Effect of temperature and lepidopteran host species on entomopathogenic nematode (Nematoda : steinernematidae, Heterorhabditidae) infection

Experiments were conducted to determine the effect of temperature on entomo pathogenic nematode infection of an insect host. Late instars of Pectinopho ra gossypiella (Saunders) (Lepidoptera: Gelechiidae), Heliothis virescens ( F.) (Lepidoptera: Noctuidae), Trichoplusia ni (Hubner) (Lepidoptera: Noctui dae), and Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae) were incubate d at 10 temperatures ranging between 9.9 and 40 degrees C, and exposed to 1 50 infective juvenile entomopathogenic nematodes (Nematoda: Steinernematida e; Heterorhabditidae) per larva. The number of infecting Steinernema riobra ve Cabanillas, Poinar & Raulston, S. carpocapsae (Weiser) (Kapow) and Heter orhabditis bacteriophora (Poinar) (Cruiser), nematodes was recorded. Temper ature, nematode species, and target insect all significantly affected the n umber of infective juvenile nematodes invading host insects. The temperatur e supporting the highest levels of nematode infection varied depending on i nsect host species. Larvae of P. gossypiella were then incubated at the sam e range of temperatures, and exposed to 2 dose rates (100 and 200 infective juveniles per larva) of S. riobrave, S. carpocapsae (Guardian), H. bacteri ophora (Cruiser). or H. bacteriophora (Lawn Patrol). Increasing nematode do sage had no effect on the temperature at which nematode infection of P. gos sypiella was highest. Doubling the nematode dose rate did not result in a s ignificant increase in the number of infective juveniles infecting larvae f or the nematode species tested with the exception of S. riobrave. The optim um temperature for the control of insect targets by a nematode will vary am ong target species. Assuming existing nematode temperature optima and apply ing the same conditions to untested insect species may not result in maximu m biocontrol efficacy.