الفهرس 
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Abstract
This study conducted to investigate the ability of entomopathogenic fungi to control the cotton leaf worm Spodoptera littoralis (Boisd.)
The main experimental results can be summarized in the following:
• About 12 fungus species belong to 7 genera, has been isolated from cotton leaf worm plant hosts and dead insects. It is obviously evident, from the results, that Aspergillus is the richest by showing a spectrum 6 species. However, the remaining genera represented only by one species each.
• In this study entomopathogenic fungi that isolated from healthy and infected plants are (A.flavus, A. tamarii, A .niger, A. parasiticus, A fumigatus, Penicillium sp, Rhizopus sp., Trichoderma harzianum and Cladosporium sp. ).
• In the current study A.flavus, A. niger , Eurotium sp., A . terreus, p. fumosoroseus and A. fumigatus were isolated from the dead insects.
• In order to select the most proper fungal strains for controlling cotton leaf worm; fungal biota of healthy & infected leaves of host plants of that insect and dead insects were surveyed and total number of colony for each fungus was calculated.
• A. flavus, A. tamarii, A.parasiticus, A.niger, A. terreus , A.fumigatus , Eurotium sp., Pencillium sp., T. harzianum and P. fumosoroseus are the most common. So we tested their virulence against cotton leaf worm third larval instar and calculate its mortality percentage corresponding to each fungus used in concentrations of (1×106, 1×107 and 1×108 spore /ml).
• For studying pathogensity of the isolated entomopathogenic fungi against the cotton leaf worm, dipping technique was used.
• The mortality results indicated that the mortality percentage of the 3rdinsrar larvae of S.littoralis increased with increasing time elapsed after treatment. Also, it appears that mostly 107 is the best spore suspension that gives high mortality percentage of insect cross ponding to each the isolated fungi used in the current study. It is clear that A. tamarii and P. fumosoroseus showed the lowest mortality percentage at that concentration (1×107), while A.terreus revealed the highest mortality percentage 86.66% at that concentration.
• The isolated fungi were screened for producing chitinolytic activity, but all of them don’t produce chitinase enzyme.
• Also,all the isolated fungi were screened for producing protease enzyme, and found that all the isolated fungi produce protease enzyme except Pencillium sp.
• The clearing zone around fungus colony was measured indicative of the extracellular protease activity of the fungal strain. Highest protease activity was observed in T. harizianum (1.03) while lowest one was observed with Eurotium sp. (0.1).
• The effect of gamma radiation on protease enzyme production by the isolated fungal species was studied, and it’s synergizing effect in certain entomopathogenic fungi which increase or enhance the activity or efficiency of these microorganisms in controlling a serious insect pest spodoptera littoralis also detected.
• The sporulated cultures spore suspensions with known concentration (1× 107 spore /ml) were exposed to gamma-irradiation at 400, 600, 800, 1000 and 1200 Gy and the dose which gives the best enzyme production in each fungus was detected.This dose was 400 ,800 ,600 ,1200 ,600,1200 ,1200,1200 and 600 Gy for A. niger,A.fumigatus, Eurotium sp.,A.flavus, T. harizianum, A. tamarii, A. terreus , A.parasiticus and P.fumosoroseus ,respectively.
• Using gamma irradiation to enhance the protease enzyme activity . The results indicated that the dose 1200 GY increase protease activity of A. tamarii from 0.433 to 1.366 so crossponding mortality percentage recorded in third instar larvae of Spodoptera littoralis increased from 43.33 % to 86.66 % at spore suspension concentration(1×107spore /ml) . Also, the dose of 600 GY increase protease activity of Paecilomyces fumosoroseus from 0.3 to 0.524 so crossponding mortality percentage recorded of increased from 23.33 % to 93.33% at spore suspension concentration (1×107spore/ ml) .