Aphids or plant lice are agricultural and ornamental plant pest. They are soft bodied insects that feed on plant sap by piercing stems, leaves, buds, roots and fruit. A heavily infested plant may have its leaves curl or its growth stunted. Aphids can also introduce fungus, and be vectors for bacterial and virus diseases. Aphids expel a sweety sticky honeydew. Aphids have natural enemies, the black husk in the lower right was parasitized by a wasp who laid eggs inside.