Lethal and pathogenic effects ofBeauveria bassianaandLecanicillium lecaniion the adult and nymph ofAphis craccivoraKoch

Two strains of entomopathogenic fungi such as Beauveria bassiana and Lecanicillium lecanii in two commercial formulations were screened for A. craccivora control. Entomopathogenic fungi L. lecanii showed the higher virulent pathogenicity than B. bassiana for both adult and nymph stages of A. craccivora. The virulence of L. lecanii caused 100% mortality in adults over three days at a concentration of 5.0 ml/l (5 × 106 spores/ml), while the same fungi achieved 100% mortality in nymphs over three days but at a concentration of 1.0 ml/l (1 × 106 spores/ml). The lethal time of 50% of individuals (LT50) decreased significantly as the applied spore concentration increased. L. lecanii also exhibited the highest virulence to A. craccivora. The 50% lethal concentration (LC50) of the spore suspension of this fungus was determined to be 0.638 and 0.16 ml/l for adult and nymph stages, respectively. The developmental periods of the nymphal stage increased significantly as the applied spore concentration increased. Lecanicillium lecanii fungi was more effective than Beauveria bassiana in reduction of the number of young borne produced by the adult stage. The results indicated that the nymphal stages of aphids exposed to the virulents of L. lecanii or Beauveria bassiana formulations prolonged the developmental period of its instars.