How to Manage Pests

UC Pest Management Guidelines

Citrus

Glassy-Winged Sharpshooter

Scientific Name: Homalodisca vitripennis (=H. coagulata)

(Reviewed 9/08, updated 6/13)

In this Guideline:


Description of the Pest

Glassy-winged sharpshooter is in the same insect family as leafhoppers (Cicadellidae). The glassy-winged sharpshooter feeds, reproduces, and is often abundant on a variety of host plants including agricultural crops (citrus and grapes) and a large number of ornamental plants. Glassy-winged sharpshooter was introduced into southern California in the late 1980s. Its current distribution in agricultural areas is southern California and Kern and Tulare counties. The glassy-winged sharpshooter continues to spread slowly northward in the Central Valley. Infestations that have appeared in various other counties in central and northern California have been eradicated or suppressed.

The glassy-winged sharpshooter is a large insect compared to other leafhoppers. Adults are about 0.5 inch long and are generally dark brown to black when viewed from the top or side. The abdomen is whitish or yellow. The head is brown to black and covered with numerous ivory to yellowish spots. These spots are helpful in distinguishing glassy-winged sharpshooters from smoke-tree sharpshooters, which have light-colored wavy lines on the head.

Females lay their eggs in masses of about 5 to 15 in the lower leaf surface of young, fully developed leaves. When it is first laid, the egg mass appears as a greenish blister on the leaf. The female covers the leaf blister with a secretion that resembles white chalk and is more visible than the leaf blister. Nymphs hatch in 10 to 14 days and proceed to feed on the leaf petioles or small stems.

The glassy-winged sharpshooter has two generations per year in California. In late winter and early spring, adults become active. Citrus is an especially attractive egg-laying host during late March through April and again in late June through August. The first generation of glassy-winged sharpshooter become adults by mid-June, and the number of young adults continues to increase through July and August. Glassy-winged sharpshooter will overwinter in citrus as well as weeds, ornamentals, and various trees.

Damage

Glassy-winged sharpshooter feeds on the nutrient-poor xylem of the plant and must consume copious amounts of fluid in order to gain enough nutrition to grow and reproduce. Consequently, the adults and nymphs excrete large amounts of liquid while feeding, which gives the fruit and foliage a whitewashed appearance.

Extremely high populations of glassy-winged sharpshooter have been shown to reduce fruit quality and yield of coastal lemons and Valencias in southern California. In recent years, however, very high populations are rarely seen—likely because of increased parasite activity. Currently, treatments are applied primarily to reduce sharpshooter populations that might move to grapes or to disinfest citrus trees before harvest.

The glassy-winged sharpshooter is a serious pest of grapes because it acts as a vector of the strain of Xylella fastidiosa that causes Pierce's disease in vineyards. It also vectors the strain that causes oleander leaf scorch in oleander. The bacteria multiply and block the water-conducting system of the plant causing water stress and eventual plant death. There is no known cure for the disease. Because many glassy-winged sharpshooters overwinter in citrus, citrus acts as a source of sharpshooters for neighboring vineyards. Glassy-winged sharpshooter has been reported as a vector of the Xylella fastidiosa strain of bacteria that causes citrus variegated chlorosis; however, this disease has not yet been found in the U.S.

Management

To protect vineyards in uninfested areas of the state, quarantine regulations are in effect to slow the spread of glassy-winged sharpshooter from southern California and parts of Tulare and Kern counties northward. Kern County and Tulare citrus orchards in the glassy-winged sharpshooter-infested areas must be disinfested of glassy-winged sharpshooter before citrus fruit can be harvested and shipped to uninfested regions such as northern Tulare County packinghouses. Nursery citrus trees must be treated before they can be shipped to uninfested areas. In infested areas of the state, citrus orchards with significant yellow sticky card trap catches of glassy-winged sharpshooters are treated to bring the overall population levels down and reduce the threat of sharpshooters in nearby vineyards. Although biological control agents are being released in urban areas, current management primarily involves treatment with insecticides because of the threat of Xylella to the grape industry.

Biological Control

Biological control is an organically acceptable method of reducing populations of this pest. However, at this time, it may not provide sufficient reduction of glassy-winged sharpshooter populations for areawide suppression programs. The egg parasitic wasp, Gonatocerus ashmeadi, is commonly found wherever glassy-winged sharpshooter occurs in California. In the southern and coastal areas of California a closely related species, Gonatocerus walkerjonesi, can be a very effective parasite in the late summer, when the second generation of eggs are deposited. Parasitized glassy-winged sharpshooter eggs are easily recognized by a tiny, round hole at one end of the egg through which the adult parasite emerged. Neither G. ashmeadi nor G. walkerjonesi, however, are normally present at high levels during the first generation of glassy-winged sharpshooter egg laying.

Organically Acceptable Methods

Biological control is an organically acceptable method of reducing populations of this pest.

Selectivity

Pyrethrins are selective because they are extremely short-lived but they are limited in their efficacy. Systemic imidacloprid (Admire) is the next most selective insecticide because it only affects vedalia and other predatory beetles. The foliar neonicotinoids, pyrethroids, and methomyl are highly toxic to most natural enemies.

Monitoring and Treatment Decisions

Glassy-winged sharpshooter insecticide treatments are only recommended in citrus for one of two reasons: to suppress glassy-winged sharpshooters in the orchard in order to reduce the risk to neighboring grape vineyards or to disinfest fruit just before harvest. Different insecticides are recommended for each purpose. Insecticide treatments should be avoided where possible because of their potential for disrupting biological control of citrus pests.

Glassy-winged Sharpshooter Suppression

An insecticide treatment in citrus may be needed to reduce overall numbers so that there are fewer glassy-winged sharpshooters to vector Xylella in neighboring grapes. When the weather is cool (winter, early spring), glassy-winged sharpshooter is best monitored in citrus by beating branches of 20 citrus trees per 10-acre block and counting the number of glassy-winged sharpshooter adults and nymphs that fall onto the sheet. An average of more than one per tree is considered a potential threat to neighboring vineyards. During the warmer weather, especially when egg masses are present during April and June–August, it is easier to conduct a timed search. During a 3 to 5 minute examination of each of 20 trees per 10-acre block, count the number of nymphs, adults, and live egg masses observed. Infestations of more than one mobile stage (nymph or adult) and more than one egg mass per tree are considered significant.

Disinfestation of Trees Just Before Harvest

The other reason for insecticide control of glassy-winged sharpshooters in citrus is to disinfest trees immediately before harvest so that fruit can be shipped from a generally infested region (such as southern California or Kern County) to an uninfested area (such as northern Tulare County) for packing. To detect mobile stages of glassy-winged sharpshooter, stuff citrus foliage into a sweep net, shake vigorously, and inspect the contents of the net. If any live, mobile glassy-winged sharpshooter stages are found, a treatment is needed. Treatment should be as close to harvest as the preharvest interval and restricted entry interval allow (this interval is noted in the treatment table as the minimum days before harvest). Glassy-winged sharpshooter is a very mobile pest and can rapidly move into the treated orchard from untreated areas as soon as insecticide residues begin to break down.

Common name Amount to use R.E.I.‡ P.H.I.‡
(example trade name) (type of coverage)** (hours) (days)

  Calculate impact of pesticide on air quality
 
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact.
 
PESTICIDES FOR SUPPRESSION
 
A. IMIDACLOPRID
  (Admire Pro) 7–14 fl oz/acre 12 0
  (Nuprid 1.6F) 10–20 fl oz/acre 12 0
  RANGE OF ACTIVITY: Pests: narrow (aphids, glassy-winged sharpshooters); Natural enemies: predatory beetles and parasites
  PERSISTENCE: Pests: long; Natural enemies: intermediate
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Apply to soil; remains effective 4–5 months. Moderately effective against nymphs and adults. Requires 3–4 weeks for uptake into mature citrus to begin to kill the sharpshooter nymphs and adults; does not kill eggs. Pre-wet soil before treatment is applied. Very toxic to bees; do not apply during bloom because bees may be drawn to irrigation water. For optimum uptake, apply to newly planted trees or trees irrigated by drip, microsprinkler, or low-pressure irrigation systems. Emitters must provide even, uniform distribution of water. Lightly pre-wet soil for several hours before application to break soil surface tension. Once the irrigation system reaches operating pressure, inject the treatment into the system over a calculated time interval (generally 2 hours) to allow uniform distribution throughout the system. The use of a dye marker in the treatment solution is recommended to determine when lines are clear of the treatment. Once the solution has cleared all irrigation lines and emitters, continue irrigation to move the insecticide into the active root zone but do not overirrigate or cause runoff. Wait 24 hours before subsequent irrigations. Apply in citrus orchards just before bloom (March) or after petal fall (May–July). Repeat applications of any neonicotinoid insecticide (acetamiprid-Assail; imidacloprid-Admire, Provado) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with an insecticide that has a different mode of action to help delay the development of resistance.
 
B. PYRETHRIN + PIPERONYL BUTOXIDE
  (Pyrenone Crop Spray) 10–12 oz/acre in 100–200 gal (OC) 12 When dry
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: very short; Natural enemies: very short
  MODE OF ACTIONGROUP NUMBER1: 3A + —
  COMMENTS: Very short residual insecticide. Will kill nymphs and adults. Fairly compatible with natural enemies because of its short residual. Do not apply through any type of irrigation system.
 
C. BETA-CYFLUTHRIN*
  (Baythroid XL) 1.6–3.2 fl oz/acre in 100–200 gal (OC) 12 0
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: intermediate (low rates), long (high rates)
  MODE OF ACTION GROUP NUMBER1: 3A
  COMMENTS: Treatments applied for citrus thrips will help to reduce glassy-winged sharpshooter nymphs and adults. If pyrethroids (e.g., cyfluthrin, fenpropathrin) are used to treat glassy-winged sharpshooters during the months when citrus thrips are present (generally March to October), they can select for citrus thrips resistance. Therefore, it is recommended that the total number of applications of any pyrethroid on citrus (for all pest species) be limited to a single application per season.
 
D. FENPROPATHRIN*
  (Danitol 2.4EC) 21.33 fl oz/acre in 100–200 gal (OC) 24 1
  RANGE OF ACTIVITY: Pests: broad (many insects and mites); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: long
  MODE OF ACTION GROUP NUMBER1: 3A
  COMMENTS: Apply in 50 to 200 gal water/acre. Use only on citrus trees 3 years or older. Effective in killing nymphs and adults, but residues last for only 2 to 4 weeks. If pyrethroids (e.g., cyfluthrin, fenpropathrin) are used to treat glassy-winged sharpshooters during the months when citrus thrips are present (generally March to October), they can select for citrus thrips resistance. Therefore, it is recommended that the total number of applications of any pyrethroid on citrus (for all pest species) be limited to a single application per season. Do not apply in the vicinity of aquatic areas.
 
E. ACETAMIPRID
  (Assail 70WP) 1.7–2.9 oz/acre in 100–200 gal (OC) 12 7
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: long
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: Effective in killing nymphs and adults as well as preventing nymphs from emerging from egg masses. Residues last for 4 to 6 weeks. Toxic to bees exposed to direct treatment; apply only during late evening, night, or early morning. Apply in a minimum flushed spray of 100 gal/acre by ground. Repeat applications of any neonicotinoid insecticide (acetamiprid-Assail; imidacloprid-Admire, Provado) can lead to resistance to all neonicotinoids. Alternate neonicotinoids with an insecticide that has a different mode of action to help delay the development of resistance.
 
PESTICIDES FOR DISINFESTATION OF TREES JUST BEFORE HARVEST
 
A. METHOMYL*
  (Lannate LV) 1.5–3 pt/acre in 100–200 gal (OC) 3 days 1
  RANGE OF ACTIVITY: Pests: broad (many insects) Natural enemies: most
  PERSISTENCE: Pests: short; Natural enemies: intermediate
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: Will kill nymphs and adults but not eggs. Short residual. Effectiveness of treatment is reduced if neighboring blocks are untreated and adults fly in. International maximum residue limits of 1 ppm have been established for citrus fruit.
 
B. BETA-CYFLUTHRIN
  (Baythroid XL) 1.6–3.2 fl oz/acre in 100–200 gal (OC) 12 0
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: intermediate (low rates), long (high rates)
  MODE OF ACTION GROUP NUMBER1: 3A
  COMMENTS: International maximum residue limits have not been established for Taiwan, Hong Kong, China, Malaysia, and Australia. If pyrethroids (e.g., cyfluthrin, fenpropathrin) are used to treat glassy-winged sharpshooters during the months when citrus thrips are present (generally March to October), they can select for citrus thrips resistance. Therefore, it is recommended that the total number of applications of any pyrethroid on citrus (for all pest species) be limited to a single application per season.

** OC - Outside coverage uses 100–250 gal water/acre.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
1 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode-of-action Group numbers ("un"=unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441

Insects, Mites, and Snails

  • E. E. Grafton-Cardwell, Entomology, UC Riverside and Kearney Agricultural Center, Parlier
  • J. G. Morse, Entomology, UC Riverside
  • N. V. O'Connell, UC Cooperative Extension, Tulare County
  • P. A. Phillips (emeritus), UC IPM Program, UC Cooperative Extension, Ventura County
  • C. E. Kallsen, UC Cooperative Extension, Kern County
  • D. R. Haviland, UC Cooperative Extension, Kern County
Acknowledgments for contributions to Insect, Mites, and Snails:
  • J. Barcinas, E.S.I., Corona, CA
  • R. Dunn, Badger Farming Co., Exeter, CA
  • J. Gorden, Pest Management Associates, Exeter, CA
  • H. Griffiths, E.S.I., Corona, CA
  • D. Machlitt, Consulting Entomology Services, Moorpark, CA
  • C. Musgrove, retired entomologist, Riverside, CA
  • K. Olsen, S & J Ranch, Pinedale, CA
  • T. Roberts, E.S.I., Corona, CA
  • T. Shea, UC Cooperative Extension, Riverside County
  • J. Stewart, Pest Management Associates, Exeter, CA
  • P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA

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