Leafhoppers and Sharpshooters

Leafhoppers (family Cicadellidae) include sharpshooters, which generally are larger species. Leafhoppers develop through three life stages: eggs, nymphs, and adults. Nymphs resemble adults, but are smaller, wingless, and may differ in color. Leafhoppers are relatively long and slender and most are about 1/6 inch or less in length; sharpshooters can be up to 1/2 inch long, although many species are shorter. Species vary from brightly colored (blue-green sharpshooter, two-spotted leafhopper) to dull and mostly brown, gray, green, or tan (aster leafhopper, glassy-winged sharpshooter). Adults and nymphs when disturbed often jump or walk rapidly away sideways.

Glassy-winged sharpshooter adults are about 1/2 inch long and mostly dark brown with a yellow to whitish abdomen.The nymphs are grayish and develop through five increasingly larger instars. Nymphs blend with the color of smooth, gray bark even more so than adults. As they suck xylem sap, adults and nymphs excrete a large amount of liquid that leaves behind a whitish residue on leaves and other surfaces. The broad host range includes many food crops and ornamentals including bird-of-paradise, citrus, cottonwood, crape myrtle, eucalyptus, euonymus, hibiscus, oleander, olive, pittosporum, Prunus spp., sunflower, and xylosma.

Glassy-winged sharpshooter is found mostly in Southern California and the southern Central Valley. It overwinters as adults on evergreen hosts. Starting about late February, overwintered females migrate to host plants and lay eggs in a mass inserted under the surface of leaves. There are two generations per year in California.

The aster leafhopper, also called the six-spotted leafhopper, has three pairs of black spots on the front and top of its head. Adults are about 1/8 inch long with a light green to yellowish body that appears gray when at rest and covered by the wings. The wings have prominent veins and black markings on the abdomen, head, and thorax. Nymphs are pale gray, green, yellow, or whitish. The leafhopper overwinters mostly as eggs in plant tissue, although adults and nymphs may be found throughout the year. Up to six generations may occur during spring through fall.

Blue-green sharpshooter adult has green to bright blue head, thorax, and wings and yellow legs and abdomen. It is about 2/5 inch long. Nymphs are pale, and mostly whitish. The species occurs in coastal areas and has one generation a year in most of California; a second generation occurs in portions of Southern California. Adults become active in late winter to early spring and can become abundant in ornamental landscapes and weeds along stream banks and canyons and ravines where there is dense vegetation. As natural vegetation and weeds dry and die during spring, adults disperse into crops and other irrigated plantings. Eggs hatch from May through July with some of the nymphs becoming adults by mid-June.

Two-spotted leafhopper adults are about 1/4 inch long and yellowish with a dark, reddish, lengthwise stripe along the back. Near the wing tips are two dark, eyelike spots that make it appear that the leafhopper is walking backwards. Nymphs are yellow. Two-spotted leafhopper feeds on dozens of species of ornamental plants and a few crops such as avocado.

Leafhoppers have piercing-sucking mouthparts that puncture plant tissue to consume cell contents or sap. When abundant feeding causes noticeable bleaching or stippling of leaves, which may curl, dry and turn brown, and drop prematurely. Foliage may also become fouled with leafhoppers' clear and shiny to whitish excrement on which blackish sooty mold may grow. The pale cast skins of nymphs may stick to leaf surfaces. Even where leafhopper populations are commonly low in nurseries causing little or no damage, certain species can be serious pests vectoring plant pathogens.

Aster leafhopper and several other leafhoppers can transmit the pathogen that causes aster yellows disease, the most important phytoplasma affecting herbaceous ornamentals. Phytoplasmas cause abnormal shoot growth, dwarfing and yellowing of foliage and green shoots and greening of flower parts, which develop into leaflike structures. Clusters or tufts of spindly, yellow, upright shoots commonly develop around the base of infected plants, often on one side of the plant. Corms or tubers can mature early, be undersized, or have stunted roots if infected early during the current season. Corms or tubers infected during the previous season develop many thin, yellowish, and weak leaves, distorted flower spikes, and green blossoms.

The pathogen has several hundred hosts including many vegetable crops and weeds. Ornamental hosts of aster yellows include anemone, aster, calendula, candytuft, cassia, celosia, chrysanthemum, cosmos, gladiolus, godetia, gypsophila, marigold, nasturtium, petunia, primrose, Queen Anne's lace, ranunculus, sage, snapdragon, stock, strawflower, sweet William, and vinca.

Glassy-winged sharpshooter, blue-green sharpshooter, and certain other leafhoppers can transmit the Xylella fastidiosa bacterium to plants, which clogs the water-conducting tissues (xylem). Xylella fastidiosa plant diseases are variously named according to host plants. Some strains of Xylella harmless to some plants can be pathogenic to other hosts. Diseases caused by X. fastidiosa in California include alfalfa dwarf, almond leaf scorch, and Pierce's disease of grape. Xylella strains identified mostly in southern California cause oleander leaf scorch and death of liquidambar (sweet gum), oleander, olive, and purple-leaf plum. Numerous other woody ornamentals in the eastern United States are affected by Xylella strains not yet reported in California.

Cultural controls including exclusion and insecticide application are the primary management methods for leafhoppers. No chemicals are effective at controlling the aster yellows phytoplasma or Xylella bacteria in ornamental crops.

In nurseries where glassy-winged sharpshooter is present, preventive insecticide application can be warranted or even required by regulation. Sites in areas known to be infested by glassy-winged sharpshooter are subject to California's Pierce's Disease Program, which requires specific management and pest inspection practices before plants can legally be moved from the nursery. Contact the local county agricultural commissioner's office to learn the current requirements of any plant quarantines that may apply to the crops being grown.

Leafhoppers and sharpshooters are fed upon by many parasitic wasps and predators, but these generally do not provide adequate biological control in greenhouses or nurseries. High levels of egg parasitism of glassy-winged sharpshooter are common later in the growing season due to several introduced Cosmocomoidea (=Gonatocerus) spp. wasps; these parasites' activities in landscapes and unmanaged vegetation help reduce the sharpshooter's abundance and migration into crops.

Obtain insect- and pathogen-free stock from a quality supplier. Carefully inspect new plants and propagation stock for pests and dispose of or effectively treat infested plants. Promptly remove crop debris from growing areas and dispose it in covered containers. Control weeds that may be alternative hosts of both leafhoppers and plant pathogens they can vector. If such sources cannot be removed, avoid planting crops susceptible to leafhopper-vectored pathogens near these alternative hosts.

Effectively screen greenhouses and shade structures to exclude pests; use screens of sufficient surface area to provide adequate ventilation. Grow field crops in hoop houses or beneath floating row covers that are held above plant level to prevent egg laying through the mesh onto plants.

Reflective mulch. For field-grown crops, reflective mulch can greatly reduce the extent of leafhopper infestation. Apply the material in row middles at planting time or by entirely covering the soil surface and planting through holes in the mulch. Reflective mulch reduces the extent of infection from insect-vectored pathogens when crops are young and most susceptible to these pathogens. Reflective mulch can increase crop growth and cut-flower yield and reduce crops' need for irrigation by conserving soil moisture. See Reflective Mulches for more information.

Biological and cultural controls including row covers, reflective mulches, and exclusion netting are organically acceptable management methods. Certain formulations of the botanicals azadirachtin (Azatin), neem oil, and pyrethrins without piperonyl butoxide (PyGanic), certain formulations of the fermentation product spinosad (Entrust Naturalyte, Entrust SC), and certain narrow-range oils (Organic JMS Stylet-Oil) are acceptable for organic production.

Leafhoppers are mostly inactive during the winter. Overwintered females begin egg laying in late winter to early spring, according to location and pest species. Begin monitoring for leafhoppers by late February and continue through September. Concentrate inspections in nursery borders where immigrating leafhoppers commonly are first observed. For nurseries where glassy-winged sharpshooter occurs or subject to California's Pierce's Disease Program (within its quarantine zones), make the first preventive insecticide application when adults are first detected, or otherwise as directed by regulations.

Place yellow sticky traps at canopy height around nursery borders and inside greenhouses near doors and vents. Deploy at least four traps per acre, or at least two per greenhouse or other structure. Check sticky cards at least once a week for adults of pest leafhoppers and sharpshooters. Apply insecticide if any adult glassy-winged sharpshooters are detected in the traps. If about five to ten leafhoppers or sharpshooters of other pest species are caught in sticky traps, an application may be warranted. For more information, see Monitoring With Sticky Traps and Sticky Trap Monitoring of Insect Pests.

Other monitoring methods include beat or shake sampling plant parts over an insect-collecting surface, shaking terminals into a sweep net, and visual inspection of plants and counting the pests. Beat or sweep net sampling for nymphs and adults is most effective when temperatures are cool (less than 60°F); at warmer temperatures insects tend to fly away before they can be counted. To conduct a beat or shake sample place a 2-foot square sheet of white cloth or stiff paper underneath the canopy to be sampled. Strike the canopy with a stick or shake it vigorously to dislodge insects, and count the those of concern that drop onto the sheet.

Visually inspect leaves and stems for all insect life stages and leafhopper damage symptoms. For example, glassy-winged sharpshooter egg masses can be more easily detected by examining the undersides of leaves backlight against a sunny sky. Note that leafhopper adults and nymphs tend to move to the far side of the leaf or stem, away from people or nearby motion they observe. Placing a hand close behind the stem being observed may cause the insects move to the front where they can be seen and identified.

The main considerations in deciding whether to apply insecticide are whether the site is regulated by California's Pierce's Disease Program, and if not, does the expected or potential economic damage caused by the pest equal or exceed the cost of management. For information on making application decisions, see Establishing Action Thresholds. Contact the local office of the county agricultural commissioner to learn whether your growing site is subject to California's Pierce's Disease Program or other quarantine programs, and if so follow current regulations.

Quarantine requirements. FOR SITES WHERE REGULATIONS OF THE California Pierce's Disease Program apply, the insecticides (and their mode-of-action codes) having the greatest value are neonicotinoids (4A), butenolides (4D), pyrethroids (3A), diamides (28), organophosphates (1A), and insect growth regulators (IGRs e.g., S-Kinoprene) in approximately that order.

Selected Products Registered for Greenhouse or Nursery Ornamentals
FOR SITES NOT WITHIN areas infested by glassy-winged sharpshooter and NOT subject to California Department of Food and Agriculture (CDFA) program regulations for Pierce's disease other insecticides options are available.