Mycelial information networks:

When some plants are attacked by sap-sucking aphids, they emit volatile compounds into the air. These volatiles serve as a defense mechanism, and in more ways than one. First, they serve to repel the aphids attacking the plant. Second, they attract the aphids natural enemies, wasps. But there’s more to that: a team from the University of Aberdeen and the James Hutton Institute show that some plants use fungi to communicate the presence of aphids, allowing those plants to emit wasp-attracting and and aphid-repelling  volatiles even before they have been physically attacked.