Identification of a Virulent Isolate of the Entomopathogenic Fungus Beauveria bassiana (Balsamo) Vuillemin, its Mass Multiplication and Formulation for Development into a Mycoinsecticide for Management of Helicoverpa armigera (Hubner)

Two promising isolates of Beauveria bassiana - ITCC 4513 and HaBb DOR were multiplied on wheat bran supplemented with molasses and yeast extract in a polythene bag with sponge plugs for aeration. The yield of dry conidial powder per polythene bag was 18.25 ± 1.79 g and 10.03 ± 2.47 g for ITCC 4513 and HaBb DOR isolates, respectively. Laboratory bioassays with these conidial powders against 6 days old Helicoverpa armigera larvae resulted in LC50 values of 1.8 x 108 and 2.41 x 108 conidia ml-1 for the ITCC 4513 and HaBb DOR isolates, respectively, 5 days after treatment. Conidia of both the isolates were formulated as Suspension Concentrates (SC) in groundnut, sunflower and mineral oils. The formulations gave a clear suspension in water and could be sprayed with high volume knapsack sprayers. Performance of both isolates when formulated in oils was superior to unformulated conidia as reflected by the higher mortality of H. armigera larvae in laboratory bioassays and field trials on sunflower. The ITCC 4513 isolate was, however, superior to the HaBb DOR isolate in terms of conidial yield, efficacy as an SC formulation against H. armigera and safety to the egg parasitoid Trichogramma chilonis, thus proving to be an ideal candidate for development into a mycoinsecticide.