Tomato Yellow Leaf Curl

Tomato yellow leaf curl is a devastating viral disease of tomatoes that made its way to California in 2007. Mostly limited to greenhouse environments, this disease can wipe out all of your tomato plants, so you need to know what it looks like.

Tomato yellow leaf curl (Dr. Michael Melzer) Public Domain

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This disease is spread by whiteflies and leafhoppers, and it is not limited to tomatoes. Other members of the nightshade family, such as peppers, can also be infected, as well as beans and many as yet to be identified weeds. Most often, the disease is spread through contaminated plants.


Symptoms of tomato yellow leaf curl

Infected tomato plants tend to grow unusually upright, while being stunted. This occurs because the virus shortens the internodes. Internodes are the spaces between the nodes where leaves emerge. Shortening the internodes makes the plant look bushier, but not healthier. Tomato leaf curl virus also causes up to 100% flower drop, which means no harvest. The most obvious symptom of tomato yellow leaf curl is the leaves. Infected leaves are smaller than normal, crinkled, and curled upwards. They also tend to turn yellow at the edges and between the veins. Unfortunately, many other viruses have similar symptoms. If you believe you have a plant infected with tomato yellow leaf curl, contact your local County Extension Office right away.


​Whiteflies and disease transmission

Specific varieties of whiteflies (Bemisia​) are responsible for transmitting this disease. If you look closely, you can see that some whiteflies hold their wings tent-wise, over their bodies, while others hold their wings flat. In the same way, some nymphs will have smooth edges, while others have a fringe of filaments. To see this level of detail, it is relatively easy to take a piece of clear packing tape and wrap it around your hand the same way you might to remove lint or pet hair from a pair of paints and capture the whiteflies on the tape. Then you can use a magnifying glass or hand lens for a closer look. It is the whiteflies that hold themselves under a tent and whose nymphs have smooth edges that carry the tomato yellow leaf curl virus. Leafhoppers are also believed to carry and transmit the disease.

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Preventing the spread of tomato yellow leaf curl

Tomato yellow leaf curl has the potential to temporarily eliminate tomato growing in certain areas, including your garden. This disease is the reason why tomatoes are generally not grown in tropical and semi-tropical regions. Cold winters tend to kill of the whitefly vectors, but not all winters are cold enough to provide that protection. Instead, you can use these tips to protect your tomato plants, and tomatoes, in general:

• quarantine all new plants to ensure they are disease and whitefly-free
• select varieties that are resistant to the tomato yellow leaf curl virus
• avoid transplants from affected areas (Mexico, Florida, Georgia, and Texas)
• manage whiteflies
• use crop rotation
• cover tomato plants with floating row covers
• remove weeds from the area
• remove and destroy crop residue, rather than leaving it in place

​Now you know.