Blossom end rot is a disease of fruiting crops–including tomatoes, peppers, eggplants, and cucurbits–that can result in serious damage to the crops. In fact, gardeners and farmers may lose half of their crop to blossom end rot.
Cause of Blossom End Rot
Blossom end rot results from a lack of calcium in the fruit as it develops. This may be due to a low ratio of calcium to other nutrients, extreme fluctuations in soil moisture, or lack of calcium uptake from the soil. Damage to roots, soil that is too acid or not acid enough, and cold soil contribute to the problem. A season that starts out wet and then turns dry when the fruit is setting is the ideal condition for blossom end rot.
Photo found on Flickr.com, courtesy of mrpbps.
Blossom End Rot Symptoms
With blossom end rot the first thing the gardener sees is a water-soaked area on or near the blossom end of the fruit (the end away from the stem) when the fruit is half grown. The area darkens and enlarges, turns brown and leathery and rots. The spots can be mere specks or large enough to cover more than half the fruit.
Blossom End Rot Controls
In cold climates gardeners should wait to plant until the soil warms up. Fertilizers should be high in phosphorus (the P in N-P-K) and low in nitrogen (N). Since either too much or too little water can foster blossom end rot, keeping the soil evenly moist is critical. Mulching can help with this. Mulch also eliminates the need for cultivation, which can damage roots and increase the risk of blossom end rot.
Applying lime to the soil, which makes calcium more available, can help prevent blossom end rot. The lime must be applied several months before planting in order to be effective. The only way to know how much lime to apply is to take a soil test and follow its recommendations, a good practice for any home garden.
Removing affected fruit when symptoms first appear, especially with tomatoes, may help protect later fruit. Because environmental factors–not insects or diseases—cause blossom end rot, pesticides do not control it.
For More Information About Blossom End Rot
University Extension Services are excellent sources of information on plant diseases as well has inexpensive soil testing; every state has a cooperative extension service that can help diagnose plant problems. Go to this website to find your local office.
The following extension articles give thorough and accurate information about blossom end rot:
The Ohio State University Extensionhas got plenty of info about Blossom End Rot of Tomato, Pepper, and Eggplant.
The University of Tennessee has a lot of great information in this .pdf about Blossom End Rot.
The Plant Pathology Extension from North Carolina State University has this information about Blossom-end Rot of Tomato, Pepper, and Watermelon.