Front Cover
 Title Page
 Table of Contents
 Letter of transmittal
 Board of control and station...

Group Title: Florida Agricultural Experiment station, report for the fiscal year ending June 30th.
Title: Report for the fiscal year ending June 30th
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00005173/00019
 Material Information
Title: Report for the fiscal year ending June 30th
Physical Description: 40 v. : ill. ; 23 cm.
Language: English
Creator: University of Florida -- Agricultural Experiment Station
Publisher: University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1920
Copyright Date: 1905
Frequency: annual
Subject: Agriculture -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
Statement of Responsibility: Florida Agricultural Experiment Station.
Dates or Sequential Designation: 1905-1930.
 Record Information
Bibliographic ID: UF00005173
Volume ID: VID00019
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - AMF8112
oclc - 12029638
alephbibnum - 002452807
 Related Items
Preceded by: Report for financial year ending June 30th
Succeeded by: Annual report for the fiscal year ending June 30th ...

Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Title Page
        Page 1
    Table of Contents
        Page 2
    Letter of transmittal
        Page 3
    Board of control and station staff
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
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        Page 40
        Page 41
        Page 42
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ENDING JUNE 30, 1920

With Bulletins 154-157 and
Press Bulletins 312-318

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LETTER OF TRANSMITTAL TO GOVERNOR OF FLORIDA.................................... 3R
REPORT OF DIRECTOR ..........-.. .... ;- ---,.... ..... -. ........................ 5R
Introduction, 5R; Animal Industry, 5R; Entomological Studies,
6R; Chemistry, 7R; Plant Pathological Work, 7R; Avocado
Diseases, 7R; Vegetable Diseases, 8R; Changes in Station Staff,
9R; Publications, 9R.
REPORT OF AUDITOR ...---..... ...-- ...... ............... ..... .............. .- ............... 11R
REPORT OF ANIMAL INDUSTRIALIST................................... ............................ 12R
Dairy Herd, 12R; Pig Feeding Experiments, 13R; Taking Samples
of Fat From Live Hogs, 15R; Bahia Grass, 16R; Sweet Potato
Fertilizer Experiment, 18R; Japanese Cane, 19R.
REPORT OF THE .ENTOMOLOGIST ....:.....-....;-....; ... -:-............ 20R
The Camphor Thrips, 20R; Other Thrips, 20R; The Velvet Bean
Caterpillar and 'the' Winter Weather it~-R ; Ndmatodes, 24R;
Cyanamid, 24R; Sodium Cyanide-Anmnonium Sulphate Treatment,
24R; Sulphur and Nematodes, 25R; The Summer Fallow,
25R; Cultivated Cowpeas and Velvet Beans, 25R; Whitefly Eat-
ing Delphastus, 26R; Some Insects of the Year, 26R; The Insects
of Pigeon Peas, 27R.
REPORT OF THE PLANT PATHOLOGIST................................... ........ .......... 29R
Citrus Diseases, 29R; Avocado Diseases, 30R;, Experiment to
Control Avocado Scab, 37R.
REPORT OF TRUCK PATHOLOIGIST .................. ......... ............................ 40R
Brown Rot of'Irish Potatoes, 40R; Control of Damping Off in
Seedbeds, 41R; Tomato Fruit Buckeye Rot, 41R; Pineapple Wilt,
42R; Other Truck Crop Diseases. 44R.

Hon. Sidney J. Catts,
Governor of Florida,
Tallahassee, Florida.
SIR: I have the honor to transmit herewith the annual report
of the director of the University of Florida Agricultural Experi-
ment Station for the fiscal year. ending June 30, 1920.
Chairman, Board of Control


J. B. HODGES, Chairman..-........................-......---Lake City
E. L. WARTMANN-....---... --..............--.....----Citra
J. B. SUTTON,----..............---.............-...-----Tampa
W. W. FLOURNOY,...... -------................................ --DeFuniak Springs
J. T. DIAMOND, Secretary.......-.................... Tallahassee
J. G. KELLUM, Auditor-..............-.......-..-- .... Tallahassee


P. H. ROLFS, M.S., Director
J. M. SCOTT, B.S., Animal Industrialist and Vice Director
B. F. FLOYD, A.M., Plant Physiologist
J. R. WATSON, M.A., Entomologist
H. E. STEVENS, M.S., Plant Pathologist
C. D. SHERBAKOFF, Ph.D., Associate Plant Pathologist
S. E. COLLISION, M.S., Chemist
S. L. VINSON, Editor
T. VAN HYNING, Librarian
K. H. GRAHAM, Auditor
G. UMLAUF, Assistant Horticulturist
E. G. SHAW, Secretary
RUBY NEWHALL, Bulletin and Mailing Clerk
A. W. LELAND, Farm Foreman

Report For The Fiscal Year

Ending June 30, 1920

Hon. J. B. Hodges,
Chairman, Board of Control.
SIR: I have the honor to transmit herewith my report on the
work and condition of the University of Florida Agricultural
Experiment Station for the fiscal year ending June 30, 1920;
and I request that you transmit the same, in accordance with the
law, to His Excellency, the Governor of Florida.

The work of the Florida Experiment Station during the fiscal
year ending June 30, 1920, was fairly satisfactory.
The work of the various departments was along the lines indi-
cated in the preceding report. No new projects were started
during the year, but Project 1 in Chemistry was completed.

The work of this department has been a continuation of that
described in previous reports. Special attention has been given
to the effects of certain feeds on the production of hard and
soft pork. Soft pork is one of the big problems in pork produc-
tion in the Southern states. The Florida Experiment Station
has been doing what it could to help solve the problem. During
the year three feeding experiments were conducted, the main
object of which was to study the effects of certain feeds in pro-
ducing hard and soft pork.
A new method of studying the problem has been devised and
,tried out by the Department of Animal Industry and found
practical. This method is that of taking samples of fat from
live hogs and determining their melting point. This method

Florida Agricultural Experiment Station

gives the greatest evidence of the possibility of solving the soft
pork problem. The samples of fat were taken from the posterior
part of the ham. An incision, about two inches long was made
and a piece of fat about the size of a large pecan taken out.
No muscular tissue 'was removed.- On. page 15R of this report
will be found a detailed report of the results of the first experi-
ment conducted in taking samples of fat from live hogs.
Grass and forage crops have also received attention. Farmers
and stockmen in general are now taking an active interest in
grass and forage crop work. Much of the correspondence that
comes to the. Experiment Station asks for information about
grass and forage crops. During, the last few years the Experi-
ment Station has tested out a large number of new grasses and
forage crops. Among the grasses none has given more promise
than Bahia grass, Paspalum notatum.
This year's work in fertilizing sweet potatoes completed a
five-year series of experiments along this line. The data were
quite similar to that obtained in previous years, except that for
yield of all plots, which were below the average. The one strik-
ing feature in this experiment during this time has been the
consistently low yield from the plots which received no potash.
The work of the entomologist during the year was devoted
largely to three projects.
Work on the velvet-bean caterpillar has been continued, and
included a rather close study as to how the winter temperature
affected the time of appearance and also the abundance of the
insect the following season. It was found that low winter tem-
peratures resulted in killing the host plants; in this way the
insects were starved out and the severity of their attack the
following season materially reduced. Low temperatures did
not destroy the caterpillars to any great extent.
The nematode work was continued along the same lines, as
in previous years. During this year. it was impossible to get
fresh cyanamid, and the results of using the old material con-
firmed previous experiments that cyanamid is unsafe unless
perfectly fresh. Old material causes severe burning to plants
in the seedbed. On the other hand, when fresh material is used
burning is not so severe. When sodium cyanide and ammonium
sulphate.were applied to the soil at the same time, better results

Annual Report, 1920

were. obtained than when applied successively. Sulphur was
tried but was found to be of no value in reducing nematodes
in the soil.
Summer fallowing was again tried and confirmed results of
previous years which indicate that this method is effective in
reducing the damage caused by the nematodes. However, there
are some connecting, features that cannot be ,recommended.
Where summer fallowing is practiced it is found that the. soil
loses fertility rapidly. To overcome this bad feature some plant-
ings of velvet beans and of Iron and Brabham cowpeas were
made. Special care was taken in the cultivation of these crops
to keep out all grass and weeds so that .there would be no host
plants for the nematodes. The effects on the nematodes seemed
to compare favorably with those obtained from simple summer
fallowing. This seems a promising lead and future tests will
be made to ascertain its value.

The work of the Department of Chemistry has been continued
along the same lines as in the past. The experimental work done
in the grove at Tavares was completed during the year, this be-
ing the tenth year since the grove was planted out. During these
10 years the department has had access to-the grove and the
work has been carried out in all details as originally planned.
The results of these experiments are given in Bulletin 154.

The work of the Department of Plant Pathology during the
year was confined chiefly to investigating diseases of avocados
and of vegetables.

Of late years much interest has been taken in avocados and
a considerable area in southern Florida has been planted to
them. The disease commonly called black spot by the avocado
grower was given special consideration. This is a spotting that
appears on the, fruit at almost any period from the time it is
one-third grown until it is mature. During the summer a large
number of inoculations were made with pure cultures of Cercos-
pora. The final examination of the fruits showed that 80 per-

8R Florida Agricultural Experiment Station

cent of the inoculations were developing typical blotch spots.
Therefore, it seems quite certain at this time that a fungus of the
Cercospora type is the cause of the spotting which has previ-
ously been described as avocado blotch.
Experiments to control this disease have also been in progress.
Some trees were sprayed with Bordeaux mixture, 4-4-50 form-
ula, some with lime-sulphur solution, 1 to 40 formula, and some
with ammoniacal solution of copper carbonate. The best results
were obtained when one or two additional sprayings were ap-
plied at monthly intervals about the time of blooming. In fact,
two applications of Bordeaux mixture proved very effective
in keeping the disease under control. The 3-3-50 Bordeaux
formula, or its equivalent, was used in the first two spraying
operations, and the 4-4-50 in the last.
Avocado scab was also studied, the object being to determine
the time and number of sprayings with Bordeaux necessary
to control this disease. The first application was made in the
latter part of the blooming period and was followed by four ad-
ditional applications at monthly intervals. The 3-3-50 Bordeaux,
used in this way, gave the following results: Unsprayed trees
showed 92 percent of scab-infected fruit; trees sprayed one
time showed 63 percent; and trees sprayed three or four times
showed only 4 to 6 percent. However, to be effective the first
spraying must be done when the trees are in bloom.


The vegetable diseases studied were potato blight, control of
damping-off in celery seedbeds, buckeye rot of tomatoes, and
pineapple wilt.
In the study of potato blight work Was started to find varieties
that were resistant to the disease. Six varieties of potatoes were
used. These were planted in a field that was known to be infested
with the blight. None of the varieties proved resistant.
To control damping off in the seedbed, celery seedlings were
treated with a 1/2 percent solution of copper sulphate. The treat-
ment was applied at different times during the day. In some
cases the seedlings were watered after applying the copper sul-
phate solution. It was found that if this solution is applied dur-
ing the hot and dry part of the day or is left on the seedlings for
Stood long a time without being washed off, there will be more or

Annual Report, 1920

less burning. If it is applied in the evening and the seedlings
then sprinkled with water, there will be little or no burning.
The work on buckeye rot of tomato fruit was mainly a com-
parative study of the fungus causing buckeye rot and other close-
ly related fungi.
Considerable work was done in studying pineapple wilt. An
extensive experiment consisting of 96 plots, was utilized in this
study. Plots 1 to 49 were used to test certain fertilizers as to
their effect on wilt. Plots 50 to 74 were used for determining
the effect of slip fumigation with hydrocyanic acid gas, before
planting, and of dipping slips in Bordeaux mixture, before plant-
ing, and for a selection test of slips grown locally and those re-
cently imported from Cuba. Plots 75 to 82 were for studying
clean fallowing and its effect on root-knot in the soil. Another
set of plots were for determining the cause and nature of wilt.

There were a few changes in the staff during the year.
E. G. Shaw resigned as secretary October 1, 1919, and was
succeeded on the same date by Ruby Newhall, who previously
was maling and bulletin clerk.
Miss Newhall was succeeded immediately as mailing and bulle-
tin clerk by Mary E. Roux.
November 15, 1919, B. F. Floyd resigned as plant physiologist.
March 1, 1921, S. E. Collison resigned as chemist.
May 1, 1920, R. W. Ruprecht was appointed physiological
chemist, a position created by combining the Departments of
Plant Physiology and Chemistry.
May 8, 1920, S. L. Vinson resigned as editor.
Following is a list of the publications issued by the Experiment
Station during the fiscal year ending June 30, 1920:
Bulletin Title Edition Pages Total
Number Pages
154 Citrus Fertilizer Experiments....15,000 48 720,000
155 Prussic Acid in Sorghum .....--..13,000 8 104,000
156 Sweet Potato Fertilizer Experi-
ments -........---......-. ........-.--.. 10,000 8 80,000
157 Soft Pork Studies---...--....--...-..--.. 10,000 12 120,000

48,000 76 1,024,000

Florida Agricultural Experiment Station

No.- 154; Citrus Fertilizer Experiments: (S. E.' Colison), pp.
48, figs. 11; 'Results of a' 10-year fertilizer experiment with cit-
rus trees.
No. 155, Prussic Acid in Sorghum: (S. E. Collison), pp. 8,
figs. none. Results of the analyses of different varieties of sor-
ghum grown on the Ekperiment Station grounds.
No. 156, Sweet Potato Fertilizer Experiment-: '(John M.
Scott), pp. 7, figs. 1.' Discusses use of different combinations
of fertilizers for sweet potatoes, and the results of five years'
No.'157, Soft Pork Studies: (John M. Scott), pp. 10, figs.
none. Preliminary report of experiments to determine the ef-
fect of certain feeds on the melting point of fat in hogs.
No. Title Author
312 Care and Maintenance of the Bermuda
Grass Pasture ............................-------------J. B. Thompson
313 Bermuda Grass and Its Varieties..-.............J. B. Thompson
314 Starting the Bermuda Pasture---...--.........-... .B. Thompson
315 Controlling Poultry Lice -..--.....-...-------............ J. R. Watson
316 Eggplant Diseases and Their Control........C. D. Sherbakoff
317 Bulletin List
318 Bulletin List


, Annual Report, 1920

P. H. Rolfs, Director.

SIR: I respectfully submit the following report of the credits
received and expenditures vouchered out of funds as specified
during the fiscal year ending June 30, 1920.


SBalance Receipts
Adams Fund ..................................... ................ $15,000.00
Hatch Fund .....-............-...........-.......... .............-.. 15,000.00
State Appropriation ...-...............-........ $911.13 5,000.00
Sales Fund ...................................-..... 980.28 5,822.39
Winter Haven Sub.-Exp. Sta............. ................ 4,100.00

$1,891.41 $44,922.39


Salaries .......................-.......-................ $8,330.00
Labor ................--......... ....... ....-......... 1,759.49
Publications ......................................... 1,297.85
Postage and stationery........................ 828.00
Freight and express-................-........... 102.29
Heat, light, water, power---............... 280.08
Chemicals and laboratory supplies 13.23
Seed, plants, sundry supplies..........---. 151.59
Fertilizers ................................. -----....... 9.31
Feeding stuffs ................................... 1,343.40
Library ....----................................-------- 453.93
Tools, machinery and appliances...... 126.59'
Furniture and fixtures----.... --.................. 41.40
Scientific apparatus and specimens 1.75
Livestock ..................................... ..............
Traveling expenses ............................ 121.94
Contingent expenses ......................... -20.00
Buildings and land---..........................----.. 119.15
Balance............................... ...... .........----







$ 435.00



Florida Agricultural Experiment Station

P. H. Rolfs, Director.
SIR: I submit the following report of the Department of Ani-
mal Industry for the fiscal year ending June 30, 1920.
Animal Industrialist.

There have been some sales from the herd and also some addi-
tions by purchase of new animals this year. The heifer calves
from the best cows in the herd were retained. The others were
disposed of when dropped. The old Jersey bull, Prince Landseer
Tormentor No. 130,913, was sold to G. B. Massey of Dade City.
Some of the most unprofitable cows were butchered. The Jer-
sey bull, Florida Lasifoso No. 181522, was purchased from Fair-
view Farms, Atlanta, Georgia. Florida Lasifoso No. 181522 was
sired by Lass 64th's Son No. 106612, he by Pogis 99th of Hood
farm No. 94502. The dam of this young bull is Victorious But-
tercup No. 279264. In the Register of Merit, Class AA, she pro-
duced in one year 10,730.9 pounds of milk and 681.47 pounds
of 85 percent butter. This is an exceptionally well bred bull.
A Holstein-Friesian bull was purchased from J. C. DeBeVoise,
Jacksonville. This bull is known as Burke Neptune Korndyke
No. 304599. He was sired by King Veenan Mutual Burke No.
231603, H.-F. H. B., and out of Lilith Pontiac Neptune Korn-
dyke No. 452154, H.-F. H. B. Four high grade Holstein-Friesian
heifer calves were purchased from a breeder in Wisconsin. The
Holstein bull and the four grade heifers will be the foundation
for a grade herd of Holsteins.
No feeding experiments have been conducted with the herd
during the year.
The following table gives the amount of milk produced by
each cow in the herd and the number of days in milk during
the year:


Annual Report, 1920

MILK FOR THE YEAR, JULY 1, 1919, TO JUNE 30, 1920.

"o 4

U04 0
l i i ^ P-4






Three pig-feeding experiments were conducted during the
year. The main object in these experiments was to study the
effect certain feeds had on producing hard or soft pork.
The first experiment was started August 26, 1919, and closed
January 3, 1920. Sixteen pigs were used 'in this experiment.
These were divided into four lots of four pigs each.'
The pigs of Lot I were fed ground corn only. '
The pigs of Lot II were fed ground corn and tankage in the
proportion of 10 to 1, in a self-feeder .' :.. :


, . _

Florida Agricultural Experiment Station

The pigs of Lot' II were fed ground corn, 2 parts, and pea-
nut meal without:hulls, i part (by weight).
The pigs of Lot IV were fed ground corn and peanut meal
without hulls, equal parts by weight.
Each lot-was weighed on three consecutive days and the aver-
age of the three taken. The following table gives the weights
and gains in detail:

I Lot I I Lot II ILot IIIILot IV
Weight at beginning, Aug. 26, 1919................ 360.0 395.0 358.3 401.6
Weight at end, Jan. 3, 1920........................... 662.1 1097.0 793.2 870.4
Total gain in 130 days................................ 302.1 702.0 434.9 468.8
Average daily gain ........-------....... --.. -------: .581 1.35 .837 .902
Pounds of feed to make 100 pounds of gain 730.0 429.0 512.0 586.0

At the close of the experiment the hogs were shipped to a
Jacksonville broker. All were ear-marked so they could be iden-
tified in the cooler, where they were placed for 48 hours after
being slaughtered. The carcasses were then examined with the
following results:
Of Lot I, fed ground corn only, two carcasses chilled hard
and one remained soft.
Of Lot II, fed ground corn and tankage, 10 to 1, all carcasses
chilled .hard.
Of Lot III, fed ground corn, 2 parts, and peanut meal with-
out hulls, 1 part by weight, all carcasses were soft.
Of Lot IV, fed ground corn and peanut meal, equal parts by
weight, two carcasses chilled hard and two soft.
These results, so far as throwing light on hard pork produc-
tion, are rather confusing.
Another lot of four hogs was fed on. corn.and peanut meal,
equal parts by weight, and a little skimmilk. The feeding
period wasfrom June.15, 1919, to January 3, 1920. In this lot
three carcasses chilled hard and one soft..
These results are very similar to those obtained here in the
*past. Or, in otherwords, no definite results have been obtained
from comparing feeds for the production of hard and soft pork.


* Annual Report, 1920

It was believed that the only satisfactory way to determine the
effects of feed was to find out before starting the feeding ex-
periment whether the fat of the animals was hard or soft.
Taking a sample of fat from a live hog and determining its
melting point was a new venture, but there seemed no other
way of solving the problem.
On January 21, 1920, with the assistance of A. L. Shealy,
professor of veterinary science, College of Agriculture, Univer-
sity of Florida, samples of fat were secured from three Berk-
shire sows. An incision about two inches long was made in the
posterior part of the ham, and a piece of fat taken out. No
muscular tissue was taken with the fat sample. In sewing up
the incision two stitches were usually taken. The parts were
thoroly disinfected before and- after the operation. Much to
our surprise we found that taking fat samples did not interfere
with the animals making normal gains in weight during the
The accompanying illustration (fig. 1) shows how the opera-
tion is performed.

Fig. 1.-Taking a sample of fat from a live hog.


Florida Agricultural Experiment Station

The fat samples obtained were rendered at 1100 C. and the
melting point of the fat determined.
A number of the samples were taken during the month of
February, 1920.
On March 8, 1920, a feeding experiment was started, the ob-
ject being to make a study of how certain feeds affect the melt-
ing point of fat.
Nine shoats about 11 months old at the start, were selected
for the experiment, six being barrows and three sows. Fat
samples from each of these animals were taken and the melting
points determined. Two barrows and one sow were placed in
each lot. Each pig was earmarked, and given an identifying
number. A record of the individual weights and gains was kept.
The results of this experiment give information on two or
three phases of the work, about which little was previously
First, there is a marked difference in the melting point of
fat of hogs when fed on the same feed. Second, the feeding of
peanuts lowers the melting point of the fat. Third, the feeding
of corn, shorts and cottonseed meal or corn, shorts, peanut meal
and skimmmilk raised the melting point of the fat.
For detailed results of this experiment see Bulletin 157 of this

Bahia grass, Paspalum notatum, originated in South America.
It was introduced into the United States in 1913 by the Bureau
of Plant Industry under Seed Plant Introduction No. 35067.
Bahia grass was first planted at the Experiment Station in
May, 1913, and from the first it gave promise of being valuable.
On March 31, 1915, a plot was planted in the Station pasture.
The ground was plowed and a good seedbed prepared. Plants
were taken from the original bed and set out 24 inches apart
in 24-inch rows. Two 200-foot rows were planted. The plot
was fenced to keep off stock. The grass made good growth the
first sumhiner and produced a good crop of seed. Late in Sep-
temiber, 1915, the fence was removed and cattle have pastured
on it constantly since that time and this pasturing has been heavy
during the last five years. However, the grass has continued to


Annual Report, 1920

grow and has made a complete sod from 10 to 12 feet wide (see
fig. 2).

Fig. 2.-Plot of Bahia grass in pasture.

In addition to this a number of plants have sprung up adja-
cent to the planting, indicating that the seed have been scattered
by cattle, birds, wind, etc.
This is, we believe, a new method of testing a grass for its
value as a pasture plant. In addition to being nutritious, a
pasture grass should have good staying qualities. That is, it
must stand hard and close pasturing under all conditions. A
grass that needs to be nursed and coaxed after it is once estab-
lished is not desirable for pasture purposes.
The method here employed gives information on two impor-
tant points; namely, the ability of the grass to spread and make
a good sod while being pastured, and its palatability. The re-
sults of this test show that Bahia grass will spread and make a
complete sod under pasture conditions, and that cattle like it.
Bahia grass seems best adapted to a rather moist soil. This
does not necessarily mean a low, poorly drained soil, but rather
one that holds moisture well. However, it has been grown on

Florida Agricultural Experiment Station

rather dry, sandy soil on the Experiment Station grounds with
fairly satisfactory results. It is not likely to be of any value
when planted on dry, sandy land. Neither is it likely to be a
success when grown on land that is subject to overflow, especi-
ally where the water stands for several days. The original seed
plot and the plot in a pasture are what is ordinarily considered
first-class Florida farm soil.
Bahia grass is rather sensitive to cold. A temperature of 34
to 26 degrees, Fahrenheit, will nearly always kill all of its
green growth. However, the roots are not injured, apparently,
by frost or light freezes. When moisture conditions are favor-
able, growth starts in the spring about the same time as other
perennial grasses.
No commercial seed of this grass is yet available, but efforts
are being made to provide a supply. It seeds freely in Florida
when not pastured. When once established it should not be diffi-
cult to harvest the seed.


The sweet potato fertilizer experiment, as given in the pre-
vious -report, was continued. This. experiment was'-started in
the spring of 1915.

Pounds to the Acre

Kind of Fertilizer > >
0 0 0 0 0 0 0

Dried blood .......................... 112 112 112 112 1 112 112
Sulphate of ammonia-........ ...... ... ...... 72 -..- 72 ...... ..-.
Muriate of potash -------- 84 84...... 84 84 ...... .. ......
Sulphate of potash ........... .... ...... ...... ...... ...... 84 84 84
Acid phosphate .......................... 224 224 224 224 224 224 224
Ground limestone* ............. .. ..... .. .... ... ... ...... 2000
*Applied only in 1915, 1917, and 1919.


The sweet potato fertilizer experiment has been conducted for
five years. This should give some definite information as to
the effect of fertilizers on the yield of sweet potatoes.


Annual Report, 1920

Plot 1915 1916 1917 1918 1919 Five-Yr.
S, Average
I .......................... 245.6 153.6 222.4 113.6 24.0 151.8
II ........................ 221.6 177.6 240.0 161.6 33.6 166.8
III ...................... 99.6 86.4 72.0 60.8 6.4 65.0
IV --..................... 259.6 228.8 294.4 161.6 57.6 200.4
V ....................... 252.0 182.6 276.8 249.6 59.2 204.0
VI ...................... 216.0 128.0 320.0 163.2 40.0 173.4
VII .................... 222.0 203.2 251.2 153.6 99.2 185.8
VIII ................... 269.6 110.4 232.0 153.6 168.0 186.7

It will be seen from the above table that the yields for 1919, in
most cases, were lower than for any previous year. This cannot
be accounted for.
However, Plot III, which has received no potash since the ex-
periment began in 1915, produced the lowest yield. In fact,
this plot has produced the lowest yield every year of the experi-
ment. This shows clearly that potash is very necessary, if a maxi-
mum yield of sweet potatoes is expected.
Plot II, which has received no ammonia, has always, until
1919, produced a satisfactory yield.
The yield of the plots that received complete fertilizers were
about the same as those of other plots.
The addition of ground limestone did not increase the yield of

The Japanese cane fertilizer experiment has been continued
under the same plan as reported in previous reports.

: Pounds to the Acre

Kind of Fertilizers Used ''

Sulphate of ammonia ......... ........ ...... 72 .....- 72 ...
Dried blood ......................... 112 ...... 112 ...... 112 ...... 112 112
Muriate of potash .............. 84 84 ...... 84 84 ...... ..........
Sulphate of potash .............. ...... ..... ...... ...... ...... 84 84 84
Acid phosphate ..................... -- 224 224 224 224 224 224 224
Ground limestone* ........ .... .... .:.... ...... ..... .. ..- 2000
Yield tons green material. 14.8 18.2 .48 14.8 17.7 13.6 10.3 12.0
*Applied only in 1915, 1917, and 1919.

Florida Agricultural Experiment Station

P. H. Rolfs, Director.
SIR: I submit the following report of the Department of En-
tomology for the fiscal year ending June 30, 1920.
J. R. WATSON, Entomologist.

Increasing damage to the camphor plantation at Satsuma and
the invasion of the DuPont plantation at Waller by this insect
led to requests for help. As a result, the entomologist and a
couple of temporary assistants spent considerable time on this
project. The life history of the insect has been thoroly worked
out, as well as its distribution in the state. It seems to be en-
tirely absent in the southeastern part of the state, as a careful
search failed to reveal its presence between Haines City and
Moore Haven or south of Cocoa on the East Coast. Even at
Cocoa the thrips seems to have difficulty in maintaining itself,
at least one infestation there died out spontaneously.

Our studies this year have revealed that the common flower
thrips are composed of two species. In most of the state the
common one is Frankliniella bispinosa (Morgan). Around
Miami a species found to be at least equally common is a hitherto
undescribed variety of F. cephalica (Crawford). It is smaller
than F. bispinosa and yellower, showing less of either brown or
orange. It has been named Var. mason. Its habits and life
history are apparently very similar to F. bispinosa.
The flower thrips did less than the usual amount of damage
to citrus bloom this year. Altho abundant in some localities,
they were as a whole distinctly less numerous than usual. This
was probably due to the unusually heavy rains of winter and
The Western Bean thrips (Heliothrips fasciatus Perg.) was
discovered for the first time in Florida. As it was found on a
wild plant far from any cultivated ground, it is probably a na-
tive insect, but it is scarce.
*Cryptothrips floridensis (Watson).


Annual Report, 1920

This insect again did less damage than usual, tho more than
last year. Their comparative scarcity for the last three years
seems to be due to the severe winters of 1916-17 and 1917-18.
A study of the relation between the abundance of this insect
and the length and the severity of the frosts of the preceding win-
ter is interesting and suggestive and leads to some valuable
As has been pointed out before (Entomological News, Vol.
XXVI, p. 419), this insect is not exterminated by the direct
action of cold in the northern and central parts of Florida, but
is starved out thru the destruction of its food plants by frost ;
it cannot hibernate thru all the winter, and, therefore, emerges
and starves. The moths invariably hatch out during the warm
periods of January. The longest time during which the moths
were observed to remain in the pupa cases was six weeks. As
the moths live only two or three weeks, a period of seven or
eight weeks between the first and the last killing frost-a period
during which there is no food available for the caterpillars-is
sufficient to completely exterminate the insect. This calculation
allows a week after the last frost for the seed of the host plants
to germinate; usually a longer time is required. Eight weeks,
then, is about the maximum length of time that this insect can
live without food. The average length of time required to exter-
minate the species in any given region probably is considerably
One would expect, then, that, following a long winter, i. e.,
one with severe early and late frosts extending far down the
peninsula, the insect would be killed out to a lower latitude
than usual and would be later in returning the following year
and, other factors being equal, would be less numerous than
after a short and mild winter.
A study of the accompanying table and chart of the frosts
in the Gainesville region for the last four years shows that
there has been such a correlation.
The winter of 1916-17 was characterized by an unusually se-
vere freeze during the first week of February. In addition a
killing frost occurred on November 16, and a month later a se-
vere freeze which extended far down the peninsula. The cater-
pillars were not nearly as abundant as usual during the fol-
lowing summer.



November December
Winter Date Min. Date Min.
Temp. Temp.
1916-17 16-31 3-37
17-37 13-30
18-36 14-37
19-35 16-26
20-34 17-30
21-38 19-26









Date Min.




Date Min.



Date Min.



April Abundance the
Date Min. Following Summer


S 6-36

Few Anticarcia

Few Anticarsia


Moths Arrived


Annual Report, 1920

Altho the interval between the first and last killing frosts in
1917-18 was short (35 days), both were severe and extended
far down the peninsula. The caterpillars were scarce during
the summer of 1918.
The winter of 1918-19 was moderately long (94 days be-
tween the first and last frosts), but the interval between se-
vere frosts (26 degrees) was only eight days. The lowest tem-
perature for that winter was 26 degrees. The following sum-
mer the caterpillars were much more numerous than during the
preceding two years, but still were not up to normal.
Last winter the interval between frosts was 84 days, but the
lowest temperature was only 25 degrees (at Gainesville). The
moths arrived in early July and in greater abundance than at
any time for three years.
It would seem that we have in the severity of the preceding
winter a rather definite indication of the probable abundance
of the caterpillars during at least the early part of the follow-
lowing season. After the middle of September "cholera" is
liable to break out among the caterpillars and entirely obliterate
this and all other factors governing the abundance of this in-
sect. But by the middle of September all but the latest varieties
of velvet beans have set a fair crop of pods and the defoliation
by the caterpillars is not such a serious matter.
If we could predict before planting time, with even a fair
degree of certainty, the probable abundance of the caterpillars
during at least the early part of the season, it would be of much
value to our farmers. If the season promises to be one of abun-
dant and early-appearing caterpillars, the beans should be plant-
ed as early as possible, using seed of early-maturing varieties.
A trap crop of later varieties should be planted about the edges
of the fields. Also the fields can be planted in such a way as
to facilitate dusting. On the other hand, if the season promises
to be one of few caterpillars, farmers need not be in such a
hurry to plant in the spring and they can use later-maturing
The study of the parasites and predators of this insect was
continued. The insect parasites continue to be of little impor-
tance but the predators, both birds and insects, and the fungous
parasites are very important checks on multiplication.


Florida Agricultural Experiment Station

The attempts to find the best methods of controlling the root-
knot nematode were continued practically unchanged, and the
results were similar to those of previous years. Results of the
different tests follow:
No freshly made cyanamid was available. That which we
had had for three years caused serious burning when applied
to seedbeds, thus confirming our previous experience that this
material is decidedly unsafe to use unless perfectly fresh.

This still remains our most thoro method of quickly reduc-
ing the number of nematodes in the soil. Trials of weaker
doses have shown that 600 pounds of sodium cyanide and 900
pounds of ammonium sulphate to the acre is about the minimum
dosage which will render a seedbed reasonably free of nema-
In our greenhouse beds this year we observed a cumulative
effect. A bed treated with the above standard dose in Decem-
ber, 1918, was again treated with the same dose in December,
1919. Tomatoes planted in January failed to grow on this
bed. They came up promptly but remained stunted and fin-
ally died. Replants a month later responded in the same man-
ner. It is not likely that plots out in the open, exposed to the
leaching effects of our heavy summer rains, will be injured to
any extent. Trial plots have been started to test out this point,
however. Nevertheless, some of the nitrogen from this treat-
ment remains in the soil of our field plots a long time; plots
treated with the standard amount two years ago still plainly
show the effects of the nitrogen on plant growth.
Some tests were made to determine the effect of delaying the
application of ammonium sulphate. The cyanide was applied
one day and the sulphate the next. There were noticeably more
nematodes on these plots than on those to which the sulphate
was applied the same day.
Tomatoes planted on land previously treated with the standard
dosage remained almost free of nematodes. The growth was
luxuriant and the plants were very dark green in color, but the


Annual Report, 19202

crop was late and not very heavy. This was due doubtless to
a poorly balanced fertilizer, one lacking in phosphates and pot-
ash salts.
Two 1/100-acre plots were treated with finely ground sulphur,
one at the rate of 500 pounds and the other at 1000 pounds to
the acre. There was absolutely no effect on the nematodes, while
the plants grown on the land were seriously affected. They were
stunted but matured early and set a good number of small
The fallowing experiments of previous years were continued
with similar results. Nematodes were markedly reduced in
numbers. The soil was seriously impoverished, however. This
serious defect of this method limits its application. On poor,
light land, particularly, it should be used only as a last resort.
Land so treated must be heavily fertilized before a crop can be
grown on it and a part, at least, of the fertilizer used should
consist of manures so as to restore the depleted bacterial flora
of the soil.

In order to avoid the impoverishing effects of the summer
fallow, tests were started early in 1919 and again in 1920 to
determine the effect of planting cowpeas and velvet beans on the
land, as compared with the summer fallow. Only nematode-re-
sistant varieties of cowpeas, such as Iron and Brabham, were
used. They were planted in rows and cultivated at least once
a week. The plots were kept absolutely free of weeds. The vel-
vet beans were also planted in rows and cultivated until they
had covered the land, after which cultivation was necessarily
Next year the bush velvet bean will be used for this work.
By this means it seems possible to secure the benefits of the
summer fallow; i. e., satisfactory aeration of the soil and a lack
of host plants for the nematodes. At the same time, the severe
leaching and burning, resulting from summer fallow, should
be avoided. More labor will be necessary on plots treated by
this method than on a fallow field, as some hoeing must be done


Florida Agricultural Experiment Station

to eliminate absolutely all weeds and grass. This extra cost, how-
ever, is well repaid thru both the saving of soil fertility and
the value of the crops grown for feed and green manure. The
effects on the nematodes seemed to compare favorably with
those obtained from summer fallow. More tests, however, are
necessary to establish the value of this method.

Colonies of Delphastus were sent out from Bradentown thru-
out the summer of 1919. By September, however, they had re-
duced the whitefly in the groves to such an extent that they them-
selves were dying of starvation. The degree of control was
fully as high as that obtained by ordinary commercial spray-
ing. Part of the grove was sprayed with an oil emulsion in
the fall to control purple scale. This probably hastened the de-
cline in numbers of the Delphastus. I visited that section in
September and found both beetles and whiteflies scarce in the
grove where the beetles were first liberated. The beetles were
found in groves and isolated trees all about Bradentown, some
being miles from the grove where first colonized. As the coun-
ty agent scattered these beetles quite generally thruout the re-
gion it is impossible to say how much of this general spread of
the Delphastus is due to their own flight.
The beetles became quite noticeable in several groves into
which they were carried, including one as far north as Cres-
cent City. As in previous years, however, their numbers
dwindled greatly during the winter. At the present time (June
30) we have not as yet located a grove in which they are suf-
ficiently abundant to make collection and distribution practical.
Arrangements have been made for the introduction from Cal-
ifornia of the parasite that has beep doing good work there
against the citrus mealy bugs.

The fall army worm appeared in destructive numbers in sev-
eral places in July, 1919. About Bartow the summer brood
had become nearly full grown by the middle of that month, near-
ly two weeks earlier than the year before, according to Polk
County Agent Wm. Gomme.
The cottony cushion scale has continued to spread with rather
surprising rapidity in view of the quarantine measures in force.


Annual Report, 1920

It is now quite generally distributed thruout the peninsular
part of the state. During the year it was reported from vari-
ous places from Okeechobee in the south to Jacksonville and
Pablo Beach in the north.
The cabbage aphis was unusually abundant during January.
This was probably due to the unusual rains of December and Jan-
uary. It is well known that cold winter rains favor the increase
of aphids by checking the development of their parasites.
The puss moth was more numerous than usual during spring
and early summer and many complaints were received. A mem-
ber of the State Board of Health reported that "a boy nearly
died from contact with one of these caterpillars. The effect
was similar to the bite of a rattlesnake."
The predaceous bug Euthrynchus floridanus was sent in from
Polk County with the statement that it was destructive to honey
Epicaerus formidulosus was sent in from Leesburg in Novem-
ber with the statement that it had "ruined a crop of English
peas and peppers. They attack the plant about a fourth of an
inch below the surface of the ground." This large gray weevil
is a general feeder, being common on cotton where it is some-
times mistaken for the boll weevil. At times it attacks young
tobacco plants. This is, however, our first record of its feed-
ing underground.
In April, June bugs were sent in from Orlando with the state-
ment that they were defoliating citrus.
October, 1919, was abnormally warm, enabling the pumpkin
bug, Nezara viridula, to continue breeding a month later than
usual. On November 7, 34 adults and 13 nymphs were collected
from a half dozen plants of petsai.
For the same reason corn weevils were unusually destructive
in the fall.
The unusually warm and late fall enabled pigeon peas to
mature at Gainesville, thus affording an opportunity to study
the insect enemies of the plant. Nothing seems to have been
published on the insect enemies of this legume in Florida. Its
most destructive pest is the corn ear-worm, Heliothis obsoleta,
which eats into the pods and consumes the peas much as it does
beans and English peas. Another severe pest is the leaf-footed


28R Florida Agricultural Experiment Station

plant-bug, Leptoglossus phyllopus, which attacks the green pods.
The northern green stink bug, Nezara hilaris, was also quite
common on both pods and stalks. Bumblebees, were common
about the blossoms. They seemed to be the chief agents in cross

Annual Report, 1920

P. H. Rolfs, Director.
SIR: I submit the following report of the Department of
Plant Pathology for the fiscal year ending June 30, 1920, and
the two months following, July and August, 1920.
H. E. STEVENS, Plant Pathologist.

The work of the pathologist during the time covered by this
report has been confined chiefly to investigating avocado dis-
eases. Very little attention has been given to citrus disease in-
vestigations, other than field observations from time to time.
The lack of efficient laboratory and field help, the shortage
of funds and other facilities, have forced a narrowing down
of the work. Hence, most of the time has been devoted to avo-
cado disease investigations, since it seemed advisable to push
this work as rapidly as possible. The pathologist's. time has
also been drawn on to a very large extent in answering in-
quiries and giving out information concerning diseases of the
various Florida crops.

The work on melanose of citrus fruit during the last few years
has been summarized and published in Bulletin 145 of this Sta-
tion. Investigation of this disease, however, is by no means
complete and there should be further study given to the possi-
bilities of controlling this disease by spraying. A system of
well-planned spraying experiments should be inaugurated for
the control of this disease and should be carried on for several
years in order to determine the proper fungicide to use and the
number of applications necessary.
During the last eight years a considerable amount of study
has been given to gummosis. Various experiments have been
planned and carried thru a number of years. The results of
these investigations are summarized in Bulletin 150. The disease
has been studied on the basis of being due to some parasitic
organism. Our investigations thus far have not proven this to
be true, and indications are that the disease is not parasitic. All
attempts to transfer the disease artificially to healthy citrus trees
have failed and no specific organism has been isolated from
gummosis lesions with sufficient frequency to consider any par-


Florida Agricultural Experiment Station

ticular organism responsible.for the. cause. I think it useless
to continue the investigation of this disease further on the as-
sumption that it is due to some parasitic organism.

During the last two years some study was given to a fruit
spotting of avocados in the southern part of Dade County.
This year a more extensive study of this disease was made in
that county and five weeks, July-14 to August 21, 1919, were
spent at the Redland Laboratory. This was considered the period
when the fruit probably would be more susceptible to the dis-
ease, and it was planned to be in the field to observe the disease
at its beginning and to follow its development thru the season.
The spotting of the fruit was noticeable July 14, as the disease
appeared two or three weeks earlier than it had the season
Two types of fruit spotting have been mentioned in a pre-
vious report and both of these were noticeable on the early ma-
turing fruit. However, the blotch type appeared to be more
prevalent. Colletotrichum spots were observed on the fruit
and fruit stems at this early date. A number of fruits were
kept under observation, the same as last season. Fifty fruits
were tagged and notes made at weekly intervals from July 14 to
August 21. The two distinct types of spots were evident this
season that were noted last. The blotch type and a hard
corky spot, caused by Colletotrichum, will be referred to as
"black spot" in the future. Black spot is the name commonly
given to this disease by avocado growers of Redland.
The season's observations indicated that the blotch spots in-
creased rapidly during the period and became more numerous
as the fruit matured. In many cases fruits showing five or
six spots at the beginning of the period of observation showed
that 50 or 75 percent of their surfaces were covered five weeks
later. While blotch spotting is more evident on nearly mature
fruit, it may develop on that which is only half mature, Se-
vere attacks of younger fruit usually stunt or arrest its devel-
opment. Black spot frequently follows in the areas affected
by blotch. During this period of observation a white fungous
growth, fuzzy in appearance, was noted on the surface of the
younger blotch spots, which was found to be tufts of Cerco-
spora spores. These Cercospora spores generally appear a week


Annual Report, 1920

or 10 days after the blotch area becomes visible, forming a white,
erect covering on the surface, which may be seen with the naked
eye. In two or three days this white growth changes to a
brownish color that is not easily detected from the normal color
of the blotch surface. The growth is no longer erect but flattened
Cultures were made in cornmeal agar from Cercospora spores
taken from the surfaces of the young blotch spots. After planting
the spores, their location was marked and their germination and
growth watched. In from five to seven days colonies developed
in this plate typical of those produced by the dark fungus, pre-
viously isolated from the interior tissue of blotch spots and
which has formerly been designated as "Dark Fungus." .The
mycelium and growth characteristics of the colonies resulting.
from these spores appear to be identical in every respect to the
dark fungus of previous isolations. This was the first indica-
tion as to the probable identity of the dark fungus.

Cultures were made from about 75 spots again this season.
These spots represented both the blotch and black spot types.
Spots were selected in various stages of development and cul-
tures were made by taking small bits of interior tissue after the
surface of the fruit had been thoroly sterilized in bichloride
solution (1 to 1,000). The surfaces of the spots were then cut
away and small bits of the interior tissue were plated in corn-
meal agar. From young beginning blotch spots, Cercospora
was invariably isolated. Occasionally Colletotrichum and Cer-
cospora were associated in the more advanced blotch spots, and
the latter was frequently isolated from typical black spots.
Colletotrichum was also isolated on a number of occasions
from anthracnose lesions on fruit stems.

Three series of inoculations were made at Redland during
July and August, 1919. In the first series were four fruits, all
free from spotting at the time of inoculation. These were large
avocados of a late maturing variety, and the fruits were about
half grown at the time. The inoculations were made on and
in the surface of the fruits, in circular areas outlined with blue
pencil. Ten such areas were marked on each fruit, and numbered


Florida Agricultural Experiment Station

from 1 to 10. The centers of the first five were punctured with
a sterilized needle and the inoculum inserted in these punctures.
In the other five the inoculum was just laid on the surface of
the fruit, near the center of the area; the inoculated areas were
immediately covered with moist sterilized cotton and the fruits
wrapped in waxed paper. Inoculations were made July 24 and
the wrappings were removed five days later.
Fruit designated "A" was used as a check and received the
same treatment as the others, except that no inoculum was
Fruit "B."-This fruit was inoculated with mycelium of the
dark fungus (Cercospora), isolated from the interior tissue of
a blotch spot the previous season.
Fruit "D."-This fruit was inoculated with Cercospora spores
scraped from the surface of blotch spots. Final notes were
taken on these August 20, 1919.
Fruit "A."-Remained free from spotting thruout the period.
The puncture made in the rind soon healed with a slight kill-
ing of the tissue around the edge of the puncture. In Fruit
"B," in the punctured areas, spots suggestive of black spot
were developing, but could not be considered very typical of
black spot.
Fruit "C."-No indications of infection and the punctured
areas healed similar to those on check.
Fruit "D."-No indications of infection. The punctured
areas healed and were similar to the check.
SERIES II.-On July 29, a second series of inoculations were
made into three other fruits on the tree used in the first series.
Ten inoculations and five checks were made in each fruit. In
making the inoculations the skin of the fruit was punctured
and the wound immediately covered with melted paraffin.
Fruit "A."-Inoculated with mycelium of Cercospora from
a single spore strain isolated just a few days previously.
Fruit "B."-Inoculated with Colletotrichum mycelium and
spores. Recent isolations from black spots.
Fruit "C."-Inoculated with Colletotrichum in which five
different strains were used, isolations of a few days previously.
Final notes were taken August 20.
Fruit "A" showed no definite infections at this.date and was
discarded as negative. On Fruits "B" and "C" diseased areas
typical of black spot were developing in many of the inoculated


Annual Report, 1920

punctures. The checks remained free thruout the period, the
wounds soon healing.
SERIES III.-The third series of inoculations were made
August 2 and included two fruits. Ten inoculations and five
checks were made into each. The area of inoculation was out-
lined with a wax pencil and the areas on each fruit numbered
from 1 to 15. The surfaces of the first five were pricked at
several points in the center with a needle. The inoculum was
placed on small sterilized disks of cloth which were applied
to the indicated areas. The inoculated fruits were then wrapped
in waxed paper, and the wrappings allowed to remain for seven
Fruit "A."-Inoculated with spores of Colletotrichum from
different isolations.
Fruit "B."-Inoculated with mycelium of Cercospora from
a single spore colony. Final notes were made August 24.
On this date Fruit "A" showed typical black spot infections
in the pricked areas but no infections developed in the areas
where the surface was not pricked. All the checks on this fruit
remained free. Fruit "B" showed no typical blotch infections
but in some of the punctured areas a slight suggestion of infec-
tion was apparent. The checks remained free and the pricked
places soon healed. This fruit was collected and the suspected
infected areas examined. Cultures from the interior tissue
failed to give Cercospora. No positive results were obtained in
any of the inoculations made with Cercospora (dark fungus)
this season. This organism has been suspected of being the
cause of blotch for sometime past, as it has been repeatedly iso-
lated from spots of this type during this and past seasons.
In June, 1920, another series of inoculations was made to fur-
ther test out this fungus. Mexican avocado fruit on trees in
the novelty orchard of the Station grounds were inoculated.
Ten fruits were included in the series. Four were pricked and
mycelium of the fungus inserted. On the other six fruits
areas were outlined on the surface with a wax pencil and the
mycelium of the fungus placed at the center of these areas. All
punctured areas were immediately covered with moist sterilized
cotton. The fruits were then wrapped in wax paper. In the
majority of cases the fruits were kept wrapped for seven days.
However, three retained their wrappings for nearly a month.
The inoculations were made with pure cultures of Cercospora
isolated a few days previously from the interior tissue of the


Florida Agricultural Experiment Station

blotch type spots. This specimen was collected at Redland.
Mycelium of this fungus from cornmeal agar cultures was used
as an inoculum. This culture was'not over two weeks'old when
the inoculations were made June 30.
The fruits were carefully examined at intervals during July
and August. On July 23 no indication of infection was evident
on any of the inoculated fruits and it was thought that the re-
sults would all be negative. The final examination was made
August 14, and it was found that eight fruits out of the 10
were developing blotch spots. In some cases the spots were
just appearing and in others already formed, producing at the
time the white fuzzy surface growth noted in naturally formed
spots at Redland. Isolations'were made' from some of the spots
resulting from these inoculations, and the fungus obtained from
the interior tissue was identical in growth characteristics with
the one used in the inoculations. Cultures were made from Cercos-
pora spores taken from the surfaces of some of these spots and
these spores produced mycelium and colony growths identical to
those characteristic of the fungus used in inoculating the fruits.
The time required for the development of spots from these inocu-
latiofis was very much greater than, anticipated, probably 35 to
45 days. This 'may explain the repeated negative results ob-
tained in former inoculations with this fungus, for in former ex-
periments observations on the inoculated fruits were not con-
tinued for a greater period than three or four weeks.
The foregoing experiment proves that a fungus of the Cerco-
spora type is the cause of the spotting on avocados, which has
been previously described as avocado blotch. Whether this is
a new or described species of Cercospora the writer has not had
the time to determine. A detailed description of the fungus
will appear later.
During the year ending several experiments for the control
of avocado fruit spotting were tried out at Redland. Results
from the first of these were not very encouraging, but an ex-
periment recently conducted in the same section has given very
promising results. In July and August, 1919, some trees were
sprayed on Geo. Kosel's place for the control of fruit spotting.
These were seedling trees and the fruit had spotted badly on
the trees 'selected in previous seasons. At the beginning of this
experiment spotting was evident on fruits on many of the trees


* Annual Report,-1920

and it was evidently too late at that time to prevent the disease
by the use of fungicides. However, we hoped to- hold the dis-
ease in check until the fruit matured and prevent further spread
of the spotting by spraying at certain intervals thruout this
In one experiment seven trees were selected. Some were
sprayed with Bordeaux mixture, 4-4-50; some with lime-sulphur
solution, 1 in 40; and some with ammoniacal solution of copper
carbonate. Three applications were to be given at intervals of
two weeks. The trees were sprayed with a hand pump
and the work was fairly thoro. The trees were sprayed first
on July 16, second July 30, and third (and last) August 14.
In checking over the experiments it was found that not one of
the sprays was effective in keeping the disease in check. The
ammoniacal solution of copper carbonate seemed to give a shade
better results but not sufficient to warrant its use, this late in
the season. There was no difference in the use of the other
solutions, and even in the case of Bordeaux spots developed after
the third spraying.
Another experiment was tried out about the same time on
a late maturing variety of the avocado in which the ammoniacal
solution of copper carbonate was used. When the first spray-
ing was made the fruit was carefully checked over and no vis-
ible spotting was noted. Two applications of this solution were
applied, the first on July 28 and the second August 11. Half
of the tree was sprayed and half left unsprayed as a check. The
results from this experiment were rather discouraging since a
larger percentage of infected fruits were found on the sprayed
half than on the unsprayed half. It was evident, from the re-
sults of these experiments, that, after the disease was visible
on the fruit, spraying is of little value in keeping the disease in
Later another experiment was planned and carried out thru
the spring and summer of 1920. The object of this experiment
was to determine if monthly spraying would control fruit spot-
ting and the number of applications necessary, using Bordeaux
mixture as a fungicide. Thirty-six trees were selected in Mr.
Kosel's grove at Redland, many of which had been badly affected
in previous seasons by fruit spotting. These were seedling trees
from 15 to 18 years old. The spraying was done with a spray
gun at a pressure of 200 pounds. The trees were divided into
groups as follows and received the indicated treatment:


Florida Agricultural Experiment Station

Group "A," 4 trees, sprayed 4 times during the season, first
in the bloom and at monthly intervals.
Group "B", 4 trees, sprayed 3 times, first in the bloom and at
monthly intervals.
Group "C," 4 trees, sprayed twice, first in the bloom and sec-
ond a month later.
Group "D," 4 trees, sprayed 3 times. In this group the first
spraying was made coincident with the second spraying in
Groups "A," "B," and "C." The other sprayings were applied
at monthly intervals.
Group. "E," 4 trees, sprayed twice, the first the same as in
Group "D," the second a month later.
Group "F," 4 trees, sprayed once, the same as Group "D" the
first time.
Group "G," 4 trees, sprayed twice, first one month after the
first spraying in Group "D," second a month later.
Group "H," 4 trees, sprayed once, first same as Group "H" the
first time.
Group "I," 4 trees, unsprayed, as checks.
The 3-3-50 Bordeaux mixture, or its equivalent, was used in
the first two spraying operations, and 4-4-50 in the last two. The
first spraying was made March 23, spraying during the latter
part of the bloom period and into the open bloom. Subsequent
sprayings were made at intervals of a month. Trees in
Group "A" were sprayed four times during the season, March
23, April 21, May 21, and June 22. In August the fruits
were examined and only 1.6 percent were found infected. This
group contained one tree that had been severely affected last
season with black spot and blotch. Not a single infected fruit
was found on this tree. In Group "B" the trees were sprayed
March 23, April 21 and May 21. Five percent of infected fruits
were found in this group. These probably resulted from fail-
ure to reach the top of the trees with the spray solution. There
were several tall trees in this lot and it was difficult to thoroly
cover the fruits in all the trees.
Group "C" was sprayed March 23 and April 21. Only 1.2 per-
cent of infected fruit was found in this group.
Group "D" was sprayed April 21, May 21, and June 22. Two
and six-tenths percent of the fruits in this group were infected.
Group "E" was sprayed April 21, and May 21. Only 2.6
percent of the fruits in this group were infected.


Annual Report, 1920

Group "F" was sprayed once, April 21. The infected fruits
found in this group were 18.8 percent of the whole.
Group "G" was sprayed May 21 and June 22. In checking
over the fruits in this group 60 percent were found infected.
Group "H" was sprayed once, May 21. Ninety-seven percent
of the fruit were found infected.
The check or unsprayed trees were found to have 84 percent
of infected fruits.
The foregoing results indicate rather conclusively that black
spot and blotch can be controlled by proper spraying, and ap-
parently two applications of Bordeaux mixture is sufficient for
the purpose. This is demonstrated rather strikingly in Group
"E," the disease history of these trees being pretty well known
to the writer.
In former seasons the trees in this group were badly affected
with black spot and this season two applications of Bordeaux
mixture reduced the infected fruits down to 2.6 percent. It
would seem that from the middle to the last of April is the prop-
er time to do the first spraying. This, however, depends largely
on the earliness or lateness of the blooming period. For the
control of fruit spotting it is hardly necessary to spray into the
bloom, and applications of fungicide after the middle of June,
and in July and August, are apparently useless.

Along with the control experiments for fruit spotting an ex-
periment was made for the control of avocado scab. The object
of this experiment was to determine the time and approximate
number of applications of Bordeaux mixture necessary to con-
trol avocado scab, spraying at monthly intervals. Spraying
was commenced in the beginning of the blooming period and con-
tinued until four applications had been made.
A number of trees were selected in the grove of R. E. Gold-
berg, at Redland, and were grouped into seven blocks. These
trees were of the Trapp variety and were between four and five
years of age. They had borne considerable fruit the previous
year and were full of bloom at the time of spraying.
Block 1 was sprayed once, on March 23, Bordeaux mixture
being used and sprayed directly into the bloom.
Block 2 was sprayed into the bloom twice, first on March 23
and again on April 21.


Florida Agricultural Experiment Station

Block 3 was sprayed. into the bloom on March 23, April 21, and
May 21.
Block 4 was sprayed into the, bloom on March 23, April 21,
May 21, and June.22.
Block 5 was sprayed on April 21-after the bloom had
dropped,-May 21, and June 22.
Block 6 was sprayed on April 21-after the bloom had disap-
peared,-and May 21.
Block 7 was sprayed once, on April 21, after ,the bloom had
One block of trees served as a check. on this experiment and
was not sprayed during the season.
In checking over the fruits after the final spraying the effec-
tiveness of Bordeaux mixture in keeping the disease in check
was quite evident. One hundred fruits were examined from each
block and carefully noted for scab infections. The following
percentage of infected fruits were noted in each.block:
Block 1 showed slightscab infections on 25 percent of the
Block 2 showed slight scab infections on 6 percent of the
Block 3 showed 9 percent of scab infections.
Block 4 showed 4 percent of scab infections.
Block 5 showed 9 percent of scab infections.
Block 6 showed 20 percent of scab infections.
Block 7 showed 63 percent of scab infections.
In the block that served as a check, 92 percent of the fruit
were found infected. In this block the surfaces of the fruits
were badly infected. Treesin this block, thru a. mistake were
also sprayed into the bloom. This accounts for the low per-
centage of. scab on the fruits from this block.
For the control.of scab, bloom spraying seems necessary and
probably advisable. There is some objection, however, to spray-
ing into the bloom by the various growers, who fear a loss or
shedding of bloom due to Bordeaux mixture. However, in this
experiment there was no difference noted in the shedding of the
bloom in the sprayed and unsprayed blocks, as the sprayed
seemed to set equally as well as the unsprayed trees. Probably
three sprayings would be necessary to keep the disease in check.
A fourth spraying, if thoroly applied, would give almost per-
fect control.


Annual Report, 1920 39R

These conclusions are drawn from the results of one year's
work, and these experiments should be repeated for another
season or two. However, in several cases theresults are suf-
ficiently conclusive.

Florida Agricultural Experiment Station

P. H. Rolfs, Director.
SIR: I submit the following report for the fiscal year ending
June 30, 1920.
C. D. SHERBAKOFF, Truck Pathologist.

The study of brown rot of Irish potatoes, the disease caused
by Bacterium solanacearum E. F. Sm., which was begun during
the fiscal year 1917-18, has been continued, chiefly to determine
whether or not there is a disease-resistant variety or strain of
Irish potatoes and, if so, to locate it. For this purpose two ex-
periments were conducted, using in one potatoes of the Spauld-
ing Rose variety, selected during the preceding spring for its
resistance to blight (see report of this Station for 1919) ; while
in the other we used several varieties (Early Ohio, Rose No. 4,
Early Rose, Irish Cobbler, and Green Mountain) which were
secured from local markets and thru the courtesy of Wm. Stuart,
of the Bureau of Plant Industry, United States Department of
Fifty-four hill units of Spaulding potatoes were selected dur-
ing the preceding spring and kept in the local ice plant (at a
temperature of about 40 degrees F.) until planting time, March
2, 1920. In planting it was found that some of the units were
more or less distinctly affected with brown rot, and these were
discarded. From each of the remaining 46 units, one large
tuber, cut into four seed pieces, was planted, thus giving four
hills of each. The potatoes were planted in a field that had pro-
duced Irish potatoes and tomatoes during the preceding season
and was pretty generally affected with the blight.
During the harvest, June 3, 1920, every unit of the four hills
was first carefully examined for blight, as shown by the tops;
and each unit which showed any symptom of the disease in any
of the four plants was discarded. Then the remaining units
were separately dug by hand and again examined for external
symptoms of blight on the tubers; the units which showed any
symptoms were discarded. Seventeen units of Spaulding Rose
did not show any symptom of the blight, and were packed sepa-
rately and stored in an ice box at'the Experiment Station to be
planted next spring for further tests.


Annual Report, 1920

In the second experiment the six different varieties of pota-
toes were planted in two different fields. In one field only about
two pounds of each variety were planted, while in the other one
a peck of each variety were used. The fields in each case showed
a very general infection with blight, but none of the six varie-
ties tested showed any noticeable resistance to the disease.

The work this season in the control of damping off in seed-
beds was restricted to one line, that of testing for the effect of
treating young celery seedlings with a' 1/-percent solution of
copper sulphate. It has been proven that this treatment will
satisfactorily control damping off (see page 83R of the 1916
report of this Station), but in other cases (see page 77R of
the 1917 report) it has appeared that under certain conditions
the treatment may have a detrimental effect on the plants them-
selves. To determine the conditions under which the treatment
is injurious to the plants, the writer conducted some experi-
ments during the early fall of 1919. In these tests celery seed,
of the French self-blanching variety, were planted in concrete
seedbeds at the Experiment Station, the planting time and the
care for the seedbeds being the same as that adopted by success-
ful celery growers of Sanford.
From the time they were an inch high till ready to transplant,
some rows of the celery seedlings were treated with a 1/-per-
cent solution of copper sulphate at the rate of 1 pint of the so-
lution to 1 square foot of seedbed surface. Some of the rows
were treated late in the evening and some either in the morn-
ing or about noon. Six to fourteen hours later some of the rows
thus treated were thoroly sprinkled with water, while others
were left unsprinkled. From observations it appears clear that
this treatment is detrimental to the plants. More or less severe
burning occurred, if the solution was applied during a hot and
dry part of the day, or if it was left on the plants for too long
without being washed off. However, when the seedlings were
treated late in the evening and then thoroly sprinkled with water
early the next morning, no injury resulted.

Work with this disease during the year was confined pri-
marily to a comparative study of the fungus causing buckeye


Florida Agricultural Experiment Station

rot and of closely related fungi. A preliminary note on the sub-
ject was published in the 1919 annual report of this Station.
Further inoculation experiments with all of the fungi were con-
ducted this year mainly, with tomato and castor-bean seedlings.
These experiments so far show.that in every case the Phytoph-
thoras* from.tomato fruit rot (buckeye), lupine stem rot, cocoa-
nut rot, castor bean stem rot, tomato seedling damping off,
roselle stem rot, and citrus foot rot; were able to produce damp-
ing off of young tomato and castor bean plants and also infect
leaves, terminal buds, and eventually to invade leaf petioles and
stems. However, there seems some difference in the virulence of
the different fungi in infecting different plants. There were also
some morphological differences between them. These differences
were not sufficiently great to separate the different fungi with-
out further study, and it can not be said that all are of the same
species, namely, Phytophthora parasitica Dastur, the name ap-
plied to the castor bean fungus before the publication of the
P. terrestria of the writer.

The work on pineapple wilt this year has been conducted on
a considerably enlarged scale which was made possible by the
splendid cooperation given by county agents and growers.
Growers and other interested parties have contributed nearly
$1,500 for this work.
The wilt situation is such that a series of comprehensive ex-
periments are required. Included should be experiments to de-
termine not only the best methods of root-knot control, but also
to give more positive information concerning the actual nature
of the disease as well as other contributing factors; such as,
soil conditions, kind of plants used for sets, and fertilizers.
This is necessary because as yet we have no positive or com-
plete knowledge of either of the factors; the only positive in-
formation at hand being that nematodes play an important
part in the development of what is known as pineapple wilt

*The Phytophthoras from buckeye rot and from lupine stem rot
were isolated by the writer, while cultures of the others were received
from workers; namely, the Phytophthora of cocoanut from S. F. Ashby
of Jamaica; of castor bean from Prof. Ashby (received in turn by him from
Prof. Dastur of India), and from S. Bruner of Cuba; of roselle from Prof.
Bruner; of citrus foot rot from H. E. Stevens of Florida and H. S. Fawcett
of California; of tomato seedling damping off from D. Reddick of Ithaca,
N. -Y.; and of roselle from Prof. Bruner.


Annual Report, 1920

(see 1916 report of this Station, pp. 93-98), and,that either a
lack of plant food.in the soil or a wrong application .of fertilizers
will often produce an effect that may be confused with wilt.
. During this fiscal year the writer secured,,as already stated
sufficient financial ,assistance and personal cooperation from the
people interested in pineapple culture, to enable him to start
some of the experiments that may yield information leading
toward a,proper solution of the problem. This, problem may
be outlined,as follows: "Is wilt the main trouble?, What other
factors .contributed to the failure ,of pineapple culture during
recent years? Are there any other, practical means besides
crop rotation for thecontrol of root-knot under field conditions?
What plants are most suitable for a crop rotation.? What com-
bination of fertilizers is apt to give best. results under prevail-
ing conditions?"
The experiments conducted last fall are given in detail in a
separate report. Therefore, it is sufficient here to give a de-
scription of the plots and experiments and to call brief attention
to the main features of our recent work.
The land on which the experiments were conducted was di-
vided into 96 plots. The first 49 plots are used to test certain
fertilizers. Plots 50 to 74 are. to determine the effect of fumi-
gating slips with hydrocyanic acid gas before planting, of dip-
ping slips in Bordeaux mixture, and of selecting slips in regard
to their apparent freedom from wilt; and to determine the rela-
tive value of healthy slips produced locally and slips obtained
from plants recently (18 months ago) introduced from Cuba.
Plots 75 to 82 are for experiments to determine the effect of
bare fallow on root-knot in the soil, the cultivation to consist
of alternative frequent plowing and discing for different periods
of time before planting pineapple slips. Plot 83 was planted to
Napier grass and plot, 83a to rattler-box (Crotalaria usaromo-
ensis) to test the adaptabilities of these plants to the soil. It
was planned to use these plants for crop rotation to control
root-knot, if their adaptabilities were proven. However, both
plantings were practically failures, due to range cattle and the
time of planting.
Plots 84 to 96 are to determine the nature of wilt. Some of
these plots were treated with carbon disulphide (an ounce to
the square foot), while others were treated with formaldehyde
(a half gallon of 1 to 25 to the square foot). The soil of some
plots was sterilized with steam (live.steam.was.run thru "steam


Florida Agricultural Experiment Station

rakes" for 40 minutes, at a pressure of 100 pounds). The re-
maining plots in this group were left without any soil treat-
ment. All treatments were given before the slips were planted
and all treated plots were isolated by sheets of galvanized iron
sunk to a depth of 20 inches along the dividing line.
Outside of the experimental field were planted some pineapple
plants which had escaped wilt. These were selected by the
writer and an experienced grower (Charles Edwards of Ft.
Pierce) from several old pineapple fields which were to all ap-
pearances badly affected with wilt. Unfortunately the plants,
during last June, were found to be greatly injured by pineapple
scales and, thus, were in too poor condition to give any indica-
tion as to their ability to resist wilt.
It is thought that only by continuing this work for a series
of years will reliable information be secured from these experi-
All other truck crop diseases that were of common occur-
rence during the preceding years were prevalent again this
year, altho some of the diseases naturally were more conspicu-
ous and others less conspicuous this year.
Of the more conspicuous diseases should be mentioned the bac-
terial warty spot of the leaves and fruit of pepper, several dis-
eases of watermelon, angular bacterial leaf spot of cucumber,
and buckeye fruit rot of tomatoes, In regard to the first, it
should be stated that, according to information received from
Dr. Jeggar of the United States Department of Agriculture, in
charge of a field laboratory at Sanford, the warty spot has been
unusually prevalent and early in the season. However, with
the coming of slightly drier weather, trouble from this disease
was greatly reduced, causing an average damage of only about
2 percent. From Dr. Jeggar's trials it appears that spraying
with Bordeaux mixture will keep the trouble in check to a con-
siderable extent.
Buckeye rot of tomatoes was observed by the writer for the
first time on sandy soil (at Sanford), and according to Dr.
Jeggar the disease was quite common this season in that dis-
Watermelons this year, due to excessive rains, suffered more
than usual from various diseases, mainly from Mycosphaerella
wilt and anthracnose. It is of interest to know that according


Annual Report, 1920

to the report of C. M. Tucker, temporarily of the Agricultural
Extension Division, seed disinfection invariably resulted in
freedom from wilt in watermelon fields, while there were num-
erous cases of Mycosphaerella wilt infection when the seed
were not treated. Regular and proper spraying with Bordeaux
mixture, according to Mr. Tucker, controlled anthracnose even
in seasons highly favorable to the disease, if the spraying was
started early in the season. The spraying is not satisfactory,
if started late in the season.
This season, for the first time, the writer observed many
severe cases of Alternaria leaf spot on watermelons. The speci-
mens were collected and sent to the writer by Mr. Tucker as
"probable Phyllosticta spots, because the zonations are very
much like those of this disease." However, the spots were a
distinct bright brown color (much like those of Alternaria on
potatoes) and had somewhat closer zones. Microscopic and cul-
tural work showed that only an Alternaria fungus was associated
with the spots. No determination of the species was made nor
infection work conducted.


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