Potential insecticidal activity of Sarocladium strictum, an endophyte of Cynanchum acutum, against Spodoptera littoralis, a polyphagous insect pest

Spodoptera littoralis has been recognized as the major destructive cause of various economic crops in Egypt. Chemical insecticides have been frequently used, however, the development of insecticidal resistance is the current challenge, thus searching for novel ecofriendly biocontrol agents is the prospective challenge. Fungal endophytes of plants have been recognized as a repertoire for bioactive metabolites. Thus, the objective of this study was to isolate a potential endophytic fungal isolates from different medicinal plants, with an efficient insecticidal activity against S. littoralis. Fifteen plant genera were selected, and their endogenous endophytic fungi were recovered, and their insecticidal activity were resolved. Forty-five isolates were recovered from these plants, Sarocladium strictum, endophyte of Cynancum acutum, and Aspergillus nidulans, endophyte of Lantana camara, displayed the highest insecticidal activity against 2nd larval instar of S. littoralis. The identity of S. strictum and A. nidulans has been confirmed based on their ITS sequence and deposited on genbank with accession # MK367604 and MK367603, and deposition # AUMC14096 and AUMC14095, respectively. The EtOAc and DCM extracts of S. strictum exhibited a strong effect on the total larval period, pupal period and development period of S. littoralis immature. The LC50 were 11.8, 15.3 mg/ml for S. strictum EtOAc and DCM extracts, while it was 22.6 and 34.4 mg/ml for A. nidulans DCM and EtOAc extract. A strong deformation was observed to the adults of S. littoralis by about 25.1% individuals descending from larvae treated with S. strictum EtOAc. The four major compounds from S. strictum EtOAc extract were resolved as Cis-13-octadecenoic acid, sebacic acid, pentamethoxy flavone and n-hexadecanoic acid.