**Leafhoppers** (family Cicadellidae) are small, slender insects found globally that are serious economic pests of numerous plants, including crops, fruits, vegetables, and ornamental trees. They cause damage in two ways: through **direct feeding** (sucking plant sap), which causes stippling or browning of foliage, and, more significantly, by acting as **vectors** for numerous debilitating plant diseases, including phytoplasmas and viruses, which can kill entire crops.
Taxonomy and Classification
Leafhoppers belong to the family Cicadellidae in the order Hemiptera (true bugs). They are part of the suborder Auchenorrhyncha, which also includes cicadas and treehoppers. They undergo incomplete metamorphosis (egg, nymph, adult). Leafhoppers are highly diverse, and many species are specialized feeders on a few host plant types, while others, like the **Potato Leafhopper** (*Empoasca fabae*), are generalists with extremely wide host ranges.
Physical Description
Adult Leafhoppers are small, usually 2–15 millimeters long, characterized by a slender, wedge-shaped body and powerful hind legs adapted for jumping. They are often green, yellow, or mottled brown, providing camouflage. Their wings are held roof-like over the abdomen. When disturbed, they typically scuttle sideways or hop vigorously.
The **nymphs** resemble miniature, wingless versions of the adults. A key field identification feature of the nymph is that it often runs sideways or backwards when threatened, and it is usually found feeding on the undersides of leaves or on the terminal shoots.
Distribution and Habitat
Leafhoppers are found everywhere plants grow, from forests and grasslands to agricultural fields and vineyards. Their habitat is the foliage of their host plants. Some species are migratory, moving northward seasonally, which can lead to sudden, widespread infestations in agricultural areas.
Behavior and Life Cycle
Leafhoppers typically have multiple generations per year in warm climates. Females lay eggs singly within the plant tissue (stems or leaf veins). The nymphs hatch and immediately begin feeding using their piercing-sucking mouthparts. They pass through five nymphal stages (instars), completing their development quickly in warm weather.
Their most defining behavior is their rapid, darting movement and their ability to jump long distances relative to their size, which they use to evade predators.
Feeding and Damage
Leafhoppers cause two major types of damage:
- **Direct Feeding Damage:** They suck the sap from the plant’s vascular system. In high numbers, this causes the leaves to develop pale spots, stippling, or curling. For certain species (like the Potato Leafhopper), the injection of toxic saliva causes a systemic reaction called **hopperburn**, where leaf margins turn brown and curl upwards, significantly reducing yield.
- **Disease Transmission (Vectors):** This is the most serious form of damage. Leafhoppers transmit numerous plant pathogens, including the bacterial agent causing **Pierce’s disease** in grapes and **Aster Yellows** (a phytoplasma) in carrots, lettuce, and ornamentals. Once infected, plants often cannot be cured and must be removed.
Management and Prevention
Management focuses heavily on **early detection** and **controlling disease spread**.
- **Exclusion:** For high-value crops and gardens, using fine-mesh row covers can physically exclude the pests.
- Chemical Control: Insecticides are used, often targeting the migratory adults immediately upon arrival, to prevent feeding and, more importantly, to prevent the initial inoculation of plants with pathogens. Systemic insecticides are often used in nurseries.
- **Cultural Control:** Removing weedy hosts (like clover and asters) near crops helps eliminate overwintering sites and sources of infection for the leafhoppers.
Conservation and Research
Leafhoppers are aggressive economic pests. Research focuses on their migration patterns, the specific mechanisms of disease transmission, and developing genetic resistance in crop plants to both the leafhopper feeding toxins and the pathogens they transmit.