Last season nearly every local gardener I know had tomatoes die from Fusarium wilt. We lost a large percentage of our crop to it (although with 80 tomato plants, we still had plenty to harvest).
Then I saw GOFO’s office garden at Crescent Studios and could not believe my eyes. Unlike the other gardens I’d seen, their tomatoes didn’t have a single spotted leaf. These plants were lush, gorgeously green, and very productive. They were also intensively planted and had woven themselves into an impenetrable mat (air circulation? not really!) So why were these plants so healthy?
GOFO wasn’t sure of the secret to their success. It turned out that when they limed their soil to boost the availability of calcium it also happened to raise their soil pH to 6.5 – 7.0. Fusarium wilt prefers a pH under 6.5 or the spores have a hard time taking hold. After seeing the GOFO plants, I’m a believer! Winter is the perfect time of year to amend soil with lime so I’ll be having my soil pH tested through our local Cooperative Extension office in order to find out the application rate of pelleted limestone in my garden.
Fertilizers made with ammonium nitrate are another problem because they cause tomato plants to be more susceptible to Fusarium wilt. This isn’t much of an issue for organic gardeners, but click here to read about different forms of fertilizer including ammonium nitrate.
Another excellent option is to plant varieties that are resistant to strains 1 & 2 of Fusarium wilt. If a seed packet or catalog entry has an “F” it indicates resistance to Fusarium wilt. “FF” indicates resistance to both strains of the disease.
I find Fusarium wilt to be a bigger problem in my garden than the more infamous blight diseases because it destroys the plants before I get much (or any) harvest. You can read the blog post I wrote on how to identify this fungus vs. other early tomato diseases by clicking here.