The virulence of 25Metarhizium anisopliaeisolates was testedunder laboratory conditions and the two most effective isolateswere evaluated in the field for control of theAilanthusdefoliator,Atteva fabriciella. A bioassay was carried out to determine the doseand time mortality responses. The LC50of the isolates ranged from3.16 to 647.81105conidia mL-1. Toxicity tests of the isolatesMIS7 and MIS13 and 0.5%Pongamia pinnataseed oil, individu-ally and in different combinations, indicated improved efficacyof the isolates when used in combination and also when com-bined with seed oil. Evaluation of these formulations in the fieldshowed 66.36% reduction of infestation with MIS7+MIS13+0.5%P. pinnataseed oil and 61.15% reduction with MIS7+MIS13. Thestudy indicated a possibility of employing combined formulationsofM. anisopliaeand also combination withP. pinnataseed oil foraugmenting the effectiveness of the fungus.