How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Glassy-winged sharpshooter (family Cicadellidae) sucks leaf and stem xylem tissue, and vectors Xylella fastidiosa bacteria lethal to certain crops. While feeding, adults and nymphs excrete large amounts of liquid, which gives fruit and foliage a whitewashed appearance. Glassy-winged sharpshooter adults feed on over 300 plant species and can reproduce (lay eggs) in about 100 species.

Sharpshooters are active insects that walk rapidly sideways or readily jump when disturbed. The glassy-winged sharpshooter is a larger than most other leafhoppers. Adults are about 1/2 inch (13 mm) long and dark brownish with white and yellowish patches and spots. Pale head spots help to distinguish glassy-winged sharpshooter from the native smoke-tree sharpshooter (Homalodisca lacerta), which has light-colored wavy lines on the head.

Females lay eggs in a cluster of about one dozen eggs within the lower surface of leaves. Eggs initially resemble a greenish blister on the leaf, which females cover with a white chalky secretion. Eggs turn brown as they mature and leave a permanent brown to gray scar in leaf tissue after nymphs emerge.

Immature glassy-winged sharpshooters develop through several stages (instars) and resemble small adults, except the immatures are wingless, uniformly olive gray, and have prominent bulging red eyes. Smoke-tree sharpshooter nymphs appear very similar but have blue eyes.

The glassy-winged sharpshooter has two generations per year in California. Although all life stages can be found year-round, reproduction and immature stages occur mostly from late winter through fall. Overwintering adults oviposit in late winter and early spring. Nymphs mature into first generation adults during about April through early June. Most second generation adults appear during later summer through fall, and can survive overwinter until the following season.

DAMAGE

Glassy-winged sharpshooter is not currently damaging in avocado. Quarantines may require treatment of nursery stock before young avocado trees can be shipped.

Glassy-winged sharpshooter is a serious pest of certain other crops because it vectors lethal Xylella fastidiosa diseases such as almond leaf scorch, oleander leaf scorch, and Pierce's disease of grapes. No leafhopper-vectored avocado diseases have been observed in the United States. However, strains of Xylella in other parts of the world, such as one reportedly damaging avocado in Costa Rica, could be damaging if introduced into California.

MANAGEMENT

Avocado nurseries may be required to treat stock and meet other requirements when producing and shipping young avocado trees. Contact the county department of agriculture for current quarantine compliance rules.

In established avocado groves, glassy-winged sharpshooter generally requires no management. However, monitoring may be warranted if avocado are grown near untreated citrus or other favored hosts. Yellow sticky traps are useful for monitoring adults of glassy-winged sharpshooter and their primary parasites (Gonatocerus spp.) Mid-summer through fall are the best times to deploy and inspect traps. Glassy-winged sharpshooters become most abundant during their second generation, when they move into avocado from nearby citrus.

If abundant in avocado, consider removing or replacing nearby alternate hosts such as favored ornamentals and abandoned citrus. Because glassy-winged sharpshooters reproduce in great numbers on citrus, consult with nearby citrus growers regarding any plans to promote biological control (e.g., conserve egg parasites) or treat sharpshooters in citrus.

Biological Control
Several Gonatocerus spp. wasps parasitize glassy-winged sharpshooter eggs. Parasitized eggs are easily recognized by a tiny, round hole at one end of the glassy-winged sharpshooter egg through which the adult parasite emerged. Gonatocerus ashmeadi is commonly found wherever glassy-winged sharpshooter occurs in California. In southern and coastal areas of California, Gonatocerus morrilli, can be very effective in the late summer, when the second generation of eggs are deposited. Gonatocerus fasciatus, G. novifasciatus, and G. triguttatus also occur at low levels in California.

Organically Acceptable Methods
Biological controls are organically acceptable.

PUBLICATION

UC IPM Pest Management Guidelines: Avocado
UC ANR Publication 3436
Invertebrates
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura County
B. A. Faber, UC Cooperative Extension, Santa Barbara/Ventura counties
J. G. Morse, Entomology, UC Riverside
M. S. Hoddle, Entomology, UC Riverside
Acknowledgment for contributions to Invertebrates:
M. Blua, Entomology, UC Riverside
P. Oevering, UC Cooperative Extension, Ventura County
D. Machlitt, Consulting Entomology Services, Moorpark, CA
T. Roberts, Integrated Consulting Entomology, Ventura, CA
B. B. Westerdahl, Nematology, UC Davis

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