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Abstract Laboratory studies were conducted to determine the efficacy of some native and introduced nematode strains against some larval instars of Agrotis ipsilon. It was found that the native species were more efficient than the imported ones. The fourth larval ins tar of A. ipsilon was found to be more susceptible to all tested nematode species than the 5th and 6th ins tar larvae. Susceptibility of A. ipsilon pupal stage to Steinernema glaseri and Heterorhabditis bacteriophora nematodes was also studied . H. bacteriophora was more effective against this stage than S. glaseri. Susceptibility of three larval instars of Spodoptera littoralis to infective stages of S. glaseri nematode was examined. Both 4th and 6th larval instars were more susceptible than the 5th one. All the tested inoculum levels of entomopathogenic nematodes were effective against the larval instars of both insects and the level of 100 dauer stages/ml distilled water achieved 100 , mortality of the host. Malformations as a result of nematode infection in larval and pupal stages were determined. Results indicated that decreasing the nematode inoculum levels caused in an increase in the malformation percentages. ---------~. -75- A study was carried out to determine the efficacy of two introduced and two native nematode species against Z. pyrina and Synanthedon myopaeformis. The native species achieved a higher pest control than the imported two species. The tested nematode species proved to be more effective against Z. pyrina than S. myopaefor.mis. The employed technique is very important in application of entomopathogenic nematodes. It was found that inserting of cotton piece soaked in nematode suspension into insect gallery gave the best larval mortality followed by injection method. While the spray of nematode suspensions induced the lowest percentage of mortality. ~_------- -74- pupation percent and percentages of moth emergence decreased as the inoculum levels increased. The nematode recovery of three nematode species from the tested individual insects was studied. The resulted dauer stages of all the tested nematodes from cadavers of the 6th larval instar of A. ipsilon were the most followed by that of the 5th and 4th larval instare. The native strain of Heterorhabditis sp. propagated with numbers of dauer stages from cadaver of A. ipsilon more than that given by H. bacteriophora or S. glaseri. Also, the resulted nematodes from pupae or adult moths of A. ipsilon were recorded. H. bacteriophora propagated better than S. glaseri and the adult moths yielded infective stages more than pupae or larvae. Field trials to control some fruit trees borers were conducted. Over 90 \ larval mortality of Zeuzera pyrina was gained in olive or apple orchards when some nematode species were either injected or sprayed 5 times in 8 days intervals. Mixing the nematode suspensions with the recommended dose of B. thuringiensis did not achieve any increase in the mortality percentages of z. pyrina in both olive and apple orchards. |