Blossom-end rot, referred to by its acronym BER, is a commonly occurring tomato fruit disorder that also can occur in other similar fruiting plants, such as pepper. Its occurrence is due to a calcium deficiency in the developing fruit. Without sufficient calcium, the cellular structure at the blossom (developing) end collapses and the tissue dies, leaving a darken area on the fruit with advancing maturity. Blossom-end rot occurs only on initially developing green fruit and will not occur on maturing fruit. Growers are advised to remove BER-effected fruit when first observed as the continuing developing fruit will not be suitable for use.
The occurrence of blossom-end rot is a result of several causative factors coupled with inadequate calcium. This disorder is triggered by plant stress, stress caused by inadequate moisture (plant wilting), periods of high air temperature and/or light intensity, and periods of stagnate air. When BER-affected fruit begin to appear on the tomato plant, it was triggered by weather and plant conditions several weeks prior. Other than calcium insufficiency, other elements can trigger the occurrence of BER. In the hydroponic culture of tomato, the use of ammonium-nitrogen as a major nitrogen source can result in the high incidence of BER. When tomato plants are grown in soil, low soil pH and inadequate or excessive nutrient element levels in the soil can trigger the occurrence of BER.
Some have suggested that the occurrence of BER can be mitigated by applying a calcium-containing solution onto the plant foliage and developing fruit. Calcium does not easily penetrate plant leaf and fruit cells, and if absorbed at the point of contact, will not be translocated from that entry point. Calcium moves in the plant in the transpiration stream, and the calcium needed for developing fruits is carried into these fruits through the connecting stem tissue. Those factors (see above) that would diminish this flow will trigger the occurrence of BER.
For the soil grower, have the soil tested and follow the given soil test recommendation, ensuring that the soil pH is at the proper level, and if not, adjusted by liming. This article discusses how to adjust the pH of your soil. A deep profile loamy fertile soil is ideal, whose fertility status has been established by following soil test-recommended lime and fertilizer practices over time. Avoid over fertilization as it can be a causative trigger also. Keep the soil moist, but don’t over irrigate. Mulching around the tomato plant can control soil moisture loss, but it can also keep the soil cool and wet – not ideal for active plant root growth and function. Remember the occurrence of BER is triggered by plant stress, with a cool and wet soil being potentially such a trigger, if the atmospheric conditions are hot and dry.
Blossom-end rot is a preventable fruit disorder when the plant is being supplied sufficient calcium and the growing condition extremes are moderate. It is the calcium that is found in the transpiration stream in the plant that ensures normal fruit development, that being root absorbed from a fertile soil or properly balanced nutrient solution formulation. The primary factor is adequate calcium, and then plant stress will have a minimal affect on triggering the occurrence of BER.
Dr. J. Benton Jones, Jr. has a PhD in Agronomy and is the author of several books. Dr. Jones has written extensively on hydroponic growing and outdoor vegetable gardening employing sub-irrigation hydroponic growing systems.