Biological and molecular characterization of Cladosporium sp. and Acremonium zeylanicum as biocontrol agents of Aphis fabae in a tri-trophic system

Entomopathogenic fungi (EPF) are the most important category of microbial agents and considered to be crucial elements in biological control. In this study, two species of EPF, Cladosporium sp. AF98 (Ascomycota: Davidiellaceae) and Acremonium zeylanicum IR87 (Petch) W. Gams & H.C. Evans (Ascomycota: Hypocreaceae), were isolated from infected individuals of the citrus cottony scale, Pulvinaria aurantia Cockerell (Hemiptera: Coccidae), and the melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), respectively. Based on the nucleotide sequence of the ribosomal DNA, the fungal isolates were subjected to molecular identification and phylogenetic analysis. Pathogenicity of the fungal isolates to the black bean aphid, Aphis fabae Scopoli, was evaluated under laboratory conditions. Both fungal isolates caused considerable aphid mortality and no significant differences were observed in pathogenicity of the isolates. The severity of the fungal isolate effect on the aphid increased as the conidial concentration increased. Time was found to be a more important factor than conidia concentration in isolate efficacy. Olfactory experiments indicated that Lysiphlebus fabarum Marshall (Hymenoptera: Braconidae, Aphidiinae), an important parasitoid wasp of A. fabae, can detect cues from the fungus-infected aphids and can avoid them. Therefore, fungal isolates have considerable potential for the microbiological control of the aphid and are also compatible with other means of biological control of the pest.