Abstract
The infectivity of the nematodes Steinernema feltiae (DD-136), S. bibionis and S. glaseri to the last instar larvae of G. mellonella and S. litura was higher in this order of nematodes. As the body size of the S. litura larva increased, the three species of nematodes required a longer time to kill the host. However, such tendency was not observed in the Ga mellonella larva which was highly susceptible to the three species of nematodes. Based on the fresh weight of the host insect, the number of S. feltiae and S. glaseri nematodes which were recovered 14 days after the inoculation of ca. 1, 000 infective juveniles from G. mellonella larvae was 2.5 or 3.1 times larger than that from S. litura ones, respectively. Similarly, the number of S. feltiae, and S. glaseri nematodes recovered from G. mellonella larvae was large and 7.7 and 9.2 times as large as that from S. litura larvae, respectively. The highest infectivity and propagation of Se feltiae on S. litura larvae were observed at temperatures ranging from 24 to 27°C. At temperatures higher or lower than this range, the insect cadavers were readily colonized by fungi, mainly Aspergillus oryzae, and produced fewer nematodes. The propagation and establishment of the nematodes appear to be difficult in moist soil containing a large number of fungi and other saprophytic microorganisms.
