Insects and diseases of the pecan in Florida

Material Information

Insects and diseases of the pecan in Florida
Series Title:
Bulletin University of Florida. Agricultural Experiment Station
Phillips, Arthur M., 1903-
Cole, J. R ( John Rufus ), 1900-
Place of Publication:
Gainesville Fla
University of Florida Agricultural Experiment Station
Publication Date:
Physical Description:
62 p. : ill. ; 23 cm.


Subjects / Keywords:
Pecan -- Diseases and pests -- Florida ( lcsh )
Pecan -- Diseases and pests -- Control -- Florida ( lcsh )
non-fiction ( marcgt )


General Note:
Cover title.
General Note:
"In cooperation with United States Department of Agriculture"-- T.p.
Bulletin (University of Florida. Agricultural Experiment Station)
Statement of Responsibility:
by Arthur M. Phillips and John R. Cole.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
027118964 ( ALEPH )
18236989 ( OCLC )
AEN5869 ( NOTIS )


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Bulletin 411 June, 1945

In Cooperation with United States Department of Agriculture




H. P. Adair, Chairman, Jacksonville
N. B. Jordan, Quincy
T. T. Scott, Live Oak
Thos. W. Bryant, Lakeland
M. L. Mershon, Miami
J. T. Diamond, Secretary, Tallahassee


John J. Tigert, M.A., LL.D., President of the
H. Harold Hume, D.Sc., Provost for Agricul-
Harold Mowry, M.S.A., Director
L. O. Gratz, Ph.D., Asst. Dir., Research
W. M. Fifield, M.S., Asst. Dir., Admin.4
J. Francis Cooper, M.S.A., Editors
Clyde Beale, A.B.J., Assistant Editor3
Jefferson Thomas, Assistant Editor3
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Managers
K. H. Graham, LL.D., Business Managers
Claranelle Alderman, Accountants



W. E. Stokes, M.S., Agronomist1
Fred H. Hull, Ph.D., Agronomist
G. E. Ritchey, M.S., Agronomist2
G. B. Killinger, Ph.D., Agronomist
W. A. Carver, Ph.D., Associate
Boy E. Blaser, M.S., Associate
H. C. Harris, Ph.D., Associate
R. W. Bledsoe, Ph.D., Associate
Fred A. Clark, B.S., Assistant


A. L. Shealy, D.V.M., An. Industrialist1 3
R. B. Becker, Ph.D., Dairy Husbandmans
E. L. Fouts, Ph.D., Dairy Technologist8
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarians
L. E. Swanson, D.V.M., Parasitologist,
N. R. Mehrhof, M.Agr., Poultry Husb.3
T. R. Freeman, Ph.D., Asso. in airy Mfg.
R. S. Glasscock, Ph.D., An. Husbandman
D. J. Smith, B.S.A.. Asst. An. Husb.4
P. T. Dix Arnold, M.S.A., Asst. Dairy Hush.8
G. K. Davis, Ph.D., Animal Nutritionist
C. L. Comar, Ph.D., Asso. Biochemist-
L. E. Mull, M.S., Asst. in Dairy Tech.'
J. E. Pace, B.S., Asst. An. Husbandman
S. P. Marshall, M.S., Asst. in An. Nutrition
C. B. Reeves, B.S., Asst. Dairy Tech.
Katherine Boney, B.S., Asst. Chem.
Ruth Faulds, A.B., Asst. Biochemist
Peggy R. Lockwood, B.S., Asst. in Dairy Mfs.


C. V. Noble, Ph.D., Agr. Economist1 s
Zach Savage, M.S.A., Associates
A. H. Spurlock. M.S.A., Associate
Max E. Brunk, M.S., Associate


Ouida D. Abbott, Ph.D., Home Econ.1
R. B. French, Ph.D., Biochemist


SJ. R. Watson, A.M., Entomologist1
A. N. Tissot, Ph.D., Associates
H. E. Bratley, M.S.A., Assistant


G. H. Blackmon, M.S.A., Horticulturist1
A. L. Stahl, Ph.D., Asso. Horticulturist
F. S. Jamison, Ph.D., Truck Hort.
R. J. Wilmot, M.S.A., Asst. Hort.
R. D. Dickey, M.S.A., Asst. Hort.'
Victor F. Nettles, M.S.A., Asst. Hort.'
J. Carlton Cain, B.S.A., Asst. Hort.4
Byron E. Janes, Ph.D., Asso. Hort.
F. S. Lagasse, Ph.D., Asso. Hort."


W. B. Tisdale, Ph.D., Plant Pathologist'1
Phares Decker, Ph.D., Asso. Plant Path.
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Asst. Botanist


F. B. Smith, Ph.D., Chemist'
Gaylord M. Volk, M.S., Chemist
J. R. Henderson, M.S.A., Soil Technologist
J. R. Neller, Ph.D., Soils Chemist
C. E. Bell, Ph.D., Associate Chemist
L. H. Rogers, Ph.D., Associate Biochemist'
R. A. Carrigan, B.S., Asso. Biochemist
G. T. Sims, M.S.A., Associate Chemist
T. C. Erwin, Assistant Chemist
H. W. Winsor, B.S.A., Assistant Chemist
Geo. D. Thornton, M.S., Asst. Microbiologist
R. E. Caldwell, M.S.A., Asst. Soil Surveyor*
Olaf C. Olson, B.S., Asst. Soil Surveyor

x Head of Department.
2 In cooperation with U. S.
a Cooperative, other divisions, U. of F.
In Military Service.
5 Qn leave.



J. D. Warner, M.S., Vice-Director in Charge
R. R. Kineaid, Ph.D., Plant Pathologist
V. E. Whitehurst, Jr., B.S.A., Asst. Animal
Jesse Reeves, Asst. Agron., Tobacco
W. H. Chapman, M.S., Asst. Agron.'
R. C. Bond, M.S.A., Asst. Agronomist

Mobile Unit, Monticello

R. W. Wallace, B.S., Associate Agronomist

Mobile Unit, Milton

Ralph L. Smith, M.S., Associate Agronomist

Mobile Unit, Marianna

R. W. Lipscomb, M.S., Associate Agronomist

Mobile Unit, Wewahitchka

J. B. White, B.S.A., Associate Agronomist


A. F. Camp, Ph.D., Vice-Director in Charge
V. C. Jamison, Ph.D., Soils Chemist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson, B.S., Entomologist
W. W. Lawless, B.S., Asst. Horticulturist'
C. R. Stearns, Jr., B.S.A., Asso. Chemist
H. O. Sterling, B.S., Asst. Horticulturist
T. W. Young, Ph.D., Asso. Horticulturist
J. W. Sites, M.S.A., Asso. Horticulturist5


JR. V. Allison, Ph.D., Vice-Director in Charge
J. W. Wilson, Sc.D., Entomologist'
F. D. Stevens, B.S., Sugarcane Agron.
Thomas Bregger, Ph.D., Sugarcane
Physiologist I
G. R. Townsend, Ph.D., Plant Pathologist
R. W. Kidder, M.S., Asst. An. Hush.
W. T. Forsee, Jr., Ph.D., Asso. Chemist
B. S. Clayton, B.S.C.E., Drainage Eng.2
F. S. Andrews, Ph.D., Asso. Truck Hort.'
R. A. Bair, Ph.D., Asst. Agronomist
E. C. Minnum, M.S., Asst. Truck Hort.
N. C. Hayslip, B.S.A., Asst. Entomologist
Earl L. Felix, Ph.D., Asst. Plant Path.
C. L. Serrano, B.S.A., Asst. Chemist

\Geo. D. Ruehle, Ph.D., Vice-Director in
P. J. Westgate, Ph.D., Asso. Horticulturist
H. I. Borders, M.S., Asso. Plant Path.

Clement D. Gordon, Ph.D., Asso. Poultry
Geneticist in Charge2

W. G. Kirk, Ph.D.. Vice-Director in Charge
E. M. Hodges, Ph.D., Asso. Agron., Wauchula
Gilbert A. Tucker, B.S.A., Asst. An. Husb.4


G. K. Parris, Ph.D., Plant Path. in Charge

Plant City
A. N. Brooks, Ph.D., Plant Pathologist

A. H. Eddins, Ph.D., Plant Pathologist
E. N. McCubbin. Ph.D., Truck Horticulturist

S. O. Hill, B.S., Asst. Entomologist2 *
A. M. Phillips, B.S., Asst. Entomologist2

/ J. R. Beckenbach, Ph.D., Horticulturist in
E. G. Kelsheimer, Ph.D., Entomologist
D. B. Creager, Ph.D., Plant Path., Gladiolus
A. L. Harrison, Ph.D., Plant Pathologist
David G. Kelbert, Asst. Plant Pathologist
E. L. Spencer, Ph.D., Soils Chemist

R. W. Ruprecht, Ph.D., Chemist in Charge
J. C. Russell, M.S., Asst. Entomologist5

E. S. Ellison, Meteorologist 2 5
Warren O. Johnson, Meteorologist2

1 Head of Department.
'In cooperation with U. S.
s Cooperative, other divisions, U. of F.
'In Military Service.
s On leave.

* )

INSECTS OF THE PECAN ...--.............-- .. ----- .......... .. ----- 5
Pecan Nut Casebearer ..................... --.....------- ..--...... ... 5
Pecan Leaf Casebearer ...................................------- 8
Hickory Shuckworm .............- ...- ....-.....-- .....--------.. 12
Southern Green Stinkbug .....................- ........ ...--...... 15
Black Pecan Aphid ...........~....-..... .....................- 18
Fall Webworm .............-~..........................-------- 19
W alnut Caterpillar .........................-- ... -. .. .... ....--... 22
Twig Girdler ...........--.....-........ ....... -... ........... 23
Pecan Budmoth .............-...-..- ..- ..-.....---- .. .. ------.... 25
Pecan Nursery Casebearer ......................--........--......- 25
Pecan Phylloxera ................. ............- ......... ...........- 26
Pecan Cigar Casebearer ...........-.........-..----..--...-.......- 26
May Beetles ............. ......................... ...--....... 28
Spittle Bug .............--- .....-.......- ..... .... ...--.......--. .- 29
Flatheaded Apple Tree Borer ..............................----....... 29
Red-Shouldered Shot-Hole Borer ................ .... ... ....... ...... 31
Termites .................-.......-.......... .....-----.. 32
Hickory Horned Devil ..................... .... ......-........... ....... 33
DISEASES OF THE PECAN ............................... ..... ...... .. ...-- .------ 33
Diseases Due to Specific Organisms ........--..-...-........ --.......... 33
Scab ........................ .......- .... ....... ........- 33
Downy Spot ............. ............. .............. 40
Pecan teaf Blotch ........................ ....-..... .....-- .....- 42
Brown Leaf Spot ....... ....-..-....-... ..- ...... ........----.... -- 43
Nursery Blight .............. ........................ .....- 44
Thread Blight ................. ............... ... ............ 45
Powdery Mildew ............-.... ........ ... .. ....... ........ 48
W ood Rot ................. ~.... ..... ...................- 48
Crown Gall .................................- --. ------......------ 50
Diseases Due to Nutritional or Environmental Factors ...............-...... 52
Rosette ......................... ..............-- ......... 52
Winter Injury ............................. .--------.....56
Sunscald .........-........... ..-. -.. ............................. 57
INSECTICIDES AND FUNGICIDES .......................---- .......... .. .......... 57
Preparation of Bordeaux Mixture .................................... 57
Lead and Calcium Arsenate .............. ..... ....................... 58
Summer Oil Emulsions ......--................ ..................- 59
Nicotine ....................................... -----------..... .... 59
Lime-Sulfur .......................... ............ ..........- ....... ..... ........ .....- 59
Combined Sprays for Insects and Disease Control ........................... 59
Spray Program for Control of Pecan Insects and Diseases ................ 60
THE SPRAY OUTFIT .............................. ................. 60
APPLYING THE SPRAY MATERIAL .......................-------------....----- 61
WARNING ON USE AND STORAGE OF POISONS ............................. ........... 61




The planting and cultivation of pecans began extensively about
1900. At that time some insects and diseases were found to
be affecting pecans in Louisiana and Texas, but they were of
little economic importance. However, like other horticultural
crops, once the pecan industry was firmly established serious
economic losses were soon caused by insects and diseases. This
was especially true in the areas where extensive orchards were
developed in close proximity to one another or where stands of
hickory trees prevailed, thus providing favorable conditions for
the building up of populations of injurious insects and diseases
and for their dissemination.

In this bulletin the insects attacking the nuts, foliage, shoots
and trunks of the pecan are dealt with somewhat in the order
of their economic importance in Florida.3

The pecan nut casebearer (Acrobasis caryae Grote) is one
of the most serious insect pests attacking the pecan in Florida.
The damage caused by this insect is especially serious during
seasons when pecan trees set a light crop of nuts or on varieties
which generally are not heavy producers.
This insect passes the winter as a partly grown larva in an
inconspicuous small case, or hibernaculum, which is generally
found at the base of the bud where it joins the stem. The larvae
become active in the spring about the time the buds begin to
1Assistant Entomologist in Charge, Pecan Investigations Laboratory.
Pathologist, Division of Fruit and Vegetable Crops and Diseases,
Bureau of Plant Industry, Soils and Agricultural Engineering, Agricultural
Research Administration, USDA.
3Although the statements on pecan insects in this bulletin are based
to a considerable extent on the work and experience of the senior author,
the available information elsewhere, especially that in "Insects and Diseases
of the Pecan and Their Control," USDA Farmers' Bulletin No. 1829, has
been drawn on freely, for which acknowledgment is here made. Acknowl-
edgment is also made for the photographs furnished by the U. S. Depart-
ment of Agriculture. This bulletin supersedes Florida Experiment Station
Bulletin 147.

Florida Agricultural Experiment Station

open. After feeding on the buds for a short time the larvae
bore into the young tender shoots, where they feed until full
grown, and then transform into the pupal stage mostly within
the tunnelled shoots.
In Florida the adults, or moths, emerge from the latter part
of April to May 20. The appearance of the maximum number
of moths of this generation usually coincides fairly well with
the setting of the nuts. The moth is small (measuring only
about 5/8 inch across the expanded wings) and of a rather in-
conspicuous dark-gray color, with a ridge or tuft of long, dark
scales extending across the fore wing near the middle. The
moths lay their tiny, greenish-white eggs singly on the blossom
end of the nut, and usually at or near the base of the calyx
lobes. A single egg is usually laid in a cluster of nuts, although
occasionally 2 eggs may be present.
Severest damage by this insect is caused by the larvae of the
first generation, which appear in May and early June. Soon
after hatching the young larvae usually descend and feed for
a short period on the buds just below the cluster of nuts and
then crawl back up and attack the newly set nuts, usually enter-

i/ "

ii^ I

Fig. 1.-Young nuts showing injury by larvae of the pecan nut casebearer.

Insects and Diseases of the Pecan in Florida

ing them near the stem end. Infested nuts are easily recognized
by the characteristic masses of borings cast out by the larvae.
They are held together by fine silken threads (Fig. 1). A single
larva of this generation may destroy from 1 to several nuts,
or an entire cluster. The larvae mature and pupate in the nuts
and the moths of the second generation appear from the middle
of June to the first of July. As a rule the larvae of the second
generation cause much less damage than those of the first, be-
cause at that time the nuts are larger and only 1 or 2 are neces-
sary for the development of an individual larva (Fig. 2). The
larvae of the later generations cause very little damage as the
nuts are approaching maturity, and the larvae feed on the outer
part of the shucks and on the foliage instead of in the nuts them-

Fig. 2.-Cluster of nuts infested by the pecan nut casebearer.

Usually there are only 3 generations of this insect a year,
although sometimes there is a partial fourth generation in Flor-
ida. The larvae of the third generation that do not complete
their life cycle the first year and the larvae of the fourth gener-
ation (if there is a fourth) form the hibernacula or cases about
the buds.
Contrary to the belief formerly held, it has been proved that
the pecan nut is not essential for the development of the pecan

Florida Agricultural Experiment Station

nut casebearer.4 The larvae can feed and develop entirely on
foliage. This explains to some extent why this insect survives
in orchards when there are no nuts on the trees.
Control.-Since the larvae of the first generation cause the
greatest damage, spraying when the nuts are small, or shortly
after the first-generation eggs begin to hatch, is one of the most
effective methods of controlling the pecan nut casebearer. In
northern Florida a high degree of control has been obtained
with a single spray application of 13 fluid ounces of nicotine
sulfate (40 percent nicotine) with 2 quarts of mineral oil emul-
sion of the white or summer oil type, in each 100 gallons of
water. In severe infestations, in which the destruction of 1/3
or more of the crop is expected, 2 applications may be necessary.
This spray may be used in combination with a 6-2-100 bordeaux
mixture if a fungicide is needed to control scab or foliage
To obtain best results the spray application must be ac-
curately timed and the trees sprayed before many of the first-
generation larvae have entered the nuts. The period for apply-
ing the spray is very short, usually about 4 days, and varies
with the season, locality and variety of pecans. The most
accurate method of determining the period to apply this spray
is for the grower to collect the pecan nut casebearer eggs to
determine the hatching period in his own locality. The eggs
are small but can be seen without a magnifying glass. They
are usually found on or near the tips or stigmas of the nuts;
they are greenish white when freshly laid, but turn red-spotted
and then red before hatching. After the egg hatches the shell
is white and a small round hole where the larvae emerged is
usually visible. When the eggs are not collected to determine
the time for applying the spray, the spray should, as a general
rule, be applied soon after the nuts have formed and most of
the tips or stigmas have turned brown. In Florida this is
usually between May 10 and 20. If 2 applications of spray are
made, they. should be about a week apart.

The pecan leaf casebearer (Acrobasis juglandis (LeB)) is
also considered a serious pest of the pecan in Florida. It does
its greatest damage in early spring after the larvae emerge from
Hill, S. 0., Pecan foliage as food for the pecan nut casebearer. Fla.
Ext. 23: 2: 27-29. 1940.

Insects and Diseases of the Pecan in Florida

their overwintering
cases, when they feed on .
the unfolding buds and
leaves (Fig. 3). In se-
vere infestations pecan
trees may be kept in a
defoliated condition for
3 or 4 weeks (Fig. 4). ~
This injury often causes
a reduction in the nut
crop, and trees deprived
of their foliage in this
manner may be mate-
rially weakened.
These insects pass the
winter as larvae in small
cases or hibernacula
about the buds, similar
to those constructed by
the pecan nut casebearer.
After completing their
development they trans-
form to pupae within
their cases. The moths
usually appear from .
about the middle of May
until the first of August.
The moth measures only
about 2/3 inch across the
expanded wings, and the
general color is grayish /
brown. The adults are
usually found hiding in
debris at the base of the
trees or in the thick foli-
age. There is only 1
generation a year. Fig. 3.-Injury to young buds in spring
The moths deposit caused by larvae of the pecan leaf case-
their eggs on the under
side of the leaves along a vein or near the junction of a vein
with the midrib. The young larvae may be found in their sum-
mer feeding cases (Fig. 5) on the under side of the leaves from

Florida Agricultural Experiment Station

the middle of May until November. The larvae feed very spar-
ingly during the summer, and rarely attain a length more than
1/16 inch by fall. During the latter part of August or in early
September the partly grown larvae start migrating from their
summer feeding cases on the leaves and form their overwinter-
ing cases around the buds. Observations indicate that there
is a very close connection between the falling of the leaves and
the migration of the leaf casebearer larvae, so the migration
period varies, depending on the variety of pecans and the season.
Control.-The leaf casebearer can be controlled with either

Fig. 4.-Pecan tree defoliated by larvae of the pecan leaf casebearer
in early spring.

Insects and Diseases of the Pecan in Florida

lead or calcium arsenate, the lead arsenate being preferable
since it involves less danger of foliage injury. Three pounds
of lead arsenate to
100 gallons of bor-
bordeaux mixture is
recommended. For r
varieties that scab a
6-2-100 bordeaux
should be used (to
make a 6-2-100 bor-
deaux mixture use 6
pounds of powdered
bluestone (copper sul-
fate) and 2 pounds
of hydrated lime in
100 gallons of water),
but on varieties that
do not scab a 2-1-100
and a 3-1-100 bor-
deaux have both
proved satisfactory.
For best results, this
spray should be ap-
plied late in June or
early in July. Only
1 thorough applica-
tion is necessary. The
under sides of the .-
leaves, where the )
larvae are feeding,
should be well cover- ,
ed with spray.
This pest can also
be controlled in the
early spring by add-
ing 3 pounds of lead
arsenate to each 100 Fig. 5.-Feeding cases of young leaf casebearer
larvae (enlarged).
gallons of bordeaux
mixture in the first application or the pre-pollination spray for
control of scab.

Florida Agricultural Experiment Station

The hickory shuckworm (Laspeyresia caryana (Fitch)), also
commonly called the pecan shuckworm, is one of the most gener-
ally prevalent insect pests with which the pecan grower has to
contend. This insect is primarily a nut-infesting pest. A few
of the developing nuts are destroyed by the worms, or larvae,
during June, but the
greatest damage oc-
curs during July and
August, when the in-
sect is capable of de-
stroying 50 percent
or more of the pecan
crop in seasons when
the trees have a light
set of nuts. Those
nuts that are punc-
tured during mid-
summer drop from
the trees, and the lar-
4 vae complete their
their development in
the interior of the
Fig. 6.-Larvae of the hickory shuckworm in immature nuts (Fig.
immature pecan nut (enlarged). D
6). During Septem-
ber and late fall, after the nut shells have hardened, the larvae
mine or tunnel the shucks (Fig. 7), which may prevent proper
development of the kernels and delay maturity. At harvest,
heavily infested nuts have tight shucks and the shells are stained
with black marks.
This insect also feeds upon the various species of hickory and
the injury is similar, but the damage is often much greater than
that done to the pecan. The larvae are often found also feeding
in phylloxera galls on pecans in early spring.
There are sometimes as many as 4 or 5 generations of the
shuckworm in a year in Florida. Moths of the spring brood,
or those that develop from the larvae that spend the winter in
pecan and hickory shucks, emerge from about the middle of
February through April or later, and most of them die before
the pecan nuts have set. The emergence of this brood seems
to be timed for the development of the early species of hickory

Insects and Diseases of the Pecan in Florida

The moths are very inconspicuous and are rarely noticed in
the orchard. Eggs are deposited on the young nuts or leaves.
Upon hatching, the tiny larvae gnaw their way into the green
nuts. Until the shell hardens, the larvae work in the interior
of the immature nuts and cause them to drop. Larvae of the
last generation attack only the shucks of the nuts after the
shells have become hard and the nuts are approaching maturity.
The full-grown larvae pass the winter in shucks on the ground
or in the trees.

Fig. 7.-Larvae of the hickory shuckworm in shuck of nearly mature
pecan nut (enlarged).

Control.-Insecticides have not proved satisfactory in the con-
trol of the hickory shuckworm. A high percentage of the larvae
that winter in old pecan shucks may be killed by gathering and
destroying the shucks at harvest. However, this is feasible only
when the nuts are harvested on sheets. Plowing the shucks
under about March 1, after the larvae have pupated, will also
help to reduce the infestation of shuckworm during the summer.
The best method of attack against the hickory shuckworm
is to keep the infested nut drops covered with soil during July
and August, which prevents the immature larvae from develop-

Florida Agricultural Experiment Station

ing through deterioration of the drops in the soil.5 This can
best be accomplished by cultivating twice with a disk tiller,
sometimes called tiller plow or Wheatland plow (Fig. 8). The
ordinary disk harrow does not give effective control because the
soil is stirred without 'covering the drops uniformly. The first
turning under of drops with a disk tiller should be made about
July 15 and the second during the first week in August, or after

Fig. 8.-Disk tiller in operation for control of hickory shuckworm.

approximately a 3-week interval. The second turning should
begin at exactly the same place where the first commenced.
It has been found that where infested drops are buried in the
soil over a 3-week period and then uncovered, no more moths
emerge than where the drops remained covered. Hence it is
perfectly safe for the grower to start the second operation 3
weeks after the first. The interval between the first and second
operations, however, should not be much greater than 3 weeks,
since by the end of that period moths would be emerging from
nuts that had dropped since the first cultivation. In order to
cover with 1 tiller as much of the orchard as possible within

6 From unpublished data of G. F. Moznette, USDA, Bureau of Ento-
mology and Plant Quarantine, Albany, Georgia.

Insects and Diseases of the Pecan in Florida

the limited time permitted for control, the cultivation should
be first restricted to the area where infested drops are present
by plowing only the actual area from the trunks of the trees
to the edge of the branches.
Where the orchard has received little or no cultivation in
former years, the disk tiller should be set to plow 3 inches deep
the first season to avoid severe root damage. The second season
the root system will have become adjusted to a lower level in the
soil and the implement should be set at 4 inches, which depth
will be more effective in covering the drops. In no case should
the tiller bet set deeper than 4 inches, as too many feeder roots
may be destroyed.
If a grower has only a few trees he should pick up the drops
during midsummer and remove them from the orchard and
destroy them.

The Southern green stinkbug (Nezara viridula (L.)), or
"pumpkin bug," and certain other plant-feeding bugs have fre-
quently caused serious damage to the pecan crops of individual
growers in Florida. The feeding of these sucking insects pro-
duces the trouble known to the pecan grower as "black pit,"
and causes the nuts to drop prematurely if injured before the
shells have become hard; however, a similar condition is caused
by the hickory shuckworm. During the midsummer drop it
may be difficult for the grower to tell whether the drop was
caused by the work of the shuckworm or the sucking bugs.
After the nuts have passed the water stage and the shells
have become hard the puncture or injury by the stinkbug pro-
duces a condition known as kernel spot (Fig. 9) instead of black
pit. The spots produced on the kernel are decidedly bitter and
this injury, cannot be detected until the kernel has been removed
from the shell.
The adult of the Southern green stinkbug is shield-shaped
(Fig. 10), which is the characteristic form for this family of
insects. It passes the winter in the adult stage and is often
active during periods of mild weather. The eggs may be found
in clusters on the under side of the leaves of the host plants
from April to November. This bug begins feeding on the nuts
about the time they reach the water stage and continues until
the nuts are practically mature. There may be as many as 4
generations in a year.

Florida Agricultural Experiment Station

The Southern green stinkbug attacks a large number of plants,
both cultivated and wild, that serve as food for the young, often
referred to as the "nymphs," until they reach the adult stage.
The pecan nuts are attacked only by the adult bugs, which fly
to the trees from plants on which they feed as nymphs.
Control.-Owing to the feeding habits of the Southern green


4 $m:

4I -,'~-'

Iv I

Fig. 9.-Kernel spots on Schley pecan kernels. The upper and central
views show the location on the ridges and edges of the kernels. The lower
sections of kernels, cut through the spots, show the depth and extent of
the injury.

.: ..

Insects and Diseases of the Pecan in Florida

stinkbug on the pecan nut no effective control by the use of
insecticides has been found. Where practical, elimination and
destruction of plants on which the insects breed, in and near
the orchard, is the only control measure available to growers
for the protection of the crop against this insect and other plant
bugs that cause black pit and kernel spot. Where the stinkbugs
are a serious problem, such crops as cowpeas, soybeans, bean,
squash, tomatoes and Crotalaria striata should not be planted



Fig. 10.-Southern green stinkbug feeding on pecan nuts.

6 AL


Florida Agricultural Experiment Station

in or near the orchard, and the orchard should be disked 2 or 3
times during the summer so as to destroy any native food plants
of these insects that might be present.

Some seasons the black pecan aphid (Melanocallis caryaefoliae
(Davis)) causes considerable premature defoliation of pecan
trees. This aphid is usually more prevalent on trees that have
received a number of
applications of bor-
deaux mixture than
on similar unsprayed
trees. However, trees
not sprayed with bor-
deaux mixture also
may become heavily
infested. The injury
caused by this insect
is usually most no-
ticeable during Au-
gust and September.
The first signs of the
presence of this in-
sect are bright yellow
spots, more or less
rectangular in shape,
which appear on the
leaflets around the
punctures where the
aphids feed. These
spots on the leaflets
turn brown (Fig. 11)
and may cause the
leaflet to drop pre-
maturely. Heavy pre-
mature defoliation
has a direct effect on
the quality of the cur-
rent pecan crop and
also affects produc-
Fig. 11.-Pecan leaflet injured by the black tion the following
pecan aphid. year.

Insects and Diseases of the Pecan in Florida

The insect passes the winter in the egg stage in the crevices
of the bark. The eggs hatch in the spring and the young aphids
at first are pale green in color, but as they feed they turn a
darker green and the adults have a series of large black tubercles
or spots on the back and sides. The adults are very active.
These aphids are not found in crowded colonies. They feed on
both sides of the leaves and seem to prefer the shaded inner
parts of the trees. There may be as many as 15 generations
of females during the season, all of which produce living young
except the last fall generation, which includes both males and
females, the latter laying eggs for the overwintering generation.
Control.-The black pecan aphid can be controlled by thorough
spraying with nicotine sulfate (40 percent nicotine) at a strength
of 1 to 2,000 (approximately 61/2 fluid ounces per 100 gallons),
with 2 quarts of summer oil emulsion per 100 gallons of water,
or combined with bordeaux mixture as used for the control of
pecan scab. In orchards in which serious aphid injury has been
experienced the first application should be made soon after the
first yellow spots appear on the leaves. The number of applica-
tions must be determined by each grower from observations
of his own orchard.

The fall webworm (Hyphantria cunea (Drury)) is perhaps
the most conspicuous of the pecan insects, as the larvae form
the familiar and unsightly webs over the twigs and foliage
(Fig. 12). The adult moth is about an inch across when the
wings are spread, and is usually pure white, although sometimes
there are black or brown spots on the wings. The eggs are de-
posited in masses on the leaves and hatch in about a week. The
larvae feed in colonies on the leaves within the web. When
they need additional food the web is enlarged. When full grown,
the larvae are more than an inch long and covered with white
and black hairs.
In Florida there are 2 broods a year of the webworm. The
moths of the first brood appear in April and May and the second
brood of moths appear during the middle of the summer. The
larvae of the second brood feed during the summer and fall.
The webworm passes the winter in the pupal stage in a cocoon
under loose rubbish on the ground or just below the surface
of the soil.
Control.-Spraying with either lead arsenate or calcium ar-

Florida Agricultural Experiment Station

senate at 3 pounds to 100 gallons will control the webworm.
The arsenicals should be used in combination with a 2-1-100
bordeaux mixture, which reduces the danger of injury to the
foliage and also serves as a spreader. In severe infestations it
may be necessary to make 2 applications of spray, 1 for each

r F

.. J'e

Fig. 12.-Young pecan tree defoliated by fall webworm.

Insects and Diseases of the Pecan in Florida

brood. When the insects are not very abundant they may be
controlled by destroying the webs with the larvae in them. The
webs may be removed from the trees with a long bamboo pole
or a long-handled tree pruner.



Fig. 13.-Colony of walnut caterpillars on pecan shoot.

Florida Agricultural Experiment Station

In Florida the walnut caterpillar (Datana integerrima (G.
& R.)) is a major pest during some seasons. In one section of
the State in 1942 many bearing pecan trees were completely
defoliated during July by the first brood of this insect. These
trees put out a hew
growth but were
c again defoliated by
the second brood in
Sthe fall.
There are 2 gen-
erations of this insect
in Florida. The moths
from the overwinter-
Sming pupae emerge
from the ground
from the middle of
April to the middle
of July. The eggs
are laid in masses on
the under side of the
leaflets and hatch in
about a week. The
larvae feed in colon-
ies but do not form
a web over the leaves
(Fig. 13). When
molting, the larvae
crawl to the trunk or
larger limbs (Fig.
14), where each sheds
its skin. After molt-
Fig. 14.-Larvae of walnut caterpillar prior to ing they return to the
molting on trunk of pecan tree. upper branches and
continue feeding. The caterpillars feed for 25 days or longer
and when full grown they crawl down to the ground and enter
the soil to pupate. The development of the second brood is
similar to that of the first and late in the fall the larvae enter
the soil, where they pass the winter as pupae.
Control.-The same spray treatment should be used as for
control of the fall webworm, or the colonies of caterpillars may
be removed from the trees and destroyed by crushing or burn-

Insects and Diseases of the Pecan in Florida

ing. They are easily destroyed when found massed on the tree
trunks in the act of molting.

The twig girdler (Oncideres cingulatus (Say)) is probably
complained of more than any other pecan insect, because of its
habit of cutting off the twigs during the late summer and fall.
When the girdlers are abundant they may cause serious damage.
Large numbers of twigs have been counted under a single tree

Fig. 15.-Twigs cut off of a single tree by the twig girdler.

Florida Agricultural Experiment Station

and many of them had clusters of immature nuts attached (Fig.
15). The severing of so many twigs also greatly reduces the
fruiting area of the tree for the following year or more. Pecan
nurseries also may suffer heavy losses if adjacent to heavily
infested areas. The twig girdler attacks a large number of
trees and shrubs, including "Australian pine" (not a true pine),
hackberry and cajuput tree, but it is especially bad on pecan,
hickory and persimmon.

Fig. 16.-Adult, or beetle, of the twig girdler at work on a persimmon
branch. Girdler more than twice natural size.

The adult beetles (Fig. 16) range in length from 1/2 to 5/8 inch,
are grayish brown and are rather inconspicuous on the trees
owing to this coloring. The beetles appear in the pecan orchards
the latter part of August. The twigs are girdled to provide
proper conditions for the development of the larvae, which are
unable to subsist on wood containing sap. The eggs are always
deposited in the severed portion of the twig. The eggs hatch
in about 3 weeks but the larvae grow very little during the fall
and winter. In the spring the larvae grow rapidly and com-
plete their transformation to adult beetles in the twigs by the
latter part of August.

Insects and Diseases of the Pecan in Florida

Control.-The simplest and most effective method of con-
trolling the twig girdler is to gather and burn the severed
branches during the fall and winter. Special care should be
taken to collect all branches on the ground as well as those
lodged in the trees. If there are hickory or persimmon trees
adjacent to the pecan orchard the severed branches from these
also should be destroyed.

The pecan budmoth (Gretchena bolliana (Sling.)) sometimes
causes considerable damage to pecan nursery stock. The larvae
feed on and in the terminal buds of the young trees, causing
excessive branching and stunted growth. This insect causes
very little damage in bearing orchards.
This insect passes the winter as a moth, which is gray with
blackish-brown patches and about 2/3 inch across the expanded
wings. When the buds begin to open the overwintered moths
lay their eggs on the twigs near the buds. Moths of later gen-
erations lay their eggs on the leaves. There are probably 5 or
6 generations in 1 season.
Control.-Young nursery trees should be kept in a vigorously
growing condition by proper cultivation and fertilization, as
vigorously growing trees unfold their buds so rapidly that this
will help to prevent the larvae from causing serious damage.
Spraying with either lead arsenate or calcium arsenate at
the rate of 3 pounds to 100 gallons of spray in combination with
bordeaux mixture as used for control of nursery blight will
help to keep this insect under control. Four or 5 applications
of this spray should be made at intervals of 3 or 4 weeks.

The pecan nursery casebearer (Acrobasis caryivorella Rago-
not) is found chiefly on pecan nursery stock and in northern
Florida it causes considerable damage in nurseries. The feed-
ing on and in the buds of the young trees is very similar to
that of the pecan budmoth. This casebearer also feeds on the
foliage of bearing trees but, like the budmoth, causes very little
damage to such trees.
Like the other casebearers these insects pass the winter as
partly grown larvae in hibernacula. However, the overwinter-
ing larvae and hibernacula are more than twice the size of those
of either the nut casebearer or leaf casebearer. In the nursery

26 Florida Agricultural Experiment Station
the larvae emerge in the early spring and feed in the buds and
on the leaves until full grown, when they pupate in a cocoon
in the leaves folded up in the top of the young nursery tree. The
moths are dark grayish with some light spots on the wings.
They are much larger than those of the nut casebearer or leaf
casebearer. There are probably 3 or 4 generations in 1 season.
Control.-The same nursery practices and control measures
recommended for the pecan budmoth should control this case-
The injury caused by the pecan phylloxera (Phylloxera de-
vastatrix Perg.) and related species is usually not very serious
in Florida, although sometimes it is very conspicuous. The
galls, or tumor-like swellings (Fig. 17) are often seen on any
part of the current season's growth of either seedling or
improved varieties of the pecan, and also on various species of
hickory. The phylloxera which causes these galls is a very
small insect closely related to the aphids or plant lice.
This insect passes the winter in the egg stage in protected
places on the branches. The young appear in the early spring,
about the time the buds unfold, and insert their beaks into the
new growth. Their feeding seems to stimulate the growth of
a gall which soon covers the insect. The insect develops in the
gall and lays a large number of eggs and then dies. When the
nymphs that hatch from the eggs develop into adults the gall
splits open and releases them.
Control.-A spray mixture containing 13 fluid ounces of nico-
tine sulfate to 100 gallons of water, with the addition of 21/2
gallons of liquid lime-sulfur for control of heavy infestations,
has been successfully used against this insect. For light to
moderate infestations the 13 ounces of nicotine plus 2 quarts
of summer oil emulsion per 100 gallons of water is effective.
These sprays should be applied during the late dormant period,
just as the buds begin to swell.
The pecan cigar casebearer (Coleophora caryaefoliella
(Clem.)), although usually considered a minor pest, sometimes
causes serious damage to pecans, especially in the western part
of the State. This insect passes the winter as a partly grown
larva in a light-brown case resembling a miniature cigar, usually
attached to twigs and limbs. The larvae become active in the

Insects and Diseases of the Pecan in Florida

,. e 1


'q I

Fig. 17.-Galls of phylloxera on pecan shoot and leaves.

Florida Agricultural Experiment Station

spring about the time the buds open and feed on the buds and
foliage (Fig. 18) until about the middle of May. The adults
appear during the latter part of May and first of June and lay
their eggs on the
A7 I leaves. There may be
several generations
during the season.
Control.-If this in-
Ssect requires control
measures spraying in
the spring with
either lead arsenate
or calcium arsenate
at the rate of 3
pounds to 100 gallons
of a 3-1-100 bordeaux
mixture, to prevent
injury to foliage by
the arsenical, is rec-

May beetles (Phyl-
lophaga spp. and Ano-
mala spp.), also com-
.__ .___.__ only called "June
Fig. 18.-Pecan leaflets injured by larvae of the bugs," are leaf-feed-
pecan cigar casebearer. ing insects w h i c h

* );-,*> A

Fig. 19.-Adult May beetles (about 1/2 times natural size).

: i
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Insects and Diseases of the Pecan in Florida

may cause serious defoliation of young pecan trees in early
spring. Trees near grass or other uncultivated land are usually
injured most. The adults feed only at night.
The adult beetles (Fig. 19) are robust, of a brown color, and
vary in size. The larvae are the well-known white grubs that
feed in the soil upon the roots of plants, especially grasses. Two
or more years usually are required for larval development.
Control.-The beetles may be removed from small trees at
night by collecting them and dropping them in a pail of kerosene,
or by jarring them onto a sheet on the ground and then destroy-
ing them.
Lead arsenate at the rate of 4 pounds per 100 gallons (in a
6-2-100 bordeaux mixture to prevent injury to foliage) applied
early in the period of flight should control the beetles.

The spittle bug (Clastoptera obtusa (Say)) is very common
on pecans in northern Florida during the early spring and
summer. The presence of the froth-like material about the
buds or young pecans, in which from 1 to 4 or 5 small insects
or spittle bugs may be found, often causes many inquiries from
.growers. This white substance probably serves as a protection
for the young or nymphs from parasites and other insect enemies.
The adult spittle bugs are commonly called frog-hoppers and
are usually found wandering around on shrubs and trees.
Numerous observations have failed, thus far, to show any
evidence of serious injury to pecans caused by this insect.
Control.-Where the spittle bugs are abundant and a control
is desired nicotine sulfate at 1 to 1,000, or 13 fluid ounces in 100
gallons, with 3 quarts of summer oil emulsion, to 100 gallons of
water, applied in the middle of May will control this insect. If
the regular spray program for control of pecan scab is being
followed, 13 fluid ounces of nicotine sulfate should be added to
100 gallons of bordeaux mixture in the second application.

The flatheaded apple tree borer (Chrysobothris femorata
(Oliv.)) attacks many kinds of deciduous trees as well as the
pecan. The injury results from the tunnelling of the borer
grubs in the bark and sapwood of the trunk and larger branches
(Fig. 20). Generally it is previously weakened trees that suffer
most from this insect, although vigorously growing trees some-

Florida Agricultural Experiment Station

Fig. 20.-Pupa and larval burrow of the flatheaded apple tree borer in
the .trunk of a young pecan tree.

Insects and Diseases of the Pecan in Florida

times become infested. Trees that have been injured in culti-
vation or affected by sunscald and winter injury are usually
very susceptible to attacks of this borer. The borers usually
begin work on the south or southwest side of the trunk and
most of the damage is found in this area.
The adult beetle is bright copper colored and may be found
in pecan orchards from spring to late fall. The eggs are laid on
the sun-exposed side of the tree in cracks in the bark or injured
places on the tree. The larvae or borers are creamy white and
are easily recognized by the greatly enlarged and flattened head.
When full grown the borer is about 1 inch long. There is only
1 generation of this beetle a year.
Contro.-When trees are infested the borers should be re-
moved from their burrows with a knife, taking care to injure
the healthy bark as little as possible. The exposed woody parts
should be painted over with a prepared pruning compound or
with a mixture of 1 part of creosote and 3 parts of coal tar.
Newly transplanted trees should be given the best possible
care until they are well established. Proper practices of culti-
vation, fertilization and pruning are important. Normally vigor-
ous trees with low heads rarely suffer severe injury from this
Preventive measures that may be employed against this insect
include wrapping the trunks of young trees with heavy paper
or burlap during the period March to November to prevent egg
laying on the trunks of the trees. Trap logs may be used in
heavily infested orchards. These consist of newly cut logs of
pecan, hickory or oak placed at intervals in the orchard to attract
the egg-laying beetles to the dying wood, which they prefer.
These logs should be placed in the orchard in early spring and
destroyed the following winter. Logs or prunings should never
be left lying about in the orchard from one season to another.
Fastening a board to the south side of a tree often is effective.
This insect (Xylobiops basilare (Say)) attacks only trees or
parts of trees that have been injured or are dying. It makes
small round holes in the bark of the pecan and other trees
(Fig 21).1 There are several other similar species of shot-hole
borers that also attack devitalized trees.
Control.-Trees should be kept in a healthy growing condi-
tion, as these insects do not often attack healthy wood. Remove

Florida Agricultural Experiment Station

Fig. 21.-Exit holes of adult beetles of the red-
shouldered shot-hole borer.

all dead limbs and
dying pecan trees
and reduce as far as
possible all sources
of infestation near
the orchard.

Termites are more
commonly known as
wood lice or white
ants. These insects
usually live in dead
wood and for this
reason, no doubt,
many growers never
think of them as an
insect pest of the
pecan. However, pe-
can nursery stock
and small trees are
sometimes killed by
the feeding of the
termites in the roots.
Trees planted on re-
cently cleared land
containing stumps
and dead roots are
most likely to be in-
jured. The termites
attack the trees un-
derground and affect-
ed trees may show
no signs of injury
until they are seri-
ously damaged or die.
The tree may have
the taproot or its
branches tunnelled
until only a shell or
the bark remains.

Insects and Diseases of the Pecan in Florida

cleared land should not be used for a pecan nursery or orchard
until all dead wood and stumps are removed. Only termite-
resistant stakes as iron, heart pine or wood treated with creosote
should be used near newly planted trees, as the stakes might
become infested and the termites spread to the trees.

Fig. 22.-Larva of the regal moth, commonly called "hickory horned devil."

Although the hickory horned devil (Citheronia regalis (F.))
is a very minor pecan pest, many inquiries are received concern-
ing it. This large caterpillar (Fig. 22) is the larva of the regal
moth, the largest and most magnificent of the royal moths (Fig.
23). The fore wings of the moth are olive colored, spotted with
yellow, and the hind wings are orange-red, spotted with yellow.
The larva is our largest caterpillar and can be easily recog-
nized by the large spiny horns with which it is armed. It feeds
on various trees and shrubs, though the larvae are never very
Control.-Control measures are rarely required for this insect
on pecans. When the larvae are found they may be removed
by hand and destroyed. In spite of their appearance they will
do no harm to one handling them. If necessary, lead arsenate
may be applied as for control of the fall webworm when the
larvae are small.

Florida Agricultural Experiment Station

Fig. 23.-Adult of the regal moth (male).


Three classes of diseases now found to be seriously affecting
pecans in Florida are: (1) Fungous, (2) bacterial and (3) nu-
tritional or environmental. The first 2 are caused by specific
organisms while the last is caused by a deficiency of 1 or more
mineral elements or by sudden changes in temperature and

Pecan scab (Cladosporium effusum (Wint.) Demaree) is one
of the most important limiting factors in nut production, espe-
cially in the Southeastern States, and its control is of vital im-
portance to the pecan industry. In Florida the following
varieties planted more or less extensively are scabbing in certain
orchards in some parts of the State: Schley, Success, Mahan,
Frotscher, Randall, Kennedy, Moneymaker, Moore, Nelson,
Teche, Curtis, Stuart and Elliot. It now appears probable that
all varieties of pecans will be found to be susceptible to the

kj~w' N


Insects and Diseases of the Pecan in Florida

scab disease when the proper strains of the fungus become estab-
lished in an orchard. For example, Moneymaker, Teche, Curtis
and Stuart varieties formerly were considered immune to scab,
but they have now been found to be susceptible in some localities.
However, scab on Curtis is mostly confined to young trees grow-
ing in nurseries.
The scab fungus attacks the rapidly growing tissues of the
leaves, shoots and nuts. When these tissues cease growing they
reach a state of com-
plete immunity. On
highly susceptible va-
rieties such as the
S c h I e y defoliation
often results, espe-
cially when frequent
infections occur be-
ginning in early
spring; but the great-
est damage is to the
nuts, the losses fre-
quently ranging from
75 to 95o%.
The scab fungus is
carried over winter
in the infected spots
on old leaves and
shucks (Fig. 24) and
in lesions on the
shoots of the trees.
In the spring when
weather conditions Fig. 24.-Schley nuts that received no spray.
weather conditions The shucks are severely infected with the fungus
become favorable the causing scab disease and they are opening pre-
dormant fungus be- maturely.
comes active and produces spores which are spread to the new
leaves, shoots and nuts where, under suitable conditions, they
may cause infections (Fig. 25).
On varieties very susceptible to scab, such ai Schley, the
primary infections on the foliage (Fig. 26) are irregular in out-
line and may be followed by some secondary infections. On
varieties more resistant to scab, such as Moore and Stuart, pri-
mary scab infections usually take place relatively late in the
season when the leaves are almost immune; therefore, the infec-

Florida Agricultural Experiment Station

tions are mostly confined to the nuts. Occasionally, though,
during ideal scab infection periods in early spring the foliage
of these more resistant varieties does become infected. The
spots are usually regular in outline and are surrounded by a
distinct halo (Fig. 27).
Infection of the leaves, shoots and nuts by the scab fungus is
correlated with the rainfall during spring and early summer.
Frequent rains and cloudy weather which keep the leaves wet

Fig. 25.-Early spring infections on Schley variety resulting from scab
carried over on old shucks from the previous season. Some of the leaflets
are infected with the fungus causing scab.

Insects and Diseases of the Pecan in Florida

over night or for 12 hours or more favor infection. Under such
conditions initial infections may occur prior to the middle of
April, and these develop rapidly. By the latter part of April or
the first week in May new crops of spores are produced which
cause secondary infections under favorable conditions if no
spraying has been done. Rainy periods or late afternoon rains,
which keep the leaves and nuts wet for 12 to 18 hours, provide
a condition very favorable for infection, as it requires from 6


Fig. 26.-Primary scab infections
on foliage of Schley, a variety
highly susceptible to scab in most

Fig. 27.-Primary scab infections
on foliage of Moore, a variety
highly resistant to scab in most
localities. Scab infections are regu-
lar in outline and only occur on
foliage during very favorable in-
fection periods in early spring.

Florida Agricultural Experiment Station

to 8 hours for the spores to germinate and cause infection.
Under these conditions it is usually from 1 to 2 weeks from
the time of infection until the scab lesions may be observed on
the new tissue of either leaves or nuts. To prevent infection
or to control scab, old leaves and shucks from which the spores
may be spread should
Snot remain exposed
in the orchards. Fur-
thermore, d u r i n g
rainy periods in early
spring and summer
the leaves, shoots and
nuts should have a
coating of bordeaux
The primary infec-
tions are first ob-
served as elongated,
olive-brown lesions
usually occurring on
the veins of the under
sides of the leaves of
susceptible varieties.
These spots first ap-
pear as very small
pin points but soon
enlarge and, with the
Fig. 28.-Schley nuts that received 1 pre- occurrence of second-
pollination spray of 4-1-100 bordeaux mixture, ary infections, may
followed by 3 applications of 6-2-100 bordeaux.
Photographed latter part of November. cause areas of the
leaves to appear al-
most black due to the coalescing of the spots. On the nuts the
spots of infection are small, black, circular and slightly raised
at first but later they may become sunken. The nuts of highly
susceptible varieties may have many infections on them until
practically the whole surface of the nut appears black. Un-
treated, severely infected nuts may drop prematurely or they
may almost entirely stop growth and remain attached to the
shoots indefinitely. On the other hand, those nuts sprayed as
recommended usually remain free of scab until they reach ma-
turity (Fig. 28).

Insects and Diseases of the Pecan in Florida

In the control of scab all old shucks and leaf stems should be
knocked off before the trees begin to leaf out in the spring.
A slight jarring of the trees or branches will cause most of the
old shucks and leaf stems to fall when they are wet and for
that reason this operation should be done after a rain or on
misty or foggy days. It is preferable to plow the shucks and
leaves under with a turning plow deep enough so that they will
not be turned up again by disk harrows or other means of culti-
vation. Since most successful orchardists plant winter cover
crops in their orchards, turning under the shucks and leaves
is not practical. However, the scab spores are washed down
by the rain; therefore, to get these shucks and leaves on the
ground will assist materially in preventing infection of the
The pruning off of low limbs that prevent plowing near trees
will aid materially in scab control by letting in sunlight, thereby
assisting in better air circulation.
A large number of fungicides, including various strengths of
bordeaux mixture, insoluble copper compounds and wettable sul-
furs have been used in experimental work for the control of
pecan scab during the past quarter century. Of all the materials
tested home-made bordeaux mixture has given best results.
When bordeaux mixture is applied according to the schedule and
instructions given below, the disease can be controlled with
slight or no injury to the trees.
The following spray schedule has given the most satisfactory
control of pecan scab during the 10-year period 1935-44 in south
Georgia and it is recommended for use by pecan growers in
First Application.-When the leaves are 1/4 to 1/2 grown and
before pollination 6 a 4-1-100 bordeaux mixture is used. (In-
structions for preparation of bordeaux mixture are given in
paragraph entitled "Preparation of Bordeaux Mixture," page
57.) In the vicinity of Monticello, Fla., this application should
usually be made between April 10 and 20.

6 Care must be used in making the prepollination spray application since
injury may result to the foliage if the temperature is as low as 50*-55' F.
at the time the spray is applied.

Florida Agricultural Experiment Station

Second Application.-A 6-2-100 bordeaux mixture should be
applied soon after pollination is complete or when the tips of
the small nuts have turned brown.
Third and Fourth Applications.-The third spray application
should be made about 3 to 4 weeks after the second, and the

^*o --7

Fig. 29.-Schley nuts showing results of
early spring infection. Secondary infection was
prevented by 3 thorough applications of 6-2-100
bordeaux, the last about July 15. Photographed
October 1.


may be produced (Fig. 29). On varieties such as Moore
and Moneymaker that are more resistant to scab than Schley
and become infected only in some localities the last 2 applica-
tions are usually sufficient to control the disease.

Downy spot (Mycosphaerella caryigena Demaree and Cole)
is a foliage disease of pecans that was first observed in south
Georgia and north Florida in 1927. In the vicinity of Monticello,
Fla., the disease may be seen first during late spring or early

'Add nicotine sulfate for the fourth spraying at the rate of 1 gallon
in 2,000 gallons (7 ounces in 100 gallons) if the black aphis (Melanocallis
caryaefoliae (Davis)) is present.

fourth about 3 to 4
weeks after the third,
using a 6-2-100 bor-
deaux mixture 7 (see
complete spray
schedule on page
60). Both timing
and thoroughness of
the spray application
are very important.
Sometimes weather
conditions are such
that it is not possible
to spray at the proper
time to prevent early
infection on the
young nuts, but when
this does occur and
the trees are properly
sprayed during the
later applications
secondary infection
can be prevented and
good quality nuts

Insects and Diseases of the Pecan in Florida

summer as downy or frosty spots on the lower sides of the leaves
(Fig. 30). This appearance is due to production of spores by
the fungus. Dew, fog and rain assist in spreading the spores
from one leaf to another. Later,
after these spores have been
washed away or have deterior-
ated, greenish-yellow spots re-
main that are clearly visible on
both sides of the leaves. As the
season advances the diseased
areas die and some premature
defoliation may occur.
The downy spot organism
lives over winter in the diseased
leaves, completing its life cycle
in them, and spores from the
perithecial or winter stage are
liberated in large quantities the
following spring, thereby infect-
ing the new foliage.
While all varieties are attack-
ed to some extent by the fungus,
Moneymaker and Stuart are
most susceptible.
Control.-Where winter cover
crops are turned under about
the first of April the sanitation
effects from burying diseased
leaves will be very beneficial in
controlling downy spot. Since
the winter spores of the causal
organism are liberated from the
fruiting bodies in the old leaves
during rainy periods of the
spring months and since foli-
ation of most varieties begins at
about that time, plowing under
infected leaves will assist ma-
terially in reducing this infec- Fig. 30.-White or "frosty" spots
tion. on the under side of a pecan leaf
showing characteristic markings of
Where spraying is done to downy spot disease in the early
co the first 2 scab ap- stages soon after formation of
control scab the first 2 scab ap- conidiophores and conidia.

Florida Agricultural Experiment Station

plications of bordeaux mixture are properly timed to control the
downy spot disease also. In orchards where it is not necessary
to spray for the control of scab the first 2 applications in the
scab spray (see p. 60) schedule will give control of the downy
spot disease.


Fig. 31.-Early stage of leaf blotch
on the under side of a leaflet. At this
stage the conidiophores and conidia are
in clusters and the pimple-like peri-
thecia are just appearing to form the

Pecan leaf blotch (Myco-
sphaerella dendroides (Cke.)
Demaree and Cole) is a foli-
age disease of nursery and
orchard trees and is especial-
ly prevalent in the vicinity
of Monticello, Fla. The fruit-
ing bodies first appear on
mature leaves in June or July
as olive green velvety tufts
of conidiophores and spores
on the under surface, while
yellow spots appear later
on the upper surface of the
leaves (Fig. 31). Fruiting
bodies of the perfect stage,
black pimple-like structures,
make their appearance
among the conidiophores
about midsummer; and after
the spores have been washed
away by rain, or have other-
wise deteriorated, groups of
these pimple-like structures
unite, giving the leaves a
black, shiny, blotched ap-
pearance. Occasionally an
entire leaflet is enveloped by
coalescence of these blotches
and premature defoliation
Control.-The leaf blotch
and downy spot diseases are
similar in that both causal
organisms overwinter on fal-

Insects and Diseases of the Pecan in Florida

len, decaying leaves. Therefore, the same sanitation measures
used in plowing under these old leaves in the early spring will
materially reduce the infection later in the growing season.
In contrast to the downy spot disease, the leaft blotch patho-
gen is only a weak parasite and does not attack orchard trees
unless they have been lowered in vigor by overcrowding, rosette
or attacks from borers, or
have suffered from general
neglect. Nursery trees are
more susceptible to attack
than old trees and the dis-
ease is especially prevalent
where the nursery blight dis-
ease is present. Under such
conditions defoliation begins
with the basal leaves and
the disease gradually pro-
gresses upward until defoli-
ation is complete with the
exception of a few leaves in
the tops of the trees.
Control measures for scab
and downy spot will also con-
trol the blotch disease. In
localities where only leaf
blotch is present 1 applica-
tion in June of low-lime bor-
deaux mixture of the 6-2-100
formula will prevent the dis-

Brown leaf spot (Cerco-
spora fusca Rand) is a dis-
ease of minor importance,
especially on healthy, vigor-
ous trees. It is prevalent
throughout the entire pecan
belt, but causes serious pre-
mature defoliation only in Fig. 32.-Pecan brown leaf spot on
localities having a high rain- under side of leaf. The diseased spots
are characterized by concentric mark-
fall and in orchards where wings.

Florida Agricultural Experiment Station

the trees lack vigor as a result of neglect. A typical diseased
leaflet is shown in Figure 32. The primary infections of the
diseased spots are circular in outline, reddish brown, and often
develop grayish concentric
zones, while later these spots
F are very irregular in out-
h line. Like pecan scab, the
brown leaf spot inoculum is
carried overwinter in the in-
fected spots on the old leaves.
iIn Florida the disease first
appears in June or July, at-
tacks only the mature leaves,
and if not controlled causes
premature defoliation early
in October. The Stuart is
very susceptible to the dis-
ease while all others are more
or less resistant, especially
if a good cultural program
is followed in an orchard.
Control.-In spraying for
the control of brown leaf
spot only 1 application of
6-2-100 bordeaux mixture
made at any time between
May 15 and June 15 usually
will be sufficient.

In seasons of excessive
rainfall pecan nursery blight
(Elsinoe randii Jenkins and
Bitancourt) becomes one of
the most important limiting
Fig. 33.-Early stages of nursery factors in the production of
blight on pecan leaflet. budded pecan trees, espe-
cially in north Florida. As its name implies, this diseases is
confined almost entirely to nursery trees. The fungus causing
nursery blight invades both young and old leaflets, and infec-
tions that are first observed in April result in small reddish
lesions that develop on both surfaces of the leaves (Fig. 33).

Insects and Diseases of the Pecan in Florida

Later in the season the spots on the upper surface of the leaves
turn ash-gray. Single lesions usually are about 1/8 inch in
diameter. These spots, however, may unite by secondary in-
fections and form a continuous lesion along each side of a vein.
Late season infections are most numerous along the midrib and
larger veins. The diseased areas are soon killed by the invading
fungus, the tissues becoming brittle and breaking out, resulting
in ragged margins and perforations.
Control.-Nursery blight in Florida can be controlled by ap-
plying 4-1-100 bordeaux mixture about April 5 to 15, and follow-
ing this with 3 applications of 6-2-100 bordeaux mixture. These
later applications should be made at monthly intervals, with
the last 1 on or about July 10 (Fig. 34).
Since the disease is carried over winter on the fallen leaves
in the nursery, destroying these old leaves by plowing them
under will aid materially in effecting control.

Thread blight (Pellicularia koleroga Cke.) attacks pecans and
numerous other woody plants throughout Florida. The fungus
overwinters in compact masses of fungous tissues known as
sclerotia, which adhere to the bark of twigs and leaf petioles
(Fig. 35). The fungus threads or mycelium grow rapidly in

Fig. 34.-Spraying nursery trees with 6-2-100 bordeaux mixture, Monti-
cello, Florida. Approximately 100 gallons of spray material per acre re-
quired for this type of spraying.

Florida Agricultural Experiment Station

May and June from the sclerotia on the twigs onto the new
petioles and leaflets. In this manner the thread-like mycelium
spreads over the lower surface of the leaves, completely para-
sitizing and killing them (Fig. 36), causing premature defoli-
ation of the affected trees. Under particularly favorable condi-
tions the fungus growing on the leaves produces tiny spores
(basidio-spores) which are disseminated by wind, rain and dews.
These spores probably cause infection and explain the wide
spreading of the disease which is sometimes observed, although
little is known about them.
The most common symptoms of the thread blight disease dur-


Fig. 35.-Left, compact masses (sclerotia) of the thread blight fungus
on a leaf petiole. Right, similar masses on a twig.

Insects and Diseases of the Pecan in Florida

ing the summer months is the matting together of the dead
leaves. These mats of dead leaves hang from the shoots by
the spider-web-like threads of the fungus until frost kills the
threads, which allows the leaves to fall to the ground.
Control.-The thread blight fungus usually attacks pecan
trees that are near forests or wood lots in which the fungus
is present, and spreads rapidly in damp localities or especially
where the pecan trees are crowded or neglected. Pruning away

L *
Fig. 36.-The thread blight disease on pecan foliage. The leaflets are
withered and discolored.

Florida Agricultural Experiment Station

the lower limbs and removing trees where they are crowding
will assist in controlling the disease. Where the infection is
severe, 2 applications of 6-2-100 bordeaux mixture, second and
third in the scab schedule (see p. 60) will prevent or control
the disease.
Powdery mildew (Microsphaera alni Wint.) is of minor im-
portance on pecans in Florida. This disease, like scab, affects
both foliage and nuts,
forming a white
superficial fungous
growth early in the
growing season (Fig.
37), generally in
S July, while later the
-. perithecial or winter
stage develops on the
diseased spots. Oc-
casionally premature
defoliation occurs un-
der conditions very
favorable for the
spread and develop-
ment of the fungus.
Where the nuts are
infected early in the
season premature
splitting of the
shucks results and
Fig. 37.-Powdery mildew in its early stages this causes shriveled
on Farley nuts. The white mycelium has mostly kernels.
covered the surface of the nuts.
Control.-Most va-
rieties of pecans grown commercially in Florida are resistant to
mildew, and where this disease is present it is easily controlled
by making 2 applications of 6-2-100 bordeaux mixture in June
and July (see spray schedule p. 60). The same sanitary meas-
ures as those recommended for scab, downy spot, leaf blotch and
nursery blight will also assist in controlling powdery mildew.
All wounds on pecan trees provide a point of entrance for
wood-rotting fungi unless the injured surfaces are properly

Insects and Diseases of the Pecan in Florida

treated. Once these fungi gain entrance they spread quite
rapidly through the wood and may endanger the life of the en-
tire tree. Some wounds heal very much more quickly than
others. Wounds that are made flush with the trunk of the tree
or the main branches heal more quickly than those even of
smaller size that are not flush with the remaining tree part (Fig.
38). Smooth, carefully made wounds heal more quickly than
do those that have rough, jagged or irregular surface. In re-
moving limbs stubs should not be left, since they rarely ever
heal over and they provide ideal entrance places for the wood-
rotting fungi (Fig. 39).
Wood-rotting fungi usually can be prevented from entering


Fig. 38.-Wrong way to prune trees. Wounds of this type will be slow
in healing and thus will usually allow the entrance of wood-rotting fungi.
See Fig. 39.

Florida Agricultural Experiment Station

wounds by painting them once annually with a creosote and coal
tar paint mixture made by adding 1 part of commercial creosote
to 3 parts of coal tar. This mixture is caustic and will slightly
injure the cambium but the wound will generally remain free
of wood-rotting fungi and eventually heal.
There are several tree wound paints sold under various trade
names, most of them having asphalt, tar or vegetable gums as
their base, but they are more expensive and usually do not
furnish any better wound protection than the recommended
creosote and coal tar mixture.

Crown gall (Bacterium tumefaciens E. F. Sm. and Town) is
a bacterial disease of pecan which does extensive damage under
certain conditions. Formerly it was considered a disease of
nursery trees only (Fig. 40) but in more recent years it has
been found well established in orchards, especially on old trees,


Fig. 39.-In pruning make the cuts flush with the tree trunk to prevent
the entrance of wood-rotting fungi as well as to hasten healing of the
wound. These cuts were painted with the recommended coal tar-creosote
paint mixture. Photographed 2 years after cuts were made.

Insects and Diseases of the Pecan in Florida

where it may become so severe as to kill them (Fig. 41). On
trees of bearing age the disease is confined mostly to the roots
and base of the tree trunk, but occasionally lateral roots also are
affected. Wart like,
somewhat fragile
growths, often ex-
tending several
inches above the sur-
face soil and from a
few inches to a foot
or more in diameter,
describe fairly well

characteristics of the
crown gall disease.
Because of their fra-
gility these galls are
often broken off the
roots and become
scattered on top of
the soil when the or-
chard is being culti-
Control.-It is im-
portant that all in-
fected nursery stock
be destroyed, prefer-
ably by burning at
the time of digging. Fig. 40.-Crown gall disease on nursery
A few unreliable stock. Trees of this type should be burned to
nurserymen have prevent further spread of the disease. (From
USDA Farmers' Bul. No. 1829.)
been known to re-
move the galls, paint the wounds and sell the diseased trees to
their customers. This practice is certain to disseminate the
disease wherever the trees are planted.
Where orchard trees are infected with crown gall the galls
should be removed and the wounds painted with a mixture of
1 part creosote to 3 parts coal tar. This procedure will assist
in preventing the spread of the disease to healthy parts of the
tree. To prevent the spread of the disease to healthy ones, in-
fected trees should not be cultivated nor harrowed.

52 Florida Agricultural Experiment Station



Rosette (zinc deficiency) is a nutritional disease caused by an

>..'- 'as .^ b*

Fig. 41.-The crown gall disease on an older tree. Note enlarged growth
at base as result of this disease.

Insects and Diseases of the Pecan in Florida

inadequate amount of available zinc in the soil to provide the
tree with its requirements for growth and nut production.
Prior to the discovery in 1931 of the cause and control of
rosette most of the bearing pecan trees in the Southeastern
States were affected by the disease. Since that time the ma-
jority of the growers in this region have treated the soil with
zinc sulfate, and when once overcome in this way, rosette can
be classed as a minor problem, since repeated applications usually
are not needed.
Yellow mottling, or chlorosis, and crinkling of the leaves in
the tops of trees are characteristic of rosette in the early stage
of its development. As the disease progresses the symptoms
appear on the leaves on the lower branches. In advanced stages
the leaves become dwarfed, the internodes are shortened, and
gradually the twigs and branches in the tops of the trees die
(Fig. 42). Often the grower experiences difficulty in detecting
rosette because the first symptoms usually are in the tops of
the trees and severe damage may result to the trees before he
is fully aware of its presence. Any abnormal color of the foli-
age in the top of a tree should suggest the possibility of rosette.
If the leaflets of the terminal shoots near the ground are exam-
ined carefully they frequently show yellowing between the veins
which is characteristic of the disease. Severely rosetted trees
are usually non-productive and may become so weakened that
they die from attacks of borers or from other causes. However,
rosette alone has never been known to kill pecan trees.
Rosette occurs under variable conditions in Florida. Eroded
or light sandy soils or those deficient in organic matter seem
to favor its development. Trees on well-drained, medium to
heavy soil types are mostly free from rosette except under un-
usual conditions, such as the addition of heavy applications of
lime to the soil in order to facilitate the growth of winter cover
A varietal resistance or susceptibility to rosette seems to exist.
Stuart is most susceptible, while Moneymaker in most localities
usually is quite resistant.

Spraying.-Rosette may be corrected by applying zinc sulfate
in a spray on the trees or by applying it to the soil; the method
of application being determined largely by conditions confront-
ing the grower. Soil applications are not practical in orchards

Florida Agricultural Experiment Station

growing on neutral or alkaline soils and under these conditions
spraying is necessary. Where growers are prepared to spray,
this method is satisfactory regardless of the soil condition.
Three applications of spray consisting of 2 pounds of zinc sulfate,
analyzing approximately 36% zinc, added to 100 gallons of water
will overcome rosette where the disease is present only in the
mild form. The first spray application should be made as soon
after pollination as possible and this should be followed by addi-
tional applications at intervals of 3 to 4 weeks. This schedule
should be followed annually until all signs of the disease have
been eliminated; then observations should be made at regular

Fig. 42.-A tree seriously affected with the rosette disease. The broad-
casting over the soil of 20 pounds of zinc sulfate in 2 equal annual applica-
tions was required to overcome the trouble. See Fig. 43.

Insects and Diseases of the Pecan in Florida

intervals for the first signs of its recurrence, since it is likely
to reappear at any time.
Growers who are spraying to control scab and other parasitic
diseases can combine zinc sulfate with bordeaux mixture (see
combination insect and disease spray schedule). Four pounds
of zinc sulfate to 100 gallons of bordeaux mixture should be
used, since the lime in the bordeaux mixture somewhat reduces
the effectiveness of the zinc. Since zinc sulfate is very corrosive
it is essential that the spray tank and pump be thoroughly rinsed
with water at the conclusion of each day's spraying.
Soil Applications.-Since most Florida soils where pecans are

Fig. 43.-The same tree shown in Fig. 42 2 years later, after 2 annual
applications of 10 pounds of zinc sulfate to the soil.

Florida Agricultural Experiment Station

commercially grown are acid, zinc sulfate applied to the soil will
produce more satisfactory results than spray applications be-
cause of its lasting effect. The zinc sulfate should be evenly
broadcast from near the trunk to beyond the limb spread, the
rate of application being determined to a large extent by se-
verity of the disease, nature of the soil and size of the trees.
On bearing trees not severely affected by rosette the symp-
toms usually disappear after 1 application of 5 pounds of zinc
sulfate per tree. Trees severely affected require more than 5
pounds, and amounts up to 10 pounds annually, over a period of
2 or more years, may be required in some instances to overcome
the disease (Figs. 42 and 43).
February and March are the best months to apply the zinc
sulfate for rosette control. It may be applied later, but the time
of recovery will be delayed. If not applied until the deficiency
symptoms are present on the leaves little or no correction of
the disorder will be evident until the following year.
Cultivating the zinc sulfate into the soil is desirable where
practicable, as this brings about quicker results and prevents
the possibility that heavy rains will wash it away from the
trees. However, where winter cover crops are grown it is not
practical to cultivate immediately if the zinc sulfate is applied
in February or March as recommended. The chemical may
cause slight burning of the winter cover crop, especially if it
is not evenly distributed, but the plants usually show no perma-
nent damage under good growing conditions.

Winter injury is a disorder usually found on young, vigorous,
late-growing pecan trees or those that were defoliated in summer
and put out a new crop of leaves late in the season.
It is not always confined to young trees. Older trees, espe-
cially those that have received heavy applications of nitrogen
which tend to keep them in a vegetative condition late in the
season, may be severely injured by sudden freezes.
Winter injury is easily detected by the experienced pecan
grower. The indications are dead or dying trees in early sum-
mer, with vigorous sprouts growing up from the roots some-
what later. Close examination will show that the trunks of the
trees have been damaged near the ground. The affected tree
usually foliates and grows normally in the spring but the leaves
wither and the tree suddenly dies as soon as hot weather begins.

Insects and Diseases of the Pecan in Florida

Shot-hole borers and other insects are sometimes present but
their damage is of a secondary nature. By cutting through the
bark into the cambium layer it is easy to detect the "sour-sap"
and discolored wood.
Control.-A young pecan orchard should be handled with ex-
treme care so that winter injury will be prevented. Young trees
should be fertilized only in early spring and should not be culti-
vated later than mid-summer, except at the time of planting
winter cover crops in the fall when the trees are approaching
dormancy. This method of handling young trees will assist in
preventing vegetative growth late in the season and the trees
will go into the winter with the wood in a mature and hardy
Injury resulting from sunscald is sometimes confused with
winter injury. The symptoms are dead or cankerous areas,
usaully on the southwest side of the trees or on the tops of
large branches. Like winter injury, sunscald occurs mostly
on young trees but also on older ones that have been cut back for
topworking to some other variety. Bright sunshine on summer
days which raises the temperature of unshaded bark to a lethal
point or on winter days which raises the bark temperature dur-
the daytime only, followed by a sudden and relatively severe drop
in temperature at night, is the probable cause of sunscald. The
dead areas in the bark furnish ideal entrance places for borers
and other insects and for wood-rotting fungi.
Control.-One of the best methods of control is to head the
young trees as close to the ground as practicable. Pruning off
the lower limbs should not be done until the trees have advanced
several growing seasons, as the low lateral limbs increase the
protective shading of the trunk. Wrapping the trunks of the
trees with gunny sacks or whitewashing them will aid in pre-
venting sunscald.

Low-lime bordeaux mixture can be used safely, economically
and effectively in pecan orchards for the control of pecan scab
and parasitic leaf diseases. Furthermore, there is no better or
cheaper form of bordeaux mixture known that that made at

Florida Agricultural Experiment Station

home with bluestone (copper sulfate), lime and water. For the
sake of simplicity of equipment, economy of labor and uniformity
of the product, growers are advised to use the finely powdered
or "snow" form of bluestone and a high-calcium hydrated lime
for making the bordeaux mixture. Powdered bluestone or cop-
per sulfate is in particles about the size of granulated sugar
and dissolves rapidly in water. This "snow" form of bluestone
costs slightly more than the large crystals, but the added cost
is offset by the saving of time and labor in dissolving it.
Hydrated lime can be purchased in 50-pound sacks in most
towns. Although hydrated lime as ordinarily sold in the South-
eastern States, especially that manufactured in Alabama and
Tennessee, is usually satisfactory for making bordeaux mixture,
growers nevertheless should demand that it contain at least
98% calcium hydroxide. The use of hydrated lime has several
advantages over quick lime. It is properly slaked when pur-
chased, and if stored in the bags and in a dry place it deteriorates
slowly; it is relatively free from grit, and a "milk of lime" (a
suspension of 6 pounds of lime stirred into about 5 gallons of
water) can be prepared in less time than is required with quick
A 6-2-100 bordeaux mixture for use in a 300-gallon spray tank
may be prepared in the following manner: Weigh out 18 pounds
of powdered (snow-form) bluestone (copper sulfate) and 6
pounds of hydrated lime.8 Add about 5 gallons of water to the
lime in a separate container to make the milk of lime mixture.
The bluestone may be dissolved by placing it in the strainer of
the spray tank while the tank is being filled. When the tank
is about 3/ full and all the bluestone is dissolved, the milk of
lime should be slowly added with the agitator running so as to
mix thoroughly the lime with the bluestone solution.

Lead arsenate and calcium arsenate are generally sold in the
powder form, formerly white but now colored pink in Florida
as a safety measure. Both arsenicals, and especially the calcium
compound, are liable to cause foliage injury when used alone in
humid climates. To overcome this difficulty some material must
be added to the mixture to absorb the free arsenic present or

8 In preparing the prepollination, or 4-1-100 bordeaux mixture, weigh
out 12 pounds of copper sulfate and 3 pounds of hydrated lime for a 300
gallon spray tank.

Insects and Diseases of the Pecan in Florida

change it to an insoluble form. Bordeaux mixture as used for
control of the various diseases of the pecan is the best material
for this purpose. As a preventive for arsenical injury the bor-
deaux mixture may be used as weak as 2-1-100.
The summer oil emulsions are chemically inert and are not
likely to injure the foliage or nuts, especially when used with
nicotine sulfate at a low strength as specified for the control of
the pecan nut casebearer or black pecan aphid. The emulsion
should contain not less than 80 percent of oil having a viscosity
of not more than 70 seconds by the Saybolt test and an un-
solfonated residue of at least 85 percent.
Nicotine is an extract obtained from the stems and leaves of
tobacco, mostly from the waste products in cigar and cigarette
manufacture. It is usually sold as nicotine sulfate, containing
40 percent of actual nicotine. The nicotine sulfate is not rapidly
volatile and is employed chiefly in the preparation of orchard
sprays. To control aphids nicotine sulfate must be combined
with some alkaline material to liberate the nicotine more rapidly.
Bordeaux mixture is effective for this purpose.

The concentrated commercial liquid lime-sulfur usually tests
about 33 on the Baume hydrometer. This material should al-
ways be diluted. Lime-sulfur should never be used with soap
or with soap-oil emulsions without stabilizers.

When desirable it is possible to combine in 1 mixture and
application the spray materials recommended for the control of
insects and diseases, thus saving the time and labor required to
make separate applications. The spray schedule for combating
pecan insects and diseases, if carefully followed, will give com-
mercial control of most of the important insects and diseases
that are present in Florida. However, a general spray schedule
is not always the most satisfactory one and the details of the
control program should be worked out to meet local conditions.
9 The following paragraphs and the spray program for control of pecan
insects and diseases have been taken with little change from USDA
Farmers' Bulletin No. 1829, Feb. 1940.

Florida Agricultural Experiment Station


What may be termed medium-sized portable spray outfits have
been extensively used for spraying pecan trees. Such machines
may be equipped with motors capable of developing from 15 to
25 horsepower or they may be driven by power take-offs on
tractors or trucks. Tanks should hold at least 300 gallons of


Name and Time For Control of: Materials Remarks
of Spray _

First cover or Scab, downy 4-1-100 A very important dis-
prepollination spot, nursery bordeaux ease spray.
spray. When blight, mixture.
first leaves are
half grown.

.Second cover Scab, nursery 6-2-100 Important spray to
spray. About blight, pecan bordeaux protect the nuts and
time tips of nut case- mixture, nico- foliage. Cover nuts
of small nuts bearer, aphids, tine sulfate 13 and leaves thorough-
have turned blotch, brown ounces, zinc ly. Use zinc sulfate
brown, leaf spot, sulfate only if rosette is
downy spot, 4 pounds. present. Important
thread blight, spray for pecan nut
casebearer and
should be applied at
the proper time to
obtain good results.

Third cover Scab, nursery 6-2-100 Use zinc sulfate only
spray. Three blight, pow- bordeaux if rosette is present.
weeks after dery mildew, mixture, zinc If the fall webworm
second cover blotch, brown sulfate or the walnut cater-
spray. leaf spot, 4 pounds. pillar is usually
thread blight, abundant and a seri-
rosette. ous pest, add 3
pounds of arsenate

Fourth cover Scab, nursery 6-2-100 On varieties that do
spray. Three blight, pow- bordeaux not scab and where
weeks after dery mildew, mixture, arse- it is necessary to
third cover pecan leaf nate lead control the pecan
spray, casebearer, 3 pounds, nico- leaf casebearer, use
aphids. tine sulfate 2-1-100 bordeaux
7 ounces, zinc mixture and 3 pounds
sulfate of lead arsenate.
4 pounds. Bordeaux mixture is
used in this case
merely as a correc-
tive for arsenical in-
jury. Use nicotine
sulfate only if black
aphids are present.

Insects and Diseases of the Pecan in Florida

spray material: The machine should have a pump capacity rang-
ing from 25 to 35 gallons per minute and be capable of main-
taining a pressure of 400 to 600 pounds with the spray gun open.
Machines of this type, under average conditions, will spray trees
from 40 to 60 feet in height. Since the operator should stand
on top of the machine, a spray gun that can be adjusted to
produce both a wide-angled mist and a narrow, driving spray,
with a short hose, 8 to 10 feet long and 3/4 inch in inside diameter,
is preferable.
The size of the machine purchased should coincide with the
size and number of trees that are to be sprayed. For instance,
if the grower has a small orchard of young trees he could pur-
chase a smaller machine than the one recommended above. If
at all possible he should purchase the machine from a dealer
who carries in stock a supply of parts and equipment for needed
The availability of the water supply is as important as the
selection of the spray machine. It should be centrally located
and, if a well is used, an elevated water tank holding several
thousand gallons should be provided. A 4-inch outlet should
be placed in this tank which will allow the filling of a 300-gallon
spray tank in 3 to 5 minutes. If the equipment and labor are
available a supply tank that will carry the water directly to the
spray machine will save much time. With equipment of this
type under ordinary conditions an operator should be able to
apply 4,000 gallons of spray per day. Such equipment should
be adequate for an orchard of 1,500 to 2,000 trees, ranging in
height of from 40 to 60 feet.

In applying all sprays it is essential that all leaves and nuts
be evenly covered with a thin film. The tops of the trees, as
well as the lower branches, must be sprayed. Do not drench or
overspray, as this wastes material and does no good and may
result in injury. The best spraying is done when all the leaves
and nuts are wet but little or none of the material runs off the
wet surface.

Many of the insecticides listed in this bulletin are poisonous
to human beings and to animals and should be handled with care.
All poisons should be kept properly labeled and should be stored

Insects and Diseases of the Pecan in Florida

spray material: The machine should have a pump capacity rang-
ing from 25 to 35 gallons per minute and be capable of main-
taining a pressure of 400 to 600 pounds with the spray gun open.
Machines of this type, under average conditions, will spray trees
from 40 to 60 feet in height. Since the operator should stand
on top of the machine, a spray gun that can be adjusted to
produce both a wide-angled mist and a narrow, driving spray,
with a short hose, 8 to 10 feet long and 3/4 inch in inside diameter,
is preferable.
The size of the machine purchased should coincide with the
size and number of trees that are to be sprayed. For instance,
if the grower has a small orchard of young trees he could pur-
chase a smaller machine than the one recommended above. If
at all possible he should purchase the machine from a dealer
who carries in stock a supply of parts and equipment for needed
The availability of the water supply is as important as the
selection of the spray machine. It should be centrally located
and, if a well is used, an elevated water tank holding several
thousand gallons should be provided. A 4-inch outlet should
be placed in this tank which will allow the filling of a 300-gallon
spray tank in 3 to 5 minutes. If the equipment and labor are
available a supply tank that will carry the water directly to the
spray machine will save much time. With equipment of this
type under ordinary conditions an operator should be able to
apply 4,000 gallons of spray per day. Such equipment should
be adequate for an orchard of 1,500 to 2,000 trees, ranging in
height of from 40 to 60 feet.

In applying all sprays it is essential that all leaves and nuts
be evenly covered with a thin film. The tops of the trees, as
well as the lower branches, must be sprayed. Do not drench or
overspray, as this wastes material and does no good and may
result in injury. The best spraying is done when all the leaves
and nuts are wet but little or none of the material runs off the
wet surface.

Many of the insecticides listed in this bulletin are poisonous
to human beings and to animals and should be handled with care.
All poisons should be kept properly labeled and should be stored

Florida Agricultural Experiment Station

where they will not be mistaken for food or medicine, and where
children and others unaware of their danger cannot have access
to them.
Lead arsenate and calcium arsenate are poisonous when taken
into the system. When they are being prepared for use as spray
mixtures the breathing of the dry material should be avoided.
When handling these poisons keep hands away from the mouth
and wash before handling food.
Nicotine is a very poisonous material. Some persons are very
susceptible to the effects of nicotine and may develop acute
nausea, while others can handle it freely without suffering any
noticeable effects. Illness can be caused also by the absorption
of nicotine through the skin, and operators should avoid the
wearing of clothing that is wet with spray solution containing
Lime-sulfur is very caustic to the skin, when used in high con-
centrations. Persons exposed to this material should protect
their faces by covering them with grease or petroleum jelly
before they begin spraying, and should avoid getting the ma-
terial in the eyes, as this would cause temporary discomfort.
The hands may be protected by wearing oiled leather gloves.