Effects of insect growth regulators on Bagrada hilaris (Hemiptera: Pentatomidae).
Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae) is a serious pest of cruciferous crops in the central coast of California. Management of B. hilaris primarily involves the use of broad spectrum insecticides, such as pyrethroids and neonicotinoids, when the pest invades a crop field. Insect growth regulators (IGRs) are known for their efficacy on nymphal stages of B. hilaris, but little is known about their transovarial effects. Thus, the major objective of this study was to determine the transovarial effects of IGRs such as novaluron, diflubenzuron, and azadirachtin, when adults are exposed to direct topical spraying and dried residues. In addition, a direct topical spray of IGRs on older instars (fourth and fifth instars) was examined at 1-, 3-, and 7-d post-treatment. The number of young instars (first and second instars) and adults was recorded up to ∼31 d after exposure. In the topical spray assays, the number of young instars was significantly lower for novaluron, diflubenzuron, and azadirachtin than for the nontreated control. The number of young instars that emerged after novaluron treatment was low (0-11%). In the assays with dried residues, the number of young instars that developed was significantly lower for novaluron treatment than for the other IGRs and the nontreated control. There was no significant difference among diflubenzuron, azadirachtin, and nontreated control treatments in the development of young instars. In the assays with a topical spray of IGRs on older instars, significantly more nymphs died at 3 and 7 d after exposure. The IGRs had no clear impact on adults.