Tasty and easy to grow, tomatoes are the most popular garden vegetable. However, diseases can harm your tomato crop.
Don't let those potential problems scare you away. Growing healthy, pest- and disease-free tomato plants is relatively simple. Keep your plants healthy by rotating crops, planting disease-resistant varieties, spacing plants properly, mulching, and watering at least 1 inch per week.
Start your tomatoes off right.
As tomato plants grow, keep an eye out for troublemakers that may come in the form of fungi, bacteria, or viruses.
Get tips for growing healthy tomatoes.
In the fall, if you have had disease problems of any kind, remove the entire plant.
Rotate tomatoes so they grow in the same ground only every four years or so. Many diseases lurk in the soil.
Septoria leaf spot is one of the most common diseases of tomato plant leaves. You can first detect this fungus as it creates a small, circular spot with a grayish-white center and dark edges. Small black spots may show up in the center. Affected leaves turn yellow, wither, and fall off.
Long periods of warm, wet weather contribute to the problem, and splashing water spreads spores to other leaves.
Control leaf spot by not crowding your tomatoes. Leave enough space so air circulates and dries leaves.
Avoid overhead watering. When watering tomatoes, water at the base of the plant. Also, water in the morning so wet leaves have time to dry before evening.
A fungicide formulated for tomatoes can be used to treat affected plants.
Follow the same procedures used for septoria leaf spot against anthracnose. This fungus shows up as a small, circular, indented area on tomato fruits. Eventually, rings surround the original spot.
The flesh of the fruits may rot completely through, especially on overripe tomatoes, so keep fruits picked as they ripen.
Spores are spread by rain splash, and the fungus is most common in warm, wet weather.
These wilt diseases are caused by fungi in the soil that enter through young roots, then begin to plug the vessels that move water to the roots and stems of the plants. Without water, the plants begin to wilt on sunny days, although they appear to recover at night. Wilting may first appear in the top or lower leaves of the plant, causing them to lose color, then die back from the tips. The process continues until the entire plant is affected.
Heirloom varieties that have not been bred to withstand these diseases are commonly attacked. New strains of the diseases attack cultivars that are resistant to only one type of wilt.
Learn about growing heirloom tomatoes.
Fusarium wilt is most common in warm-weather regions and occurs during the warmest weather in cool areas.
To avoid these diseases, plant tomatoes bred for disease resistance. They should be labeled V (for verticillium), F, FF, or FFF (for fusarium variations). See "Understand the Tomato Code," below, for more about tomato plant labels.
Avoid overwatering tomato plants; just because a plant is wilted doesn't mean it needs more water. Check the soil; if the soil is dry, then water the plant.
If your tomatoes are affected by one of these wilts, remove and destroy all affected plants. Do not place them in your compost pile. Avoid using this location for tomato, eggplant, potato, and pepper plants for four to six years, because the fungi remain in the soil. Corn and beans won't be affected.
Keep weeds out of affected areas because their roots can continue feeding these pathogens.
Continued on page 2: More Diseases