Canadian Steinernematid (Nematoda) Isolates and Their Infectivity, under Cold Conditions, to Greater Wax Moth (Galleria mellonella) Larvae

Nematode species, strains, or isolates of the entomopathogenic family Steinernematidae differ in their ability to infect insects at low temperatures. Some steinernematid isolates from British Columbia, probably a new species, killedGalleria mellonella larvae at 7°C. In laboratory experiments, these nematode isolates (isolates 69, 76, 99, 102, or D) were applied to petri dishes at concentrations of 50, 100, 200, 400, or 800 infective juvenile nematodes (IJs)/dish. Each petri dish contained 10 Galleria larvae and was kept at 4, 7, or 10°C for 250 to 255 h. More than 5600 G. mellonella larvae were examined to determine larval mortality and the number of adult nematodes developing in the insect. Excluding 69, isolate, all other isolates showed a significant level of infectivity at these temperatures. At 10°C the mortality reached 100% at 400 and 800 IJs/dish of the D isolate, and at 4°C the highest mortality was 81.7% at 800 IJs/dish of isolate 99. The penetration efficiency, as determined by the number of adult nematodes recovered when the larvae were dissected, decreased with temperature and IJ concentration and ranged from 28.5% (isolate D at 10°C and 800 IJs/dish) to 0% (isolates 102 and 69 at 4°C and 50 IJs/dish). Steinernema cubana with supposed warm temperature infectivity was used as a comparative control and was only slightly infective at 10°C and 800 IJs/dish. The rate of infection, evaluated by Anderson’s model, proved to be a useful tool for comparing the infectivity of various isolates and species of entomopathogenic nematodes, as it is independent of experimental conditions. r 1997Academic Press