Garden Word of the Day
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Blue-green sharpshooters are sap-sucking, disease-carrying cousins of leafhoppers. Native to California, blue-green sharpshooters (Graphocephala atropunctata) have only recently become serious pests.
As blue-green sharpshooters feed, they inject plants with a bacteria that causes Pierce’s disease.
Pierce’s disease primarily affects grapes, but it can also appear on alfalfa, almond, avocado, blackberry, citrus, elderberry, and olive. The bacteria that cause Pierce’s disease block the flow of water and nutrients through the xylem, causing scorching, stunting, bleaching, leaf stippling, “matchstick” petioles, ‘green islands’ on stems, raisined grapes, defoliation and dieback. But symptoms do not always appear in the year the plant is infected. This results in many more plants becoming infected as sharpshooters move from plant to plant as they feed. Plants infected the previous year often exhibit delayed or absent budbreak. Plants infected early in the growing season are more likely to look as though they have recovered, even though they haven’t.
There is no cure for Pierce’s disease and infected plants usually die within 1 to 3 years. Other diseases caused by the same bacteria include almond leaf scorch, oleander leaf scorch, and olive leaf scorch. These bacteria can also be carried by spittlebugs and glassy-winged sharpshooters.
Outbreaks of Pierce’s disease have been growing dramatically. This is believed to be due to warmer temperatures allowing vectors, such as blue-green sharpshooters, and the bacteria they carry, to live through the winter.
Blue-green sharpshooter description
Unlike glassy-winged sharpshooters, which average 1/2” in length, blue-green sharpshooters are much smaller and easy to miss. As far as pests go, the blue-green sharpshooter is quite colorful. From a distance, it simply looks like a wedge-shaped green insect. If you look closely, with a hand lens, you suddenly see striking bright blue to green wings, thorax, and head, with a yellow abdomen and legs. There are sometimes red, yellow, or green markings. You may also be able to see red drops of sap attached to their legs.
Blue-green sharpshooter lifecycle
Until recently, only one generation of blue-green sharpshooter appeared each year. Rising temperatures and stressed predator insects are making multiple generations possible. Most sharpshooters overwinter near creeks, becoming active in spring. Eggs are laid just after budbreak. As surrounding vegetation begins to dry up, concentrations of sharpshooters in gardens, vineyards, and orchards increases. Sharpshooters go through complete metamorphosis, frequently leaving pale discarded exoskeletons behind on the underside of leaves. Nymphs and adults feed on nutrient-rich sap throughout the summer, moving back into nearby weeds and vegetation at the end of summer.
Blue-green sharpshooters use vocalization to communicate and to find a mate. Males have 3 distinct calls: a complex mating call, a gulping call, and a chirping call. Females have a call they use to respond to males’ mating calls. The pair sings a type of duet before mating, which is all very nice, but they still spread disease. Because there is no cure for Pierce’s disease, interrupting the disease cycle is the only way to prevent plant loss.
Controlling blue-green sharpshooters
The first step to controlling blue-green sharpshooters is to make sure they are present. This is done with yellow sticky sheets. Sharpshooters are most commonly found in locations with abundant soil moisture and some shade. Unshaded, dry areas and areas of deep shade are less likely habitats for sharpshooters.
You can reduce the chance of infection of Pierce’s disease with these tips:
Famers have found that installing bluebird boxes goes a long way toward reducing blue-green sharpshooter populations. Insecticides aimed at sharpshooters are only marginally effective, while insecticidal soap and horticultural oil provide some control.
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