Saturday, May 30, 2009

Wilting in Wet Weather

Two of my tomato plants have a problem. They are being affected by either fusarium or verticillium wilt. Both of these conditions are caused by soil-borne fungi, and it is hard to distinguish between the two. The photo above of the main stem of one of the affected plants shows a collapsed vessel running up the stem, an early indicator of the infection.

The fact sheet on “Fusarium and Verticillium Wilts of Tomato, Potato, Pepper, and Eggplant” from Ohio State University Extension shows a very similar photo that features the collapsed vessel. It also shows pictures of affected leaves from a plant that is showing the additional (and usual) signs of infection.

When I pulled the two plants out and cut the stems open, the brown streaking described in the Ohio State fact sheet was also apparent, so I am extra-glad that I decided to trust my prior experience and remove those plants now, instead of waiting for the more standard signs.

Usually, the first symptom a gardener notices is some yellowing and/or wilted leaves on one side of the plant. However, we have had so much rain and so many cloudy days that the wilting hasn’t yet manifested. I only noticed the affected stems because a few weeds had popped up through the mulch in the tomato area, and I sat down to pull them out.

The affected plants are both Mortgage Lifters, grown from the same seed packet I have been using for three years now. This is the first year the Mortgage Lifters have had this problem. I am a little puzzled by the change, but it is possible that the cool and very wet weather—the previous two years were drought years!— has made the fungus especially vigorous.

To replace the diseased plants, I have purchased a couple of Better Boys. These are, like the Mortgage Lifters, indeterminate plants that produce large tomatoes. Hopefully, though, the Better Boys will resist the fungus. This variety has been officially declared VFN resistant, so their chances are good.

Luckily, the two new-to-me tomato varieties, Wuhib and Amish, that are planted in that same bed still look fine. However, I won’t declare them to be essentially resistant to whichever fungus in my yard is ruining the Mortgage Lifters for a few more weeks.

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