Plants infected with the curly top virus show a striking down-cupping, puckering, and wrinkling of infected leaves. The leaves become thick and brittle and may turn dark green. Portions between two joints on the stem of infected plants become shortened, resulting in a striking dwarfing and stunting of infected plants, particularly when plants are infected at an early stage of growth. Older plants may turn yellow and die. The upper portion of infected plants resembles a rosette or small flower bouquet. Fruit are small and remain upright instead of drooping. Infected fruit have a dull surface unlike the glossy skin of normal fruit.
The curly top virus has a wide host range that includes beans, tomatoes, peppers, sugarbeet, melons, and other crops. It is not known if a single virus strain infects all these crops or whether distinct strains damage different crops. It is known that the virus overwinters in perennial and annual weeds in areas such as the foothills surrounding the Central Valley of California. The occurrence of curly top follows the seasonal cycle of its vector, the beet leafhopper. Beet leafhoppers overwinter in uncultivated places, where they pick up the curly top virus by feeding on infected wild plants. In spring, when wild hosts begin to dry out, the leafhoppers migrate into the valleys where they settle on crops. Symptoms of curly top appear after the leafhoppers are gone. The disease does not spread from one plant to another; new infestations are caused by new flights of leafhoppers.
Plant varieties that are resistant or tolerant to the curly top virus if curly top is in your area. Control of leafhoppers with insecticides will not reduce the incidence of disease.
Curled and wrinkled leaves of curly top on beans
Stunted tomato plant infected with curly top
Stunted cantaloupe plant infected with curly top (lower right) compared with healthy plant
Early ripening of curly top on tomato