So named for the dark stripes it forms inside afflicted tubers when cut and fried to make chips or cooked at high temperatures for other dishes, zebra chip has caused millions of dollars in production and processing losses since its first reported U.S. occurrence in potato fields near McAllen and Pearsall, Texas, in 2000.
The disease, whose above-ground symptoms include necrosis and purplish, upward-curling leaves, among others, has since been reported in several other states (California, Nevada, Kansas, Nebraska, New Mexico, Colorado, Wyoming, Washington, Oregon, and Idaho), Mexico, parts of Central America, and New Zealand.
Intensive collaborative research by university, industry, and government scientists, including teams from three ARS laboratories-the Yakima Agricultural Research Laboratory (YARL) in Wapato, Washington; the Vegetable and Forage Crops Research Laboratory (VFCRL) in Prosser, Washington; and the Beneficial Insects Research Unit (BIRU) in Weslaco, Texas-narrowed the list of likely suspects to a fastidious (nonculturable) bacterium, Candidatus Liberibacter solanacearum, and the potato psyllid, Bactericera cockerelli, as its insect accomplice or "vector."
The discovery is helping growers in affected regions improve their timing and use of insecticide sprays to prevent psyllids from feeding on and infecting potato crops with the zebra chip bacterium.
Longer term, researchers aim to recommend alternative controls for use in integrated approaches to managing the disease-spreading pest.
Besides savings on insecticide use, other benefits of integrated pest management (IPM) include preservation of beneficial insects, prevention of secondary pests, and decreased risk of insecticide resistance developing in psyllid populations. Genetic resistance in plants to the pathogen or host is yet another benefit.