Why Are My Tomatoes Withered & Yellow?

Weather

• Overexposure to sun may burn and bleach tomatoes, the condition is known as sunscald. Tomatoes exposed to sunscald may have white to yellow areas of discoloration. The overexposed areas may collapse and become wrinkled and yellow. Fruit withers and decays as the condition worsens. Plant tomato plants in partial shade, if the plants are grown in warm southern regions, to protect them from sunscald -- while ensuring that they receive at least six hours of sunlight. When the shoulders of tomato fruits become yellowed and discolored, it's a mild symptom of sunscald.

Disease

• Septoria leaf spot is a common tomato disease. In early stages, septoria leaf spot looks like small, whitish spots that slowly become larger and more discolored. Leaves will turn yellow, wither and drop from the plant as leaf spot progresses. Early blight, also known as target spot, also creates spots on tomato plants. The brown and black spots get larger in size to create large blotches. Even in early stages, leaves will being to turn yellow and wither when early blight is present. Verticillium wilt also strikes tomato plants, creating yellow blotches and withering of leaves. Verticillium wilt reduces fruiting of tomato plants.

Pests

• Pests cause damage and spread virus to tomato plants. Tomato spotted wilt virus, is spread by tiny thrips. The virus creates yellow rings on fruits, and may cause discoloration and distortion of leaves. Aphids and leafhoppers both create damage that makes tomato plants look withered and yellow. Leaves may curl and fruits turn bronzed or yellowed when either of these two pests are present. Psyllids feed on the sap within tomato plants, depriving them of nutrients and turning leaves yellow.

Treatment

• Prevent fungal disease and pest infestation of tomato plants with proper cultivation and care. Water plants at the base, and do not splash water onto the foliage. Wet plants are prone to fungal growth. Keep tomato beds clean and weed-free, to prevent hiding places for pests and fungus. Rotate tomato crops every three or four years. When severe problems are present, treat tomato plants with fungicide and pesticide.