Though small and gentle, the glassy-winged sharpshooter can pose a major threat to familiar plants such as orange, lemon, and almond trees; grapevines; and oleander bushes; as well as to alfalfa and coffee.
In fact, this invasive insect represents a multibillion-dollar hazard to American agriculture. That's mainly because of its impressive ability to spread a plant-disease-causing bacterium, Xylella fastidiosa. Both insect and microbe are harmless to humans.
Scientists don't yet know how to sufficiently control Xylella. The same is true for the little leafhopper.
The leafhopper has some peculiarities that make it especially difficult to combat. Apparently, it can thrive exclusively on the sap that it sucks from target plants. It is remarkably effective at extracting whatever nutrients the sap might contain.
Efforts of ARS scientists and their co-investigators to rein in Xylella and the sharpshooters have won them a USDA Honor Award (see page 17).
Besides developing short-term solutions, such as insecticides and repellents, ARS is investigating tactics that may give long-term control.
In planning our sharpshooter research and our other investigations of unwanted invasive or exotic organisms, we coordinate with the National Invasive Species Council. The council is composed of pros from USDA and other federal departments and agencies.
Interestingly, even though the glassy-winged sharpshooter is native to Texas and the southeastern United States, it meets the council's definition of an invader: "Any plant, animal, or organism that is not native to the ecosystem under consideration and whose introduction is likely to cause harm to human health, the environment, or the economy."
The sharpshooter squarely fits this profile. It has wandered from its native range, first showing up in southern California in 1989. It has wreaked agricultural havoc there, spreading X. fastidiosa that killed 50 to 90 percent of the grapevines in affected vineyards within only 2 to 3 years.
The variety of crops that the glassy-winged sharpshooter attacks and the assortment of costly X. fastidiosa strains that it transmits warrant our nationwide efforts to rein in this invasive pest. We have carefully apportioned key aspects of the insect-bacterium-plant interactions into researchable projects. And we have expanded our staffing to broaden the array of scientific specialties that we are bringing to bear on this problem. Our approach may serve as a model for other federal "first-responder" research strategies to counteract the menace of invasive or exotic organisms.
Kevin J. Hackett
"Forum" was published in the September 2003 issue of Agricultural Research magazine.