Abstract
The nematode isolates tested were collected from different localities in Egypt. Some experiments evaluate the infectivity of Heterorhabditis bacteriophora and H.indica as biocontrol candidates against some economic agricultural insect pests; Spodoptera littoralis, Agrotis ipsilon, Sesamia cretica, Phthorimaea operculella and Spodoptera exigua,. The tested nematode species grew faster in S.littoralis and Ph.operculella larvae than in the other host larvae. The Survival of H.bacteriophora and H.indica in distilled water was affected by the two combined factors, exposure time and temperatures. All individuals of H. bacteriophora and H. indica were viable after exposure for 48 hours to temperatures ranged from 5-30 degrees C. At lower (0 degrees C and -5 degrees C) and higher temperatures (35 and 40 degrees C), the survival decreased especially at higher temperatures. Effect of temperature and exposure time on the infectivity of the nematode H. indica (EASD77 isolate) and H. bacteriophora (EASD98 isolate) was higher against S. littoralis. The highest mortality percentages were recorded at the highest two temperatures tested (30 and 35 degrees C). In contrast, there was no mortality at the lower temperature (10 degrees C). The changes in total haemocyte counts (THCs) and differential haemocyte counts (DHCs) in S. littoralis larvae treated with H. indica nematode (EASD77 isolate) are important criteria determining cellular immune reactions.