Sublethal Effects of Insecticides on the Parasitism of Acerophagus flavidulus (Hymenoptera: Encyrtidae) Parasitoid of the Obscure Mealybug, Pseudococcus viburni (Hemiptera: Pseudococcidae)

Abstract

Insecticides used to control agricultural pests can interfere with beneficial arthropods. This study determined the sublethal effects of two insect growth regulators—buprofezin and pyriproxyfen—and the neonicotinoid insecticide acetamiprid on adults of Acerophagus flavidulus (Brethés), a parasitoid of the obscure mealybug, Pseudococcus viburni (Signoret). A. flavidulus was exposed to insecticide residues at the minimum recommended rate of buprofezin and pyriproxyfen (1×) and 0.005× of acetamiprid on apple leaves under laboratory conditions. Each female parasitoid was in contact with the insecticide residues for 24 h and then allowed to parasitize three mealybug densities (two, four, and six nymphs) per parasitoid for 24 h. Parasitism, emergence rate, clutch size, development time, longevity, and secondary sex ratio were evaluated under each insecticide treatment and mealybug density. Application of the growth regulators buprofezin and pyriproxyfen at the labeled rate (1×) induced less sublethal effects than acetamiprid applied at a low rate (0.005×) on A. flavidulus. Pyriproxyfen and acetamiprid reduced parasitism, but they did not affect other aspects of development such as emergence rate, clutch size, development time, longevity, and secondary sex ratio. Our data suggest that buprofezin and pyriproxyfen are more compatible with A. flavidulus than acetamiprid, which could be integrated with parasitoid activity only when low residue levels in the field are attained.