Lethal and sublethal effects of two insect growth regulators on adult Delphastus catalinae (Coleoptera: Coccinellidae), a predator of whiteflies (Homoptera: Aleyrodidae)

Pyriproxyfen, a juvenile hormone analog, and buprofezin, a chitin synthesis inhibitor, are two insect growth regulators (IGRs) considered as selective and effective insecticides for controlling whiteflies. Delphastus catalinae (Horn) is a commercially produced whitefly predator considered to be a valuable biological control agent of whiteflies, especially of Bemisia tabaci (Gennadius) (B. argentifolii Bellows & Perring) in greenhouses. The compatibility of these two control strategies was tested by evaluating the lethal and sublethal effects resulting from ingestion of insect growth regulator (IGR) residues on treated B. tabaci eggs by adult lady beetles in the laboratory. Feeding on pyriproxyfen-treated whitefly eggs caused no significant decrease in longevity of either male or female beetles, whereas feeding on buprofezin-treated eggs reduced longevity significantly. Likewise, preoviposition period was not affected by pyriproxyfen, but was lengthened 3–6 days by buprofezin. Buprofezin reduced D. catalinae egg production and oviposition periods while a 28-day treatment with the low rate of pyriproxyfen actually increased these parameters. Both IGRs reduced D. catalinae egg fertility, especially the higher rate of pyriproxyfen and both rates of buprofezin. However, the process was largely reversed in the case of pyriproxyfen by a transfer of D. catalinae to water-treated whitefly eggs. Because D. catalinae fecundity was actually increased by 28 day exposure to the low rate of pyriproxyfen, there was no net effect on viable egg production. Thus, while both growth regulators negatively impacted D. catalinae, fewest side effects were observed with pyriproxyfen, and the worst of these, egg sterility, was reversible following removal of treated eggs.