What makes tomato leaves twist or curl?

Published on Saturday, 19 July 2014 23:00 - Written by Chad Gulley Extension Agent

Many gardeners plant tomatoes in their gardens and flower beds. If the leaves of your tomato plants are twisted or curled, the problem could be environmental, chemical or even biological.

There are five primary reasons that tomato leaves twist or curl. These are wind damage, herbicide drift, herbicide residue, broad mite and tomato viruses. During periods of high winds, blowing dust and low humidity can damage leaves and stems on tomato plants. Hot, dry weather also may cause a symptom called physiological leaf roll. This is a self-defense response in the tomato plant.

Herbicide drift may be a cause as well. In situations where herbicides are used in a nearby field to control unwanted plant species, sensitive plants like the tomato plant could be damaged by any drift from the application.

To avoid herbicide drift, read and follow all label instructions when applying herbicides. Avoid applying herbicides with wind speeds exceeding 5 to 10 miles per hour. This will vary from product to product so read the label to determine this.

Herbicide residue also can cause leaf twist or curl in tomato plants. Mulch, compost, animal manures, hay or straw used in the garden may contain some herbicide residue. With the proper amount of time the herbicide will break down and not be present. Avoid applying fresh manure or hay and straw you suspect may have herbicide residue to the sensitive crops in your garden.

Broad mites affect many plant families including tomatoes. Broad mites avoid light and feed on young leaves and flowers. As they feed, they inject toxins that severely twist and distort the leaves. Severe broad mite infestations can make the underside of leaves and fruit look bronzed or russetted. These mites are invisible to the human eye. Broad mites are oval in shape and can be translucent to pale brown or yellow.

Broad mite populations vary depending on food, weather and light. Proper identification is important to make sure you have broad mites on your plants. Samples may need to be collected and sent in for analysis if broad mites are suspected.

Tomato viruses also can cause leaf curling or twisting. In Texas, the most common virus is the tomato yellow leaf curl virus. To reduce the spread of a virus on your plans, manage whitefly populations. There are a number of viruses that affect various vegetable crops. Proper identification is important. It may require samples to be sent to the Texas Plant Disease Diagnostic Laboratory on campus of Texas A&M University or by accessing the following website:www.plantclinic

.tamu.edu/factsheets.

 

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