I have had my raised beds for 3 years this summer. i have never had tomato blight before living here in Sterchi hills subdivision.For the last two years I have early tomato blight. I planted the tomato plants about 2wks ago. I have used the baking soda. oil,, castile soap spray. How do I get the fungus out of my soil?
Knox County Tennessee
The short answer is, you can't rid your soil of it. The fungus is in many places and will move. Eventually, as you found out, it found your raised beds. So, proactively, what can you do to avoid the fungus?
First, resistant varieties are usually an option but not for early blight (I'm assuming this is the blight you're referring to). There are only a few that tout being resistant and you won't be able to just walk into a garden center and buy those.
Secondly, water only at the base of your plants, avoid wetting the foliage. I understand you can't avoid rain, but no wetting the foliage by your own hand. Foliage wetness drives disease.
Third, mulch around the base of your plants. This will help stave off the disease for some time as it helps to alleviate soil splash from rain up to the lower leaves. This starts the disease cycle.
Fourth, make sure you are trellising those tomatoes and that they are not allowed to fall over on the ground.
Fifth, keep your tomatoes fertilized. Healthy plants are better at resisting disease than those that are starved.
Lastly, proactively apply fungicides that contain chlorothalonil or mancozeb. Refer to labels and adhere to those -- they are the law. Protectant fungicides like these can be washed off with rainfall so the spray schedule tightens with rain.
Once the disease has started, it's very difficult to control unless we get a dry spring/summer. These fungicides are not curative, they can only provide protection from further infection. Good spray coverage is essential.