This NebFact discusses the causes, prevention and treatment of blossom end rot in tomatoes

Hodges, Laurie

Steinegger, Don

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Historical Materials from University of Nebraska-Lincoln Extension Extension 1991 NF91-43 Blossom End Rot in Tomatoes Laurie Hodges University of Nebraska--Lincoln, lhodges1@unl.edu Don Steinegger University of Nebraska--Lincoln, dsteinegger1@unl.edu Follow this and additional works at: https://digitalcommons.unl.edu/extensionhist  Part of the Agriculture Commons, and the Curriculum and Instruction Commons Hodges, Laurie and Steinegger, Don, "NF91-43 Blossom End Rot in Tomatoes" (1991). Historical Materials from University of Nebraska-Lincoln Extension. 791. https://digitalcommons.unl.edu/extensionhist/791 This Article is brought to you for free and open access by the Extension at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Historical Materials from University of Nebraska-Lincoln Extension by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Nebraska Cooperative Extension NF91-43Blossom End Rot in Tomatoes Laurie Hodges, Ph. D. Extension Specialist, Horticulture Don Steinegger, Ph.D. Extension Specialist, Horticulture  Blossom end rot of tomatoes is a common problem. It occurs under conditions of high plant water stress and heavy fruit load. The first sign is a small, water-soaked area around the blossom end of the fruit that rapidly darkens and enlarges. As this lesion enlarges, it shrinks and the area becomes sunken and leather-like. This depressed area may become infected with secondary pathogens. Early fruits on the plant may have blossom end rot, while those that develop later are normal. Blossom end rot is a symptom of calcium deficiency in the fruit. It can occur even when there is abundant calcium in the soil and tissue tests show high levels of calcium in the plant. Poor calcium distribution in the plant results in low calcium levels where the lesion occurs. Calcium, dissolved in water, moves through the plant in the vascular system from the roots to the leaves. Leaves are the primary sink for movement of water because of water loss through transpiration. Under high moisture stress, the water containing calcium and other minerals moves rapidly to the leaves. Fruit does not transpire as much as leaves and thus tends to be bypassed. This results in a localized calcium deficiency. This calcium deficiency in an area of rapid growth, the end of the fruit, causes cells to collapse and the sunken-lesion symptom of blossom end rot. Blossom end rot may appear on some of the first fruit clusters on a plant. This is attributed to the combination of rapid plant growth with a large leaf area for water transpiration, water stress, and fruit enlargement. Even a temporary water stress during early fruit enlargement can cause blossom end rot because the fruits are the last to receive adequate calcium. Calcium, unlike potassium or phosphorus, is not remobilized from the leaves to the fruits. Thus, foliar sprays of calcium won't correct blossom end rot. Tomato fruits do not have openings in the epidermis (skin) where moisture can be lost or where calcium can enter the fruit from surface application. Thus, direct application of calcium to fruit is ineffective. Another cause of blossom end rot is over-fertilization, especially of nitrogen, which stimulates vegetative growth. Excessive vegetative growth increases the transpiration surface and further prevents calcium accumulation in the fruit. Tomato varieties with large amounts of foliage tend to be more susceptible to blossom end rot. Adjust the nitrogen rate for each cultivar to reduce blossom end rot. Avoid ammoniacal forms of nitrogen that compete with calcium during uptake from the soil. Hot, windy conditions with low relative humidity can cause high transpiration rates ideal for inducing blossom end rot. Fluctuations in soil moisture during periods of rapid plant growth create moisture stress and limits calcium distribution to the fruit. Preventing moisture stress is important to control blossom end rot, especially during fruit set and fruit enlargement. Plants require 1 acre-inch of water per week or more in sandy soil and during hot, windy weather. Mulch to conserve moisture and adjust the nitrogen rate to the type of tomato being grown to avoid excessive vegetation. Use nitrogen in the form of potassium or calcium nitrate and avoid ammonium nitrate. Check soil pH and soil nutrient levels annually and adjust the pH to between 6.5 to 6.7 if necessary. Apply potassium, phosphorus, and magnesium as recommended because balancing these nutrients with calcium is also important in preventing blossom end rot. The primary factor, however, is maintaining uniformly adequate soil moisture throughout the season.  File NF43 under HORTICULTURE C-1, Vegetables Issued September 1991  Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Elbert C. Dickey, Director of Cooperative Extension, University of Nebraska, Institute of Agriculture and Natural Resources.  University of Nebraska Cooperative Extension educational programs abide with the non-discrimination policies of the University of Nebraska-Lincoln and the United States Department of Agriculture. 

NF91-43 Blossom End Rot in Tomatoes

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University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Historical Materials from University of 
Nebraska-Lincoln Extension Extension 
1991 
NF91-43 Blossom End Rot in Tomatoes 
Laurie Hodges 
University of Nebraska--Lincoln, lhodges1@unl.edu 
Don Steinegger 
University of Nebraska--Lincoln, dsteinegger1@unl.edu 
Follow this and additional works at: https://digitalcommons.unl.edu/extensionhist 
 Part of the Agriculture Commons, and the Curriculum and Instruction Commons 
Hodges, Laurie and Steinegger, Don, "NF91-43 Blossom End Rot in Tomatoes" (1991). Historical Materials 
from University of Nebraska-Lincoln Extension. 791. 
https://digitalcommons.unl.edu/extensionhist/791 
This Article is brought to you for free and open access by the Extension at DigitalCommons@University of Nebraska - 
Lincoln. It has been accepted for inclusion in Historical Materials from University of Nebraska-Lincoln Extension by an 
authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 
Nebraska Cooperative Extension NF91-43
Blossom End Rot in Tomatoes 
Laurie Hodges, Ph. D. Extension Specialist, Horticulture 
Don Steinegger, Ph.D. Extension Specialist, Horticulture  
Blossom end rot of tomatoes is a common problem. It occurs under conditions of high plant water stress 
and heavy fruit load. The first sign is a small, water-soaked area around the blossom end of the fruit that 
rapidly darkens and enlarges. As this lesion enlarges, it shrinks and the area becomes sunken and 
leather-like. This depressed area may become infected with secondary pathogens. Early fruits on the 
plant may have blossom end rot, while those that develop later are normal. 
Blossom end rot is a symptom of calcium deficiency in the fruit. It can occur even when there is 
abundant calcium in the soil and tissue tests show high levels of calcium in the plant. Poor calcium 
distribution in the plant results in low calcium levels where the lesion occurs. 
Calcium, dissolved in water, moves through the plant in the vascular system from the roots to the leaves. 
Leaves are the primary sink for movement of water because of water loss through transpiration. Under 
high moisture stress, the water containing calcium and other minerals moves rapidly to the leaves. Fruit 
does not transpire as much as leaves and thus tends to be bypassed. This results in a localized calcium 
deficiency. This calcium deficiency in an area of rapid growth, the end of the fruit, causes cells to 
collapse and the sunken-lesion symptom of blossom end rot. 
Blossom end rot may appear on some of the first fruit clusters on a plant. This is attributed to the 
combination of rapid plant growth with a large leaf area for water transpiration, water stress, and fruit 
enlargement. Even a temporary water stress during early fruit enlargement can cause blossom end rot 
because the fruits are the last to receive adequate calcium. 
Calcium, unlike potassium or phosphorus, is not remobilized from the leaves to the fruits. Thus, foliar 
sprays of calcium won't correct blossom end rot. Tomato fruits do not have openings in the epidermis 
(skin) where moisture can be lost or where calcium can enter the fruit from surface application. Thus, 
direct application of calcium to fruit is ineffective. 
Another cause of blossom end rot is over-fertilization, especially of nitrogen, which stimulates 
vegetative growth. Excessive vegetative growth increases the transpiration surface and further prevents 
calcium accumulation in the fruit. Tomato varieties with large amounts of foliage tend to be more 
susceptible to blossom end rot. Adjust the nitrogen rate for each cultivar to reduce blossom end rot. 
Avoid ammoniacal forms of nitrogen that compete with calcium during uptake from the soil. 
Hot, windy conditions with low relative humidity can cause high transpiration rates ideal for inducing 
blossom end rot. Fluctuations in soil moisture during periods of rapid plant growth create moisture stress 
and limits calcium distribution to the fruit. 
Preventing moisture stress is important to control blossom end rot, especially during fruit set and fruit 
enlargement. Plants require 1 acre-inch of water per week or more in sandy soil and during hot, windy 
weather. 
Mulch to conserve moisture and adjust the nitrogen rate to the type of tomato being grown to avoid 
excessive vegetation. Use nitrogen in the form of potassium or calcium nitrate and avoid ammonium 
nitrate. Check soil pH and soil nutrient levels annually and adjust the pH to between 6.5 to 6.7 if 
necessary. Apply potassium, phosphorus, and magnesium as recommended because balancing these 
nutrients with calcium is also important in preventing blossom end rot. The primary factor, however, is 
maintaining uniformly adequate soil moisture throughout the season.  
File NF43 under HORTICULTURE 
C-1, Vegetables 
Issued September 1991  
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation 
with the U.S. Department of Agriculture. Elbert C. Dickey, Director of Cooperative Extension, 
University of Nebraska, Institute of Agriculture and Natural Resources.  
University of Nebraska Cooperative Extension educational programs abide with the non-discrimination 
policies of the University of Nebraska-Lincoln and the United States Department of Agriculture. 


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NF91-43 Blossom End Rot in Tomatoes

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