BOISE—Curly top virus seems minor or absent some years; other years it’s destroying gardens all over the Valley. I’ve heard of several gardens afflicted with this virus this year. Curly top is a virus spread by a tiny beet leafhopper, and if you’re not near beet fields (such as sugarbeets), be aware these leafhoppers can ride the winds for up to 200 miles.
Whatever they bite transmits the virus to them. They do not suffer ill effects, but the next thing they bite receives the virus. One favored plant is tomato. Large vigorous tomato plants suddenly curl top leaves, showing purple veins on what had been the undersides of the leaves. Leaves at this point feel leathery. I discard tomatoes from diseased plants. Curly top virus may also damage and kill beets, squash, peppers, spinach, celery, melons, potatoes and several ornamental plants. In leafy plants, symptoms are distorted and discolored leaves, swollen dark veins, stunting of the plant and/or deformation of fruit.
Curly top virus is climate specific, occurring in arid areas such as the desert areas of the Middle East and the Intermountain West, from Canada to Mexico. If winds blow in the right direction, it may invade southeastern Colorado. The other “outside its normal range” area is the east Bay Area of California. Some years it has devastated the commercial chile pepper crop in southern New Mexico.
You may prevent the virus by planting tomato varieties known to be resistant to curly top virus, by shading crops that don’t require full sun exposure, or surrounding or interplanting treasured plants with strong-smelling herbs such as dill. The tomato varieties known to be resistant to that virus are all salad types of tomatoes; varieties are Rowpac, Columbia, Latah, Payette, Owyhee, Roza and Saladmaster. The only commercial seed source I know of for them is Sand Hill Preservation Center (www.sandhillpreservation.com). These seed vendors don’t claim that resistance, but these varieties were developed and tested by University of Idaho faculty members many years ago.