Solutions for Tomato Plant DiseasesIt seems that the incidence of many tomato plant diseases depends on an area's climate. In my research, I also noticed that most of them are cause by fungus. Since I garden in the Pacific Northwest, late blight is my highest concern. I avoid the fungus that causes this problem by: --Covering tomato plants with plastic to protect them from rain and dew as well as keep temperatures consistent; --Watering close to the soil to avoid water spray on the leaves; --Spacing, staking or caging to keep plants off the ground; --Pruning to keep good air circulation around the base of my plants; --Applying compost tea to the leaves, stem and soil every couple of weeks. Seven of the most common tomato plant diseases are described here with information on how to deal with them. Fortunately I have not experienced any of these myself, so I am sharing the following information from articles published in Organic Gardening Magazine. Early Blight Dark spots surrounded by concentric bull's-eye rings on the leaves. Fruits rot inside, starting at the stem. Seedlings may have dark, sunken-in spots around the soil line. This tomato plant disease is actually caused by a fungus that survives the winter on old vines. Clean up and throw away all debris after harvest, rotate crops and plant resistant cultivars. Avoid crowding and prune for air circulation. Septoria Leaf Spot Begins as yellow dots that quickly turn into brown zones surrounded by yellow halos. Cells in the center of the spots die and turn whitish. Caused by a fungus. Remove infected leaves to contain. Tobacco Mosaic Virus Leaves take on a mottled yellow appearance and can lead to a stringy growth habit, particularly in cool weather. Wash hands before working with plants. Choose varieties denoted with a "T" on the seed package or plant marker. Verticullium Wilt Plants become wilted and limp (even well-watered ones). Leaf edges may curl and older leaves turn yellow in a uniform manner and start to die between the veins. Stems will have dark centers. Caused by a fungus. Rotate crops. Remove and destroy all debris, do not plant tomatoes where the disease has occurred in the past. Select resistent varieties denoted with the initial "V" on the seed package or plant marker. Fusarium Wilt Starts as a downward leaf curl--older leaves yellow and die as the branch wilts. Symptoms may only appear on one section of plant. The stem may also have brown or black lesions, and inside there will be dark streaking. Common in the South. Caused by a fungus. Rotate crops. Remove and destroy all debris, do not plant tomatoes where the disease has occurred in the past. Choose resistant varieties denoted with the intial "F" on the seed package or plant marker. Late Blight Produces dark spots on the leaves that turn brown and then papery. Late blight can cause the entire plant to collapse all at once and become a bad-smelling mess. Caused by a fungus that is favored by wet weather--the spores can travel great distances to affect plants. I've also heard that blight can happen after a sudden drop in temperature. Avoid crowding. Enhance air circulation within and among plants by staking or caging and by pruning. Keep leaves dry. Anthracnose Watery, sunken spots on ripe fruits. A dark center with fungal spores may show up in the center of the sunken spot. Caused by a fungus. Harvest fruit as soon as possible after ripening; remove and destroy severely infected plants. Clean up debris, control weeds and rotate crops. It may also be a good idea to check with gardeners in your area and the local college extension service to find out what tomato plant diseases may be prevalent in your area so you can take steps to avoid them. References: Common Problems Solved. April 2007. Organic Gardening Magazine. 8 Cagey Culprits. May 2003. Organic Gardening Magazine.
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