The curly top tomato leaf curl virus is a common and damaging plant disease affecting tomato plants. This viral infection can severely impact plant health and yield. Understanding its characteristics, spread, and effective management strategies is important for protecting your tomato crop.
Recognizing the Symptoms
Tomato plants infected with the curly top virus show distinct symptoms. Leaves may become dwarfed, crinkled, and show an upward curling or cupping, often appearing thickened and leathery. General yellowing (chlorosis) can occur, especially between leaf veins.
Veins on the underside of leaves may also develop a purplish discoloration. Infected plants often display stunted growth and a bushy appearance, with minimal or absent fruit production. Young plants are particularly susceptible and may die quickly after infection.
The Source of the Infection
The curly top virus is transmitted to tomato plants primarily by the beet leafhopper, Circulifer tenellus. These small insects acquire the virus by feeding on infected host plants, which include various weeds like Russian thistle, lambsquarter, and saltbush, as well as other crops such as beets, beans, and spinach. Once a leafhopper has acquired the virus, it can transmit it to healthy tomato plants as it feeds, often for the remainder of its life. The virus itself is not spread through seeds or soil.
Responding to Infected Plants
There is no chemical cure or direct treatment for infected tomato plants. Once symptoms appear, the virus has already spread throughout the plant’s system. Prompt removal and destruction of affected plants is recommended to prevent further spread. Do not compost infected plant material, as this could allow the virus to persist or infect other plants if leafhoppers feed on it.
Careful monitoring of nearby plants for new symptoms is advisable after removal. Removing infected plants eliminates a source from which leafhoppers can acquire and transmit the virus. Even if an infected plant is not removed, leafhoppers will likely move on to other plants after feeding. Cutting back the top of an infected plant may encourage some side growth, but the plant will likely still produce dull, wrinkled, or prematurely ripened fruit, if any.
Preventing the Virus
Proactive strategies are the most effective approach to managing curly top virus in tomato plants. Using physical barriers like row covers can deter beet leafhoppers from reaching young plants. These covers should be applied early in the growing season and can be removed once plants are more mature or when flowering begins to allow for pollination.
Planting resistant or tolerant tomato varieties can also reduce the risk of infection, though complete resistance is uncommon. Some varieties, such as ‘Columbian’, ‘Rowpac’, ‘Roza’, and ‘Saladmaster’, have shown some level of tolerance to the virus. Practicing good weed control around the garden is also important, as weeds can serve as hosts for both the beet leafhopper and the virus. Companion planting with reflective mulches may help confuse or deter leafhoppers, and strategic site selection to avoid areas historically prone to high leafhopper activity can further minimize risk.