Effects of four entomopathogenic fungi isolates on larvae of the Sugar beet worm, Spodoptera exigua,hubner,Lepidoptera:Noctuidae,
2012
Ali, S.S.
This study was conducted to clear the difference in virulence among ýfour fungi isolates. ( Two isolates of Metarhizium anisopliae, Ml and ýM2, and another two isolates of Beauveria bassiana, B1 and B2 were ýisolated from soil and dead insects. The most important results could be ýsummarized as follows: Variation in quantity of spores produced was ýstudied on different solid media; grains media , rice, wheat, maize and ýsoybean produced conidia and Czapek Dox Agar medium with small ýglass balls, (CzDA+b ) and CZA medium as the control for comparison. ýTemperature of 25°C was found optimum. It gave maximum production ýof spores for all isolates. Ml produced the highest amount of conidia ( ýý11.2 x 10. spore / plate) on (CzDA+b.) M2 gave 10.09 x 10. spore / ýplate on the same medium, B 1 produced 1.92 x 10. spore, /plate and ýB2 gave 2.02 x 10. spore / plate. The isolate M1( M anisopliae) was the ýmost effective against S. exigua 3rd instar larvae. M 1 at high ýconcentration (1.Ox 10. ) achieved 87.0 % mortality within 5.6 ± 1.9 ýdays. The highest effective toxin was produced by M anisopliae (Ml) ýinducing mortality percentage of 92.15%. The maximum activity of ýenzymes was recorded in Ml; chitinolytic activity( 0.597µg ýNAGA/min./ml) . In case of protease, M1 recorded the greatest activity ýý(1017.0 O.D. unit x 10. / hr./ml). The same trend in the activity pattern ýwas obtained for lipase (42.980 U/ml). Complete extraction of destruxins ýfrom the crude toxins of M anisopliae isolates showed that M1 ýcontained the molecular weights of destruxins A,B and D, M2 contained ýthe molecular weights of dex. D B and cytochalasin A.ý
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