Control method

Group Title: Mimeo report - Gulf Coast Station - 57-2 (Rev. 56-4)
Title: Control of blossom-end rot of tomatoes
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00067642/00001
 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: 1957
Edition: Rev. ed.
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: Gulf Coast Station mimeo report ;
 Record Information
Bibliographic ID: UF00067642
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 - 71353750

Table of Contents
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    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

Gulf Coast Station Mimeo Report 57-2 (Rev. 56-4) Y A
Bradenton, Florida
t DEC 171956p-

0. M. Geraldson

The physiological disorder of tomatoes known as blossom-end rot is of

general occurrence wherever tomatoes are grown. In Florida, where approximately

50,000 acres of tomatoes are grown annually, estimated average losses amount to

3-5 percent of a crop that is valued from $500 to $2500 per acre. A loss of

fruit as high as 50 to 75 percent has been observed in some fields. Certain

fields or areas tend to produce varying amounts of blossom-end rot every season

while other fields may be affected one season, but not the next. There is also

considerable variation in the susceptibility of different varieties.

Blossom-end rot first becomes nppnrent 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 (which feed on dead and dying tis-

sue). Another form of the disorder occurs as an internal browning or blackening

and may be present without the characteristic end rot being visible.

Recent research at the Gulf Coast Experiment Station hns indicated that

a deficiency of calcium is a fundamental cause of blossom-end rot. All of the

factors, frequently associated with the prevalence and severity of blossom-end

rot of tomatoes, can be grouped into two major categories according to the mechan-

ism by which they adversely affect calcium uptake. These are as follows:

1. Excessive soluble magnesium, potassium, sodium or ammonium salts or

a deficiency of soluble calcium salts (low calcium ratio) cause a decreased calci-

um uptake and an increased prevalence and severity of blossom-end rot. Comparing

equal amounts of the competitive salts indicates that ammonium decreases calcium

uptake to the greatest degree; sodium the least.

2. Excess total salts also can cause a calcium deficiency and has fre-

quently been associated with blossom-end rot even when the measurable calcium

ratio is considered high or adequate.


Needless to say, excess salts plus a low calcium ratio are most favor-

able for severe outbreaks of blossom-end rot.

Unfavorable moisture relationships have been associated more often

with blossom-end rot and blackheart than any other factor. The role of moisture

is considered as secondary in that it facilitates the operation of the primary

factors. Salts, during dry weather or as a result of fertilizer top dressings,

accumulate in the surface soil and rainfall moves these salts downward into the

'effective' root zone, decreasing the calcium ratio and often also increasing

total salt concentration in that zone. Insufficient soil moisture (decreasing

the soil moisture concentrates the salts already present) as well as addition

and accumulation of fertilizers can cause excessive concentrations of salts. Ex-

cessive soil moisture favors the accumulation of ammonium salts inhich on an equiv-

alent basis (compared with the other cations) causes the most severe calcium de-


Excess soluble salt and excess of certain nutrients such as nitrogen

and potash have frequently been associated with the prevalence and severity of

blackheart and blossom-end rot. Additions of lime or superphosphate have some-

times been associated with a reduction of the incidence. These factors would bo

considered primary in that they directly affect the calcium rating or total splt


Rapid growth, another associated factor, would be considered as accen-

tuating because it tends to increase the calcium requirement per unit of time.

A consistent supply of calcium from the soil solution is especially

important because for all practical purposes, calcium within the plant is not

trenslocated from older plant tissue to younger. Therefore, the soil solution

supply must be constant as well as adequate at all times. Any combination of

factors that causes the plant requirement for calcium to exceed the supply,

whether it is of a temporary nature or a deficiency of longer duration, can be

a3soeinted with the disorder.


Control Method

1. Primary objective maintain to the best degree possible a favorable

calcium ratio by supplying more soluble calcium salts and avoiding excesses, as

much as possible, of soluble potassium, magnesium or ammonium salts as well as

excess total soluble salts.

Most virgin sandy soils in Florida contain insufficient amounts of poten-

tially soluble calcium. Calcium from the common liming materials is usually only

slowly soluble. When liming materials containing magnesium are utilized, less

calcium as well as greater amounts of a competitive salt are being supplied pr"

,nit of liming material. However, the more soluble magnesium, potassium or ?-1-

mcnium salts, supplied mainly from fertilizers and decomposing organic material,

are potentially main sources of competitive soluble salts. Amounts of nitrate

or ammonium nitrogen can vary with the amount and rate of breakdown of organic

matter as well as with amounts added in fertilizers. A high ammonium level i.

favored by low soil pH's and excessive soil moisture. (It is not recommended

that the nitrate sources of nitrogen replace the ammonium, because excess nitrate

can inczsase the calcium requirement). Superphosphate, gypsum, calcium nitrat.,

and calcium chloride are good sources of potential soil solution calcium. S.:ils

cropped for a number of years and receiving periodic additions of liming material

and superphosphate gradually accumulate a good supply of potentially soluble cal-

cium. The subsoil calcium, whether native or due to movement from that added to

the top soil, is also important when considering the calcium supplying capacity

of a soil.

2. Supplementary Objective periodically utilizing 4 pounds of calcium

chloride/100 gal./acre as a foliar spray during the time when the plant requile-

r.ent is expected to exceed the supply.

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

blossom-end rot and is governed to a great extent by considerations discussed

above. Calcium sprays should be applied within 24-48 hours after rains (es-

pecially if surface salts had accumulated and have been leached into the 'effec-

tive root zone. When excess salts are causing blossom-end rot, sprays are the

only successful means of supplying the calcium soil amendments in such cases

are generally not recommended. Sprays should also be used during period of mo"t

rapid growth. Calcium sprays should always be considered as supplementary to that

supplied from the soil solution and used accordingly.

If trouble is anticipated in the immediate future or if blossom-end rot

is developing, a calcium chloride spray (4#/100 gal. has been mixed and applied

with most fungicides and insecticides with no observed or known ill effects) can

be used as frequently as twice a week until the unfavorable balance no longer ea:-

ists. A regular spray program cannot be recommended because prolonged perioic.s

application may cause a leaf burn (found to be serious only during hot weather and

at concentrations in excess of 4#/100 gal.) Also such a procedure, if on a weekly

basis, may not necessarily be successful in controlling blossom-end rot because

proper timing often requires more frequent application.

The interrelated effects of the several contributing factors will be -'-

centuated to the degree the primary objective (favorable calcium ratio) of the con-

trol method has been neglected and thus make the supplementary objective (calc.:!-

sprays) that much more difficult.

Points of Emphasis in Control of Blossom-end Rot of Tomatoes

1. Florida tomato soils often contain insufficient amounts of soluble cal-

cinm end application of such a material as gypsum is frequently recommended as a

moans of obtaining a more favorable calcium ratio.

2. Overall foliage sprays supply calcium to the leaves which probably sl.oows

more of the limited soil solution calcium to reach the fruit and thus prevent de-

velopment of blossom-end rot. Although sprays are successfully used for control,

it is not as efficient as if the calcium could be supplied directly into the fruit.

3. Depending on the causal factors, various combinations of the primary end

supplementary objectives of the control method are recommended to try and insure a

constant and adequate supply of calcium at all times.

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