Lethal and sublethal effects of insecticides on two parasitoids attacking Bemisia argentifolii (Homoptera: Aleyrodidae)

The long-term goal of this report is the documentation of the sublethal effects of pesticides to parasitic Hymenoptera. The objective of this laboratory study was to determine if parasitoids can be conserved or augmented against Bemisia argentifolii in crops where insecticides are also applied for other pests. Lethal and sublethal effects were measured for six insecticides applied in the laboratory to host larvae containing two different developmental stages each of Eretmocerus mundus Mercet from Spain and a common local species Eretmocerus tejanus Rose and Zolnerowich. Survival varied according to insecticide and developmental stage. When applied 5 days after parasitoid oviposition, thiodicarb allowed the highest rates of adult emergence by E. tejanus (65.9%) and E. mundus (35.8%). Endosulfan was the next least-toxic material, followed by the organophosphates azinphos-methyl and methyl parathion, and the insect growth regulator buprofezin. The pyrethroid bifenthrin was most toxic to both parasitoids in both developmental stages. When applied just before the expected emergence of adults, survival ranged from 47.2 to 92.2% with buprofezin, thiodicarb, and endosulfan. Some significant differences among treatments in longevity of emerged adults were detected, but females of both parasitoid species that survived the least-toxic materials were able to mate and reproduce. These findings demonstrate that there exists a wide range of responses by Bemisia parasitoids across a variety of chemicals, and that sublethal effects on the subsequent longevity and reproductive ability among survivors of the least-toxic chemicals were not severe. This study demonstrates the value of assessing sublethal effects of pesticides by showing that adult parasitoids that survive pesticides applied to immature stages within their host do not necessarily suffer latent detrimental effects on important biological parameters.