Group Title: Bulletin - University of Florida Agricultural Experiment Station ; no. 318
Title: A preliminary report on frenching of tung trees
Full Citation
Permanent Link:
 Material Information
Title: A preliminary report on frenching of tung trees
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 21 p. : ill. ; 23 cm.
Language: English
Creator: Reuther, Walter, 1911-
Dickey, R. D ( Ralph Davis ), 1904-
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1937
Subject: Tung tree -- Diseases and pests -- Florida   ( lcsh )
Deficiency diseases in plants   ( lcsh )
Chlorosis (Plants)   ( lcsh )
Plants -- Effect of manganese on   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Bibliography: p. 21.
Statement of Responsibility: by Walter Reuther and R.D. Dickey.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station) ;
 Record Information
Bibliographic ID: UF00027036
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000924544
oclc - 18213287
notis - AEN5171

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

December, 1937





Fig. I.-A mature tung leaf (A. fordi) showing a characteristic
frenching symptom-partial chlorosis.

Bulletins will be sent free to Florida residents upon application to

Bulletin 318


John J. Tigert, MLA., LL.D.. President of
the University
Wilmon Newell, D.Sc., Director
H. Harold Hume, D.Sc., Asst. Dir.. Research
Harold Mowry, M.S.A., Asst. Dir., Adm.
J. F'rancis Cooper, M.S.A., Editor
Jefferson Thomas, Assistant Editor
Clyde Beale, A.B.J., Assistant Editor
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Manager
K. H. Graham, Business Manager
Rachel McQuarrie, Accountant


W. E. Stokes, M.S., Agronomist*
W. A. Leukel, Ph.D., Agronomist
G. E. Ritchey, M.S., Associate*
Fred H. Hull, Ph.D., Associate
W. A. Carver, Ph.D., Associate
John P. Camp, M.S., Assistant
Roy E. Blaser, M.S., Assistant

A. L. Shealy, D.V.M., Animal Husbandman**
R. B. Becker, Ph.D., Dairy Husbandman
L. M. Thurston, Ph.D., Dairy Technologist
W. M. Neal, Ph.D., Asso. in An. Nutrition
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarian
N. R. Mehrhof, M.Agr., Poultry Husbandman
W. G. Kirk, Ph.D., Asst. An. Husbandman
R. M. Crown, B.S.A., Asst. An. Husban'mar
P. T. Dix Arnold, M.S.A., Assistant Dairy
L. L. Rusoff, M.S., Asst. in An. Nutrition
R. V. Allison, Ph.D., Chemist**
R. M. Barnette, Ph.D., Chemist
C. E. Bell, Ph.D., Associate
R. B. French. Ph.D., Associate
H. W. Winsor, B.S.A., Assistant
J. Russell Henderson, M.S.A., Assistant

C. V. Noble, Ph.D., Agricultural Economist**
Bruce McKinley, A.B., B.S.A., Associate
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Assistant

Ouida Davis Abbott, Ph.D., Specialist**

J. R. Watson, A.M., Entomologist**
A. N. Tissot, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant

G. H. Blackmon, M.S.A., Horticulturist and
Acting Head of Department
A. L. Stahl, Ph.D., Associate
F. S. Jamison, Ph.D., Truck Horticulturist
R. J. Wilmot, M.S.A., Specialist, Fumigation
R. D. Dickey, B.S.A., Assistant Horticulturist
W. B. Tisdale, Ph.D., Plant Pathologist**
George F. Weber, Ph.D., Plant Pathologist
R. K. Vorhees, M.S., Assistant
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Assistant Botanist

L. W. Gaddum, Ph.D., Biochemist
L. H. Rogers, M.A., Spectroscopic Analyst

R. P. Terry, Chairman, Miami
Thomas W. Bryant, Lakeland
W. M. Palmer, Ocala
H. P. Adair, Jacksonville
Chas. P. Helfenstein, Live Oak
J. T. Diamond, Secretary, Tallahassee

L. O. Gratz, Ph.D., Plant Pathologist in
R. R. Kincaid, Ph.D., Asso. Plant Pathologist
J. D. Warner, M.S., Agronomist
Jesse Reeves, Farm Superintendent
A. F. Camp, Ph.D., Horticulturist in Charge
John H. Jefferies, Superintendent
W. A. Kuntz, A.M., Asso. Plant Pathologist
Michael Peech, Ph.D., Soils Chemist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson, B.S., Asst. Entomologist
John A. Granger, B.S., Asst. Horticulturist

J. R. Neller, Ph.D., Biochemist in Charge
R. N. Lobdell, M.S., Entomologist
F. D. Stevens, B.S., Sugarcane Agronomist
Thomas Bregger, Ph.D., Sugarcane
G. R. Townsend, Ph.D., Assistant Plant
R. W. Kid er, B.S., Asst. Animal Husbandman
Ross E. Robertson, B.S., Assistant Chemist
W. T. Foresee, Ph.D., Asst. Chemist
B. S. Clayton, B.S.C.E., Drainage Engineer*

H. S. Wolfe, Ph.D., Horticulturist in Charge
W. M. Fifield, M.S., Asst. Horticulturist
Geo. D. Ruehle, Ph.D., Asso. Plant Pathologist

W. F. Ward, M.S., Asst. An. Husbandman
in Charge*

M. N. Walker, Ph.D., Plant Pathologist In
K. W. Loucks, M.S., Asst. Plant Pathologist
C. C. Goff, M.S., Assistant Entomologist
Plant City
A. N. Brooks, Ph.D., Plant Pathologist
J. W. Wilson, Sc.D., Associate Entomologist
A. S. Rhoads, Ph.D., Plant Pathologist
A. H. Eddins, Ph.D., Plant Pathologist
Sam O. Hill. B.S., Asst. Entomologist*
David G. Kelbert, Asst. Plant Pathologist
R. W. Ruprecht, Ph.D., Chemist in Charge
Celery Investigations
W. B. Shippy, Ph.D., Asso. Plant Pathologist
E. S. Ellison, Meteorologist*
B. H. Moore, A.B., Asst. Meteorologist*

*In cooperation with U.S.D.A.
** Head of Department.



SYMPTOMS OF FRENCHING .......... ... .... ... .. .. 4
E XPERIM EN TAL STUDIES ..................... .... .. .... .. .. .................................... ..... .... ----....- S
Foliage T reatm ents ................. ......... .............................. ...... .......... 8
Soil Treatm ents ................ ............. ........... .......... ......... .... .............................. 11
Soil Reaction and Amount of Available Manganese in Relation to the Occurrence of
Frenching of Tung Trees ................... ..................................... 14
E xperim ents w ith M u-oil T rees ................. ................ ......... ......................... ..... 17
D ISCUSSION .............. ............. ............ .... ....... .. ......................................................... 19
SUM M ARY .......... ..... ..... ...... .. ........ .. .... .... ........... ................ ............... -- 20
LITERATURE .. . ... ... ... .... ... .... ... .......... 21

During the first few years of extensive commercial planting
of tung trees (Aleurites fordi Hemsl.) in Florida many groves
were affected with a serious growth-retarding physiological dis-
order known as "bronzing". The work of Mowry (6)1 and
Mowry and Camp (7) showed that this trouble could be success-
fully controlled by the application of certain soluble zinc salts
to the soil around affected trees. As a result of this work, zinc
sulfate is used extensively in tung tree culture at present, and
has been for the past four years. Consequently, comparatively
little bronzing is to be found in properly cared for tung plant-
ings today. However, another quite different physiological
disorder possibly previously masked in part by bronzing symp-
toms, has been found to occur in varying degree over a rather
widespread area. It is a type of partial chlorosis which suggests
the term "frenching". This term will be used throughout this
bulletin to designate this disorder.
As early as 1925 Gardner (2) included in a progress report
a picture of a tung leaf showing a partial chlorosis reported to
be due to overliming. The symptoms were quite similar to those
of "frenching" as herein described. In 1933 and subsequent
years the authors observed certain isolated instances of a
"frenching" type of chlorosis occurring not only in apparently
normal plantings receiving no zinc treatment, but also in plant-
ings which had recovered from bronzing as a result of zinc
treatments. This disorder was given scant attention, because

Acknowledgments: The authors wish to thank Dr. A. F. Camp, Mr.
Harold Mowry and Dr. Michael Peech for helpful suggestions and criti-
lItalic figures in parentheses refer to "Literature Cited" in the back
of this bulletin.

Florida Agricultural Experiment Station

of its comparative rarity, until the spring of 1936 when experi-
ments were inaugurated on two severely affected trees which
appeared in an experimental planting in Columbia County,
Florida. These initial experiments gave indications that "french-
ing" was a manganese deficiency. A subsequent inspection of
additional plantings that summer located several other trees
severely affected with this disorder and a number mildly af-
fected. Additional experiments on some of these trees con-
firmed the findings of the first experiments and these results
led to the initiation of more extensive studies on various phases
of this problem.
Inasmuch as the literature on the relation of manganese to
plant growth has been adequately reviewed by Hopkins (4),
Mann (5) and others, no formal discussion on this subject will
be included.
The symptoms of "frenching" as described here are confined
entirely to the foliage and are of three principal types, namely:
A condition of partial chlorosis, necrotic spots in chlorotic areas,
and premature abscission of some of the leaves.

Fig. 2.-Tung leaves (A. fordi) showing typical steps in the development of symptoms.
From left to right: (1) immature leaf showing first visible evidence of partial chlorosis:
(2, 3) progressive stages in the development of partial chlorosis; (4, 5) development of
necrotic spots in chlorotic areas of more mature leaves.

Partial chlorosis is a condition in which light green to de-
cidedly yellow areas of varying shape and extent appear between
the main and secondary veins, the remainder of the leaf being
green (Figs. 1, 2 and 4). Light green to yellow areas first
appear on the margin and extend inward between the main and
secondary veins (Fig. 2, leaf 1). These areas are irregular in
extent and outline, appearing as a series of patches separated

A Preliminary Report on Frenching of Tung Trees

by narrow green strips bordering the cross veins (Fig. 1). In
advanced stages, only the areas immediately surrounding the
main and secondary veins remain green, with some of the cross
veins appearing as fine green lines (Fig. 2, leaves 2 and 3)%.


Fig. 3.-Tung leaves (A. fordi) showing some typical symptoms of bronzing. The left
leaf illustrates malformation, a characteristic of severely bronzed foliage. The right leaf
shows necrotic (dead) areas which form in the more advanced stages.

In still more advanced stages, small dark brown necrotic
spots form in the chlorotic areas, increasing in size to produce
larger areas of dead tissue irregular in extent and outline. These
spots usually appear first in the chlorotic areas at the leaf's
margin, extending from there inward between the main and
secondary veins. As necrosis progresses, adjacent spots, par-
ticularly along the margin, may coalesce to form extended dead
areas and later may show ragged margins or irregular breaks
due to the brittleness of the dead tissue (Fig. 2, leaves 4 and.5).
A considerable amount of premature leaf-fall takes place,.par-
ticularly if the leaves show a large amount of dead tissue.
The chlorotic pattern of frenching as described above is not
characteristic of bronzing (Fig. 3). Frenching may be readily
distinguished from bronzing as it lacks the characteristic mal-
formation of terminal leaves and bronze color of the foliage.
In addition, the abnormal formation of purple pigment (prob-
ably anthocyanin), particularly on the under surface of: the
leaf, so characteristic of bronzing, is not associated with freich-

Florida Agricultural Experiment Station

ing as a rule. Both disorders are characterized by the forma-
tion of necrotic areas, but unlike frenched leaves which form
dead spots in accordance with the pattern of the chlorotic areas,
bronzed leaves form relatively large dead areas scattered at
random over the leaf surface.

Fig. 4.-Treated and frenched tung leaves (A. fordi). A.-Typical frenched leaf
(selected control) showing considerable chlorosis. B.-Leaf dipped in 0.5 percent man-
ganese sulfate solution in June, 1937, at which time its appearance was similar to that
of leaf A. Photo taken five weeks after treatment.

Fig. 5.-Typical treated and frenched tung shoots (A. fordi). A.-From tree treated with
Y/ pound of manganese sulfate to the soil on 7/1/36 followed by a 5 pound treatment on
5/1/37. Photo taken 6/20/37. B.-From tree receiving no manganese treatment. The
condition of A was similar to that of B at the time of the 1937 treatment. In addition,
the tree from which shoot A was obtained showed slight toxic symptoms on certain shoots
(see Fig. 7).

'TABLE I.-8UKV&Y OUl lil DiJliNKlBU'TlUN U b'KENcHiNw u oU TUNU.

Location of Planting
Planting Number
Near Lake City,
Columbia Co. 1
Exp. Sta. Farm,
Gainesville 3

Near LaCrosse, 4
Alachua Co.
Near Alachua,
Alachua Co. 5
Near Gainesville,
Alachua Co. 6

Near Gainesville,
Alachua Co. 7

Near LaCrosse,
Alachua Co. 9
Near Paradise,
Alachua Co. 10
Near Hawthorne,
Alachua Co. 11
Near Lament,
Jefferson Co. 12
Near Greenville,
Madison Co. 13
Near Interlachen,
Putnam Co. 14
Near Morriston,
Levy Co. 15
Near Bel eview,
Marion Co. 16
Penney Farms,
Clay Co. i 17
*These soils are being reclassified.

Soil Type

Norfolk fine sand

Norfolk sand

Norfolk fine sand

Hernando fine sand*
Leon and Bladen
fine sands

Gainesville and Hernando
fine sands*

Norfolk fine sand

Leon fine sand

Norfolk sand
Orangeburg and Norfolk
fine sandy loams

Norfolk fine sand

Norfolk sand

Norfolk fine sand

Norfolk sand

Norfolk fine sand

Prevalence of Frenching
Spring, 1937
Approximately 75% of the trees affected with mild
to severe frenching.
About 12 trees show mild symptoms of frenching in
one area. Majority of planting free from wrenching.
Very small percentage of slight to mildly frenched
trees scattered through most of planting. Certain
extensive areas entirely free.
Majority of planting affected with mild to severe
Small percentage of slight to mildly frenched trees
scattered through most of planting.
One rather extensive area affected with mild to
severe frenching. Small percentage of slight to
mildly frenched trees in other portions of plant-
ing. Certain extensive areas entirely free.

Planting entirely free from frenching.

A few trees affected with slight frenching.
Small percentage of slight to mildly frenched trees
sea'tered throughout entire planting.

Planting entirely free of frenching.
Small percentage of slight to mildly frenched trees
scattered throughout entire planting.
Very small percentage of slightly frenched trees
scattered over portion of planting.
Small percentage of slight to mildly frenched trees
scattered over majority of planting.
Small percentage of slight to mildly frenched trees
localized in certain areas.
Sma.l percentage of slight to mildly frenched trees
scattered over most of planting.

Florida Agricultural Experiment Station

During the spring of 1937 a survey was made to determine,
in a general way, the prevalence of frenching in commercial
tung p antings in Florida. This survey did not include all such
plantings but a representative number were visited and the
results are summarized in Table 1. The plantings studied
aggregated approximately 8,000 acres and varied in age from
5 to 16 years. Of these plantings two large ones were entirely
free, three had extensive severely affected areas and the re-
mainder showed only a small percentage of slight to mildly
affected trees. Considering the acreage as a whole, it is esti-
mated that between 5 and 10 percent of the trees show french-
ing symptoms in some degree.

Foliage Treatments:-Initial response of frenching to man-
ganese treatment was obtained on two severely affected trees
in a planting in Columbia County. In June, 1936, severely
frenched shoots were selected, tagged and dipped in solutions
of the following compounds to most of which hydrated lime
had been added:
Copper sulfate (CuSO4.7HO) ........... 1% solution plus 1% hydrated lime
Iron sulfate (FeSO4.7HLO) .......... 2% solution plus 1% hydrated t!i;e
Aluminum sulfate (AI (SO4),.18HlO) 2% solution plus 1% hydrated lime
Manganese sulfate (MnSO1.2H O) .... 1% solution plus 1% hydrated lime
Zinc sulfate (ZnSO4.1HO) ................ 1% solution plus 1% hydrated lime
Magnesium sulfate (MgSO4.7H.O) .... 1% solution plus 1% hydrated lime
Barium sulfate (BaS04) ................ .. 1% solution (No lime)
Borax (Na2B407.10HO0) .......................0.2% solution (No lime)
Approximately 1 percent of calcium caseinate spreader was
added to all mixtures. Similar untreated shoots in comparable
number were selected, tagged, and used as controls. Within
30 days the shoots treated with the manganese mixture had
completely greenedd up"; that is, the leaves regained their
normal green color and all symptoms of chlorosis disappeared,
while the remaining treated and control .shoots showed no
material change. During the summer additional experiments
at two other locations confirmed the results obtained in Colum-
bia County.
In the spring of 1937 more extensive experiments were under-
taken with manganese treatments of frenched foliage. Frenched
shoots were simply dipped in a 0.5 percent solution of a C.P.

A Preliminary Report on Frenching of Tung Trees

grade of manganese sulfate (MnSO4.2H20) to which had been
added approximately an equal amount of calcium caseinate
spreader. In some cases distilled water, in others water from
the local supply, was utilized. The manganese solution was
prepared in a 12-quart galvanized bucket, using 50 grams (ap-
proximately 2 ounces) of the manganese salt to 21/ gallons
of water. Leaves dipped in this solution become coated with
a brown to black deposit probably containing a considerable
quantity of manganese in oxide forms. The results of these
"dipping" experiments are tabulated in Tab'e 2.
In some cases the frenched leaves showed visible response
("greening up" of chlorotic tissue) within two weeks after
treatment, and complete recovery was noted after three weeks.
In the majority of cases, however, four to six weeks were
required for complete response in the spring and early summer.
Fig. 4 shows typical response obtained five weeks after treat-
ment with manganese solution.

Fig. 6.-Typical treated and frenched mu-oil shoots (A. montana). A.-From tree
treated with pound of manganese sulfate in August, 1936, followed by a 5 pound soil
treatment in March, 1937. Photo taken 6/20/37. B.-From tree receiving no manganese
soil treatment. The condition of A was similar to that of B at the March, 1937, treat-
ment. No toxic symptoms have developed to date (Aug., 1937).

In general, the slightly immature leaves on rapidly growing
shoots are most prone to show severe frenching symptoms and
respond most rapidly to manganese foliage treatment, provided
severe necrosis has not begun. The more mature, hardened
leaves have less tendency to show severe symptoms and are
slower to respond as a rule. In many instances mild frenching


Location of

Near Lake City,
Columbia Co.
Alachua Co.
Exp. Sta. Farm,
Alachua Co.
Alachua Co.
Near Lake City,
Columbia Co.
Near LaCrosse,
Alachua Co.
Near Alachua,
Alachua Co.
Near Gainesville,
A'achua Co.
Alachua Co.
Near Gainesville,
Alachua Co.
Exp. Sta. Farm,
Seffner, Fla.,
Hillsborough Co.

I Planting







S 4

__ 4





of '


| 1

mber of
Trees Treated

2 2

2 3

1 7

2 3

3 6

7 44

6 8

7 14

6 10

2 1 5

6 33

1 6

1 2


Date of














*Response refers to the degree of "greening up" of the chlorotic portions of frenched leaves on treated shoots as compared to the leaves of
corresponding control shoots selected ani tagged at the time of treatment. Thus complete response as used in this table indicates that the frenched
leaves resumed a normal over-all green color subsequent to treatment, while 80 to 90% response indicates that some of the treated leaves remained
slightly chlorotic, but showed a quite pronounced improvement as compared to the untreated controls.
**In tahulating results, where less than complete response is indicated, these represent the total response obtained as verified by a later inspection.

Date of Final














All showed complete response.

All showed 75% response.

All showed 75% response.

All showed complete response.

All showed complete response.
36 showed complete response.
8 showed from 80 to 90% response.
7 showed complete response.
1 showed 90% response.
13 showed complete response.
1 showed 90% response.
9 showed complete response.
1 showed 90% response.

All showed complete response.
29 showed complete response.
4 showed from 80 to 90% response.
5 showed complete response.
1 showed 80% response.

All showed complete response.


A Preliminary Report on Frenching of Tung Trees

symptoms appear only when the tree enters a cycle of rapid
growth. However, frenching is not necessarily confined to ten-
der, rapidly growing shoots, as it has been frequently observed
on unthrifty trees showing little or no growth.
Certain limited experiments not listed in the above table
indicate that mature leaves in advanced stages of frenching
respond only slightly to dipping treatments made in the fall.
To date the data and observations on frenching of tung trees
and its response to manganese treatment, in the opinion of the
authors, suggest that frenching, and hence manganese utiliza-
tion, is associated with rapid vegetative growth.
Soil Treatments:-Field trials with soil applications of man-
ganese materials for the control of frenching are as yet limited.
However, several test plots had been laid out with the objective
of determining the effect of various minor elements including
manganese on the growth and yield of tung trees. Unfortunately
some of these plots were set up before the symptoms of french-
ing were clearly recognized and associated with manganese
treatment. The usable results in these experiments are sum-
marized in Table 3.

Fig. 7.-Upper and lower surfaces of leaves affected with symptoms probably caused
by excessive quantities of soluble manganese in the soil. These typical leaves were obtained
from a tree which had been treated with 5 pounds of commercial manganese sulfate. The
spotting symptoms illustrated above developed within six weeks after treatment.

Florida Agricultural Experinment Station



3 1

2 1

4 6

13 34

14 14

1 1

Pounds of
(per tree)

/V (C.P.)

/4 (C.P.) & 5
1 (C.P.) & 5
1 &5


Y & %
1 & 1










*See Table 1 for location of planting and soil type.
**Commercial 65% manganese sulfate useJ unless otherwise indicated.
***The method of judging response is explained in the footnote of Table 1. In this case.
however, control trees, instead of shoots, were selected and tagged.

These results are obviously inconclusive, but do show that
small applications of manganese can be made without evident
harmful effects. In only one case were toxic symptoms noted


Partial response visible in fall, 1936,
and marked recovery noted in spring,
1937. No toxic symptoms.
Slight response noted on all trees in
fall. 1936. and very slight in spring,
1937, before 5 pound application.
After 5 pound application, complete
response was noted within six weeks.
However, toxic symptoms also de-
veloped within this period (Figs. 5
and 7).
These trees were affected with slight
frenching at the time of treatment.
In the course of two months both
treated and control trees have re-
covered completely from chlorotic
symptoms. No toxic symptoms noted.
These treatments are part of a soil
amendment experiment, the purpose
of which is to examine various
materials for value in tung culture.
No symptoms are to be found in
either manganese treated or control
blocks. However, frenching is pres-
ent in other portions of planting.
No toxic symptoms no'ed.
These treatments are part of a soil
amendment experiment the purpose
of which is to examine various pro-
grams for value in correcting the
unthrifty growth condition in this
planting. Only a very small per-
centage of the trees were affected
with slight frenching symptoms at
the outset in 1936. No symptoms
are to be found in either manganese
treated blocks this current season.
However, no toxic symptoms have
been noted.
Approximately 50%' response no.ed
to date (Aug., 1937). These un-
thrifty trees were affected with mild
frenching at the time of treatment.
No toxic symptoms noted.

A Preliminary Report on Frenching of Tung Trees

in connection with such applications. In a roadside planting
(planting number 2), three trees were treated with small appli-
cations of manganese sulfate in the summer of 1936. A slight
response was noted in the fall, but the following spring the
new foliage was affected with frenching almost as severely
as the control trees. Six weeks after an additional application
of 5 pounds per tree of manganese sulfate was made in May,
1937, complete response was noted on all three of the treated
trees, but a peculiar spotting of the leaves also developed (Fig.
7). This spotting was present only on the three trees receiving
the soil applications. It is quite probable that this spotting
is evidence of a toxic condition produced by excessive amounts
of soluble manganese in the soil; although the possibility that
this effect is produced by some impurity in manganese sulfate
should not be altogether rejected. It should a'so be taken into
consideration that these trees are planted in a "made" soil
along the spoil bank of a ditch bordering a limerock founda-
tion road. The surrounding land is low, poorly drained soil of
the Leon series.
No toxic effects have been noted from manganese soil treat-
ments in commercial plantings to date. Nevertheless, on the
basis of the limited trials thus far conducted no definite recom-
mendations as yet can be made for the large scale use, on com-
mercial plantings, of manganese materials as soil applications
for the control of frenching of tung. However, it is suggested
that growers having trees severely affected with frenching
should limit, for the time being, their treatments to small ex-
perimental plots and refrain from making any widespread soil
applications until sufficient time has elapsed to determine the
results obtained from these plots. It is further suggested that
such experimental applications should be made preferably in
the months of April, May and June, and it is suggested also
that on the heavier types of soils containing considerable clay
or organic matter, or poorly drained soils, the treatments range
from 1/4 to 1 pound per tree according to tree size. On well
drained, light sandy soils distinctly acid in reaction and low in
organic matter (such as Norfolk sand), the treatments should
range from 1 to 3 pounds per tree. Manganese sulfate is sold
in two forms, one containing approximately 80 percent and the
other 65 percent manganese sulfate. If the 80 percent material
is used the amounts suggested above should be reduced about
20 percent.

Florida Agricultural Experiment Station

It should be pointed out that several years of developmental
work and extended fie:d experiments will be required before
sufficient information can be acquired to make definite recom-
mendations. Inasmuch as frenching does not appear to be a
disorder of any great magnitude as yet, growers are cautioned
not to make any widespread soil applications of manganese
sulfate until such time as adequate experimental work can be
carried out. Since tung growers generally do not possess spray-
ing equipment, and limited field trials indicate that soil applica-
tions of manganese materials will effect satisfactory control,
it is thought not necessary to purchase such equipment at
Soil Reaction and Amount of Available Manganese in Relation
to the Occurrence of Frenching of Tung Trees:-As was pre-
viously noted, Gardner (2) described briefly a condition of par-
tial chlorosis of tung very similar to frenching as defined in this
bulletin. He noted that this condition was probably due to
excessive quantities of lime in the soil. In a later publication,
Newell, et. al. (8) described a condition of chlorosiss and bronz-
ing" (as distinguished from true bronzing) associated with ex-
cessive quantities of lime in the soil. Data were presented
indicating that the condition was definitely correlated with an
alkaline soil reaction. They demonstrated that the removal of
affected trees from overlimed soil and replanting in an acid soil
caused the tree to start normal growth in most cases. It was
concluded that the condition was closely related to bronzing
inasmuch as many symptoms were common to both disorders.
In the light of the recent developments treated in this paper,
the writers are of the opinion that the condition described as
chlorosiss and bronzing" associated with overlimed soils of
neutral to alkaline reaction was a complication of frenching,
bronzing and possibly certain other physiological disorders.
In recent years much literature has been published indicating
that many physiological disorders of plants which respond to
manganese treatment are associated with the more alkaline soils
such as overlimed or naturally calcareous soils. Considerable
work has been done along these lines in Florida. Skinner and
Ruprecht (11) reported control of chlorosis and marked increase
in yield of many truck crops resulting from the use of man-
ganese salts as a fertilizer supplement on the highly calcareous
glade soils of Dade County. Skinner, Bahrt and Hughes (12)
noted that manganese was particularly effective in controlling

A Preliminary Report on Frenching of Tung Trees

chlorosis and increasing yield of citrus on calcareous soils of
neutral to alkaline reaction. Townsend and Wedgeworth (13)
described a manganese deficiency affecting beans and other crops
occurring on peat soils of the Everglades region having a neutral


1 |9 Norfolk fine None 0-8 5.4 2.8 Fair
2 sand 8-18 5.4 0.7
3 5 Hernando fine Severe 0-6 5.9 | 1.3 Poor
| '

6 sand 6-18 6.2 1.0

8 sand 7-18 5.3 1.2
94 4 Norfolk fine None 0-6 5.2 8.4 Poor
10 sand 6-18 5.3 2.5 1
11 4 Norfolk fine Slight 0-6 5.8 1.0 Fair
12 sand 6-18 5.7 0.6
13 1 Norfolk fine Severe 0-6 5.7 1.9 Fair
14 sand 6-18 5.3 0.9
15 13 Norfolk fine Slight 0-6 5.6 2.0 Fair
16 sand 6-18 5.3 1.5
17 12 Norfolk sandy None 0-6 5.4 23.4 Good
18 sloam 6-18 5.0 3.4
19 7 Gainesville Moderate 0-6 6.6 1.0 Good
20 fine sand 6-18 6.0 0.7

21 7 Gainesville Severe 0-6 6.1 0.9 Fair
22 fine sand 6-18 5.8 0.6

23 7 Gainesville None 0-6 6.5 1.0 Excellent
24 fine sandy loam 6-18 5.6 0.7
25 14 I Norfolk sand None S t 0-6 5.3 2.3 Poor
26 ] s a 6-18 5.1 1.1
27 2 Leon fine sand Severe 0-6 6.8 0.6 Poor
28 (lime-rock added) 6-18 7.5 0.4
29 6 Bladen fine Moderate 0-8 6.1 1.3 Fair
30 finsand 8-18 5.7 0.7
31 8 Norfolk fine Severe 0-7 6.6 0.8 Fair
32 sand 7-18 6.4 0.3

'Refer to Table 1 for location of planting.
2Glass electrode m asuremen6s.
aExtracted with 1 N. ammonium acetate of pH 7.0, determined by the method of Willard
and Greathouse (14), and the color intensities measured by means of a photoelectric colori-
Area sampled treated with one pound per tree (70 per acre) of 65% manganese
sulfate in June, 1937. Samples taken two months after treatment.
sulfate in June, 1917. Samples taken two months after treatment.

Florida Agricultural Experiment Station

to alkaline reaction because of soil burning or underlying marl
Mann (5) has shown that the solubility of manganese decreases
as the hydrogen-ion concentration decreases (pH increases) in
certain sandy loam soils treated with varying amounts of ca'.lium
or magnesium carbonate. The decrease in manganese solubility
was accompanied by an increase in chlorosis of soybeans.
This background of literature suggested that a study be made
of soil reaction and available manganese in relation to the oc-
currence of frenching of tung trees. The data obtained are
presented in Table 4.
Of all the sampled2 areas having severe frenching only two
or possibly three were overlimed in the strictest sense. How-
ever, several other areas, though acid in reaction, were possibly
too close to the neutral point for optimum tung growth because
of the relatively low native manganese content of these soils,
and hence might be, in a sense, considered to be overlimed.
It will be noted also that several of the sampled areas affected
with frenching were too acid in reaction to be considered over-
limed in any sense. Broadly interpreted, the soil reaction data
presented indicate that this disorder is associated with a fairly
wide range of soil reaction, and is not necessarily confined to
overlimed or highly calcareous soils.
The exchangeable3 manganese analyses show, with a few ex-
ceptions, a correlation with the occurrence of frenching. As
was to be expected, the highest exchangeable manganese con-
tent, around 8 pounds per acre4, was noted on a soil sample
from an area which had been treated with 1 pound per tree
of 65 percent manganese sulfate two months before the sample
was taken. Considering only the surface-soil layers, four of
the five other sampled areas which were free of chlorosis showed
a replaceable manganese content ranging from 2.3 to 3.4 pounds

2Samples representing two soil layers were taken in each area. The
depth of the surface sample was governed by the depth of the surface
horizon in most cases. In a few instances no sharp break in horizons was
discernible, in which case the arbitrary depth of six inches was chosen
for the surface sample. The subsoil sample extended from the surface layer
to an empirical depth of 18 inches in all cases. Each sample was com-
posited of six borings from six trees in the area of maximum root concen-
tration. A sharpened steel tube having an inside diameter of 11/2 inches
was used to make the borings.
SExchangeable manganese is generally considered to be a fair chemical
indication of the amount of the element available for plant use.
4The conventional 2 million pounds per acre six inches was the basis
used for the calculation of all the pounds-per-acre figures.

A Preliminary Report on Frenching of Tung Trees

per acre, averaging slightly less than 3 pounds per acre. How-
ever, one sample from an unaffected area contained only 1 pound
per acre of exchangeable manganese. Surface-soil samples from
the 10 areas evidencing frenching in some degree contained
from 0.6 to 2.0 pounds per acre, averaging slightly more than
1 pound per acre.
As a general rule the sub-soil samples examined contained
considerably less manganese than the corresponding surface
soils, but the same correlations are found by treating these
figures in a manner similar to those pertaining to the surface
To summarize briefly then, this study indicates that french-
ing of tung trees is not confi:-ed to any particular soil series
or narrow range of soil reaction, but is correlated with the
exchangeable manganese content of the soil.
Experiments with Mu-Oil Trees:-Inasmuch as there are only
about eight mu-oil (A. montana) trees of any size in the state,
insofar as the authors know, and only three affected with french-
ing, experiments with this species are necessarily limited. How-
ever, some experiments confirming the results obtained with
A. fordi have been made with these trees which are located
near Seffner in Hillsborough County on Norfolk fine sand.
These trees grew off very rapidly from seed their first year
(1935) and the following year made remarkably rapid growth,
but became affected with mild frenching in the summer. All
the trees have received annual applications of zinc sulfate and
have never evidenced bronzing symptoms as yet.
The symptoms of frenching as they appear on A. montana
are quite similar to those of A. fordi in most respects (compare
Figs. 8 and 9 with Figs. 1 and 2).

Fig, 8.-Immature mu-oil leaves (A. montana) showing typical steps in the develop-
ment of wrenching symptoms. Left to right: (1) first traces of partial chlorosis on young
leaf, and (2, 3, 4) successive stages in its development on immature leaves.

Florida Agricultural Experiment Station

In August, 1936, one of the trees received an application
of 1/2 pound of manganese sulfate while the other two trees
were not treated. In the spring of 1937 a slight response was
noted from the soil treatment and the untreated trees became
very severely affected with frenching. In March, 1937, an
additional 5 pounds of the same material was applied to the

Fig. 9.-Mature mu-oil leaves (A. montana) showing progressive stages in the develop-
ment of necrosis. Note the small dark necrotic (dead) spots prevalent in chlorotic areas
of the left leaf. The right leaf is affected with an advanced stage of necrosis.

treated tree. Within three months after the second soil treat-
ment the tree made a striking recovery from the chlorotic
condition (see Fig. 6). When recently inspected (August,
1937) the tree showed almost complete recovery as indicated
by the absence of chlorotic foliage. No toxic effects have been
noted to date from this soil treatment.
In June, 1937, four severely frenched shoots on the trees
receiving no soil treatment were dipped in a manganese sulfate
solution made with a C.P. grade of manganese sulfate and dis-
tilled water in a Pyrex glass jar. Corresponding control shoots
were selected and tagged. Within four weeks complete recovery
was noted on most leaves of the treated shoots. It is of interest
to note that in this case leaves affected with advanced stages
of frenching (Fig. 9) did not respond completely, while less
severely affected leaves responded well.

A Preliminary Report on Frenching of Tung Trees

The experimental work herein reported is somewhat limited
in scope. The primary purpose of this bulletin is to identify
and describe the physiological trouble designated as frenching
found affecting two species of tung trees and point out that
it responds to manganese treatment.
Much additional experimental work is needed to formulate
a sound program for the control of this disorder if it be a
serious menace to the future development of the tung industry.
To this end there is need to determine to what extent this
physiological disorder, as evidenced by frenching symptoms,
affects the growth, production and oil quality of tung trees.
Although a preliminary survey made in the spring of 1937
indicates that only a small percentage of the trees in commercial
tung plantings are affected with this disorder, it has been the
observation of the authors that its prevalence has apparently
been increasing somewhat in the past few years. However,
the apparent increase in the prevalence of frenching may be
coincident, to a considerable extent, at least, with the general
decrease in bronzing in the past few years as effected by the
widespread use of zinc sulfate. It is possible that bronzing,
occurring simultaneously with frenching, may have modified
and thus obscured typical frenching symptoms as they are now
recognized, hence the increase noted may be apparent rather
than real.
Since the basic work of Bertrand (1) and Richard (9), much
evidence has been accumulated by numerous workers which
indicates that manganese is an essential element for the normal
growth of green plants. Manganese materials have found
rather widespread use as fertilizer supplements in the control
of certain physiological disorders of agricultural crops within
recent years. Schreiner and Dawson (10) were the first to
report resp-nse from manganese on crops growing on calcareous
soils in Florida. Related literature of several other Florida
workers (11, 12, 13) already has been briefly reviewed.
It may be readily seen that the use of manganese in Florida
agriculture is not new and its value is not to be questioned.
However, just what physiological role this metallic salt plays
in the correction of certain disorders is a controversial matter.
The majority of the experimental work in Florida favors the
theory that disorders susceptible to manganese treatment are
caused by an actual deficiency of manganese in the basic nutri-

Florida Agricultural Experiment Station

tion of the plant, assuming the fairly well established theory
be true that manganese is essential for the normal growth of
green plants. The manganese deficiency, in turn, is caused
either by a lack of sufficient available manganese in the soil.
as is the case in overiimed or calcareous soils, or an actual dearth
of manganese in any form in the soil. The experimental work
with frenching of tung trees in no way conflicts with this
theory. However, the recent work of Gerretsen (3) has pointed
out that the possibility should not be overlooked that true man-
ganese deficiency symptoms may be modified, and the undesirable
effects on plant growth intensified, by the entrance of secondary
soil micro-organisms when the manganese content of plant
tissues falls below a certain level.
The relation of soil reaction and exchangeable manganese
content of the tung soils examined to the occurrence of french-
ing suggests the hypothesis that many of these soils are very
low in native manganese from the standpoint of tung require-
ments. Frequently the availability of this scant native supply
is greatly reduced by an unfavorable soil reaction. In certain
instances it is possible that the natural supply of this element
has been largely depleted by prolonged cropping, leaching, or
other forces associated with the cultivation of land; hence a
deficiency occurs even on soils of more favorable reaction. Sev-
eral tung plantings evidencing severe frenching have been
observed on fairly acid soil of old cotton plantation land which
previously had been intensively cropped for a long period of
years. Further, plantings located on new land of the same type
appear to be comparatively free of this disorder as a rule.

A type of partial chlorosis and necrosis affecting tung foliage
is described. The name "frenching" is suggested.
The observations made on a preliminary survey conducted
in the spring of 1937 indicate that between 5 and 10 percent
of tung trees in commercial plantings evidence frenching symp-
toms in some degree.
Data are presented which indicate strongly that control can
be effected by treatment with manganese sulfate.
In view of the fact that experiments with soil treatments
are as yet limited, no definite recommendations for control
measures are made. However, tentative suggestions for treat-
ment in an experimental way are outlined.

A Preliminary Report on. Frenching of Tngy Trees

Toxic symptoms probably produced by excessive quantities
of soluble manganese in the soil are described.
Certain data are presented which indicate that frenching of
tung trees is not confined to any particular soil series or narrow
range of soil reaction, but is correlated with the exchangeable
manganese content of the soil.

1. BERTRAND, G. Sur l'action oxydante des sels manganeux et sur la
constitution chimique des oxydases. Compt. Rend. Acad. Sci. Paris
124: 1355-1358. 1897.
2. GARDNER, H. A. Report of progress on cultural work on tung-oil
groves. Nat'l. Paint. Varnish and Lacquer Assoc. Inc.. Sci. Section
Cir. 241. 1925.
3. GERRETSEN, F. C. Manganese deficiency of oats and its relation to
soil bacteria. Annals of Botany 1: 207. 1937. New Series.
1. HOPKINS, E. F. Manganese an essential element for green plants.
Cornell University Agr. Exp. Sta. Memoir 151. 1934.
5. MANN, H. B. Availability of manganese and iron as affected by
applications of calcium and magnesium carbonates to the soil. Soil
Sci. 30: 117-141. 1930.
(. MowRY, HAROLD. Propagation, planting and fertilizing tests with
tung-oil trees. Univ. of Fla. Agr. Exp. Sta. Ann. Rept. 91-95. 1933.
7. MOWRY, HAROLD, and A. F. CAMP. A preliminary report on zinc
sulfate as a corrective for bronzing of tung trees. Univ. of Fla.
Agr. Exp. Sta. Bul. 273. 1934.
8. NEWELL, W., H. MOWRY, R. M. BARNETTE; revised by A. F. CAMP
and R. D. DICKEY. The tung-oil tree. Univ. of Fla. Agr. Exp.
Sta. Bul. 280. 1935.
9. RICHARD, P. Contribution a le recherche due manganese dans les
mineraux, les vegetaux et les animaux. Compt. Rend. Acad. Sci.
Paris 126: 1882-85. 1898.
10. SCHREINER, 0., and P. R. DAWSON. Manganese deficiency in soils and
fertilizers. Jour. Ind. Eng. Chem. 19: 400-404. 1927.
11. SKINNER, J. J., and R. W. RUPRECHT. Fertilizer experiments with
truck crops. Univ. of Fla. Agr. Exp. Sta. Bul. 218. 1930.
12. SKINNER, J. J., G. M. BAHRT and A. E. HUGHES. Influence of fertilizer
and soil amendments on citrus trees, fruit production and quality
of fruit. Proc. Fla. State Hort. Soc. 47: 9-20. 1934.
13. TOWNSEND, G. R., and H. H. WEDGEWORTH. A manganese deficiency
affecting beans. Univ. of Fla. Agr. Exp. Sta. Bul. 300. 1936.
14. WILLARD, H. H., and L. H. GREATHOUSE. The colorimetric determina-
tion of manganese by oxidation with periodate. Jour. Amer. Chem.
Soc. 39: 2366. 1917.

Florida Leads

In Tung Development

From the wilds of interior China in 1905 the United
States Department of Agriculture brought seeds of
the tung tree for trial plantings in extreme Southern
states, from California to Florida. In 1912 some seeds
were planted on the grounds of the Florida Agricul-
tural Experiment Station in Gainesville. They thrived,
proving well adapted to soils and climate of the area.
In the early 1920s interest in the crop grew and com-
mercial plantings in Florida were made. Under proper
soil and climatic conditions, given proper attention,
these plantings succeeded. Interest spread to other
areas and states. Now more than 100,000 acres are
growing tung trees in Gulf coast states from Florida
to Texas.

The Florida Experiment Station
Showed the Way
In tung planting and culture (Bulletin 280)
In prolific and cluster types (Bulletin 247-Out
of Print)
In bronzing treatment with zinc sulfate (Bulletin
and now
In frenching treatments with manganese materials
(Bulletin 318)
Florida growers of tung are invited to submit their
problems to Experiment Station workers for counsel
and suggestions.

University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs