Why Do The Leaves On My Tomatoes Change Color?

Did all the change color?

Did the leaves turn yellow?

Do you grow tomato seedlings under artificial lights?

Are the leaves distorted and sticky?

Does the whole plant looks stunted and wilts in hot weather?

Did only the older leaves turn yellow?

Are there any black walnut trees or stumps nearby?

Are the leaves stippled or bronzed?

Do the leaves have dark, water-soaked patches on them?

Do the water-soaked patches turn brown and dry?

Are the leaves mottled-yellow and is the young growth narrow and twisted?

Do the leaves have small dark spots on them?

Seedlings grown under lights will turn purple if the lights are left on continuously. Give seedlings 8 hours of darkness each night to reverse or prevent this condition.

Phosphorus deficiency may cause tomato leaves to turn purple. This usually happens when the soil is too cold. Spray plants with seaweed extract to alleviate symptoms.

Distorted, sticky, yellow leaves usually indicate aphids. These tiny insects can vary in color (green, pink, black, gray or white). They cluster under leaves and on growing tips where they feed on plant sap. Leaves become distorted and later drop from the plant. You can control them by washing them off the plant with water spray. Introducing ladybugs will keep their number low. Insecticidal soap or neem oil should be used with severe infestations.

These symptoms are usually caused by root-knot nematodes. Prevent root-knot nematodes by applying chitin or introducing parasitic nematodes to the soil before planting. Solarizing the soil also helps in preventing root-knot nematodes.

Walnut wilt occurs in soil containing black walnut roots, which secrete a substance that is toxic to many kinds of plants. The toxic compound remains in the soil for several years after trees are cut down. Plant your tomatoes far from walnut trees. If this is impossible, grow tomatoes in containers in a good organic potting mix.

Your tomato might have been affected by Fusarium or Verticillium wilt. Both Fusarium and Verticillium wilts begin with yellowing and wilting of the lower leaves. Both diseases are incurable. Destroy infected plants. Prevent problems by pre-soaking seeds in a 10 percent bleach solution or by planting resistant cultivars.

Your plant might have a nutrient deficiency. If young leaves are yellow with green veins - iron deficiency. If dark spots develop in the yellow areas, and leaves are small and narrow - zinc deficiency. If older leaves are yellow with green veins, and then become bronzed - potassium deficiency. If young leaves are pale and growing tips die - calcium deficiency. Plants that are stunted and have yellow or pale older leaves - nitrogen deficient.

The most likely culprits are mites. These tiny, spiderlike insects feed on plant sap and thrive in hot, dry weather. Spray plants with insecticidal soap or sulfur to control mites.

A fungal disease - Late blight is the most likely cause. This disease often occurs during periods of humid weather with cool nights (below 60°F) and warm days (70°-85°F). Spray plants with compost tea to help prevent further symptom development, or with copper if the disease is severe.

If the patches develop into circular, dark spots with light centers peppered with dark specks, suspect fungal disease - Septoria leaf spot. Spray plants with copper to prevent further symptom development.

These symptoms usually indicate the tobacco mosaic virus. There is no cure, remove and destroy infected plants. Pre-soak seeds in 10 percent bleach solution before planting, or choose resistant cultivars to prevent problems. Control aphids as they are the most likely carriers of the tobacco mosaic virus.

Diseases known as bacterial spot or bacterial spec cause small dark spots on tomato leaves. Centers of spots may dry and fall out. The leaves may turn yellow, then brown, and fall off. Spray infected plants with copper to prevent the development of further symptoms.

If the leaves have dark, concentrically ringed spots on them, the cause might be fungal disease - Alternaria blight. The disease occurs when plants are loaded with fruit and during humid, warm (75°-85°F) weather. Spray infected plants with copper and/or sulfur to prevent further disease development.