No gardener wants to see yellow leaves on her tomato plants. This discolouration is more than unsightly, it's a sign of distress. Although the symptom has a variety of causes, it always has the same effect. Yellow leaves will drop too soon, leaving the fruit vulnerable to sun and other elements. Educate yourself on what this symptom means and how to prevent it for a healthy and tasty crop of tomatoes year after year.
Fungus is one cause of yellow leaves in tomato plants. Fungus lives in dirt and soil, making it difficult to eliminate. To prevent a fungus from grabbing hold of your tomato plant, never plant your tomatoes in the same spot two years in a row.
Too much water can lead to root rot in tomato plants, a cause of yellow leaves. To prevent rot from occurring, ensure your plants have proper drainage by planting them in raised beds. Always leave at least 15 inches between your tomato plants. Proper air circulation will help reduce the chance of rot. Also, pick up any debris near the base of your plants, such as fallen leaves and fruit, as soon as it appears to keep rot from happening.
Insects feed on tomato plants, causing damage that leads to yellow leaves. They also transfer diseases from one plant to another, such as curly top virus. These diseases also cause leaf yellowing. To prevent insect infestations, surround your tomato plants with marigolds, a flowering plant that deters most predators. You can also drape your plants with row covers to prevent bugs from hopping from plant to plant. A dusting of sulphur, which can be purchased at most garden supply stores, will also keep many insects at bay.
The leaves on your tomato plants may be turning yellow due to a lack of nutrients. Be sure to water them during dry spells. They will likely need water every day during the hottest part of the growing season. You can also add fertiliser to the soil or plant food to the water to help bolster the nutrients your plants receive. Talk to a professional at your local garden supply store to recommend a product that fits your climate, as well as your particular breed of tomato plant.