UF/IFAS Okeechobee County Extension Service

458 Highway 98 North

Okeechobee, FL 34972-2578

Phone: (863) 763-6469

E- mail: dfculbert@ifas.ufl.edu

21 May 2003

Feature Article - for release the week of May 25, 2003

Dan Culbert - Extension Horticulture Agent

I’ve received a number of calls concerning a common problem found in vegetable gardens - blossom end rot. Dark brown or black blotches on the bottom of tomato fruit are a sure sign of blossom-end rot, which can also cause problems in other crops such as peppers and melons. This problem shows up in many home gardens each year, but drought and water stress has made this problem severe this spring.

Steps taken before planting your garden will help prevent blossom-end rot. Today’s column will offer some advice to help eliminate this problem, courtesy of UF/Hendry County Horticulture Agent Gene McAvoy.

Home gardeners sometimes confuse blossom-end rot with other tomato diseases. The first indication is a slight water soaked appearance at the bottom of the fruit. This discolored area enlarges rapidly, producing a brown or black sunken area. The skin over the affected area then becomes dry and leathery.

Blossom-end rot is caused by a shortage of calcium in developing fruit. A lack of calcium in the tomato fruit may occur because it is not present in the soil, because of an extreme soil pH or because soil moisture alternates between wet and dry conditions during fruit development. The problem is more severe when plants are over-fertilized with nitrogen.

Often there is little that can be done in your current garden if your fruit are already showing blossom-end rot. But there are several steps that can be taken to correct this in the future - and summer is a good time to carry out these steps:

Collect a soil sample in the summer to determine how much calcium is in your garden’s soil. If there is a low level, the soil test results may suggest that it can be corrected through an application of lime. Since it takes time for lime to make changes in the pH and soil calcium levels, this step should be done well before the fall planting season. If you’re not sure about the procedure for collecting soil samples, check with our office for details.

Blossom-end rot is also related to moisture supply. During the growing season, keep a close eye on your plants and irrigate before wilting occurs. As a general rule, tomato plants need at least one inch of water per week - either from rain or irrigation. And consider mulching your tomato plants, since this will help maintain uniform soil moisture conditions.

If blossom-end rot does appear, several sprays of calcium chloride may help prevent further development of the problem, but it will not cure those fruits that are already growing on the plant. Sprays containing calcium chloride are available at garden supply stores under a variety of trade names. Follow label directions carefully to prevent possible burning from excess or improperly applied calcium chloride!

Remove fruit showing symptoms of blossom-end rot when the problem is first observed. This will reduce the drain of food and nutrients going to fruit which will rot anyway and make more of these building blocks available for development of other unaffected fruit.

It's especially important to follow a recommended program of fertility and avoid excessive application of nitrogen fertilizer. Excess nitrogen will promote leaf growth and moves calcium away from developing fruits and into leaves.

If you are not a gardener, but purchase your tomatoes at the market, UF Researcher Dr. Amy Simonne is conducting a survey of tomato preferences - check it out at http://simonneusdatstar.ifas.ufl.edu. And for those planning for a successful vegetable garden this fall, the Florida Vegetable Gardening guide is available on the internet at http://edis.ifas.ufl.edu/VH021, or it can be picked up at the Okeechobee Extension office at 458 Hwy 98 North. Our phone number is (863) 763-6469, and you can email us at okeechobee@ifas.ufl.edu. Happy Memorial Day to all our veterans!

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