Tomatoes are the favorite crop for many gardeners, but they can face several diseases and disorders. Understanding these issues and how to address them can make a big difference in your garden’s success. Here’s a guide to some common problems with tomatoes and how to manage them effectively.
Blossom End Rot
Blossom end rot is not a disease but a physiological disorder caused by calcium deficiency. This issue occurs when the plant struggles to absorb enough calcium from the soil due to inconsistent moisture levels—either too much or too little water. Even if the soil is rich in calcium, plants might not be able to use it properly. In such cases, plants will divert what little calcium they have to their leaves instead of their fruits. Besides uneven moisture, high nitrogen levels and soil acidity can also lead to blossom end rot.
To prevent blossom end rot, ensure your soil has enough calcium. Many fertilizers for tomatoes, often labeled as “tomato tone,” contain extra calcium. Additionally, crushed eggshells can provide a natural source of calcium. To prepare the eggshells, bake them in the oven for 20 minutes or microwave them on high for two minutes to sterilize. Then, crush them and mix them into the soil around your tomato plants. Use about two eggshells per plant. Sometimes, the primary cause of blossom end rot is irregular watering, which makes it difficult for plants to absorb the necessary nutrients. Mulching around your plants can help maintain consistent soil moisture. Learn more about how to treat blossom end rot.
Early Blight
Early blight is a common tomato disease. It often shows up as dark spots on the plant’s stems or the ends of the fruit stems. One of our ‘Early Goliath’ plants has shown signs of early blight but continues to thrive, producing plenty of tomatoes with minimal damage. Regularly removing infected lower leaves seems to help manage the disease and keep the plant healthy.
Late Blight
Late blight is a more severe problem and can be devastating. It can turn entire plants and fruits into a slimy mess almost overnight. You can monitor the spread of late blight across the country at usablight.org. To prevent late blight, ensure good air circulation around your tomato plants and water them at the base to keep the leaves dry. Some gardeners also remove the lowest leaves to improve airflow and reduce the chance of water splashing onto the leaves. Keeping the fruit off the ground with clean, dry organic mulch, like straw, can also help.
For next season, consider planting blight-resistant tomato varieties. While we typically grow heirlooms for their flavor, we also include some hybrid varieties like ‘Mountain Magic,’ which is bred to resist both early and late blight.
Anthracnose and Other Fungal Diseases
Anthracnose affects tomatoes, causing small (1/4- to 1/2-inch) spots on the fruit. Another fungal disease, Septoria, causes small brown spots with black centers on older leaves, eventually causing them to turn yellow and fall off. To avoid fungal diseases, clean up all plant debris in the fall. Remove and discard any old leaves and fruits, especially those showing signs of disease. Do not compost diseased plant material.
Wilts
Several tomato varieties are bred for resistance to wilt diseases like Verticillium and Fusarium, which have no cure. When buying tomato seeds, look for varieties labeled with “V” and “F” for resistance to these diseases. Other codes can indicate resistance to additional diseases: “A” for Alternaria, “LB” for late blight, “EB” for early blight, “N” for nematodes, “T” for tobacco mosaic virus, “St” for Stemphylium (leaf spot), “Sw” for tomato spotted wilt virus, and “TYLC” for tomato yellow leaf curl virus.
Proper Watering and Feeding Practices
Proper watering can prevent many tomato diseases. While the plants are getting established, aim for consistent moisture. However, once the tomatoes start to set fruit, allow the soil to dry out between watering. It’s okay to let the plants show early signs of wilting before watering again, but don’t wait too long. Inconsistent watering (fluctuating between very dry and very wet soil) can cause the fruit to crack as it swells with water. The best time to water is in the morning when plants can absorb moisture more effectively.
Healthy, tasty tomatoes come from plants that receive all the nutrients they need. Use a slow-release organic fertilizer at planting time, or apply a liquid fertilizer formulated for tomatoes regularly. Proper feeding can also help prevent blossom end rot.
Growing tomatoes can seem challenging with all the potential problems, from germination to harvesting the first ripe fruit. But knowing what issues to watch for and how to address them can significantly increase your chances of enjoying a bountiful tomato harvest. Remember, preparation and knowledge are key to a successful tomato garden.
