University of Maryland Extension

Internal Discoloration - Vegetables

          white, pithy tissue inside tomato


Environmental Stress

Chilling injury will cause internal fruit parts to darken.

Very hot, dry weather conditions combined with low potassium levels in the soil can cause tomato fruits to develop white, pithy tissue (see above photo) next to the outer fruit wall or near the core. This problem varies depending on the variety grown. Keep plants well-watered during dry periods and avoid tomato cultivars that consistently have this problem.

Gray wall

Gray wall is another fruit disorder of tomato that causes internal fruit wall tissues to turn brown to black and die. The result is that the outer fruit skin breaks down, becomes wrinkled and soft, and develops a gray color. Cool weather, low light, compacted soil and excessive soil moisture are all associated with the incidence of gray wall.

gray wall affected tomato
Gray wall

internal photo of tomato affected with gray wall
Internal view of gray wall

Various Diseases and Disorders That Cause Potatoes and Other Root Crops to Rot

A large number of diseases, nutritional and physiological disorders may cause the internal tissues of fruits to become discolored and rot. This is more likely to occur in crops that are harvested and stored- potato, sweet potato, onion, carrot and other root crops. Only store roots and tubers that are solid and free of insect or disease injury. Handle crops gently and store at the recommended temperature and humidity level. Ensure that air can move freely around stored crops and check them periodically for signs of rotting.

potato tuber with black heart
Black heart of potato

internal decay of potato
Internal decay-potato



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