Blossom end rot kills tomatoes, peppers and eggplant fruits. The rot looks ghastly and destroys up to 50 percent of crops, according to Ohio State University. The rot develops on water-soaked parts of the crop. Fruits develop a lesion that grows, sinks and turns black and leather-like. Peppers can develop tan spots. Molds attack the rotting flesh, exacerbating the disease. The rot comes from deficient calcium uptake, causing tissue breakdown during rapid growth.
Plants cannot take up calcium when the soil becomes too acidic or too alkaline, so keep the pH level as close to 6.5 as possible. Lime not only raises pH, but also introduces more calcium into the soil. Gardeners should apply lime along with gypsum. Unfortunately, researchers have not discovered how much calcium plants need to prevent blossom end rot, according to North Carolina State University.
Give plants nitrogen through nitrate nitrogen, rather than ammonium nitrogen. Ammonium displaces calcium. Only moderately fertilize the plant when fruiting. Use fertilizer with low nitrogen and high superphosphate.
Drought prevents calcium uptake, so growers must use adequate irrigation techniques and mulch. Mulch helps prevent water evaporation. Also, utilize drip irrigation to provide water directly at the roots, which minimizes the needed water and reduces evaporation. Improve drainage so that the water does not stagnate, which can keep oxygen from the roots and prevent calcium uptake. Water the plants uniformly by keeping the soil level. Check the soil for adequate moisture by rolling the soil into a ball. If the soil won’t roll, you need more water.
Some growers apply calcium to diseased fruit, but Ohio State University argues that fruit poorly absorbs calcium and the calcium doesn’t necessarily reach the diseased part. Other universities, such as Cornell University, recommend the practice, though they mention that calcium sprays can damage the plant if used excessively. Growers mix 4 tsp. of 96% calcium chloride for every one gallon of water and spray the fruit with a spray bottle. Spray once a week for three to four weeks and then stop.
Plant tomatoes in warm soil to help the roots grow and locate calcium sources. When cultivating, do so gently near the roots to avoid damage. Grow plants in the greenhouse slowly and do not transport old and hardened plants or they’ll develop rot. If you’ve cultivated the field, plant in shallow soil to avoid damaging the roots.