CORVALLIS, Ore. –The taste and fragrance of homegrown tomatoes make them one of the most popular plants to tend in home gardens. But summer heat can bring problems.
The Oregon State University Extension Service Master Gardener Program tracks the most common tomato problems and offers advice on what to do about them.
Late and early blight: "Early and late blight are among the most devastating tomato diseases," said Barb Fick, OSU Extension horticulturist in Benton County. "They are fungal diseases, usually caused by warm wet weather. Look for irregular, greenish water-soaked spots on lower leaves and stems and pick them off."
Under moist conditions, the spots rapidly enlarge to form purplish black lesions, which girdle the stems and leaves, killing the foliage. Water your tomatoes around the base and not from above to avoid prolonged wetting of leaves. Make sure to give plants space. Stake and prune to keep air circulating and plants dry.
Blossom drop: Dry soil and dry winds can cause blossoms to fall off the plant, but a sudden cold spell, heavy rains or too much nitrogen can also be the problem. Usually not all blossoms will fall off, and another set of flowers will appear.
Blossom end rot: The end of the fruit furthest away from the stem turns black, usually caused by irregular watering and calcium deficiency. Water deeply and regularly. Add lime to soil in the fall to increase the calcium level for next year’s crop. Blossom end rot is most common in western Oregon.
Leaf rolling: This problem is most often the result of heavy pruning or root injury. Plants may lose leaves but will recover.
Sun scald: Green tomatoes can get sunburned, especially those with leaf spot diseases or recently pruned. Remove damaged tissue or discard the fruit.
For more detailed information, photos and control methods for many more tomato maladies, consult OSU Extension’s “Online Guide to Plant Disease Control."
For Master Gardener help, go online to find your local county Extension office.