What is blossom-end rot?

gwtamaraJanuary 1, 2013

Blossom-end rot occurs on tomatoes, peppers, squash, and watermelons from a lack of calcium in the developing fruit. A round, sunken, water-soaked spot develops on the bottom of the fruit. The spot enlarges, turns brown to black, and feels leathery. Mold may grow on the rotted surface. This results from slowed growth and damaged roots caused by any of several factors:

1. Extreme fluctuations in soil moisture, from very wet to very dry.
2. Rapid plant growth early in the season, followed by extended dry weather.
3. Excessive rains that smother root hairs.
4. Excess soil salts or salinization 5. Cultivating too close to the plant.

The first fruit are the most severely affected. The disorder always starts at the blossom end, and may enlarge to affect up to half of the fruit. Moldy growths on the rotted area are from fungi or bacteria that invade the damaged tissue. The rotted area is unsightly but the rest of the fruit is edible.

To reduce blossom-end rot in tomato, implement the following steps:

• Lime tomato soils to pH 6.5 to 6.7 -- Home gardens not limed in the past 2 to 3 years will need 2 cups of lime for each plant. The lime should be worked into the soil 12 inches deep. To determine the exact amount of lime.
• Fertilize properly -- Applying too much plant food at one time can result in blossom-end rot. Following soil test recommendations is the best way to insure proper fertilization. For home gardens not soil tested, apply 5 pints of 8-8-8 per 100 ft of row and work it thoroughly into the top 8 inches of soil.
• Mulch plants -- Use straw, pine straw, decomposed sawdust, ground decomposed corncobs, plastic, or newspapers. Mulches conserve moisture and reduce blossom-end rot. In extreme drought, plastic may increase blossom-end rot if plants are not watered.
• Irrigate when necessary -- Tomato plants require about 1.5 inches of water per week during fruiting. This amount of water should be supplied by rain or irrigation. Extreme fluctuations in soil moisture result in a greaterincidence of blossom-end rot.
• Spray calcium -- The plants may be sprayed with a calcium solution at the rate of 4 lb of calcium nitrate or calcium chloride per 100 gal of water (or 4 level Tbs per gal 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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