Blossom-End Rot of Tomatoes
Revised 1/01 -- Author Reviewed 1/01 HIL-28-D
Douglas C. Sanders
Extension Horticultural Specialist
Department of Horticultural Science
College of Agriculture & Life Sciences
North Carolina State University
Blossom-end rot of tomatoes is a physiological disorder caused by
a lack of sufficient calcium in the blossom end of the fruit. This
disorder results in the decay of tomato fruits on their blossom end.
Dry brown or tan areas the size of a dime, that grow to the size of a
half dollar, characterize this disorder. This disorder is usually
most severe following extremes in soil moisture (either too dry or
too wet).
To reduce blossom-end rot in tomato, implement the following
steps:
- Lime tomato soils to pH 6.5 to 6.7 -- Home
gardens not limed in the past 2 to 3 years will need 2 cups of
lime for each plant. The lime should be worked into the soil 12
inches deep. To determine the exact amount of lime, send a soil
sample to the NCDA&CS Agronomic Division, 4300 Reedy Creek Road,
Raleigh, N. C. 27607-6465 for analysis and
recommendations.
- Fertilize properly -- Applying too much
fertilizer at one time can result in blossom-end rot. Following
soil test recommendations is the best way to insure proper
fertilization. For home gardens not soil tested, apply 5 pints of
8-8-8 per 100 ft of row and work it thoroughly into the top 8
inches of soil.
- Mulch plants -- Use straw, pine straw,
decomposed sawdust, ground decomposed corn cobs, plastic, or
newspapers. Mulches conserve moisture and reduce blossom-end rot.
In extreme drought, plastic may increase blossom-end rot if plants
are not watered.
- Irrigate when necessary -- Tomato plants
require about 1.5 inches of water per week during fruiting. This
amount of water should be supplied by rain or irrigation. Extreme
fluctuations in soil moisture result in a greater incidence of
blossom-end rot.
- Spray calcium -- The plants may be sprayed
with a calcium solution at the rate of 4 lb of calcium nitrate or
calcium chloride per 100 gal of water (or 4 level Tbs per gal of
water). This spray should be applied 2 to 3 times a week,
beginning at the time the second fruit clusters bloom. These
materials can be mixed with the spray that is used for control of
foliar diseases. Chelated calcium solutions also provide an
excellent source of calcium. When using these chelates, follow
label directions. Several foliar spray materials containing
calcium are available and all work well for tomatoes.
Recommendations for the use of chemicals are included in this
publication as a convenience to the reader. The use of brand names
and any mention or listing of commercial products or services in this
publication does not imply endorsement by the North Carolina
Cooperative Extension Service nor discrimination against similar
products or services not mentioned. Individuals who use chemicals are
responsible for ensuring that the intended use complies with current
regulations and conforms to the product label. Be sure to obtain
current information about usage and examine a current product label
before applying any chemical. For assistance, contact an agent of the
North Carolina Cooperative Extension Service in your county.
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Published by the North Carolina
Cooperative Extension Service
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Distributed in furtherance of the Acts of Congress of May 8 and
June 30, 1914. Employment and program opportunities are offered to
all people regardless of race, color, national origin, sex, age, or
disability. North Carolina State University at Raleigh, North
Carolina A&T State University, U.S. Department of Agriculture,
and local governments cooperating.