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'll want to know what it looks like.

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

Whiteflies and leafhoppers carry this disease, and it is not limited to tomatoes. Other members of the nightshade family, such as peppers, can also be infected, as can beans and many as yet to be identified weeds. Most often, the disease spreads through contaminated plants.

Symptoms of tomato yellow leaf curl

Infected tomato plants tend to grow unusually upright while being stunted. 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. Infected leaves are smaller, 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.

Whiteflies and disease transmission

Specific varieties of whiteflies (Bemisia) are responsible for transmitting this disease. Look closely to see that some whiteflies hold their wings tent-wise, over their bodies, like butterflies, while others hold theirs flat, like moths. In the same way, some nymphs will have smooth edges, while others have a fringe of filaments. 

You can capture whiteflies for these close inspections the same way you use clear packing tape wrapped around your hand to remove lint or pet hair from a pair of pants. Once they are stuck, you can use a magnifying glass or hand lens for a closer look. The whiteflies that hold themselves under a tent and whose nymphs have smooth edges that carry the tomato yellow leaf curl virus. Leafhoppers may also transmit the disease.

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 why tomatoes are generally not grown in tropical and semitropical regions. Cold winters tend to kill off the whitefly vectors, but not always. You can use these tips to protect your tomato plants:

• 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.
• Employ crop rotation.
• Cover tomato plants with floating row covers.
• Remove weeds from the area.
• Remove and destroy crop residue rather than leave it in place.