INTERSPECIFIC COMPETITION BETWEEN ENTOMOPATHOGENIC NEMATODES IN THE GENERA HETERORHABDITIS AND STEINERNEMA FOR AN INSECT HOST IN SAND

Interspecific competition between Heterorhabditis heliothidis and Steinernema feltiae, S. bibionis, or S. glaseri for lepidopteran hosts in sand showed that in vertical dispersal, Steinernema spp. outcompeted H. heliothidis for insect hosts located proximally, while H. heliothidis outcompeted Steinernema spp. for hosts located distally to nematode placement. In downward dispersal of H. heliothidis and S. feltiae, the latter infected 73% of the hosts located at 5 cm from nematode placement and H. heliothidis infected 20%. At 10-25 cm from placement, H. heliothidis was the only nematode species infecting the hosts. Similar trends were observed with H. heliothidis and S. bibionis and H. heliothidis and S. glaseri when these nematodes were in competition for insect hosts. In upward dispersal, H. heliothidis in the presence of S. feltiae was the dominant species at all levels. S. bibionis or S. glaseri in combination with H. heliothidis showed trends similar to those in downward dispersal. In horizontal dispersal, interspecific interaction between H. heliothidis and S. feltiae, S. bibionis, or S. glaseri also showed that the steinernematids outcompeted H. heliothidis for hosts located distally (10 to 30 cm) from nematode placement. Dual infections of H. heliothidis and a Steinernema sp. occasionally occurred resulting in interference between the two nematode species. Although development of both species occurred, they eventually died. © 1990.