Disease Prevention For Tomatoes

Many people have asked me what they can do to prevent their tomatoes from succumbing to disease. The first answer to protecting any of your crops from disease is to start with the soil. Have your soil tested and correct any imbalances with organic amendments. If your local feed store or garden supply can’t offer help with organic information, check with your state organic organization or Cooperative Extension Service. In Virginia, Countryside Organics and Seven Springs Farm are two sources of amendments. The two places I’ve used for my soil tests are Timberleaf Soil Testing and A&L Eastern Laboratories. Timberleaf results give suggestions for what product to add per 100 sq. ft. It is less expensive to have a test done at A&L. A&L gives great test results, but as usual with soil tests, their results tell you how much of each thing is needed (nitrogen, phosphorus, potassium, boron, etc) and you have to figure out what product to use and how much, since only a small percentage of that item is in the product. There are other labs and services out there that can be of help. It might be that the place you find to purchase supplies can help you interpret your test results. Dr. Mark Schonbeck, a friend of mine in Floyd, VA, can interpret soil tests and offer recommendations.

One problem with tomatoes is blossom end rot. When your tomatoes begin to ripen and you have a black spot at the end, that’s blossom end rot. If you look it up, the books will tell you that it is caused by a calcium deficiency, or too much water, or too little water. If you have had your soil tested you will know if there is a calcium deficiency. Another reason I’ve come to know is if there is a cold spell after I’ve set my tomatoes out. In that case, the first flush of tomatoes might have it, but the rest will be fine.  So, don’t get yourself too stressed if you see it. If it is calcium, well, you should have amended after your soil test. If it is too much rain, know the rain probably won’t last forever. If you’ve left those poor plants on their own in a dry time, get out the hose.

tomato plant before trimming

The biggest problem here in the mid-Atlantic is blight. It doesn’t really matter to me the exact name or if it is early blight or late blight. The bottom branches of the plants begin to turn brown and die and it gradually works its way up the plant. The fungal spores that cause that are in the soil and the disease begins in the leaves that hang down and touch the soil. Furthermore, if the soil is bare under the tomatoes, when it rains, those spores are splashed onto the plants. Now is the time you can take preventative measures. Trim the lower branches of your plants so nothing hangs down and touches the soil, and mulch around the plants. You will need to come back in a couple weeks and trim your plants again because they will have put out more growth. It is hot and humid here in the summer and giving tomatoes a little breathing room will do wonders. Open up that space at the bottom and get the air flowing. Listen carefully, your tomatoes will be thanking you.  

tomato plant trimmed and mulched

Your disease prevention should have started last fall by planting cover crops. Cover crops do wonders adding organic matter to the soil with their roots and later with the biomass grown on top. That’s where your mulch can come from. Planting cereal rye in the fall provides you with the most mulch, but your tomatoes will be planted a little later, since you cut it in place when it sheds pollen and then wait two weeks to put in the tomatoes. Legumes, such as hairy vetch, crimson clover, or Austrian winter peas, can be cut earlier, allowing earlier transplanting of your tomatoes. The resulting mulch, however, is not as long lasting. The mulch in the picture of the tomato before trimming is hairy vetch that was so prolific when I cut it in the spring. Now it is disappearing fast and I added leaves on top to keep a mulch cover. Hairy vetch is highly recommended to precede tomatoes. These cover crop mulches are slow-release fertilizers for the tomatoes, or anything else they are mulching, as they compost in place. The mulches with the most carbon will compost more slowly, which is why the rye lasts longer than the legume mulch. My daughter plants sweet potatoes next to her tomatoes and they provide a living mulch to keep the soil from splashing.

Compost, of course, should be part of your soil fertility plan. It helps build the organic matter. Throwing some fertilizer at your tomatoes when you plant, thinking the more the better, might only result in lots of foliage and less fruit. If you do want to add something extra, wait until the plants have flowered. Keep in mind, if you walk into your local garden center which sells all sorts of chemicals, and ask them what to do for your tomatoes that are showing signs of disease, telling you about cover crops, organic matter, and mulch, if they even know about those things, is not to their benefit. They are going to show you whatever product they have on the shelf that the chemical company has labeled for your problem.

Some varieties of tomatoes might work better in your area than others, so choose carefully. The seed catalogs often do a good job with their variety descriptions to help you decide. Some varieties are bred to resist certain diseases. Over the years, the ones I tried solely on disease resistance looked great, but weren’t as flavorful as others I grew. It might be that you have just bought your plants from a big-box store. That’s okay, you have to start somewhere.  However, a few years back there was a big disease problem all along the East Coast. Climate conditions made it a bad year for tomatoes anyway, but contributing to the problem were tomatoes that came from greenhouses that service those big-box stores. When everything comes from one source, and that source has problems, everything has problems. Talk to the farmers at the markets this summer and ask them what varieties of tomatoes they are selling and how well they cope with disease. If they are open-pollinated varieties, you could save the seeds yourself from the tomatoes you buy at the market, or ask the farmer if you can buy plants next spring.

Begin to take notice of your plants. Which ones survived the summer the best? If you also liked them for other reasons, save the seeds for next year. Over time you will develop a strain of that variety that works well in your spot under whatever conditions exist there.

No matter what tomatoes you have in your garden this year, you can learn a lot by watching, taking notes, and talking with others.  When you are planning your garden next year be sure to look back at your notes and plan accordingly.

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