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Dry weather causing tomato problems Over the past couple of weeks, I have received several samples of tomatoes, and watermelons that have black leathery looking areas on the end of the fruit away from the stem. The disorder is called Blossom End Rot (BER). When plants are affected by BER the fruit looks awful, and people typically think it is a disease. This particular problem is not caused by a fungus or a bacterium, and our recent weather is a big part of the reason for the number of samples that I am seeing. Blossom End Rot is a physiological disorder of tomatoes, peppers, and cucurbits caused by a calcium imbalance within the plant. Fluctuations in soil moisture, excessively wet or dry soil, excessive nitrogen fertilizer, roots damaged by cultivation, very high or low pH, or soils high in salts prevent the plants from taking up enough calcium to satisfy the plant's rapid cell development. The result is a water-soaked spot at the blossom end of the plant that enlarges, turning dark brown and leathery. Rot may set in at the spot. BER is common when plants grow rapidly in the beginning of the season, then set fruit during dry weather. As little as 30 minutes of water deficiency at any time can cause BER. Prevention and Control Since, BER is caused by calcium deficiency, usually induced by fluctuations in the plant's water supply. Proper liming and water management are keys to managing the problem. To control BER, take the following steps: + Keep the pH of the soil at 6.0 to 6.5. Perform a soil test and apply the recommended rate of lime, using dolomitic or high-calcium limestone. Be sure to apply lime 2 to 4 months before planting tomatoes. + Apply the required amount of fertilizer when necessary based on soil test results for tomato. Applying too much fertilizer at one time can induce BER. Following soil test recommendations is the surest way to fertilize properly. + Use mulches to conserve moisture. Use pine straw, straw, decomposed sawdust, plastic or newspapers. Mulches conserve soil moisture and reduce incidence of BER. + Give your plants adequate water. Tomato plants need about 1.5 inches of water per week during fruiting. Extreme fluctuations in soil moisture can result in a greater incidence of BER. + If your plants develop BER, spray them with a calcium solution at the rate of four pounds of calcium nitrate or calcium chloride per 100 gallons of water (or four level tablespoons per gallon of water). Be careful with calcium chloride. If day temperatures are greater than 85 to 90°F, calcium chloride can burn plants. Under high temperatures, use calcium nitrate. You should spray 2 or 3 times each week, beginning when the second fruit clusters are blooming. Spraying calcium is not a substitute for proper irrigation and fertility management. + Some varieties of tomato tend to be more sensitive to conditions that cause BER. Try growing several varieties and keep notes as to their performance.
If you need more information on this or other subjects related to agriculture or natural resources, call the County Extension office at (251) 275- 3121
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