Entomopathogenic nematodes (EPNs) of families Heterorhabditidae and Steinernematidae are known to be effective against a variety of pests. In the present work, different EPNs that are isolated from the Egyptian environment were tested against the onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), under field conditions. The Egyptian EPNs were tested at different concentrations and against different onion thrips stages (adult and nymph). When used as a foliage spray, the tested EPN isolates were efficient against both adult and nymph stages. Differences in pathogenicity were observed within the same EPN species as in Heterorhabditis indica (EGAZ3) that caused higher reduction in population of T. tabaci (adult and nymph) after 24 and 48 h at a concentration of 10,000 infective juveniles (IJs)/ml compared to H. indica (EGAZ2) after 24 h post treatment at a concentration of 15,000 IJs/ml. The same pattern was observed with Heterorhabditis bacteriophora (HP88), where a higher reduction percent was recorded after 24 h at a concentration of 20,000 IJs/ml. On the other hand, Steinernema carpocapsae (All), S. carpocapsae (EGAZ9), and S. carpocapsae (BA2) isolates were less effective in controlling onion thrips (adult and nymph) population. In general, controlling T. tabaci at the nymphal stage was more efficient than at the adult stage (12-73% reduction at the nymph stage compared to 6-65% at the adult stage). It was also found that increasing inoculation concentration above 15,000 IJs/ml had no significant difference in controlling onion thrips populations.

Entomopathogenic nematodes of the genera Heterorhabditis and Steinernema are used as an insect biological control in agriculture. Numerous new species are being described but generally little information is provided on their ecological or physiological information. Therefore, this paper presents examination of virulence, penetration rate, reproduction, and some energy reserves (total lipids, total proteins and total carbohydrates) for six species of entomopathogenic nematodes, 3 species of Heterorhabditids ((HP2), (HP4) and H. indica) and 3 species of Steinernema ((S3), S. riobrave and S. rarum) are extracted from soil samples at different countries and places to refer the superlative one to unfavorable environmental conditions. The tested species differed in their penetration rate to Galeria mellonella larvae. Heterorhabditis sp. (HP2) recorded the highest penetration rate (56 %) where it recorded highest total lipids (35.8 %), highest total proteins (60.3%) and the highest virulence to G. mellonella (25%). The highest total carbohydrates were recorded to the steinernema rarum (26%) while the highest reproduction was recorded to Heterorhabditis indicus (149914 IJs/larva).

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