A new species of Candidatus Liberibacter bacteria may be causing zebra chip disease in potatoes. Named zebra chip (ZC) because infected tubers form dark stripes when they’re cut and fried to make chips or fries, the disease was first detected in 2000 in Texas. Since then it has spread to Arizona, California, Nevada and other western states, causing losses to range in the millions.
In 2007, Agricultural Research Service (ARS) scientists completed studies pointing to the potato psyllid as an insect that transmits ZC. In 2008, New Zealand researchers, followed by University of California-Riverside scientists, announced their discovery of genetic evidence, indicating that a new species of Candidatus bacterium causes ZC.
Eating potatoes infected with ZC poses no consumer danger, according to Joseph Munyaneza, an ARS entomologist who’s studied zebra chip since it was detected in Texas. According to Munyaneza, potato growers had been spraying crops with insecticides to stop psyllids from transmitting ZC. Until the 2008 discovery, however, they didn’t know what actually caused the disease. They only knew that it correlated to psyllid feeding. Now, with evidence pointing to a Candidatus species, growers have more information to go on.
Source: ARS News Service. www.ars.usda.gov/is/AR/archive/oct09/zebra1009.htm