end rot is a physiological disorder that is caused by a lack of
calcium uptake from the soil and transfer to the fruits during dry
weather. The problem is costly to many tomato growers and disappointing
to home gardeners. Peppers can also be affected, although the disease
is much less common on peppers than on tomatoes. Research in Florida
indicates that excessive magnesium, potassium, sodium, ammonium
salts or a deficiency of soluble calcium salts causes a decrease
in calcium uptake, thus favoring development of the disorder. Rapid
early growth accentuates the problem because it tends to increase
the calcium requirement per unit of time.
first symptom of rot is a slight water-soaked area near the blossom
end of the fruit. The lesion soon darkens and enlarges in a constantly
widening circle until the fruit begins to ripen. The decaying spot
may be merely a speck or it may involve half or even more of the
tomato. Secondary fungi may inhabit the black area. Although a sudden
lack of water is the principal cause of blossom end rot, excessive
soil moistures early in the season may smother the root hairs and
cause blossom end rot to occur during sudden hot weather. It may
be more serious on the windward that on the leeward side of a field
and more common on staked tomatoes than on bush types. Generally,
blossom end rot is most common on the first fruits to turn red.
end rot on tomato fruit. Image from the Ohio State University
end rot on pepper. Image from the Iowa State Extension
blossom end rot is so closely related to adequacy of water supply,
an important control is to regulate the moisture supply in the soil.
The land should allow good drainage during a wet period. If drought
occurs, cultivation should be very shallow to reduce water loss
and irrigation should be used. Hoeing or cultivating should be performed
no closer than one foot from the plants to reduce root pruning.
Appropriate amounts of fertilizer high in superphosphate and low
in nitrogen should be used (1-3-1 ratio).
the greenhouse, transplants should not be grown too quickly nor
should the plants be too old and subjected to severe hardening before
transplanting. A steady growth rate as a seedling and as a field
plant will discourage much of this problem.
irrigation of any kind is available, it should be using during periods
of hot, drying winds. Start to irrigate at the beginning of the
dry spell. Mulching, which serves to maintain an even level of soil
moisture, should be practiced where feasible. Mulch with black plastic
or grass clippings to reduce moisture loss and to control weeds.
Tomatoes and peppers planted unusually early, while the soil is
still cold, are likely to have the first fruits affected by blossom
end rot. Consequently, a delay in planting until soil warms up helps
to reduce the problem.
tomato varieties Jet Star, Burpee VF, Better Boy, Early Girl, Flora-Dade,
Floramerica and Walter seem to have some tolerance.
from the Cornell Cooperative Extension, 2001