In mid-July, I found out the Mansfield Extension Office got a call about a tomato problem while I was volunteering to answer gardening questions.
I’m part of the Master Gardeners, a national volunteer group connected to the Ohio extension service. This year, I wanted to get more involved.
Usually, I’d go to the Longwood Office in Mansfield and spend a few hours looking over the week’s questions. After checking out the problems, I’d try to answer questions from people like you.
Now, I’m trying something new: getting questions by email from the office.
One of the first questions I got was about visiting an Amish man’s home to look at a disease affecting his tomatoes. Since some Amish families don’t have phones, they use a neighbor’s phone, and the neighbor passes along any returned calls.
When I first heard about the problem, it sounded urgent. He was worried he might lose a lot of his tomato plants. I was in Florida the following week, so I couldn’t visit him right away.
As soon as I got back, I went out to see him and check on the situation.
When I arrived at his place, it was clear he took tomatoes seriously. He had about 10 greenhouses, each about 100 by 50 feet, with tomatoes growing in the soil under the plastic.
Inside, I saw wilted tomato plants everywhere. The disease had really hurt his crop. He also had a big field of tomatoes, and that was affected by the blight too.
As I recall from the message, the leaves wilted quickly, some turned yellow, and he was understandably upset. Any gardener would feel the same, especially after planting thousands of tomatoes.
The wilting and yellowing weren’t the only problems — many plants died. There were still some tomatoes to pick, but these plants wouldn’t produce a second harvest.
The fungus attacked the vascular system and girdled the stem, killing the plant. At the soil line, where this disease lives, you would see this foam, and the plant looked water-soaked and developed these b-b-sized lesions.
The high humidity and hot weather we have had this summer created ideal conditions for this disease to grow and spread.
When humidity is high, this disease produces a cotton-like mycelium and b-b-sized nodules called sclerotia that turn tan to brown to pink, which is the key identifier.
Low-hanging fruit or fruit that has been in contact with the soil may develop wet rot. This rot can lead to rapid decay that you won’t smell at first.
In this case, the problem was Southern Blight in tomatoes, caused by Sclerotium rolfsii.
Temperatures were between 77 and 95 degrees, with stretches of warm rain and then hot, dry weather. This disease does best in moist, airy, acidic soils. Be aware, it can stay in the soil for up to five years even without a host plant.
Before it infects plants, the sclerotia germinate and grow on organic debris. The fungus can then spread in the soil, on tools, and even through irrigation water. This buildup makes it hard to control.
Remove dead plants as soon as you can, and burn the soil where the plant died.
The Extension service recommends planting a cover crop like mustard to help control this soil-borne disease. Mustard has high levels of glucosinolates, which help suppress the disease.
Grafting certain tomato varieties before the season starts can also help manage this disease next year.
Using rootstock from Solanum sisymbriifolium types like Maxifort, Big Power, or Beaufort can lower disease rates and boost yields in affected fields. Once you graft your chosen tomato onto the rootstock, you’re set to go.
Next year, after dealing with the disease, add lime to your garden to raise the pH to 7, which helps stop the disease from forming. Only some tomato types are at risk. Clean all your tools with a 1:9 bleach-to-water mix to reduce the spread.
The disease only survives in the top 2-3 inches of soil, so deep tilling can help control it.
Several approved fungicides can also fight this disease.
Southern Blight can really hurt your tomato crop this year, but you can plan now for a better season next year.
I hope you enjoy walking through your garden this week. If you run into any problems, feel free to reach out to me at ericlarson546@yahoo.com.