Control method

Group Title: Mimeo report - Gulf Coast Station - 56-4
Title: Control of blossom-end rot of tomatoes
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00067640/00001
 Material Information
Title: Control of blossom-end rot of tomatoes
Series Title: Gulf Coast Station mimeo report
Physical Description: 4 leaves : ; 28 cm.
Language: English
Creator: Geraldson, C. M ( Carroll Morton ), 1918-
Gulf Coast Experiment Station (Bradenton, Fla.)
Publisher: Gulf Coast Station
Place of Publication: Bradenton Fla
Publication Date: 1956
Subject: Tomatoes -- Diseases and pests -- Florida   ( lcsh )
Tomatoes -- Diseases and pests -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: C.M. Geraldson.
General Note: Caption title.
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00067640
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 71355412

Table of Contents
    Control method
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Full Text


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida



C. M. Geraldson

A physiological disorder of tomatoes known as blossom-end rot is of general

occurrence and has been reported from nearly every area that grows tomatoes. In

Florida where approximately 50,000 acres of tomatoes are grown annually, estimated

average losses range from 3 to 5 percent of a crop that is valued at 40 million


Blossom-end rot first becomes apparent as a water-soaked area under the

fruit wall on the blossom end of the fruit. The lesion usually develops rapidly,

eventually resulting in a blackened, dry sunken leathery spot. The dead tissue is

frequently attacked by saprophytic organisms. Another form of the disorder occurs

as an internal browning or blackening and may be present without the characteris-

tic end rot being visible.

A control method, based on the concept that a fundamental cause of blossom-

end rot is a calcium deficiency is described as follows:

Control Method

I. Primary Objective To maintain an adequate supply of calcium in the sub-

strate during the entire growing season. It is recommended that the CQ/SSSS (calci-

um/soil solution soluble salts ratio) be maintained at a minimum of 20 percent.

(a) Prcplanting considerations: Virgin sandy soils in Florida usually con-

tain from 5 to 15 percent Co/SSSS, depending on the amount, source and depth of cal-

cium-benring materials. Li:!ing material, used to correct the pH, supplies the ma-

jor portion of the supplementary calcium. 'Superphosphate ~rd gypsum art excellent

sources of potential soil-solution calcium. When liming materials containing mag

nesium are utilized, less calcium as well as greater amounts of a competitive ion

are being supplied per unit of liming material. Soils cropped for a number o years

generally increase in calcium-supplying capacity due to movement of calcium into

the subsoil.


The incidence and severity of blossom-end rot has been found to vary inversely with

the calcium-supplying capacity of a soil (measured as percent Ca/SSSS), other fac-

tors being equal.

(b) Post Planting Considerations:

Cultural practices and environmental factors affect the Ca/SSSS ratio

nnd calcium requirement. Fertilizers containing potassium, ammonium, magnesium and

ccdi~i supply cations which reduce the Ca/SSSS rate. Observations and preliminary

sbudii-s indicate that at relatively low concentrations of SSSS a high sodium/calcium

ratio is associated to a lesser degree with blossom-end rot than equivalent ratios

of the other cations to calcium.

Nitrogen becomes a special problem because it can exist as a cation or anion

and excesses of either can accentuate a calcium deficiency. Nitrogen levels and

nitrate/ammonium ratios can vary with the amount and rate of breakdown of organic

matter as well as with the amounts added in fertilizers. The nitrate/ammonium ratio

also varies with pH and moisture level. The movement of salts in and out of the

root zone by rainfall or irrigation water is of primary importance in these consid-

erations. Consistently wet soil will favor an accumulation of ammonium while a dry

soil tends to concentrate existing quantities of soluble salts. Excess salts cause

n decreased calcium uptake even though the apparent Ca/SSSS remains constant. Cultur-

an practices or environmental factors, which in any manner reduce the CY/SSSS ratio,

have consistently been associated with blossom-end rot.

Supplementary applications of calcium to the soil after the crop has been plant-

ed nae sometimes recommended. The addition of superphospkhte or gypsum as a side

dr .. 3if within the first 4 to 6 weeks after planting has been found to be of some

vilue in increasing the Ca/SSSS ratio. Soil applications of calcium nitrate or cal-

cium chloride applied about a month before blossom-end rot began to develop have been

partially successful in controlling blossom-end rot. The more insoluble calcium sour-

aes when applied as side or top dressing are not generally satisfactory as a supple-

lental source of calcium. The success of any soil application of calcium after

planting depends on how soon and how well it moves into the root zone soil solution.


It should be pointed out that if excess salts are causing the calcium deficiency,

soil application could not be expected to correct the difficulty.

II. Supplementary Objective: Folinr application if and when calcium require-

ment by the plant is expected to exceed the supply:

Timing is the key to successful use of calcium sprays for control of blos-

som-end rot and is governed to a great extent by considerations discussed in the

;:iriary objective' section. If trouble is anticipated in the immediate future

or if blossom-end rot is developing, a 0.04M (approxinrtely 4 pounds per 100 gals.)

solution of calcium chloride per acre can be used as frequently as twice a week

until the unfavorable balance between supply and demand no longer exists. A regu-

lar spray program cannot be recommended because continued periodic application can

cause a leaf burn. Also such a procedure, if on a weekly basis, may not necessa-

rily be successful in controlling blossom-end rot because proper timing often re-

quires more frequent applications. Moisture levels and movement in conjunction

with fertilizer usage and rate of plant growth are some of the more important in-

terrelated factors which must be considered when timing the sprays. The effects

of such factors will be accentuated to the degree the primary objective of the con-

trol method has been neglected and thus make a control program that much more


Obviously, fast growing plants will be more sensitive to the effects of con-

tributing factors because the requirement for calcium is increased per unit of

'Aim. However, variations in metabolism, other than rate of growth, can also

effect calcium requirement, uptake, translocation and assimilation. Any factor

'Thich limits the calcium supplied to the meristefntic tissue is especially impor-

tant because calcium within the plant is not readily trnslocated (if at all) from

c.ler plant parts. Calcium must be obtained from the soil solution as needed and

blossom-end rot can often be considered an indicator of a low Ca/SSSS ratio. The

prevalence and severity of blossom-end rot often depends on the duration and the

e.-ree of the lot' Ca/SSSS ratio.


The prevalence and severity of blossom-end rot of tomatoes has been consis-

tently associated with factors causing a low proportion of calcium/soil solution

soluble salts (Ca/SSSS) or factors that affect the uptake and movement of calcium

by the plant. Rapid growth tends to accentuate the effect of any contributing


The primary objective of the control method is to maintain a Ca/SSSS ratio

whi:.-' will remain above 20 percent during the entire growing season. The supple-

men.tary objective is to supply a 0.04 M OC2I foliar spray whenever demand by the

pint is expected to exceed the supply. Complete control of blossom-end rot by

this method has been accomplished in a number of commercial fields.

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