Abstract: From June 2004 to August 2005, larvae of the white grub Polyphylla olivieri and soil samples were collected in fruits orchards in seven counties of the Tehran province, Iran. Whites grubs were reared in insectarium, and monitored for possible infection by EPN and subsequent isolation of the nematodes. Isolation of EPNs from soil samples were conducted using the Galleria bait method. Three species of EPNs were identified: Heterorhabditis bacteriophora (IRAN1), Steinernema glaseri (IRAN2) and Steinernema sp. (IRAN3). In bioassays against the White grub, the LD50 of IRAN1 was 35 IJs/larva, followed by 65 IJs/larva for IRAN2. The LD50 for Steinernema sp was >10000 IJ/larva and caused only 16% mortality after 25 days. Tolerance of the three Iranian EPNs (IRAN1 of H. bacteriophora, IRAN2 of S. glaseri and IRAN3 of Steinernema sp.) were compared. Heat tolerance study showed that the H. bacteriophora strain was the most tolerant nematode at 32°C, but no nematodes could survive at 36°C after a 4 – 5-h exposure. Furthermore, life cycle and natality/ mortality data of the three Iranian isolates were studied in the wax moth larvae, G. mellonella, at a range of temperatures from 5 to 30°C.

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