Forest Preserve District of Cook County, Illinois
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Nature Bulletin No. 566-A   may 10, 1975
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

Many of us are blind to the common things about our feet Leafhoppers, for instance. They are very small and expert at playing hide-and-seek among plants, or they hop so quickly that the eye can scarcely follow them. Yet, sometimes, in a patch of tall bluegrass, swarms of them scatter right and left beneath our trampling feet. Sweep a butterfly net over any summer meadow and you are likely to collect more leafhoppers than any other insect. On hot summer nights, if reading in bed is one of your pleasures, they come through window screens, cluster about your reading light, and an occasional one stabs you with its beak.

The leafhoppers are small, slender, torpedo-shaped bugs with piercing mouth parts suited for sucking plant juices, their only food. They have large eyes set in broadly curved or triangular heads; and, at rest, adults hold their front wings roof-like over the body. About 2000 species are known in North America Commonly less than one-eighth of an inch long, they rarely reach a half-inch in length. Among the largest are the Blue Dodger which feeds on okra or sunflowers, and the gaudily decorated Red-banded Leafhopper which attacks a long list of garden flowers and ornamental shrubs. The name "dodger" comes from their habit of sidling around plant stems to conceal themselves. Some are called "sharpshooters" because, when feeding actively, they pop out droplets of unabsorbed plant sap, or honeydew. This sweetish liquid is eagerly lapped up by ants, bees, wasps and flies.

Typically, their tiny eggs are laid in the leaves or stalks of plants. The newly-hatched young, or nymphs, resemble small editions of the parents. As they feed and grow, these molt their skins 4 or 5 times, finally emerging as mature adults with two pairs of wings. One generation a year is usual, but a few have two or three. Some species hibernate as adults; others as eggs.

Leafhoppers are best known for the damage that a few of them do to garden and farm crops, cultivated flowers, ornamental shrubs, and trees. Their feeding may drain plant juices from the leaves causing them to whiten, curl, wilt and die around the edges; or they stunt a plant by injuring the green growing tips of the stems. Common instances of this direct damage are found on apple trees, roses, potatoes, and alfalfa.

Far more deadly to plants than the leafhoppers themselves are the diseases that some of them spread. The beet leafhopper, for example, is the only known carrier of "curly top, " an extremely destructive virus disease of sugar beets, beans, tomatoes, spinach, melons and other crops in our western states. The insect normally breeds on salt bush, Russian thistle, greasewood and other weeds of arid foothills and desert regions. Wintering on these wild plants, the adults lay their eggs in March. This generation matures in May and June and flies in swarms, often carried by the wind for hundreds of miles, to their summer hosts where they produce a second brood and infect beet fields with the curly top disease.

Two killing diseases, both insect-borne, are wreaking havoc among our elms in the Middle West. Within the past few years, these two epidemics have destroyed half of the elms in several down-state Illinois cities and rural regions. The Dutch elm disease, most deadly and rapidly spreading, is caused by a fungus carried from infected to healthy trees by elm bark beetles. The other killer is elm phloem necrosis, a virus disease spread entirely by the feeding of the elm leafhopper.

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