How to treat Fusarium wilt?

by Apple
(Roswell, NM)

Q. I usually buy my tomato plants from local hardware stores. Every year I add my own compost to the garden and sterilize the soil prior to planting. This year three out of 8 tomato plants (different varieties) have the same symptoms: yellowing leaves, starting at the base of the plant, wilting during the hot day time and perking up in the evening. I pulled up one plant early on, chucked it and replaced it. I just pulled up my second because almost all if its leaves had fallen off, except the new green ones at the top. I cut the stem open and it had a narrow brown band on the inside of the stem.
I have not had this problem in my garden until this year...

Any suggestions on how to rid the soil of this wilt or is my garden doomed?

A. Sounds like you rightly diagnosed your plants with fusarium wilt. So sorry about that! But don't be discouraged ... there is hope.

Fusarium wilt is caused by a fungus that lives in the soil. The fungus works its way up through the plant’s roots, clogging water-conducting tissue in the stem. That prevents water from reaching branches and leaves, starving the plant. Affected plants produce very few tomatoes. Often, the entire plant dies, as you have experienced. There are several steps you can take to rid yourself of these nasty fungi in your soil. We suggest you take as many of these steps as possible ... there is strength in a multi-pronged attack!

• Burn. One of the best solutions to combating fusarium wilt (and all other kinds of tomato diseases, for that matter) is to burn them out. At the end of the growing season, remove all garden debris of the affected area. Apply straw or dried leaves (if you have any in NM). Notify authorities that you will be burning debris on your property. Then, with a garden hose nearby, burn the affected area. You may even want to make a bonfire of it. Your late-season pow-wow will accomplish at least two things: the fire will kill overwintering fungi, bacteria, and other nasty organisms. Further, residue adds nutrients to the soil.
  
• Solarize. Bacteria, fungi, and viruses can live for several years in the home garden. You can treat infected soil to destroy as many of them as possible during the heat of the summer with a solarizing tarp. Spread a clear tarp over the selected garden plot. It will collect heat from the summer sun, raising soil temperature high enough to kill disease-spreading organisms. It is most effective when put into place during the hottest part of the summer.
  
• Rotate crops. The fusarium fungus can survive indefinitely in the soil. Plant tomatoes no more than once every four years in the same spot. Avoid planting other Solanaceous crops (potato, pepper, and eggplant) in the same area, too – they are susceptible to the fungus.
  
• Take precautions for a few seasons. Choose disease-resistant tomato varieties. An “F” listed after the variety name on its label indicates its resistance to one or more strains of the fungus.
  
• Check for nematodes. Fusarium wilt is more serious when root-knot nematodes are present. They weaken the plant and allow the fungus to spread more readily.