The Aster Leafhopper (Macrosteles quadrilineatus), can be a concern to anyone growing lettuce, tomatoes, celery, carrots (and other vegetables), endice, parsnip, and many different kinds of flowers [such as coneflowers, daisies, marigolds, zinnias, snapdragons, and chrysanthemums] because it serves as a vector for the mycoplasma-like pathogen known as aster yellows. We do not see aster yellows disease very often in samples at our Plant Disease Diagnostic Lab (in Orono, Maine) but 150 species of plants in at least 40 different plant families have been recorded as hosts of aster yellows that can be vectored by the aster leafhopper. Leafhoppers in general are notorious for transmitting plant pathogens, such as viruses, phytoplasmas, and bacteria, because of the manner in which they feed. They have piercing-sucking (i.e. straw-like) mouthparts, enabling them to feed on the sap of a plant. A leafhopper’s diet commonly consists of sap from a wide and diverse range of plants, but some are more host-specific than others. Large numbers of leafhoppers, of any kind, can stress plants, also, simply from the depletion of the sap (i.e. the water and nutrients) that they rob from the plants. That aspect can be particularly significant during periods of drought.