Tomato Fruit Spots

(News article for July 31, 2020)

The COVID-19 pandemic has produced many first-time fruit and vegetable gardeners throughout the Florida Parishes. I have enjoyed seeing and hearing about the resurgence of gardening, but, as always, gardening produces its own set of challenges. I frequently get calls about problems with tomato plants and I would like to address two common issues I see happening with tomatoes.

Blossom end rot is a common problem with tomatoes, but it can also affect other garden fruits. It causes a brown, leathery, sunken spot on the bottom of the tomato where the flower dropped off. Blossom end rot is caused by a calcium deficiency in the plant while the fruit is forming. The calcium deficiency may be caused by insufficient calcium in the soil, excessive nitrogen fertilization, rapid plant growth, pH issues with the soil, or drastic fluctuations in soil moisture. Have your soil tested before planting to prevent blossom end rot. A soil test will tell you how much calcium you should apply before planting. I also like to use calcium nitrate as my side-dress nitrogen application. Calcium nitrate contains calcium and nitrogen which will give the plant a boost for fruit production and prevent blossom end rot. Side-dress tomato plants at the first fruit set.

Keeping consistent moisture in your soil will also prevent blossom end rot. This does not mean you should water your tomatoes every day. Too much water will cause a plant’s roots to rot. Monitor your soil by sticking your finger in 2-3 inches deep. If the soil feels moist, you do not need to water. If it feels dry, you should water. Fruits and vegetables need between 1-2 inches of water per week. If you have heavy soils, watering once per week may be sufficient. Sandier soils will dry out quickly and will need water more often. Younger plants with less developed root systems will also require more frequent watering.

Buckeye rot is caused by the fungus Phytophthora parasitica. The fungus resides in the soil and will splash on the tomato fruit during heavy rainfall or overhead irrigation. The leaves and stem of the plant are not affected. Buckeye rot first presents as a brownish water-soaked spot on the bottom or side of the tomato. The spot will grow and may develop concentric rings later in its development. Buckeye rot is easily distinguished from blossom end rot by its soft, mushy, oily appearance versus the leathery appearance of blossom end rot.

Home use fungicides are not effective in preventing buckeye rot. The best thing you can do is apply mulch and reduce overhead irrigation to prevent the fungus from splashing on the tomatoes. If you see a tomato presenting with buckeye rot, remove it and discard to reduce the fungus population.

Growing tomatoes is very rewarding but they are one of the most challenging plants to keep healthy. Feel free to call me if you have any questions.

Jessie Hoover is a County Agent with the LSU AgCenter covering horticulture in East Feliciana, West Feliciana, St. Helena, and Tangipahoa parishes. For more information on these or related topics contact Jessie at 225-683-3101 or visit

Blossom End Rotjpg

Buckeye Rot- Photo by Don Ferrin, Louisiana State University Agricultural Center,

Buckeye Rotjpg

Blossom End Rot- Photo by David B. Langston, University of Georgia,
8/13/2020 3:26:38 PM
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