Laboratory evaluation of a new strain CCM 8367 of Isaria fumosorosea (syn. Paecilomyces fumosoroseus ) on Spodoptera littoralis (Boisd.).

Laboratory experiments were conducted to assess the efficiency of the new strain CCM 8367 ofIsaria fumosoroseaon different stages of the Egyptian cotton leafworm,Spodoptera littoralis(Boisd.), including soil treatments with pre-pupal and pupal stages. Treatments of larval instars showed a high susceptibility with 3rd, 5th and last instars to suspension of this fungus with concentration 5 × 107spores/ml. Larval mortality was over 90%. There were no significant differences (P = 0.7929,F = 0.2346) between instar treatments. The commercial fungus, PreFeRal® strain Apopka 97 ofI. fumosorosea, which was used in comparison with this new strain caused mortality rates of between 63.33 and 90%. Statistically, differences between the effects of CCM 8367 strain and Apopka 97 were highly significant on the last instar (P = 0.0064,F = 6.479) and extremely significant on the 3rd instar (P < 0.0001,F = 13.29). No significant differences were recorded between the two strains on the 5th instar (P = 0.0597,F = 3.233). Fungal treatments with the late stage insects (end of the last instar or pupal stage) in soil yielded interesting results: the mortality rate on end of final instar larvae was 16.66% when treated with Apopka 97 and 83.33% when treated with CCM 8367. Soil containing pupae ofS. littoralisthat were inoculated with CCM8367 resulted in a high number of malformed adults, and the mortality rate was 64.52% (32.27% of malformed adults died and 32.25% of pupae fully infected by fungus). Only 3.23% of samples produced morphologically normal adults in this test. The results conclude that the strain ofI. fumosoroseaCCM 8367 has strong insecticidal effects onS. littoralisand has the potential to be implemented as a novel biocontrol agent. [ABSTRACT FROM AUTHOR]