Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; no. 74
Title: Anthracnose of the pomelo
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Permanent Link: http://ufdc.ufl.edu/UF00026757/00001
 Material Information
Title: Anthracnose of the pomelo
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: p. 157-172 : ill. ; 22 cm.
Language: English
Creator: Hume, H. Harold ( Hardrada Harold ), 1875-1965
Publisher: Florida Agricultural Experiment Station
Place of Publication: Lake City Fla
Publication Date: 1904
 Subjects
Subject: Anthracnose   ( lcsh )
Pummelo -- Diseases and pests -- Florida   ( lcsh )
Grapefruit -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by H. Harold Hume.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station)
 Record Information
Bibliographic ID: UF00026757
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000921044
oclc - 18156755
notis - AEN1485

Full Text





HISTORIC NOTE


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
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida











BULLETIN NO. 74.


FLORIDA
AGRICULTURAL EXPERIMENT STATION



Anthracnose of the Pomelo,


Anthracnose on Pomelo Fruit,
Showing a Large Number of Different Points of Infection.

By H, HAROLD HUME,


The bulletins of this Station will be sent free to any address in Florida upon application
to the Director of the Experiment Station, Lake City, Fla.

Jacksonville, Fla.,
INDUSTRIAL RECORD PUB. CO,
1904.


AUGUST, 1904.












BOARD OF TRUSTEES.



GEO, W. WILSON, President ....................... Jacksonville.
C. A. CARSON, Vice-President ............... ....... Kissimmee.
F. L. STRINGER, Secretary ......................... Brooksville.
F. E. HARRIS .......................... ............... Ocala.
E. D. BEGGS ...................................... Pensacola.
J. R. PARROTT ................................... Jacksonville.
F. M. SIMONTON ..................................... Tampa.




STATION STAFF.



ANDREW SLEDD, M. A., Ph. D., .........................Director.
EDWARD R. FLINT, B. S., Ph. D., M. D. .............. Chemist.
E It. SELLARDS, M. A., Ph. D .................... Entomologist.
P. H. ROLFS, M. S., ................. Botanist and Horticulturist.
CHAS. F. DAWSON, M. D., D. V. S .................. Veterinarian.
*C. M. CONNER, B. S. ...........Vice-Director and Agriculturist.
A. W. BLAIR, B. S. ..............Assistant Professor Chemistry.
F. C. REIMER, B. S ................... Assistant Horticulturist.
W. P. JERNIGAN ......................Auditor and Bookkeeper.
A. TYLER ......................... Stenographer and Librarian.
JOHN H. JEFFRIES .......... Gardener, Horticultural Department.
E. F. WORTHINGTON ............ Assistant in Field Experiments.
* Superintendent of Farmers' Institutes.

















CONTENTS,


PAGE.
Anthracnose on Pomelo Fruit .................... Frontispiece.
Distribution of the Disease ............................ 161
The Disease on the Leaves ............................ 162
Anthracnose on the Twigs ............................. 164
The Disease on the Fruit .............................. 164
Suggested Causes of the Disease ........................ 168
Conditions Favoring the Disease ....................... 169
Remedies .'...........: .. .... .. .. ............ .170




ILLUSTRATIONS,


Anthraenose on Pomelo leaves ........................Plate I.
Pomelos on the tree attacked by Anthracnose ........ Plate II.
Advanced Stage of Anthracnose on Pomelo Fruit .... Plate III.
Fruit Washer ................................... Plate IV.














Anthracnose of the Pomelo,


Attention was called to this disease in Bulletin 53, Florida
Experiment Station, under the name, Leaf-Spot, as at that time it
was observed only upon the leaves.

Distribution of the Disease.
During the past fruit season, 1903-1904, a new disease ap-
peared on Pomelo fruit in a number of different sections in the
State, and a careful examination of the fruit, both in the field and
in the laboratory, proved that this new disease was caused by the
same fungus, Colletotrichum gleosporioides Penzig, as causes the
Leaf-spot. Early in the season it was observed in two or three
different and widely separated groves in the eastern part of the
State, and a little later, diseased fruit was forwarded from West
Florida. Later on, investigation of the fruit in a number of groves
in the western part of the State showed that the disease was widely
distributed in that section. Specimens of fruit were also received
from a number of different points in the interior of the State. An
examination of the pomelos held for sale by the fruitiers in Jack-
sonville, Florida, showed that the disease must have been quite prev-
alent throughout the State. It was almost impossible to find any
considerable amount of fruit exposed on the fruit stands in which
a few diseased specimens at least could not be found.
From these observations we may safely conclude that the dis-
ease on the fruit is likely to occur in any portion of the State and
that it is at the present time widely distributed, though, as pointed
out later on, there appear to be certain conditions especially favor-
able to its development.
This disease on the fruit was first observed by the writer in
the autumn of 1901, but attracted little attention at that time, as











BULLETIN NO. 74.


the damage was slight, only a few specimens of diseased fruit ha
ing been observed in a single grove. Since that time the disease
in the grove where it was first observed, has increased to such a
extent that the trees, on which it was first noticed, yielded a ver
small proportion of sound fruit during the present season. TI
disease has probably been at work for a considerable length of tim,
and as is usual in such cases, attracted little attention until it be
came serious. The loss during the past season in two or three
instances has amounted to from five hundred to a thousand dollar
in a single grove.
From our present knowledge of this disease it appears to be o
the increase and we are probably justified in predicting inat it ha
not yet reached its worst. The disease is in all likelihood an intr(
duced one and it may be looked to attack the sweet orange in add:
tion, to the lemon, lime and pomelo. It frequently occurs upo:
leaves, twigs and branches of the sweet orange, and on one oceaw
ion sweet orange fruit on one of the fruit stands in Lake CitA
Florida, were observed, covered by lesions (diseased spots) cause,
by this same fungus Colletotrichum gleosporioides.*

The Disease on the Leaves,
On the leaves, the disease first appears in the form of rathe
irregular areas from 1-8 to 3-4 inch across. Occasionally the;
become confluent or join each other so as to embrace a large por
tion of the surface of a leaf. The spots vary in color from brown
ish yellow to a dark shade of brown, depending upon the stage o:
development. Usually the diseased spots are located near an(
extend to the margin of the leaf. The tip is quite a favorite sea
of infection, the lesions (diseased, spots) may however be located
on the leaf entirely removed frdln the margin. The characteristic
color noted above marks the commencement of the disease, the pe
riod during which the mycelium (fungal threads) is growing mos
actively in the tissues of the leaf.
* This same disease also attacks the lemon and lime. See Bul. 52. Bureau Plant Indus
try, U. S. D. A., by Prof. P. H. Rolfs.






PLATE I.



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Anthracnose on Pomelo leaves, All the light areas are diseased in various stages,


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BULLETIN NO. 74.


As the disease progresses, the affected area becomes more
clearly defined. The areas representing a number of separate
spots ol infection, close to each other, become continuous. The
color changes from yellowish to the gray hue of dead tissue. The
line of division, between the dead and the green, living tissues, is
slightly elevated and as already noted, clearly defined. At this
stage, a close examination of the discolored spots on the upper
side of the leaf reveals the presence of a number of minute dark
dots. These dots are arranged more or less completely In concen-
tric circles or ovals. These minute dark dots are in reality the
spore bearing parts of the fungus (ascervuli) containing in large
numbers, the spores, by means of which the disease is spread from
one portion of the tree, from one tree, or from one grove to another.
The affected, or diseased areas are usually located near the tip or
side of the leaf, though they may be situated in the central portion
of the blade (Plate 1.)

Anthracnose on the Twigs,
Small twigs are very frequently attacked. Occasionally the dis-
ease seems to progress from an infested leaf to the twig upon which
it is borne. Twigs injured by cold or insects are usually attacked.
Soon after the entrance of the fungus, the twigs attacked become
gray and dead. Many pomelo trees may be seen throughout the
State in which numerous twigs and small branches, killed by the
disease, may be found in the interior of the top. Usually the twigs
in proximity to diseased fruit are also found to be diseased or
dead (See Plate II.)

The Disease on the Fruit,
The fruit may be attacked either on the tree or after it is
removed. Specimens of rind, removed from fruit which had been
shipped to Chicago, have been examined, on which the disease was
present. It was said to have been perfectly sound at the time of
shipment.
The most conspicuous damage, during the time the disease has




PLATE II.


Pomelos on the tree attacked by Anthracnose, Each fruit marked with an X is diseased. Note that the twigs have been de,
foliated. Most of these twigs are dead. More than a box of fruit was diseased on these branches,











BULLETIN NO. 74.


been under observation has been to the fruit while it still remained
on the tree. Upon the fruit the presence of the disease is first
manifested by an irregular brownish discoloration. The discolored
area is irregularly defined around the margin. The diseased spot
may be on any portion of the fruit and may vary from an inch or
so in diameter to an area nearly equal to that of the outside of
the fruit. As it progresses these spots gradually change in color,
sometimes becoming grayish, sometimes somewhat lighter. Ulti-
m;ately, however, the whole affected area becomes dirty black in
cclor. If the point of infection is small at first it gradually
enlarges under favorable conditions so as to embrace the whole
fruit. Sometimes the affected area remains constant in size for a
considerable time.-in which case in its older stage it varies from
black at the centre through various shades of brown, brownish yel-
low to the normal yellowish color of the healthy rind at the mar-

- The black discoloration is caused by the formation of the spore
bearing parts. These dark fruiting bodies are so numerous as to
make the fruit black. Under a hand lens they seem to be rather ir-
regular in size and shape, and are elevated above the surface of the
diseased rind. The outer ends of the oil cells are depressed, the
depressions showing a wrinkled appearance. From these fruiting
bodies sporules or spores are produced. They are very minute,
measuring only from 16-18x4-6 microns.* Under the microscope
they are seen to be cylindrical, rounded at the ends and hyaline
in color. They have but one cell. Frequently minute, round, light
colored areas may be made out in them.
The disease starts at the outside of the fruit and works inward
as well as around it. The mycelium of the fungus seems to progress
more rapidly toward the centre of the fruit along the partitions
or dividing septa than it does through the pulp: but it grows in
both. The mycelium is branched and grows at will; first through
the inner portion of the rind, later entering the fruit.
The disease is confined to the rind for a considerable period
A micron equals 1- 500 of an inch.


166






















PLATE III.


Advanced Stage of Anthracnose on Pomelo fruit,










BULLETIN NO. 74.


and the flavor of that portion of the pulp immediately beneath the
seat of infection is normal for some time, while the opposite side of
of the fruit retains its normal quality for a much longer period.
Ultimately, however, the flavor of the whole fruit is distinctly
altered. The bitterness in the flavor is probably unchanged, but
the acid and sugar in the juice are either broken down or destroyed.
In consequence the bitter'taste is very strong and being unmodified
by either sweetness or acid, is quite disagreeable. Besides this the
juice and pulp are permeated by the flavor of decay and emit the
distinct odor of citric acid.
While fruits attacked by the disease usually present the ap-
pearance already described, at other times the trouble manifests
itself by the appearance of a large number of circular or more or
less irregular brown areas. (See Frontispiece). The rind im-
mediately beneath and surrounding these areas is depressed, but
in the centre the discolored spots are frequently somewhat elevated.
They become more prominent as the rind dries, contracts 'and
becomes thinner. When placed in a moist chamber the disease
soon embraces the whole fruit and the rind becomes very dark in
color, owing to the large number of fruiting bodies of the fungus
formed.
As a general rule, all fruits attacked, drop soon after the
fungus becomes well started. Some of it remains on the tree for
a considerable time, but if attacked near the stem it always falls.
On the ground, beneath the branches, shown in Plate II, there
were nearly as many fruits as are shown on the branches.

Suggested Causes of the Disease,
It has been stated by growers that the disease was caused by
spraying, by the effects of cold, or by the strong sunlight. While.
it must be recognized that any condition which reduces the vigor of
the tree, or any part of it, acts as a predisposing cause; still the
immediate cause of the disease is the fungus already referred to
and were this not present the disease would not occur. It has been
found on sprayed and unsprayed trees, on fruit in the sun and










ANTHRACNOSE OF THE POMELO.


in the shade. The fruit may be affected on any part, base or
apex, on the side facing outward when hanging on the tree, or on
the inner side. It has been found in sections where no fruit was
touched by frost. It has been found on fruit well up in the tops of
of the trees and on fruit borne on the lower branches and touching
the ground. From these facts we must grant that neither spraying,
frost, sun, shade, nor the position of the fruit on the tree has
anything to do with the cause of the disease. It is probably true
that the fruit near the ground where the air is moist and where the
fruit is more shaded may be more subject to the disease. Aside
from this, the position of the fruit has no bearing on the virulence
of the disease or in rendering the fruit more susceptible to attack.

Conditions Favoring the Disease,
Starved Condition of the Tree. In animal so in vegetable life;
a vigorous well-fed individual withstands disease while the weak,
starved one succumbs. The pomelo is naturally a vigorous grower
and we are probably not far astray, when we say that compared
with sweet orange trees of equal size and age they require from
one-fourth to one-third more fertilizer. In a number of instances
poorly fed trees have been attacked on leaf, branch and fruit by the
disease, while better nourished ones immediately adjoining showed
no signs of its attack.
The remedy in this case is obvious.
Wind. Where trees have been badly whipped by the wind,
causing abrasions on the fruit and branches and tearing the leaves,
the disease adds to the injury already done. The wounded spots
are very readily attacked. On the other hand trees standing in
still areas, where there is little or no air movement are more sub-
ject to attack than are those about which the'air circulates freely.
The trees should not be subjected to the whipping force of the wind,
neither should they be so hedged in or walled about by standing
timber as to prevent a free circulation of air. In the matter of
forest protection the middle course should be pursued.
Frost. The disease usually follows injury to the leaves,










BULLETIN NO. 74.


branches and fruit by frost. The spores of the fungus gain access
to the tissues through the parts injured.
Disease. Trees suffering from Die-back, Foot-rot, or any other
disease are more subject to the attacks of Anthracnose than are
those which are entirely healthy. For control of these diseases, see
Bul. 53, Florida Experiment Station.
Insects. These devitalize the trees and puncture the tissues
thus making it possible for the fungus to gain a foothold. Among
those insects which appear to assist in increasing the attacks of
the fungus may be mentioned the different scales and mites in par-
ticular. Spots upon citrus leaves immediately beneath clusters of
long or purple scales are generally found to be diseased and it is
probably not too much to say that insects open up the way for the
fungus to enter leaf, branch or fruit.
Bruises: The slightest abrasion of the surface of the fruit
opens up a way for the entrance of the fungus; the greatest care
should be exercised in handling the fruit to prevent injury to the
rind.

Remedies,
Removal of Diseased Fruit. All diseased fruit should be taken
from the trees and if any should have fallen to the ground, it, too,
should be collected. Destroy all badly affected fruit; either bury
it deeply or burn it. Fruit showing only slight effects of the dis-
ease may be sold in the nearby markets. In the packing house all
fruit should be kept where fresh, dry air will have free access.
Pruning. Cut out andburn all dead and diseased branches.
Rake up ana burn all leave lying about and under affected trees.
Spraying. Trees on which diseased leaves and branches appear
should be thoroughly sprayed with Bordeaux Mixture early in the
season (May, June, July). If spraying is needful and desirable
as the fruit nears maturity, spray with Ammoniacal Solution of
Copper Carbonate. Three or four applications at intervals of ten
days may be necessary. Mr. E. P. Porcher, Cocoa, Fla., success-
fully combatted this disease and stayed its progress by this means






PLATE IV,


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-I-1 -.-


I


Fruit Washer used by W. S. Hart, Hawks Park, Fla. Operated by a small gasoline engine. This washer is one of the best.
Manufactured by S, C, Warner, Palatka,jFla.









172 BUI4jETIN NO. 74.

on our recommendation. Bear in mind that every application of
a fungicide to a citrus tree should be followed by a good insecticide
to keep down the scales.
Fruit on which the disease is likely to be present should be
sprayed before or after removal so as to prevent its development on
the way to market. Directions for the preparation of spraying
mixtures will be found in Bulletin 72, Florida Experiment Sta-
tion.
Washing. Many growers wash their fruit before shipping it.
Ammoniacal Solution of Copper Carbonate may be added to the
water used in washing. Another good substance for this purpose
would be Potassium Sulphide. One of the best washers is that
manufactured by S. C. Warner, Palatka, Fla. (See Plate IV).
No better means of control can be devised than this, but the exact
amounts which it would be best to, use have yet to be determined.
H. HAROLD HUME.
















The following publications of the Florida Experiment Sta-

tion are available for free distribution, and may be secured by

addressing the director of the Experiment Station, University of

Florida, Lake City, Fla.:


Fertilizers ..........................pp. 48
Annual Report ............... 32
Leeches and Leeching ............ 17
Big Head ................ .......... 19
Pineapple...................... 14
Liver Fluke Southern Cattle
Fever.... ..... .. .......... 15
The San Jose Scale................ 28
The Culture of Tobacco.......... 28
Cotton and Its Cultivation ........ 4
Orange Groves .................. 33
Insect Enemies ................ 96
Insects Injurious to Grain ........ 31
Pineapple.................... 15
Tobacco in Florida............... 63
Strawberries ..................... 48
The Fall Army Worm............. 8
The San Jose Scale............... 30
Some Strawberry Insects........ 55
A Chemical Study of Some Typi-
cal Florida Sols ................ 128
Some Common Florida Scales.... 24
Baking Powders................... 15


Some Citrus Troubles.............pp. 5
Pecan Culture.................... 31
Feeding With Florida Feed Stuffs 95
The Cottony Cushion Scale......." 48
Top-working of Pecans........... "124
Pomelos..........................." 43
Cauliflower .................... 20
Velvet Beans .................... 24
Two'Peach Scales. ................ 32
Peen-to Peach Group.............. 22
Packing Citrus Fruits... ........ Folio
Texas Fever and Salt Sick....... pp. 31
The Kumquats............... 14
The Mandarin Orange Group...... '. 32
The White Fly ................. 94
Pineapple Culture. I. Soils...... 35
Cultivation of Citrus Groves...... 30
Pineapple Culture. II. Varieties 32
Japanese Persimmons ............ 48
Feeding Horses and Mules on
Home-Grown Feed-Stuffs..... 16
The Honey Peach Group.......... 28


PRESS BULLETINS.


1 Directions for Preparation of Bordeaux
Mixture.
2 Lime and Its Relation to Agriculture.
3 Seed Testing.
4 The White Fly.
5 Basic Slag.
6 Nursery Inspection (part 1).
7 Nursery Inspection (part 2).
8 Care of Irish Potatoes Harvested in
the Spring and Held for Fall Planting.
9 Sore Head.
10 Plants Affected by Root Knot.
11 Vinegar.
12 Seed Beds and Their Management.
13 Treatment for San Jose Scale.
14 Beef from Velvet Beans and Cassava.
15 and 16 Some Poultry Pests.
17 Preservatives in Canned Goods
18 Cantaloupe Blight.
19 Cut Worms.
20 Hog Cholera and Swine Plague.
21 Parturient Paralysis.
22 Nitrogen as a Fertilizer,


23 Protection Against Drought.
24 Orange Mites.
25 Roup.
26 Lumpy Jaw.
27 Cover Crops.
28 Moon Blindness.
29 Food Adulteration.
30 Dehorning Cattle.
31 Coffee.
32 Foot and Mouth Disease.
33 Red Soldier Bug or Cotton Stainer.
34 Ox Warbles.
35 Butter.
36 Hook Worms in Cattle.
37 Velvet Bean.
38 Practical Results of Texas Fever Inoc-
ulations.
39 Lung Worms in Swine.
40 and 41 Glanders.
42 Food Adulterations-Spices and Con-
diments.
43 How to Feed a Horse.
44 Tree Planting.
45 The Sugar-cane Borer.




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