leafhopper
leafhopper, (family Cicadellidae), large family of more than 20,000 species of small, slender, often beautifully colored and marked sap-sucking insects. They are found on almost all types of plants; however, individual species are often host-specific. Although a single leafhopper does no noteworthy damage to a plant, collectively they can be serious economic pests.
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
- Order: Hemiptera
- Family: Cicadellidae
See also list of insects.
Most leafhoppers are several millimeters long; some may grow to 15 mm (0.6 inch). Their bodies are dorso-ventrally flattened or cylindrical, with the head varying in shape and size from short, broad, and rounded to long, thin, and bladelike. Their hairy hind legs are modified for jumping. Sexual dimorphism is common in most species, with males and females often colored differently. For example, the male leafhopper Arundanus nacreosus, a species common on cane, is orange, and the female is milk white. Size and form may also vary between males and females. For example, the male marsh leafhopper (Hecalus lineatus) is not only a different color than the female but also only half as long. As sap feeders, they have piercing-sucking mouthparts and excrete honeydew, a sweet by-product of digestion.
Life cycle
Leafhopper growth is gradual and is accompanied by periodic molting. The nymphal stages, or instars, between egg and adult usually number five. Wings develop when the fifth instar molts and the adult emerges. While most species have one generation a year, a few have two or three.
Many leafhoppers (e.g., Empoasca maligna, Gyponana mali) have annual life cycles that involve passing the winter as eggs inserted in twigs. Other leafhoppers, however, such as Empoasca recurvata and Erythroneura, hibernate as adults during the winter. The sugarbeet leafhopper, Circulifer tenellus, winters as an adult in desert areas and produces an early spring generation on desert plants. As desert plants become unfavorable for feeding, the leafhoppers migrate to available cultivated plants where from one to four summer generations are produced. When the crop is harvested or the plants become unfavorable for feeding, the leafhoppers return to desert plants. Although definite alternation of desert and cultivated host plants occurs in this life cycle, no specific plant serves as a primary or secondary host. Plant selection by migrating leafhoppers is determined largely by the amount of rainfall and succulence of both wild and cultivated plants.
Plant damage and diseases
Leafhoppers cause various types of plant injury by interfering with the normal physiology of the plant. The salivary secretion of the potato leafhopper, for example, causes leaf cell hypertrophy that impairs transport of sugars. The resulting sugar accumulation in the leaves destroys chlorophyll and causes the leaves to turn brown and die. This injury, termed “hopper burn,” can result in complete loss of a potato crop if not controlled.
Another type of injury is caused by leafhoppers that feed upon plant mesophyll tissue. In addition to removing excessive amounts of sap, these insects also destroy the plant’s chlorophyll, resulting in yellow spots on the leaves, which eventually turn yellow or brown. Erythroneura, Typhlocyba, and Empoasca species cause this injury to apple trees and grapevines. Grape leafhoppers reduce growth and foliage function and cause formation of grapes that are inferior in size, color, flavor, and sugar content.
Plants also are injured when insects lay eggs in green twigs. The egg punctures of several leafhoppers reduce the flexibility of plant limbs. Plant stunting and severe curling of leaves occur when the leafhopper Empoasca fabae punctures the undersurfaces of leaves and veins of bush beans and inhibits growth. This leafhopper also feeds on alfalfa and causes leaves to turn yellow and drop off.
In addition to feeding and egg-laying injuries, more than 100 species of leafhoppers are known to cause plant diseases. Some important plant disease viruses transmitted by leafhoppers are aster yellows (transmitted by Macrosteles fascifrons); potato yellow dwarf (several species of Aceratagallia and Agallopsis); and phony peach disease and Pierce’s disease of grape (species of Cuerna, Homalodisca, and Oncometopia). Corn stunt is transmitted by species of Dalbulus; curly top of sugar beet by Circulifer tenellus; eastern and western x-disease by species of Colladonus; and elm phloem necrosis by Scaphoideus luteolus. The bacteria that cause fire blight disease on pear, apple, and quince trees are transmitted by several types of insects including leafhoppers.
Major species
The apple leafhopper (Empoasca maligna) causes apple foliage to pale and become specked with white spots. The adult insects are greenish white, and they are host specific for either apple or rose. There is one generation per year.
The beet leafhopper (Circulifer tenellus) is the carrier of a viral disease known as curly top that curls sugar beet leaves and stunts plant growth. The adults are pale green or yellow and are about 3 mm (0.1 inch) long. There are three or more generations per year. In addition, beet leafhoppers infect tomato, cantaloupe, cucumber, spinach, and other garden plants.
The grape leafhopper (Erythroneura) is a slender yellow-colored insect with red markings and is about 3 mm long. It feeds on developing leaves and overwinters among fallen grape leaves. The insects frequently develop large populations that result in heavy plant losses, and can be found on the grapevine, Virginia creeper, and apple tree; they are controlled by spraying or dusting.
The potato leafhopper (Empoasca fabae) is a destructive potato pest that causes that plant’s leaves to turn brown and curl; the insect plugs the plant’s xylem and phloem vessels, thus interfering with the transportation of food products. Adult potato leafhoppers are green with white spots on the head and thorax and are about 3 mm long. Instead of hibernating in the north, they overwinter on legumes in warm climates. This insect carries viral diseases and infects beans and apples as well as potatoes.
The rose leafhopper (Edwardsiana rosae) is a serious rose and apple pest. It is creamy white to light yellow in color and is about 3 mm long. It overwinters in the egg stage and produces two generations per year. It does not cause hopper burn.
The six-spotted leafhopper (Macrosteles fascifrons) is greenish yellow with six black spots. It produces several generations per year. It infects asters and other garden plants and transmits aster yellow virus, which causes excessive branching, stunted growth, and foliage to turn yellow.