Trichogramma bruni (Hymenoptera: Trichogrammatidae): Capacidade de parasitismo em ovos de Neoleucinodes elegantalis (Lepidoptera: Crambidae) e susceptibilidade de fases imaturas à inseticidas

Abstract

Success in releasing natural enemies for agricultural pest control depends on factors such as environmental conditions in the region where it is practised, as well as the pest susceptibility to pesticides used in combination. The objective of this study was to evaluate the parasitism capacity of Trichogramma bruni (Hymenoptera: Trichogrammatidae) in eggs of Neoleucinodes elegantalis (Lepidoptera: Crambidae) and the susceptibility of the parasitoid to insecticides. The experiment was carried out at the Agricultural Entomology Laboratory (LEA-UFC), Fortaleza, Ceará, Brazil. A T. bruni female was used for six N. elegantalis eggs at 15, 20, 25, 30 and 35 ° C, determining the daily and accumulated parasitism capacity. It was also evaluated the impacts of four insecticides on T. bruni phases, applied to Anagasta kuehniella (Lepidoptera: Pyralidae) eggs before and after parasitism. A completely randomized design with 20 replications was used to install this experiment. The data obtained were submitted to analysis of variance (ANOVA) and the means were compared by Duncan test at 5% probability. The average total number of parasitized N. elegantalis eggs per T. bruni female was 63.3 at 15 ° C. The daily parasitism rate varied with temperature, ranging from 0.1 (35 ° C) to 3.7 (15 ° C) parasitized eggs by T. bruni female during the first 24 hours. The largest number of parasitized eggs in the shortest time (24 hours) was obtained at 15 (3.7) and 20 ° C (2.35). The average longevity of T. bruni females was 30.75 days at 15 ° C and decreased with thermal elevation, reaching 2 days at 35 ° C. The parasitism percentage of T. bruni females in A. kuehniella eggs treated with the insecticides Clorantraniliprole (77.3%) and Spinetoram (83.3%) was not negatively affected and therefore considered innocuous to the parasitoid. Bacillus thuringiensis var. kurstaki caused less than 30% reduction in parasitism being slightly harmful. Methaflumizone reduced parasitism by 99.2% and was therefore considered toxic. For application after parasitism, Metaflumizone was considered innocuous to the three phases of T. bruni (egg, larva and pupa). Chlorantraniliprole and B. thuringiensis were classified as harmless for the larval and pupal stages and slightly harmful for the egg stage. Spinetoram was the most harmful insecticide to T. bruni developmental stages, being considered as slightly harmful. The temperature changed the biological parameters. As the temperature elevated, these parameters decreased. The insecticides Spinetoram and Clorantraniliprole were innocuous to T. bruni before parasitism, and Metaflumizona innocuous to all stages of parasitoid development after parasitism