Relative Susceptibility of <I>Haeckeliania sperata</I> (Hymenoptera: Trichogrammatidae) to Pesticides Used in Citrus and Ornamental Systems in Florida

Abstract

Haeckeliania sperata Pinto is an egg-endoparasitoid of Diaprepes abbreviatus L. (Coleoptera: Curculionidae). We evaluated the relative susceptibility of H. sperata adults to commercially relevant pesticides used in citrus and ornamental production systems. Parasitoids were exposed to pesticide residues on leaf surfaces. Four concentrations of seven pesticides were tested; concentrations for each pesticide consisted of a dilution series using the label rate for field applications as the starting concentration. Lethal concentrations (LC50s and LC90s) were calculated 12 and 24 h after exposure to the pesticides. Lethal times (LT50s and LT90S) were estimated for each pesticide concentration. All tested pesticides had a negative effect on Haeckeliania's survivorship. However, some pesticides were significantly less harmful to this parasitoid. LC50s and LC90s of organophospate, carbamate, and pyrethroid pesticides were less than one eighth of the label rates. LT50s and LT90s of these insecticides were < 12 h even at the most diluted concentrations. Thus, applications of these pesticides might have a strong negative impact on the natural control of D. abbreviatus by H. sperata. Commercial formulations of imidacloprid, abamectin, petroleum oil, and a phosphonate fungicide allowed H. sperata to live longer compared with the previous pesticides, suggesting a certain degree of selectivity. Moreover, adults exposed to diluted concentrations of imidacloprid, abamectin, petroleum oil, and a phosphonate fungicide had a greater survival than those exposed to label concentrations. These findings suggest that the use of products that have less toxic effects on the introduced parasitoid will increase its chances to parasitize D. abbreviatus eggs.