Twisted Tomato leaves

Asked July 13, 2020, 3:55 PM EDT

I have 4 tomato plants and the first 2 in the row have twisted leaves. Not all of the branches have the leaf curl but it's odd that the other 2 plants are fine. Any ideas of what could be causing this? The plants are just in regular yard soil, no compost or mulch applied.

Multnomah County Oregon

1 Response

First of all, I recommend, if you are able to, that you amend your soil with compost or well-rotted manure. In our clay soil not only will your plants benefit from the added nutrients it will improve the soil's fertility and texture. For more information on soil amending please refer to How to Improve Garden Soil with Amendments.

The curling or rolling of tomato leaves can be caused by various factors, including environmental stresses, viral infection, and herbicide damage. To determine which factor is the culprit, it pays to take a close look at the plant(s). Which leaves are rolling – old leaves, new leaves, all leaves? What direction do the leaves roll – upward or downward? Are any other parts of the plant, including fruit, exhibiting symptoms?

Physiological Leaf Roll

Excessive moisture and nitrogen, heat, drought, severe pruning, root damage, and transplant shock are some of the environmental factors that can cause physiological leaf roll in tomatoes. Initial symptoms are usually apparent in the lower leaves with upward cupping of leaflets followed by an inward lengthwise rolling of the leaflets toward the mid-vein. The affected leaves tend to become thickened and have a leathery texture, but retain a normal, healthy green color. Over time all of the leaves on the plant may be affected.

Vine tomato (indeterminate) varieties tend to exhibit physiological leaf roll more often than bush tomato (determinate) varieties. While this condition can occur at any time of the growing season, it usually occurs as spring weather shifts to summer. The good news is that the condition has minimal impact on tomato fruit production and plant growth. By properly hardening off tomato seedlings before planting in the garden, maintaining a consistent moisture level in the soil, and avoiding over-fertilization, excessive pruning and root damage during cultivation, one can go a long way toward preventing tomato plants from developing this physiological problem.

Viral Infections

Some viral infections also cause leaf rolling in tomatoes. When tomato plants are infected with Tomato yellow leaf curl virus (transmitted by whiteflies), new leaves become cupped and pale green in color. The entire plant may exhibit stunted growth, yellowing leaf edges, purplish veins on the undersides of leaves, and the decline of fruit production. A second virus, Tomato mosaic virus, causes rolling of leaves, but other symptoms, including mottled-coloring of leaves, small leaflets, and internal browning of infected fruit, distinguish it from physiological or herbicide-induced leaf roll.

There is no treatment for virus-infected plants. Removal and destruction of the plant(s) are recommended. Since weeds often act as hosts to the viruses, controlling weeds around the garden can reduce virus transmission by insects. As some viruses are transmitted mechanically on garden tools, it also helps to disinfect tools that have come into contact with diseased plants. To properly disinfect your gardening tools follow this University of Minnesota link for instructions.

Herbicide Damage

When tomato plants are exposed to the herbicide, 2,4-D, typical symptoms include downward rolling of leaves and twisted growth. In addition, stems may turn white and split; fruit may be deformed. Depending on the level of exposure, the plant may or may not survive.

Herbicide injury cannot be reversed, but if the plant is not killed, new growth may be normal. Always be very careful when spraying an herbicide, as it may drift much further than anticipated. If you did not use herbicide the drifting can be from neighboring yards.

For more information about Leaf Curl read this publication from the University of Missouri.

Good luck and happy gardening.