You may experience disappointing results when growing tomatoes because the plants and fruit are susceptible to sever common disorders, as well as attack by diseases and pests. Below are some problems in our area.
Flower drop and failure to set fruit. Cause: Daytime temperatures are above 90 degrees. Excess nitrogen fertilizer. Too much shade. Control: At this time of the year, there is little you can do about flower drop.
Solar Yellowing and Green Shoulders (upper portions of tomato may remain green even though the lower portions are red. Sunburn (Tomato turns brown and leathery on side exposed to the sun.) Cause: High temperatures and high light intensity. Control: Avoid overpruning. Provide partial shade during hours of most intense sunlight.
Leaf Roll (older leaves roll upward and inward suddenly, they become stiff to the touch, brittle and leathery.) Cause: High light intensity and high soil moisture. Control: Maintain even soil moisture. Provide partial shade during the hot day.
Blossom End Rot (Water-soaked spot on blossom end of tomato enlarges and darkens. Affects both green and ripe tomatoes. Cause: Calcium nutrition and water balance. Control: Maintain even soil moisture. Amend the soil with compost. Avoid excessive nitrogen.
Fruit Cracks (Circular cracks or cracks lengthwise.) Cause: Wide fluctuations in soil moisture, usually overwatering. Control: Keep soil evenly moist. A layer of mulch helps maintain even moisture.
— For more gardening information go to cecolusa.ucanr.edu/Master_Gardeners.