Toxicity of Selected Insecticides to the Spined Soldier Bug, Podisus maculiventris (Heteroptera: Pentatomidae)

Abstract

Susceptibility of Podisus maculiventris to the insect growth regulator teflubenzuron, the carbamate methomyl, the pyrethroid deltamethrin, and the bioinsecticide Bacillus thuringiensis subsp. kurstaki (Bactospeine) was evaluated in the laboratory. Newly-moulted fourth instars and seven-day-old female adults were exposed to formulated materials of each compound via ingestion for 48 h. Teflubenzuron was highly toxic to fourth instars (LC 50 = 14.7 mg a.i. l -1 ) of the predator, but proved to be harmless to female adults. Both fourth instars and females suffered the highest mortality when they were exposed to methomyl (LC 50 = 5.4 and 10.6 mg a.i. l -1 , respectively). Deltamethrin was relatively safe for the predator in either stage; however, fourth instars were more tolerant to the pyrethroid than females (LC 50 = 158.8 and 43.4 mg a.i. l -1 , respectively). Neither fourth instars nor females were affected by B. thuringiensis at 10 000 mg formulated material l -1 . Reproductive capacity of the predator was also examined when applying field concentrations of teflubenzuron (200 mg a.i. l -1 ) or deltamethrin (12.5 mg a.i. l -1 ) via ingestion. Treatment with deltamethrin only prolonged preoviposition period. A marked decline in egg hatch was observed when the insects were exposed to teflubenzuron compared with the control (7 vs 63%, respectively). Fourth and fifth instars that had ingested sublethal doses of teflubenzuron demonstrated longer developmental times than did those of the control. Ingestion experiments suggest that use of deltamethrin and B. thuringiensis may be compatible with releases of P. maculiventris . In contrast, populations of the predator may be harmed when methomyl or teflubenzuron are applied.