The potential of endophytic fungi as bio-control agents against the cotton leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

Endophytes are promising bio-control agents and rich sources of secondary metabolites known for their biological activities. Two medicinal plants, Pelargonium graveolens and Melia azedarach, and two weeds, Chenopodium album and Malva parviflora, were selected to isolate endophytic fungi. Spore suspension of Alternaria alternata (MG786545), Alternaria solani (MG786543), Curvularia lunata (MF113056), Nigrospora sphaerica (MF113055), and Stemphylium sp. endophytes was tested for their pathogenicity to the third-instar larvae of the cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae). Two techniques were used: dipping in spore suspension and residual film assay. Secondary metabolites were extracted, and ethyl acetate extracts of A. alternata (MG786545), C. lunata (MF113056), and N. sphaerica (MF113055) were tested for their insecticidal activity by both techniques. C. lunata (MF113056) showed the most potent pathogenicity causing 60% mortality after 7 days by dipping bioassay, while A. solani (MG7865453) and A. alternata (MG786545) caused 40 and 33.3% mortality, respectively. All tested endophytes showed no effect against S. littoralis by residual film method. N. sphaerica ethyl acetate extract activated larval feeding on castor leaves causing 25% mortality by residual film at 2000 mg/l.