Curly top may sound like a cute little redheaded kid, but it’s really a viral disease of many garden plants.
Curly top host plants
This viral disease can strike beets, beans, ground cherries, peppers, pumpkins, chickpeas, tomatoes, squash, spinach, melons, horseradish, watermelon, and more. Scientists have identified different species of virus 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 plants exhibit leaves that cup upwards or downwards, depending on the plant variety. These leaves may turn a darker green than normal, or light green to yellow, and they are thicker and more brittle than normal. 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, and death is common. Infected older plants often just 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 is present, the skin will be dull, rather than shiny, it will taste bad, and will tend to 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, but they are the disease vector, so 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 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.
You can grow a surprising amount of food in your own yard. Ask me how!