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Entomopathogenic nematodes (EPNs) parasitize the insect host by entering into the host body, and they lead an endoparasitic mode of life. The symbiotic bacteria associated with them play an important role in the suppression of insect pests. Approximately 30-500 symbiotic bacteria (including Xenorhabdus and Photorhabdus spp.) are reported to be associated with the two nematodes, Steinernema and Heterorhabditis. EPNs and the symbiotic bacteria control a wide range of insect pests living in the soil and in cryptic habits. This chapter focuses on the general biology of EPNs. The symbiotic relationships of nematodes and bacteria, and the survival biology (including cold, heat and desiccation tolerance) and foraging behaviour of nematodes are discussed in detail.

Dose-mortality and repellent activity tests of the chloroform extracts of fruit, leaf, root and stem of Solanum ferox L. against the red flour beetle Tribolium castaneum (Herbst) adults have been done. The fruit, leaf and stem extracts offered promising toxicity to the beetles within 30 min. of exposure. The LD 50 values for 30 min., 12, 24, 36 and 48h of exposures were 0. 440, 0.247, 0.211, 0.207 and 0.164mg cm -2 respectively for the fruit extract; 2.394, 1.712, 1.540, 1.239 and 0.993mg cm -2 respectively for the leaf extract; and 4.918, 0.871, 0.546, 0.472 and 0.522mg cm -2 respectively for the stem extract. However, the root extract did not offer any mortality for 30 min. and 12h of exposure; and thus the LD 50 values for 24, 36 and 48h of exposure were 6.667, 5.086 and 3.357mg cm -2 respectively. While the dose-mortality activity can be arranged in the order of fruit> leaf> stem> root extracts. The fruit and stem extracts showed repellent activity against T. castaneum adults at P<0.01 and the leaf extract at P<0.05 level of significance, while the root extract did not show any repellency.

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