Nothing causes that sinking feeling like walking into the garden and seeing one or more tomato plants wilting. Not just some lower leaves that are yellowing, curling, or drying up from leaf spot diseases. No, I’m talking about healthy green leaves and stems that start to go limp. Oftentimes, this spells the beginning of the end for the affected plant(s) so it’s important to figure out what’s causing the wilting symptom. Even if you lose one or more plants this year you’ll want to prevent a recurrence next year. UME’s Home & Garden Information Center seems to be getting more tomato wilt questions this year than usual.
Wilting may indicate that roots or stems are injured, soil moisture has been too high or too low, or that the vascular tissue directly below the epidermis (skin) of tomato stems is blocked up with fungal or bacterial pathogens. Plants with disease-caused wilt should be removed. Here are some possible causes for wilted tomato plants in Maryland.
Fusarium wilt– this disease is caused by a soil-dwelling fungus. Lower leaves turn yellow and leaves and stems begin to wilt, often on one side of the plant. Leaves may revive overnight. Cutting affected stems lengthwise with a razor blade (directly below the surface) will reveal brown discoloration or streaking. The disease rarely infects all of the tomato plants in a row or a bed.
This fungus can survive in the soil for years even if the tomato is not grown in that location. One solution is to grow resistant varieties- look for those that are resistant to at least two of the three known races of fusarium wilt. Example:
Nature’s Bites F1: Fusarium Wilt 1, Fusarium Wilt 2, Fusarium Crown & Root Rot, Leaf Mold, Root Knot Nematode, Tobacco Mosaic Virus
Another option is to grow tomato plants in containers filled with compost and soilless growing media. Don’t set the containers on the garden soil that had the fusarium wilt problem last year.
Southern blight– another soil-borne disease that is worse during extended periods of hot, wet, humid weather. This fungal disease has a wide host range with tomato and pepper frequently affected. Darkening of lower main stems is an early symptom. This is quickly followed by wilting. White, fuzzy mycelium will appear near the plant base. There is no cure. Affected plants should be removed and discarded. This disease can survive in the soil but does not typically infect plants grown in the same location each year.
Tomato pith necrosis (TPN) – Dr. Jerry Brust, UME Vegetable IPM Specialist, has written about this bacterial disease seen in commercial tomato production the last few years. Gardeners also need to get familiar with this disease. I had a plant collapse in early July that had several symptoms consistent with TPN- stem lesions, wilting, and hollow and discolored pith (see photos below). Symptoms can be very mild or severe.
Less common causes of tomato plant wilt: tomato spotted wilt virus, bacterial wilt, verticillium wilt, walnut wilt (tomato planted near a walnut tree), and the common stalk borer.
General practices to reduce tomato disease risks:
- Select disease-resistant varieties. Cornell University has a fabulous web page listing disease-resistant varieties
- Avoid watering foliage in the evening. Water around the plant base where it can quickly reach the root zone
- Harvest your vegetables before they become over-ripe
- Pull up and discard entire wilted plants when disease is suspected
- At the end of the growing season, thoroughly remove all plant parts, including dropped leaves and fruits
- Keep weeds to a minimum
Boost Tomato Yields This Year
Below are some tips to keep your tomato plants healthy and productive.
Some of the problems with letting tomatoes ripen on the vine:
You can greatly reduce risks and increase the harvest by picking fruits at the “breaker stage” when they first start to turn color on the bottom. Let them ripen on the kitchen counter. You won’t be able to tell any difference in texture or flavor.
Enjoy your tomato season!
By Jon Traunfeld, Extension Specialist, University of Maryland Extension, Home & Garden Information Center. Read more posts by Jon.