الفهرس 
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Abstract
This study is an attempt to search for a fungal control agent for the desert locust, Schistocercagregaria (Forskål), based on naturally associated fungi with such insect pest and originally isolated from it. A colony of S. gregaria was reared under laboratory conditions (30 ± 2°C, 70- 80 % R.H and 8 D: 16 L). Naturally infected nymphs and adults were collected, together with the locust eggs were checked for entomopathogenic fungi. A total of 33 fungal species, belong to 12 genera were isolated. The highest total count of isolated fungi was that fromlocust nymphs (33.8CFU / nymph), and the lowest total count was isolated from egg stage (7.39 CFU/egg). Among the fungal isolates,Aspergillus (39.0%) andMucorspecies(31.1%) showed relatively high rates of incidence followed by Penicillium (17.0%), Fusarium (9.6%) and other genera (3.3%). After preliminary tests, 13 fungal isolates and a commercial product, B. bassianawere selected to determine their virulence against1stinstar nymphs. The fungus, P. aurantiogriseum(Dierekx) 800 (AUMC) spores significantly(p≤ 0.05)caused the highest rapid lethal effect, with nymph mortality of 96.6 ± 3.3 %,LT25 of 3.5days and LT50 of 5.4 days. Higherspore concentrations of P. aurantiogriseum producedsignificantly (p≤ 0.05) higher mortalities and speed insect mortality.
Positive results of the ability of the fungus P. aurantiogriseum to produce chitinase and proteolytic enzymes confirms its ability to hydrolyze chitin, resulting an easily penetration of locust cuticle. In addition, positive results of producing secondary metabolite, mycotoxincitrinin may also confirm its virulence.
Histopathological studies revealed that after 48-72 h of P. aurantiogriseuminoculation, infection was observed in all body parts. Conidia, the infective particles were observed on insect legs, head, particularly antennae, and on the thoracic and abdominal segments with preference for surfaces containing hairs and ridges. Conidial germination observed on antennal surface. Conidiophores bearing chain of conidia on thorax and abdomen was also observed in insect cadavers. Integument of the infected hoppers appeared with several changes, disruption of the parallel sheet structure of chitin,decrement of the thickness of the exo- and endocuticleand loses of attachmentof the epicuticle and exocuticle to the epidermis.