LARVICIDAL ACTIVITY OF THE SYMBIOTIC BACTERIUM XENORHABDUS-JAPONICUS FROM THE ENTOMOPATHOGENIC NEMATODE STEINERNEMA-KUSHIDAI AGAINST ANOMALA-CUPREA (COLEOPTERA, SCARABAEIDAE)

The entomopathogenicity of the symbiotic bacterium Xenorhabdus japonic us and the nematode steinernema kushidai was determined. Phase I and I I X. Japonicus were cultured on an artificial medium and inoculated in to the test insect or established into axenic S. kushidai populations. When 100, 1000, or 10,000 bacterial cells of phase I or II were direc tly injected into the hemocoels of 3rd instar cupreous chafer, Anomala cuprea, both phases in the late log period killed 100% of the larvae by the 2nd day postinoculation. However, both phases in the stationary period were less pathogenic with cupreous chafer mortality <20 and 80 % at 100 and 1000 bacterial cells/larva, respectively. In vitro studie s showed that axenic S. kushidai provided with phase I and II symbiont s grew well and produced equal numbers of progeny on a dog food medium , but nematodes with no symbionts did not grow at all. Pig liver extra cts added as a dietary supplement to the dog food medium completely re stored growth and progeny production of the nematode growth and progen y production of the nematode with no bacterial cells. Studies were con ducted with infective juveniles (IJs) harboring phase I or II or no sy mbionts that were applied against 3rd instar cupreous chafer larvae in compost or injected directly into their hemocoels. In the compost stu dy, IJs harboring phase I killed 100% within 10 days. IJs with phase I I or no symbionts caused low mortality of the cupreous chafer larvae a t 10 days (<20%). In the intrahemocoelic injection study, IJs harborin g phase I resulted in 60% larval mortality at five nematodes/larva, an d as the number of IJs injected increased, significantly higher larval mortality was obtained. (C) 1996 Academic Press, Inc.