of the food chain with pesticides, based on practices that promote agrobiodiversity, and the insertion of natural biological processes into the system, it is important to use effective phytosanitary products against, the pests and preferably selective to the populations of natural enemies. The objectives of this study were to evaluate the insecticidal potential and toxicity, through topical application of extracts of neem (Azadirachta indica) and tobacco leaf (Nicotine tabacum) produced from the alcoholic concentration of its bioactive principles in rotavapor and diluted in water, (CL50 and CL90) on eggs, larvae, and adults of their predator Coleomegilla maculata De-Geer, when fed with treated aphids (Myzus persicae), and determine the possible lethal and / or sublethal effects of these aqueous extracts (CL50 and CL90) with aqueous extracts under laboratory conditions. The creations of M. persicae and C. maculata, as well as the experiments, were performed in climatic chambers (25 ± 2ºC, 60 ± 10% RH and 12h). The extracts of the plants were prepared in the laboratory of extracts of plants in the State Center of Research in Organic Agriculture CEPAO / PESAGRO-RIO. Sprays were sprayed with a calibrated manual sprayer with 1.5 ± 0.5 mg of cm² in accordance with the methodology established by IOBC. The experimental design was completely randomized, with factorial arrangement 2 x 8 (smoke and neem) with 8 concentrations, plus the control, with 10 replicates. Evaluations were performed 24, 48 and 72 hours after application of the products. The variables were analyzed in the statistical program R, using the ExpDes.pt package and the nls function for the analysis of variance and non-linear regression, besides the use of the ecotoxicology package for Probit analysis. The extracts showed insecticidal effect on M. persicae at the doses tested, causing mortality and reduction in the number of nymphs, as the concentration increased. A matrix creation of C. maculata was fed ad libitum with M. persicae for two generations, before starting the bioassays. Three bioassays were performed: I) effects of plant extracts on C. maculata eggs; II) effects of plant extracts on third instar larvae of C. maculata fed with treated aphids; III) effects of plant extracts on adult males and females of C. maculata fed with treated aphids. In addition to mortality, the effects of the extracts on the biological parameters of insect development were evaluated. Extracts at doses equivalent to CL50 and CL90 reduced the viability of the eggs of the ladybugs, and the survival of the larvae from these eggs, influencing at each stage of development, thus reducing the emergence of adults. There was no mortality of the adults of C. maculata fed with treated aphids, however the percentage of hatching of the larvae from the postures after feeding was reduced.