Symptoms and damage
glassy-winged sharpshooter is a large leafhopper that obtains its nutrients by
feeding on plant fluids in the water-conducting tissues of a plant (the xylem).
Feeding on plants rarely causes significant plant damage, although the insects
do excrete copious amounts of liquid that can make leaves and fruit appear whitewashed when dry. The excrement is a special nuisance
when shade trees are heavily infested because cars parked under the trees tend
to become spotted. During hot weather, heavy populations of glassy-winged
sharpshooters feeding on small plants may cause them to wilt.
The real problem associated with
glassy-winged sharpshooter, however, is that it can spread the disease-causing
bacterium Xylella fastidiosa from one plant to another. This bacterium is
the causal agent of devastating plant diseases such as Pierce`s disease of grape, oleander leaf scorch, almond leaf scorch and mulberry leaf scorch.
Large, yellow sticky traps are commonly used in orchards to monitor for the adults. Sweep nets are also used to monitor for
glassy-winged sharpshooter in agricultural situations. Glassy-winged
sharpshooter infestations can also be determined by examining the underside of
plant leaves for egg masses.
There are no
known cultural controls for glassy-winged sharpshooter. But preventing
transport of infested plant material to areas where glassy-winged sharpshooter
has not been found can slow its spread in California. Nurseries shipping plants
out of an infested area must follow rigorous plant inspection and treatment
before the plants are shipped and then the plants must be inspected again after
they arrive at their destination.
The main material used to protect Xylella-susceptible plants in both commercial
agriculture and urban landscapes is imidacloprid, which is registered for home
and professional landscape use on nonfood crops. Imidacloprid is sold in two
formulations: one for soil application and one for foliar application. The
soil-application formulation provides the most effective, long-lasting control
and is less disruptive to the biological control provided by the parasitic
wasps (although it is quite toxic to some predatory lady beetles, such as the
vedalia beetle), but it takes several weeks to become effective. Foliar
applications of this material are effective for a much shorter period of time
and may disrupt biological control agents, and thus are much less desirable.
In instances where the white excrement
produced by this pest causes intolerable residues on cars or other surfaces,
other insecticides can be applied to infested foliage to provide immediate
relief. The least toxic and disruptive to biological control are insecticidal
soaps and oils. Insecticidal soaps and oils are only effective in killing the
soft-bodied nymphs of the glassy-winged sharpshooter and must directly contact
the insect to kill it, so thorough coverage of the plant or tree foliage is
essential. Applications of these materials need to be repeated at about 7- to
10-day intervals. Other insecticides are available for foliar applications.
However, these materials are much more damaging to the parasitic wasps that are being
introduced for long-term control.