Parasitism of diapausing pink bollworm Pectinoaphora gossypiella (Lepidoptera : Gelechiidae) larvae by entomopathogenic nematodes (Nematoda : Steinernematidae, Heterorhabditidae)

Diapausing larvae of Pectinophora gossypiella (Saunders) (Lepidoptera: Gele chiidae), were exposed to entomopathogenic nematodes (Nematoda: Steinernema tidae; Heterorhabditidae) at a dosage of 100 or 200 infective juveniles (IJ ) per larva. No significant differences between infection of Steinernema ri obrave (strain 355) Cabanillas, Poinar and Raulston, and Heterorhabditis ba cteriophora (strain Cruiser) (Poinar) were observed after either 6-d or 9-d of incubation. No significant difference in infection levels occurred due to increasing dose. Greatest insect mortality occurred due to parasitism by S. riobrave (355). In a second assay, diapausing larvae of P. gossypiella were exposed to S. riobrave (355), Steinernema carpocapsae (strain Kapow) ( Weiser), H. bacteriophora (strain Lawn Patrol), or H. bacteriophora (Cruise r) at dosages of 50, 100, 200, or 400 IJs per larva. S. carpocapsae and H. bacteriophora (Cruiser) infected larvae at significantly higher rates compa red with H. bacteriophora (Lawn Patrol) and S. riobrave. A significant diff erence in infection levels occurred due to nematode dose. In a third assay cotton bells infested with diapausing P. gossypiella were exposed to S. rio brave (355), or H. bacteriophora (Cruiser). Boxes were prepared with bells buried 5 cm below the soil surface or bells laid on the soil surface. Boxes also were incubated at constant temperature or exposed to ambient seasonal temperatures and light. H. bacteriophora (Cruiser) infected larvae at sign ificantly higher rates compared with S. riobrave (355). Significant differe nces in infection levels occurred due to the location of the boil placement and the incubation temperature. (C) 1999 Elsevier Science Ltd. All rights reserved.