Reduction of black vine weevil larval growth by vesicular-arbuscular mycorrhizal infection

Larvae ofOtiorhynchus sulcatus (black vine weevil) were reared at three densities (zero, two or eight), on plants ofTaraxacum officinale (dandelion) with and without infection by the mycorrhizal fungusGlomus mosseae. On plants without the fungus, survival of larvae to late final instar was 84%, but this was only 43% on infected plants. The differential survival of larvae was evident in their effects on plant biomass. Significant interactions were found between larval density and infection, indicating that mycorrhizal presence mitigated the effects of herbivory at the low larval density. Infection byG. mosseae thus conferred some degree of resistance in roots to this insect and the consequences of this for horticultural and natural situations are discussed.