INTERSPECIFIC AND INTRASPECIFIC VARIATION IN INFECTIVITY OF STEINERNEMA SPP TO LARVAE OF THE MUSHROOM FLY LYCORIELLA-SOLANI

Laboratory bioassays were done to assess the susceptibility of larvae of the mushroom sciarid fly Lycoriella solani Winnertz (Diptera; Sciar idae) to 16 isolates comprising five species of the entomopathogenic n ematode, Steinernema (Nematoda; Steinernematidae). Each isolate was te sted by challenging sciarid larvae with single nematodes, Six isolates were also tested in dose-response experiments. Variations in nematode infectivity occurred (p < 0.001) at both inter- and intraspecific lev els. Steinernema, feltiae (Filipjev) was the most virulent species: tw o isolates, Memasys (LD(50) = 1.5 - 3.9) acid Sus 94 (1.8 - 3.9) were superior to the rest. Steinernema kraussei (Steiner) was the least inf ectious nematode tested as its infection probability never exceeded 0. 10. In addition, lethal dose(50) values for this species ranged from 9 .0 - 62.6 and two isolates failed consistently to infect any hosts.