LETHAL AND PATHOGENIC EFFECTS OF THREE ENTOMOPATHOGENIC FUNGI AGAINST ADULTS AND NYMPHS OF Aphis craccivora KOCH (HEMIPTERA: APHIDIDAE)

Abstract

Three commercial formulations of entomopathogenic fungi such as Metarhizium anisopliae, Beauveria bassiana and Verticillium lecanii were investigated for Aphis craccivora Koch control. For both the adult and nymph stages of A. craccivora, M. anisopliae was shown to be more virulent than B. bassiana and V. lecanii. The virulence of M. anisopliae caused 100% mortality in adults after three days at a concentration of 6.0 ml/l (6 × 105 spores/ml), while the same fungi caused 100% mortality in nymphs after two days at a concentration of 1.2 ml/l (1 × 105 spores/ml). The lethal time of 50% of individuals (LT50) was decreased significantly as the applied spore concentration increased. Metarhizium anisopliae also exhibited the highest virulence to A. craccivora. The 50% lethal concentration (LC50) of the spore suspension of M. anisopliae, B. bassiana and V. lecanii for adults were 1.13, 2.05 and 1.36 ml/l, respectively and for nymphs, it were 0.91, 1.45, 1.15 ml/l, respectively. The developmental periods of the nymphal stage were increased significantly as the applied spore concentration increased. Metarhizium anisopliae fungi were more effective than B. bassiana and V. lecanii in reducing the number of young borne produced by the adult stage. The results indicated that the nymphal stages of aphids exposed to the virulence of M. anisopliae, B. bassiana and V. lecanii formulations prolonged the developmental period of its instars.