Compatibility and synergistic interactions of fungi, Metarhizium anisopliae, and insecticide combinations against the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae)

Abstract

Aphids are major pests affecting cereals, vegetables, fruit, forestry and horticultural produce. A multimodal approach may be an effective route to controlling this prolific pest. We assessed the individual and combined effect of eight insecticides and the entomopathogenic fungi, Metarhizium anisopliae (Metschin.) against the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), under laboratory conditions. Six of the insecticides tested were found to be highly compatible (flonicamid, imidacloprid, nitenpyram, dinotefuran, pyriproxyfen and spirotetramat), showing positive integration with the fungus and were selected for bioassays. The combination mixtures (1:1 ratio of M. anisopliae: insecticide) were significantly more toxic to A. gossypii than individual treatments. Maximum mortality (91.68%) of A. gossypii was recorded with combination of flonicamid and M. anisopliae (2.4 × 106 cfu/ml) 72 h after application. While minimum mortality (17.08%) was observed with the individual treatment of M. anisopliae (2.4 × 106 cfu/ml). The insecticides revealed toxicity consistent with their compatibility with M. anisopliae, ranking for efficacy exactly as they did for compatibility. In addition, the synergy factor (SF) and co-toxicity coefficient (CTC) values indicated synergistic interactions at different time intervals. The synergistic efficacy revealed the potential of fungus-insecticide integration against sucking insect pests.