Glassy-winged sharpshooter

What you are looking at

A large, plain brownish leafhopper, 12 to 14 mm long, wedge-shaped and carrying translucent wings marked with fine dark veins, found on woody stems and shoots rather than on leaf surfaces the way most leafhoppers are. Beneath an area where it has been feeding, leaves and fruit often carry rows or patches of white, chalky excrement residue, a distinctive sign known locally as leafhopper rain. Egg masses show as neat rows laid just under the surface of a leaf, visible as a slightly raised, blistered patch when the leaf is held up to the light.

The insect’s own feeding does some direct damage to young shoots, but the serious threat is what it carries while doing it. As a xylem feeder, it moves the bacterium behind Pierce’s disease from plant to plant as it feeds, and marginal leaf scorch, dieback and vine collapse following a population of this insect are symptoms of that infection rather than of the feeding itself.

From a minor Texan pest to California’s most damaging vine vector

Native to the south-eastern United States and north-eastern Mexico, this species stayed a minor concern for most of its range, kept in check by natural enemies and by the more limited susceptibility of its usual native hosts. That changed once it spread into southern California in the late 1980s or early 1990s, almost certainly carried in on nursery stock. Freed from the natural enemies that controlled it at home and moving through vineyards planted with susceptible grape varieties, it became the region’s most significant vector of Pierce’s disease, contributing to tens of millions of dollars in vineyard losses across areas including Temecula, Bakersfield and the Coachella Valley since the outbreak began.

It has been intercepted repeatedly in French Polynesia, Hawaii and other Pacific islands, and remains a quarantine concern both for the movement of nursery stock out of California within the United States and for any region without an established population. It has not established outside North America.

What to do about it

Buy nursery stock only from certified, pest-free sources, since infested planting material is how this insect reached California in the first place and remains the main way it could reach a new region.

Control weeds and remove overgrown or infested host material at the edges of a vineyard or orchard, since this insect breeds on a wide range of woody plants beyond the crop itself.

Monitor with yellow sticky traps at field margins to catch a rising population early, and report a sighting outside its established range in the south-eastern United States and California to the local plant health authority immediately.

Support area-wide parasitoid release as the primary control. Reserve a registered systemic insecticide for a high-value planting under heavy pressure that parasitoid release, monitoring and infected-vine removal have not brought under control on their own.

What it gets mistaken for

Aphids cluster in soft colonies on new growth and leaf undersides and leave clear, sticky honeydew rather than the chalky white spatter this leafhopper produces, and they do not feed preferentially on woody stems the way this species does.