Curly Top

Curly top may sound like a cute little redheaded kid, but it’s a viral disease of many garden plants.

​Curly top host plants

This viral disease can infect watermelon, horseradish, pumpkins, beans,  squash, spinach, melons,
peppers, chickpeas, groundcherries,  tomatoes, and more. Scientists have identified different species of viruses that cause similar symptoms. For lack of better ideas, those viruses are called beet curly top geminivirus (BCTV), beet mild curly top virus (BMCTV), and beet severe curly top virus (BSCTV).

Symptoms of curly top

Infected leaves cup upwards or downwards depending on the plant variety. These leaves may turn darker or lighter green to yellow. And they are thicker and more brittle. Puckering and wrinkling are also common. Infected tomato leaves may have veins that look purple.

​The internodes (spaces between nodes on a stem) become shortened, causing stunting and dwarfing. These symptoms are more exaggerated when infection occurs while a plant is young. 

Beet infected with curly top CC BY 3.0

This condition is often fatal in young plants. Infected older plants may only turn yellow. The telltale symptom of curly top occurs when the top of the plant turns into a rosette or tiny bouquet. If any fruit develops, it will taste bad, the skin will be dull rather than shiny, and it will ripen before it reaches full size.

Curly top virus lifecycle

The virus overwinters in annual and perennial weeds. From there, beet leafhoppers (Circulifer tenellus) carry the disease to your garden plants. Symptoms don’t start to appear until long after the leafhoppers are gone. Since they are the disease vector, controlling leafhoppers goes a long way toward preventing this disease. Unfortunately, insecticides are generally not effective against leafhoppers. Leafhoppers have many natural enemies, so make your garden hospitable to beneficial insects. You can do this by avoiding broad-spectrum insecticides, planting a variety of umbellifers, such as dill, carrot, and fennel, and providing a water source.

The symptoms and host plants of curly top look too much like several other viral diseases, such as spotted tomato wilt, to be identified by the casual gardener. Laboratory tests are needed to know for sure. In the case of viral disease, it is simpler to yank the plant and toss it in the trash rather than spreading the infection to other plants.