How to Manage Pests
UC Pest Management Guidelines
Leafhoppers, including a subgroup called sharpshooters, are in the family Cicadellidae. All have mouthparts that allow them to pierce the plant tissue and feed on plant juices. Most leafhoppers are about 0.25 inch long and slender. Species may be brightly colored or similar in color to the host plant. They often jump away or move sideways when disturbed. Pale cast skins may be found on leaf surfaces. Leafhoppers have incomplete metamorphosis. Immatures (nymphs) are similar in structure to adults, but are smaller, wingless, and may differ in color.
Glassy-winged sharpshooter. Adult glassy-winged sharpshooters are about 0.5 inches long and dark brown in color.Wings are membranous and translucent, with reddish veins. The insects overwinter as adults and begin to lay egg masses about late February. There appear to be two generations of glassy-winged sharpshooters per year in California. Eggs are laid under the surface of the leaf epidermis. The gray-colored nymphs are smaller than the adults and wingless. There are 5 immature stages. As they feed on xylem tissue, they excrete a large amount of liquid substance that drops to the leaves or the ground below. The glassy-winged sharpshooter has a broad host range that includes many ornamental plant species.
Aster leafhopper. The aster leafhopper is also called the six-spotted leafhopper because it has three pairs of black spots on its head. The adults are small (about 0.12 inch long) and usually light green to yellow, with black marking on the thorax and abdomen. Their wings are transparent. Nymphs are usually dark green.
Blue-green sharpshooter. The blue-green sharpshooter has green to bright blue wings, head, and thorax, and yellow legs and abdomen, which are visible on the underside. It is about 0.4 inches long. There is one generation a year in most of California and a second generation in some southern areas of the state. Adults become active in late winter/early spring. They can become abundant in ornamental landscaping around homes. They also feed on numerous weeds mostly along stream banks or in ravines or canyons where there is dense vegetative growth. As natural vegetation dries up, adults disperse into crops and irrigated plantings. Eggs hatch from May through July with some of the nymphs becoming adults by mid-June.
Two-spotted leafhopper. Adults are about 0.25 inches long and pale yellow with a dark stripe down the center of the back. On the end of the wings are two prominent eye spots that make it appear that the leafhopper is walking backwards. This leafhopper feeds on a wide range of ornamental plants. Feeding may cause chlorosis of leaves in some species.
Leafhoppers are pests primarily because some are vectors of plant pathogens. The glassy-winged sharpshooter and the blue-green sharpshooter transmit a bacterial pathogenXylella fastidiosa that grows in the xylem, or water-conducting tissue, of certain plant species. Xylella fastidiosa can cause a number of plant diseases in a variety of hosts. Thus far, strains of X. fastidiosa that cause oleander leaf scorch,Pierce's disease of grapevines, almond leaf scorch, and alfalfa dwarf have been identified in California. The strains of the pathogen that infect oleander do not appear to infect grape and are genetically distinct from the other strains. The aster leafhopper is one of several leafhoppers that can transmit the phytoplasma pathogens that cause aster yellows disease in many plant hosts.
In addition to the transmission of pathogens, leafhopper feeding can cause leaves to appear stippled, pale, or brown, and shoots may curl and die. Excrement exuded during feeding can serve as a substrate for the growth of sooty mold, or discolor leaves with a white chalky film.
Glassy-winged sharpshooter is under quarantine in California and shipment from infested to noninfested areas requires specific treatments.
Management of leafhoppers and sharpshooters in nursery crops is focused primarily on exclusion techniques. Plants can be protected from these pests and the transmission of pathogens with the use of row covers and screening; reflective mulches may also be useful. Good weed management is important in areas surrounding nurseries to prevent the buildup of populations and migration into the nursery when the surrounding vegetation dries. In nurseries that have had past problems with glassy-winged sharpshooters, a quarantine pest, preventive insecticide treatments are advisable. Otherwise, monitor these pests to detect an influx of populations into the nursery.
For open field flower or nursery production, silver reflective plastic mulches may be of value. Reflective mulches have been shown to repel leafhoppers in another crop (corn), thus reducing pest numbers in and around the plant canopies. In addition, Xylella transmission by the leafhopper vectors was greatly reduced, thus reducing corn stunt disease incidence. For best results, apply reflective mulches at the time of planting or transplanting the crop. Apart from reducing leafhopper and pathogen incidence, silver reflective mulch may increase cut-flower production and reduce the crop requirement for irrigation, water and fertilizer. Row covers, screening, and mulching are acceptable practices for organic production.
and Treatment Decisions
Place yellow sticky traps around the nursery border and throughout the nursery at canopy height (4 cards per acre) to detect migration of sharpshooters and leafhoppers into the nursery. Check cards at least once a week for adult sharpshooters. Treat if any adult glassy-winged sharpshooters are detected in the traps. If glassy-winged sharpshooters are not present but five to ten leafhoppers or other sharpshooters are being caught in sticky traps, a treatment may be necessary to stem the influx of these other species. A major management consideration is that economic damage caused by the leafhopper should equal or exceed the cost of any necessary management. For more information, see MONITORING WITH STICKY TRAPS.
Other monitoring methods, including beating samples and visual counts, can be used to detect the presence of leafhoppers and sharpshooters. Beat or sweep sampling for nymphs and adults is most effective when temperatures are cool (less than 60°F). At warmer temperatures the insects will fly away before they can be counted. To conduct a beat sample, place a 2-foot square sheet of white material underneath the canopy to be sampled. Strike the canopy with a stick or shake it vigorously to dislodge insects, and count the number on the sheet. A sweep net may be also used to sample foliage for the presence of adults and nymphs. Visual inspection of leaves, stems, and branches is perhaps the best method for detecting all stages. Insects may try to move to the far side of the stem to avoid detection. Placing a hand close behind the stem being observed will make the insects move to the front where they can be seen. (Glassy-winged sharpshooter egg masses can be easily detected by inspecting the undersides of leaves against a sunny sky.)
For information on making treatment decisions, see ESTABLISHING TREATMENT THRESHOLDS.
Quarantine Requirements. Nurseries are considered 'infested' if 5 or more glassy-winged sharpshooters are collected on sticky cards that are within a 300-yard radius of each other (not less than one card per half acre). Shipment of nursery stock from glassy-winged sharpshooter-infested areas to noninfested areas within and outside of California requires additional treatments. Contact your county Agricultural Commissioner's office for more information.
Selected Materials Registered for Use on Greenhouse or Nursery
UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries