Seletividade de inseticidas sobre parasitoide de ovos Telenomus podisi Ashmead 1893 (Hymenoptera: Platygastridae)

Abstract

The objective of this work was to evaluate the effects of the insecticides used in the maize crop, imidacloprid+bifenthrin (400 mL/ha), bifenthrin+carbosulfan (500 mL/ha), thiamethoxam+lambda-cyhalothrin (250 mL/ha), acephate (800 g/ha), bifenthrin (300 mL/ha) and imidacloprid (250 mL/ha), on adults of T. podisi and also evaluate the effects related to emergencies in the immature phase of this parasitoid. To evaluate two bioassays were performed: 1) the parasitoids in the adult phase, 50 eggs of Euschistus heros per cartrel containing the eggs glued by gum arabic were immersed in the chemical syrups and, after drying, offered to the female of T. podisi. Mortality, number of F0 parasitized eggs, and F1 emergence were evaluated. The effects on the immature stages of T. podisi were evaluated by immersion of E. heros eggs containing the parasitoid in the egg-larva, pre- pupae and pupa stages, analyzing the insecticidal effects on the emergence of F1 T. podisi. 2) For the two bioassays, the evaluated products were at the maximum concentrations indicated for maize, following the methodology recommended by IOBC (International Organization for Biological Control). In the evaluation of parasitoid adult selectivity, thiamethoxam + lambda-cyhalothrin affected the survival of T. podisi being classified as moderately harmful (class 3), followed by imidacloprid + bifenthrin, bifenthrin + carbosulfan, acephate, bifenthrin, which were classified as (Class 2) and only imidacloprid did not affect the mortality of T. podisi adults classified as innocuous (Class 1) according to IOBC. Regarding adult parasitism, insecticides acephate and imidacloprid were classified as slightly harmful (class 2), thiamethoxam + lambda-cyhalothrin and imidacloprid + bifenthrin moderately harmful (class 3) and insecticides bifenthrin + carbosulfan and bifenthrin were harmful (class 4) to parasitism. Regarding the emergence of the F1 generation parasitoids, the insecticide thiamethoxam + lambda-cyhalothrin were moderately harmful (class 3) following as noxious (class 4). For the immature phases of the parasitoid, imidacloprid and acephate had no effect on F1. However, insecticides bifenthrin + carbosulfan and bifenthrin were harmful to parasitoids, reducing their emergence by 100%. Thus, as the insecticides were evaluated in the laboratory, new semi-field and field tests are necessary in order to confirm their toxicities on the biological characteristics studied.