Tomato Blossom-End Rot

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Growing tomatoes in the South is a difficult, albeit rewarding, endeavor. The high humidity typical in our area favors plant diseases that defoliate plants and makes the fruits of your labor inedible. Blossom-end rot is one “disease” shows up every year, but with some planning, it is very easy to prevent.

Blossom-end rot is a physiological disorder – it is caused by a lack of calcium in the soil, not by a pathogen; therefore, it is not really a disease. Fruit expressing this disorder will develop a dry brown or tan decayed area on the end not attached to the stem (aka the blossom end). The decayed area appears small at first, but enlarges as the fruit grows. This disorder occurs on the fruit of tomatoes, peppers, and eggplants.

Prevention of blossom-end rot is easy. Before planting your garden, take a soil sample. Soil sample kits are available at our Center and testing is a free service offered through the NC Department of Agriculture. It is always a good time to sample! The soil sample results will indicate the amount of lime and fertilizer to incorporate into your garden. Calcitic lime, which contains calcium, will correct the calcium deficiency if applied at the proper rate and will also adjust the acidity of the soil. Apply lime 2-3 months prior to planting your garden since it takes time to make corrections. Apply fertilizer as indicated on your results – applying too much at one time can result in blossom-end rot.

Blossom-end rot may occur when extremes in soil moisture (too dry or too wet) are experienced. In order to moderate the amount of moisture plants are receiving, mulch using straw, pine straw or newspaper. Plastic and other mulches may also be used. Irrigate when necessary. Tomatoes require 1.0 – 1.5 inches of water per week, especially during fruiting.

Prevention is easy, but what if you already have blossom-end rot on your tomato fruit? Lime will take time to work. A more immediate solution is to use a calcium spray. A foliar spray containing calcium nitrate or calcium nitrite works well if applied 2-3 times per week. Be sure to read and follow the label.

Blossom-end rot, although a common disorder, is easy to prevent. A quick and easy (maybe dirty too!) soil sample will give you the precise information you need to make an ideal growing environment for your garden plants. For more information on blossom-end rot or on growing tomatoes in the home garden, call our Center at 919-775-5624 or reference HIL 8107-A: Blossom-End Rot of Tomatoes in the Home Garden.

Minda Daughtry is Horticulture Agent for North Carolina Cooperative Extension in Lee County.