**Glassy-winged Sharpshooters** (*Homalodisca vitripennis*) are large, invasive leafhoppers native to the southeastern United States. They are among the most serious agricultural pests globally, not primarily for their direct sap feeding, but because they are highly efficient vectors of the bacterium *Xylella fastidiosa*. This bacterium causes severe, incurable diseases in high-value perennial crops, most notably **Pierce’s Disease** in grapevines, which can devastate entire vineyards within a few seasons.
Taxonomy and Classification
Glassy-winged Sharpshooters belong to the family Cicadellidae (leafhoppers) in the order Hemiptera (true bugs). They undergo incomplete metamorphosis. They are strong flyers and their name comes from their distinct, dark, translucent (glassy) wings and their habit of quickly “shooting” a droplet of excess fluid from their rear end while feeding.
Physical Description
Adult Sharpshooters are large for a leafhopper, about $1/2$ inch long, robust, and dark-colored.
- **Appearance:** Dark brown to black, often with light specks on the head and thorax. The wings are clear and slightly smoky.
- **Feeding:** They possess piercing-sucking mouthparts (stylets) used to access the plant’s **xylem** tissue (water-conducting vessels), allowing them to feed on the water and dilute nutrients within.
- **Contamination:** Due to their xylem-feeding diet, they process and excrete large volumes of water as tiny droplets (**sharpshooter rain**), which can coat the foliage below.
Distribution and Habitat
Native to the Southeastern U.S., the Glassy-winged Sharpshooter was accidentally introduced to California and other areas, becoming a severe pest. Its habitat is diverse due to its wide host range (over 100 plant species), including citrus, avocado, landscape ornamentals, and especially grapevines and riparian (streamside) vegetation.
Behavior and Damage
The sharpshooter has multiple generations per year and is a mobile pest. The primary damage is the transmission of the *Xylella fastidiosa* bacterium:
- **Vectoring Pierce’s Disease (PD):** The bacterium colonizes the xylem vessels, blocking the flow of water and nutrients. Infected grapevines show scorched leaf margins, weak growth, and fruit failure, leading to death in 2–5 years.
- **Vectoring Other Diseases:** The same bacterium causes leaf scorch in almonds, olives, and ornamental trees (e.g., oleander).
- **Rapid Spread:** The sharpshooter’s ability to fly long distances and rapidly acquire and transmit the bacteria makes PD spread quickly in high-density host areas.
Management and Prevention
Control is highly coordinated and legally enforced in quarantine zones to protect agricultural commodities.
- **Quarantine and Monitoring:** Intensive monitoring using visual checks and yellow sticky traps is used to detect new populations, especially near nurseries and vineyards.
- **Systemic Insecticides:** Chemical control relies heavily on systemic insecticides (applied to the soil or trunk) to kill the insects before they can feed and acquire or transmit the bacterium.
- **Biological Control:** The release of specialized **parasitic wasps** (*Gonatocerus* spp.) that attack the sharpshooter’s eggs is a cornerstone of long-term biological control efforts.
- **Removal of Reservoirs:** Eliminating non-crop host plants (weeds, riparian vegetation) near vineyards can reduce the source of both the sharpshooter and the bacterium.
Conservation and Research
The Glassy-winged Sharpshooter is managed as one of the most economically devastating invasive agricultural pests. Research focuses intensely on developing grapevine varieties resistant to *X. fastidiosa* and improving early detection methods for both the vector and the disease.