Bioatividade de extratos aquosos de Serjania spp. sobre Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae) e Tetrastichus howardi (Olliff, 1893) (Hymenoptera: Eulophidae)

Abstract

The diamondback moth, Pluttella xylostella Linnaeus (Lepidoptera: Plutellidae), is amicrolepidopteran that causes important important in the cultivation of brassicas. Themain method used for its control is chemical, through the use of synthetic insecticides. However, the applications of these products have human impacts on the environment and health. In addition, the constant use of products with the same mode of actionhas favored the evolution of resistance. As an alternative, a use of insecticidal botanicals is a low cost, action and sustainable reduction method, a method of low cost, actionandreduction, as always, toxicity and low efficiency in non-target organisms. Therefore, the action and insecticidal activity of aqueous extracts of plant species and Serjaniamarginata, in activities 5% and 10%, on the life cycle, reproduction and feeding of P. xylostella were evaluated. In addition to the toxicity of aqueous extracts on eggs, larvae and pupae of P. xylostella. Finally, the effects of aquifer extracts onthereproduction and survival of Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae), an endoparasitoid of the diamondback moth, were evaluated. In all experiments, foliar disc covers were treated with distilled water (control) or with aqueous extracts of S. erecta 5 or 10% or S. marginata 5% or 10%. In the first experiment (life cycle), 50larvae of P. xylostella were selected (10 repetitions of 5 subsamples) andindividualized in plates containing leaf discs of treated cabbage. They were larval andpupal duration and survival (%), pu weight (the sex ratio (rs = female/female +male), adult pupal weight (days), pupal fecundity weight, total larvae, period of oviposition(days) and egg fertility (%). chance of choice, each cage of adults contained onlyoneleaf disc of properly treated cabbage. In the bio with chance of choice, they werechosen by coverage in each water, with four clubs treated with distilled water (control) and two clubs with serjania spp. They were the fecundity , egg fertility, egg viability(%) and Oviposition Deterrence Index (IDO). ment consisted of 15 repetitions. Twotests were performed, one with no choice and the other with choice. In the no-choicebioassay, three kale leaf discs were available on each plate. In the free-choice bioassay, 4 cabbage leaf discs were made available on each plate, two discs treated with distilledwater (control) and two discs treated with aqueous extracts of Serjania spp. They werethe larval weight (mg), the leaf area consumed, and the Antifeeding Index (AI). Inthefourth experiment, each treatment consisted of 10 replications. 300 eggs (30 eggs per replicate), 50 larvae (5 larvae per replicate) and 100 pupae (10 pupae per replicate) of P. xylostella per treatment were selected. The eggs were immersed in the respectivetreatments and as larvae and pupae they were treated topically with 20 μL of distilledwater or aqueous extract of Serjania spp. (%) the possibility of eggs (%), survival andpupal In the fifth experiment (selectivity of aqueous extracts of Serjania spp. over T. howardi) two bioassays were set up. In the first bioassay, 4th instar larvae of P. xilostella were selected and 20 μL of each treatment were applied topically. Larvaewere parasitized by T. howardi for 4 hours. It was evaluated as progeny (%) andemergence (duration), female life cycle number (days), total progeny number, sex ratioand male and female progeny (days). The second bioassay of the fifth experiment was performed using the ASPECLE system (Assessment of Pesticide SelectivityinExtended Laboratory Conditions). Leaf discs properly treated with distilled water or aqueous extracts of S. erecta or S. marginata, at 5% or 10%, or acephate, wereselected in each glass cage of the system. Ten females of T. howardi were releasedineach cage. This experiment was performed for 122 per 1 treatment subsamples, totaling 120 parasites. and. According to the results obtained, the aqueous extracts of Serjania spp. caused alterations in the biological cycle of P. xylostella (first experiment) and have a deterrent effect on the reproduction of this insect (secondexperiment). In addition, the anti-feeding activity (third experiment) of aqueous extracts of Serjania spp. was verified, being phagodeterrent for P. xylostella larvae infree-choice tests. The aqueous extracts of Serjania spp. decreased egg viability (%) and larval (%) and pupal survival (%) of P. xylostella, with the concentration being10% more effective in reducing larval survival (experiment four). Finally, it was observed that the aqueous extracts of Serjania spp. did not influence the parasitismand survival of T. howardi (fifth experiment).