Abstract:
Plants are regularly colonised by fungi and bacteria, but plant-inhabiting microbes are rarely considered
in studies on plant–herbivore interactions. Here we show that young gypsy moth (Lymantria
dispar) caterpillars prefer to feed on black poplar (Populus nigra) foliage infected by the rust
fungus Melampsora larici-populina instead of uninfected control foliage, and selectively consume
fungal spores. This consumption, also observed in a related lepidopteran species, is stimulated by
the sugar alcohol mannitol, found in much higher concentration in fungal tissue and infected
leaves than uninfected plant foliage. Gypsy moth larvae developed more rapidly on rust-infected
leaves, which cannot be attributed to mannitol but rather to greater levels of total nitrogen, essential
amino acids and B vitamins in fungal tissue and fungus-infected leaves. Herbivore consumption
of fungi and other microbes may be much more widespread than commonly believed with
important consequences for the ecology and evolution of plant–herbivore interactions.
