Some problems that affect tomato leaves include viruses or diseases, pest infestations, soil or water deficiencies, and general weather conditions. Since the health of tomato leaves are typically an indication of how well the tomato plant is doing overall, it is important to understand what issues can arise during the growing season. Many tomato leaf problems can be remedied quickly and the harvest remain unharmed.
Tomato viruses and diseases are the main problems most gardeners face. When growing tomatoes, choose a disease resistant variety to prevent most tomato fungus issues from developing. There is a standard coding system for seeds that indicate which plant diseases the variety is resistant to.
Fusarium wilt (F) is a fungus that causes the tomato leaves to turn yellow and wilt. Cucumber mosaic virus also turns tomato leaves yellow along with the rest of the plant. The leaves may also appear spotted or mottled in severe cases. Early blight (A) turns tomato leaves brown with large spots that cause the leaves to die.
Pest infestations are another problem that affect tomato leaves. The most common tomato pests are tomato horn worms, flea beetles, psyllids, beet leaf hoppers, and aphids. Horn worms are large green caterpillars that eat the leaves and stems. Flea beetles are small, black insects that eat holes through the leaves which leaves the plant open for early blight.
Psyllids are another type of insect that cause yellowing of the leaves. This is caused by the saliva secreted when the psyllids feed on the leaves. Beet leaf hoppers carry a virus called the curly top virus that is transmitted when they feed on the leaves. Tomato leaves affected by curly top virus will shrivel and turn a dark purple. Aphids feed on the leaves and secrete a substance that causes the remaining leaves to turn a yellowish brown.
Soil and water deficiencies may affect leaves as much as pests or diseases. Phosphorus deficiencies in the soil cause the entire plant to shrivel and growth is often stunted. Inadequate drainage due to soil compaction and lack of air circulation may also cause the leaves, roots, and fruit to rot.
Over watering may cause the leaves to turn yellow and is often mistaken for Fusarium wilt. Under watering may cause the leaves to appear dry and severe water restriction may turn the leaves brown. Weather conditions also have an affect on the plant's appearance. Sun scald is, as the name suggests, a burning of the leaves and fruit due to over exposure to the sun.
