Abstract
Inoculation experiments were conducted at 25°C under laboratory conditions to investigate the infectivity and propagation of Steinernema feltiae (DD-136), S. bibinois, and S. glaseri on the last instar larvae and male adults of common cutworm, Spodoptera litura. S. feltiae was the most infective on S. litura larvae, followed by S. bibionis and S. glaseri. S. feltiae was positively attracted to the intact and ligated larvae, efficiently invaded, caused acute death of the hosts, and propagated rapidly and abundantly. S. bibionis was weakly attracted to the intact larvae, inefficiently invaded, and slowly developed. These properties led this nematode to low competitive propagation against the other steinernematids which were inoculated at the same time. S. glaseri was slowly but steadily attracted, invaded, quickly developed and estabished a high population in the hosts. The propagation of S. glaseri, however, was suppressed by the mixed inoculation with S. feltiae and to a lesser extent with S. bibionis. All species of steinernematids used propagated more quickly and abundantly in the moths from which the infective juveniles emerged earlier than from the larvae.
