Info on the Dreaded Wilts

I started to respond in the comment section to several questions from Barefeet in the Kitchen and then decided my response was getting a bit long-winded for that venue.

I should qualify this advice by admitting that we are not experts in this area but have done a LOT of research and asked a lot of questions....and would welcome any contribution from gardeners who have had experience with these diseases.

We've examined our plants and have determined that the probably cause is one of the Wilts, Fusarium or Verticillium. These fungus were probably in the soil for some time but have been 'triggered' into action by the wet spring. They are similar to the fungus that causes 'damping off' and some of the same preventative measures apply. Unfortunately, sterilizing an entire gardens worth of soil is not feasible so we are choosing to do the following...

1. Treated with an organic fungicide called Actinovate, but more to prevent the disease in the adjacent plants than to cure the ones already infected. Unfortunately, the fungicide is rather expensive ($20 to treat maybe three -4x8ft. beds) so although we did use it this year, it probably won't be a regular addition to our garden expendatures.

2. Pulled out the plants that were near death and those should not be thrown in the compost pile because the fungus can survive unless subjected to intense heat. (Which means it might die in the valley but you'd be taking a chance.)We chose to leave

a lot of the plants in the ground in the hope of harvesting the tomatoes, especially in the beds where they all looked sick anyway.

3. Next year, plant resistant varieties or ones that have shown resistance this year. One of the heirlooms, Chico, looks lush and healthy despite being in a bed where even the Early Girls are suffering.

4. Limit the heirlooms to beds that have been treated or to pots for the next few years.

5. Feed plants, with compost or organic fertilizers, heavily. Healthy plants are much more capable of fending off diseases. The tomatoes in our home garden, which has a much longer history of good soil-building practices, went almost unscathed.

6. Lastly, while we try to rotate our crops, it is almost impossible to follow a strict rotation policy

with limited garden space

(because this would include the admonition of not following tomatoes with any of the Brassica family). Rather than try to avoid any possible negative crop interactions, we'll concentrate on keeping the tomatoes on a 3 year rotation.

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Here are some helpful excerpts from our Web searches ~

Fusarium wilt and Fusarium crown rot symptoms begin as yellowing of older leaves. With Fusarium crown rot, the leaves often turn brown or black and eventually wilt. With Fusarium wilt, the yellow leaves turn downward and droop.Fusarium oxysporum, the cause of both diseases, is a common tomato fungus that lives in the plant's vascular system, which carries water from the roots to the leaves. To see if either of these diseases is present:

• Check watering practices. Both over- and underwatering can mimic disease symptoms.
• Check the roots. Discolored roots indicate root rot.
• Cut the lower or main stem and look inside at the vascular tissue. Fusarium wilt causes a dark brown discoloration within the vascular tissue. Fusarium crown rot causes a rot or canker at the base of the stem and possibly a root rot. (We found when we cut open the stems of infected plants the entire diameter was brown.)

Most tomato seeds or transplants are labeled with a code such as "VFN," "VFNA," "VFNT," etc. This indicates that the plants are resistant to Verticillium wilt (V), Fusarium wilt (F), southern root-knot nematode (N), early blight (A), or tobacco (tomato) mosaic virus (T). Do not plant tomatoes, potatoes or eggplant in the affected area for two or three years.

And on another site~

The first line of defense against wilt is to use disease-free seedlings. This avoids introducing wilt fungi into the garden. Remove and destroy wilted plants and all debris of tomato and other susceptible crops at the end of the growing season. Rotate tomato-growing areas, growing tomatoes in the same part of the garden only once in four years. The benefit of rotation is less with wilts than with other diseases since both wilt fungi survive for years in the soil and the Verticillium fungus attacks many different crops. Fungicides for control of leaf blights have no effect on the wilt diseases, which are internal infections. Once soil is infested and further rotation impossible, the only possible management practice is use of resistant varieties.