EVALUATION OF 4 ENTOMOPATHOGENIC NEMATODES AGAINST SPODOPTERA-LITTORALIS (LEPID, NOCTUIDAE) LARVAE UNDER DIFFERENT TEMPERATURES

The efficacies of four strains of entomopathogenic nematodes on infect ing and killing Spodoptera littoralis were tested in the laboratory co ncerning soil temperature, nematode dose and emergence from the insect cadavers. All the tested nematodes attained almost 100% insect mortal ity at 4, 10 and 25 degrees C but at 35 degrees C, Heterorhabditis bac teriophora (HP88) achieved the least (64%). As soil temperature rise t o 35 degrees C, the most adversely affected nematode in terms of recyc ling efficiency was H. bacteriophora (EASD98) followed by Steinernema riobravis, H. bacteriophora (HP88) and finally H. indicus (EAS59). Alt hough all nematodes could infect and kill the host insects at 35 degre es C, those of H. bacteriophora (EASD98) could not emerge from the cad avers. Differences in the numbers of emerging infective juveniles as r elated to nematode concentration and different degrees of soil tempera tures were obvious and may be considered in developing a biocontrol st rategy for the management of the cotton leaf-worm.