Aggressiveness of Conidiobolus obscurus against the Pea Aphid: Influence of Cuticular Extracts on Ballistospore Germination of Aggressive and Non-aggressive Strains

SUMMARY: Cuticular extracts of Acyrthosiphon pisum, the pea aphid, stimulated the formation of germ-tubes of ballistospores of aggressive strains of Conidiobolus obscurus, but showed no influence on those of non-aggressive strains. Aggressive strains were separated into two groups: (a) those stimulated by both (i) water- or alcohol-soluble cuticular extracts originating from honeydew and (ii) lipidic extracts of the cuticle, and (b) those stimulated by (ii) only. The hydrocarbon and polar fractions of the cuticular lipids were the most active. These results obtained with C. obscurus are compared to the effect of cuticular compounds on spore germination in other entomopathogenic fungi.