Edible Gardening Series: Question of the Week – tomato yellow leaf curl virus

By Sarah Bostick and Carol Wyatt-Evens

Gardening in Florida can be incredibly rewarding and incredibly frustrating, at the same time. If you are new to the region, you soon learn that gardening in the Sunshine State can quickly become a full-time job. While our subtropical climate is perfect for growing an abundance of different vegetables, fruits, and herbs, it also can present some overwhelming challenges.

We can help! UF/IFAS Extension Sarasota County agents and staff have created an online edible gardening resource center. The website features short videos from our 25-episode “Edible Gardening Series” webinars, along with blog posts and resources lists for episodes. Get help on an array of topics that befuddle many gardeners.

This week’s Question of the Week is:

How do I manage Tomato Yellow Leaf Curl Virus in my tomatoes?

Tomato yellow leaf curl virus (TYLCV) is a very common disease in tomato plants. It is spread by a tiny insect called the Silverleaf whitefly, also known as the Sweet potato whitefly. Only adult whiteflies spread the disease and the only way they spread the disease is through the process feeding. Adult whiteflies have a long, thin, tubelike mouth that they use to puncture a plant’s veins. The whitefly uses its straw-like mouth to suck the juice out of a plant. If it feeds from a plant infected with TYLCV, it takes that virus with it to the next plant it feeds from. Think of silverleaf whitefly as the mosquito of the plant world.

Small leaves that curl upward are a classic sign of TYLCV in tomatoes. Photo credit: University of Florida

If you have gardened in Florida for more than a year or two, it is likely that you have seen the effects of TYLCV. If you are not sure, here’s what you need to know:

Plants can be infected at any stage of growth.
The virus is ONLY spread by an infected whitefly. It is not transmitted by seed or spread mechanically (e.g., by touch).
It does NOT survive in soil, on tomato stakes, on wire or string.
It can be spread by the movement of infected plants, especially tomato transplants, as well as by movement of virus-carrying whiteflies on host plants or by wind currents. It can spread quickly and have a severe impact on fruit yields.
It can take up to 3 weeks for infected plants to develop symptoms, but the infection can be transmitted during that development time by whitefly feeding on the diseased plant.
Whiteflies pick up the virus by feeding for at least 5 to 10 minutes on an infected plant. After about 10 hours, enough virus has built up in the insect that they can spread the virus by feeding on uninfected plants for at least 5 to 10 minutes.
Infected whiteflies can then retain the virus for 10-12 days so they can pass it to any susceptible plant they feed on. After that time frame, the whiteflies must reacquire this virus by feeding upon an infected plant again.
TYLCV can cause huge crop losses.

Early signs of TYLCV is evident in the leaves of tomato plants. Leaves of infected plants have a very distinct appearance: they are

A tomato plant infected with tomato yellow leaf curl virus, left, stands next to disease-resistant plant developed at the University of Florida’s Institute of Food and Agricultural Sciences. Once infected with the disease, tomato plants no longer grow normally, and no longer produce marketable fruit. Photograph by: Ernest Hiebert.

small, very crumpled, curl upward, and turn yellow at the edges and between veins.

If plants are infected at an early stage, Plants infected at an early age will not produce fruit and will stop growing while still very small.
Other symptoms that are typical for this disease are: leaf mottling, and flower drop.

As infection progresses, you will see:

Plants sprouting extra root growths along the stems
Plants can also show signs of stunting and larger than normal stems.
Stems become thick with very little space between branches, creating a stunted look
Plants infected at an older stage, may continue to mature the fruit that’s already on the vine, but it will take long to ripen and the plant will continue to be an infected host for whitefly.
Older plants have a higher viral load, so getting rid of diseased plants is recommended so that they cannot become a source of the virus for healthy plants.

TYLCV is noticed more easily by the contrast among infected and non-infected tomatoes in the garden or between nearby garden plots. As infected plants age, the more dramatic symptoms of leaf cupping, reduction in leaf size, flower drop and plant stunting is evident.

Diagnosing: visual diagnosis of TYLCV is more accurate when two or more symptoms can be confirmed from the same plant. Diagnosing based on one symptom (yellow, or leaf curl) can lead to erroneous error.

Is it possible to prevent TYLCV?

The simple answer is: kind of.

What is possible is decreasing the likelihood that your tomato plants will become infected. Here is how to decrease that likelihood.

Before planting:

Plant varieties of vegetables (especially tomatoes) that are tolerant to TYLCV. If you are using transplants, be sure to use plants that show no signs of whitefly or the virus. Remember, whitefly live on the underside of leaves, not the top of leaves, so take a peek!
Rotate susceptible crops to minimize the potential for carryover of the silverleaf whitefly between seasons:
Plantings of tomatoes should be separated in time and space from plantings of known whitefly hosts such as cabbage, collards, soybean, and weeds
Make sure to pull those weeds! There are many types of weeds that also host silverleaf whitefly.
Try to avoid planting near an old field or garden that has crop residue in it or planting near known whitefly infested areas.

During the Growing Season:

Plant tomatoes in silver reflective mulch. Silver plastic mulch reflects sunlight onto the underside of leaves, where silverleaf whitefly are busy feeding and hiding from the sun. They do not like direct sunlight. You can find silver mulch at most garden stores.
Keep up with weed management in and around the garden area
Learn to identify early symptoms of TYLCV and remove infected and infected-looking plants from your garden. Dispose of infected plants by enclosing them in plastic bags and putting them in the garbage. Remove diseased plants when incidence of virus infection is low so that you have the chance to eliminate the infection in the garden.
Make sure you are actively monitoring for whitefly. You should be visually inspecting your plants at least two-times per week for adults and immatures.
Control ants in the garden. Ants protect whiteflies from their natural enemies.

After the Growing Season:

Remove and destroy old crop residue and volunteer seedlings in the area.
Do not put crop residue or diseased plants in the compost – they can continue to host insects and spread disease for a while before breaking down.
Err on the side of caution: if you have a diseased plant – place a bag over the plant BEFORE cutting, tie it at the base and then cut the plant. This will capture any adult whitefly that are currently feeding on the plant. Throw it in the trash – not your compost!

If you would like to learn more about the silverleaf whitefly, visit this blog post in our Edible Gardening Question of the Week series.

For answers to more common tomato questions, click on the links below:

The Edible Gardening Series and blog series is a partnership between the following UF/IFAS agents and Sarasota County staff:

Sarah Bostick, Sustainable Agriculture Agent
Carol Wyatt-Evens, Chemicals in the Environment Agent
Mindy Hanak, Community & School Gardens Educator
Kevin O’Horan, Communications Associate