Managing Blossom-End Rot

One of the current issues plaguing the home gardener right now is blossom-end rot.  Often mistaken for a disease, it is primarily a disorder.  No bacteria or pest causes blossom-end rot, rather the plant cannot get what it needs - calcium.  This is caused by a lack of calcium uptake from the soil and resulting in little transfer to the fruits during dry weather.  Too much water can interfere as well.

Symptoms may occur at any stage in the development of the fruit, but, most commonly are first seen when the fruit is one-third to one-half its full size.  As the name of the disease implies, symptoms appear only at the blossom end of the fruit.  Initially a small, water-soaked spot appears which enlarges and darkens rapidly as the fruit develops.  The spot may enlarge until it covers as much as one third to one-half of the entire fruit surface, or the spot may remain small and superficial.  Large lesions soon dry out and become flattened, black, and leathery in appearance and texture.

Blossom-end rot happens when a number of conditions come into place.  The disease is especially prevalent when rapidly growing plants are exposed to wide fluctuations in water amounts.  Calcium cannot be taken from the roots to the rest of plant and sustain healthy tomatoes.  The fruit doesn’t have the necessary nutrient and the bottom of the tomato begins to rot.  Other factors include a pH out of range and damage done to the roots from cultivation too closely.  Heavy applications of nitrogen will contribute to blossom-end rot.

To manage blossom-end rot, take these steps:

• Tread lightly around the roots of the plants to avoid damage.
• Water consistently if there is a lack of rain, about one inch per week. Water slowly at the base of the plant.
• Add mulch to your garden, this conserves moisture.
• Use fertilizer low in nitrogen
• Do not spray any type of pesticide, as this is not a symptom of insect, bacteria, or fungi damage pesticides are ineffective on blossom-end rot.
• Consider a soil test, this will give you a complete analysis of what your garden needs and will give you a head start for the next growing season.

For more information on blossom-end rot, the Penn State Master Gardeners in Lackawanna County have the free factsheet “Common Tomato Problems”.  Contact us at 570-963-6842 or email LackawannaMG@psu.edu for a copy.

Steve Ward
Master Gardener Coordinator