For the first time in California, agricultural officials confirmed finding what some call the worst tomato virus in the world—tomato yellow leaf curl virus.

“It’s a significant threat to tomato growers in the state,” says Bob Gilbertson, a University of California, Davis, plant pathologist. “Right now, all of the varieties in California should be considered susceptible.”

Florida and Georgia growers have battled the viral disease since the early 1990s, and breeders have developed resistant varieties for Southeastern markets, he says.

The whitefly-spread disease was confirmed last year in Texas and more recently in Arizona and northern Mexico.

UC Cooperative Extension farm advisor Eric Natwick discovered the disease in a high school greenhouse in Brawley in the Imperial Valley. The plants had been grown from seed, and none had been moved outside.

Because the virus is not seed transmitted, Gibertson says infested silverleaf whiteflies most likely brought it into the greenhouse.

The California Department of Food and Agriculture is working to minimize the outbreak.

Whiteflies can acquire the virus in as few as five minutes of feeding and remain infected for life, he says.

Infected tomato plants develop severely curled, yellowing leaves, shattered nodes and short, upright stalks. The virus causes flowers to abort, lowering fruit set and reducing yields. Plants are stunted and upright. Symptoms are most visible on the growing tips of plants.

"It would be difficult to confuse this with too many other diseases," Gilbertson says.

If you suspect you have the virus in your field, contact the local farm adviser or Gilbertson at The university has developed a diagnostic test that can confirm the disease within 24 hours