Utah tomato growers may see yields sliced by as much as 30 percent this summer because of a virus known as curly top.

"Once curly top virus is in the plant, (the virus) multiplies rapidly," said Sherm Thomson, Utah State University Extension plant pathologist. "Fruit on infected plants will ripen prematurely and be small and leathery."Thomson said he is receiving numerous phones calls from growers wondering what's wrong with their tomatoes. These callers have seen the top-most leaflets become twisted and yellow, while older leaves have become thick and leathery, rolling upward and revealing pronounced purple veins. Branches appear stiff and erect.

Thomson has seen commercial fields with 30 percent of plants infected, and he suspects many back-yard gardens may suffer the same level of incidence.

The curly top virus is spread by the sugar beet leafhopper from infected desert vegetation into cultivated tomato plants. The disease also infects beans, squash, cucumbers, melons, spinach, beets and peppers but is most severe on tomatoes.

Infected plants should be removed as soon as they're noticed.