In late spring when gardeners have their tomato plants in the ground and growing it is stressful to see the fruit that you’ve been watching all spring has a rotted place on the bottom of the fruit. Blossom end rot is a major problem for many home gardeners. Blossom end rot is one of the most common problems occurring on tomatoes. This malady starts as a water soaked spot that darkens and enlarges into a widening circle while the first fruit ripens. The affected area may remain small or it may cover a third to half of the surface. As it increases in size, the tissue shrink and the surface becomes flattend or sunken and dark and leathery. Blossom end rot commonly occurs when plants have grown rapidly and luxuriantly toward the early part of the season, and then are subjected to a period of dry weather when the fruits are at an early stage of development. Or, abundant rain may smother root hairs and cause the rot to occur during sudden hot weather.
Blossom end rot of tomatoes is a physiological disorder caused by lack of sufficient calcium in the blossom end of the fruit. This problem results in the decay of tomato fruits on the blossom end. When excess of such soluble salts as: ammonium, magnesium, potassium, or sodium occurs, the concentrations of calcium salts available to the plant decreases more rapidly than that of other salts. Both excessively dry and excessively wet weather adversely affects the ratio of calcium salts. Super-phosphate fertilizer has shown some relief in the avoidance of blossom end rot. Fertilizer that is high in phosphorus and low in nitrogen helps avoid this malady.
Work the fertilizer into the soil before setting out your tomato plants. Calcium sulfate, better known as gypsum, can be used to treat blossom end rot. Apply gypsum at a rate of 1 to 2 pounds per 100 square feet of soil area. Have the soil tested for acidity and if the pH is less than 6.0, add enough lime to bring the pH up to 6.5 or slightly higher. Maintain a uniform moisture supply in the soil by using mulch and irrigating as necessary. Do not cultivate closer than one foot away from the plant. This avoids root pruning and subsequent damage to the plant. Mulch the plants soon after setting out using plastic, clean straw, or any type of mulching material.
To reduce blossom end rot in tomatoes, implement the following steps:
1.) Lime soils to a pH 6.5-6.7- Get a soil sample and send it to a laboratory to determine the pH of the soil, and adjust as recommended.
2.) Fertilize properly- Applying too much fertilizer at one time can result in blossom end rot. Always follow the soil test recommendations.
3.) Mulch plants- Use straw, pine straw, woodchips, newspapers, or anything that will conserve moisture and help control the temperature.
4.) Irrigate when necessary- Tomato plants require about 1.5 inches of water per week during the fruiting stage. This amount of water should be supplied by rain or irrigation. Extreme fluctuations in soil moisture result in a grater incidence of blossom end rot.
5.) Apply calcium- Apply lime if soil pH is on the acidic side and adjust to a pH of 6.5-6.7. If the soil pH is adequate, apply gypsum (calcium sulfate) at a rate of 1-2 pounds per 100 square foot of soil area, or spray the plant with a calcium solution at a rate of 4 pounds of calcium nitrate or calcium chloride per 100 gallon of water (or 4 level tablespoons per gallon of water). This spray should be applied 2 to 3 times a week, beginning at the time the second fruit clusters bloom. These materials can be mixed with the spray that is used for control of foliar diseases. Chelated calcium solutions also provide an excellent source of calcium. When using these chelates, follow label directions. Several foliar spray materials containing calcium are available and all work well for tomatoes.
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