Ask the County Agent: 'What's wrong with my tomato plants?'


By Stephanie R. Butcher
County Coordinator Agricultural & Natural Resources Agent
UGA Extension – Coweta County
QUESTION: What is wrong with my tomato plants? They started out looking great, but now the leaves are cupping and the new growth is twisted and gnarled looking.
COUNTY AGENT: If you’re seeing twisted, gnarled stems on your tomato plants like the ones in the picture, then your tomatoes are showing symptoms of herbicide damage. Although damage from viruses and some insects can also cause leaves to cup and curl, the damage from a broadleaf herbicide like 2,4-D is unmistakable and it is most noticeable in the newest growth on the plant.

Tomato plants are especially sensitive to herbicides and will show symptoms long before other plants will. Be careful when using mulch and compost in your garden. Investigate the source to ensure there haven’t been any herbicides applied on the pasture or used on the hay where you get your compost or mulch.
Most pastures and hayfields are sprayed with herbicides in order to meet consumer demand for high quality, weed-free forage. Although today’s herbicides have low toxicity to humans and animals, they are very good at killing broadleaf weeds, and they don’t know the difference between a nuisance weed and your beloved tomato plant.
Some of these herbicides also have residual control meaning that the herbicide remains active for weeks or months, so your tomatoes can be affected by herbicides remaining in the mulch or compost even if you didn’t spray or spread a herbicide near your plants or in the lawn near your vegetable garden.
Another common herbicide that can damage tomatoes is glyphosate. It is a non-selective herbicide that is often used for weed control around landscapes and gardens. This herbicide will cause bleaching of sections of the new growth, causing the plant to appear almost variegated. Although glyphosate doesn’t stay active in the soil, it can drift onto the green leaves when used near vegetable gardens and will cause the symptoms you see in the photo.
If your plants are showing symptoms of 2,4-D herbicide damage, then you should replace the mulch or compost and you will likely need to replace your plants. Depending on how much damage was done to the plant, some plants will grow out of the damage but some may not. If your tomato has been damaged by glyphosate, it may grow out of it if the damage is not too severe.
If you are unsure whether you have herbicide damage or not, you may email pictures to [email protected] or drop off a sample at the Extension office at 255 Pine Road, Newnan, 30263.
For more information on avoiding herbicide damage or growing tomatoes, contact the Coweta County Extension Office at 770-254-2620 or e-mail [email protected] and ask for the UGA Extension publication, “Georgia Home Grown Tomatoes”.
The University of Georgia College of Agricultural & Environmental Sciences is an equal opportunity, affirmative action organization.