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 Front Cover
 Table of Contents
 Introduction
 Part I-Diseases injurious to the...
 Part II-insects injurious to the...






Group Title: Bulletin University of Florida. Agricultural Experiment Station
Title: Diseases and insect pests of the pecan
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 Material Information
Title: Diseases and insect pests of the pecan
Alternate Title: Bulletin 147 ; Florida Agricultural Experiment Station
Physical Description: p. 133-163 : ill. ; 23 cm.
Language: English
Creator: Matz, J ( Julius ), b. 1886
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville, Fla.
Publication Date: May 1918
 Subjects
Subject: Pecan -- Diseases and pests   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by J. Matz.
General Note: Cover title.
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Bibliographic ID: UF00027340
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - AEN3275
oclc - 18162255
alephbibnum - 000922766

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Table of Contents
    Front Cover
        Front Cover
    Table of Contents
        Table of Contents
    Introduction
        Page 135 (MULTIPLE)
    Part I-Diseases injurious to the pecan
        Page 136
        Page 137
        Page 138
        Page 139
        Page 140
        Page 141
        Page 142
        Page 143
        Page 144
        Page 145
        Page 146
        Page 147
        Page 148
        Page 149
    Part II-insects injurious to the pecan
        Page 150
        Page 151
        Page 152
        Page 153
        Page 154
        Page 155
        Page 156
        Page 157
        Page 158
        Page 159
        Page 160
        Page 161
        Page 162
        Page 163
Full Text


Bulletin 147


UNIVERSITY OF FLORIDA

Agricultural Experiment Station


DISEASES AND


INSECT


PESTS


OF THE PECAN
By J. MATZ


FIG. 45.-Pecan nuts affected with mildew


Bulletins will be sent free upon application to Experiment Station,
GAINESVILLE, FLORIDA


May, 1918

















CONTENTS
Page

INTRODUCTION .............................. ............. ...... 135
PART I.-DISEASES INJURIOUS TO THE PECAN ....................... 135
Diseases of Foliage and Nuts-
Scab ................................................... 135
Anthracnose .......................................... 137
M ildew ............................................. 138
Diseases Primarily Affecting the Wood-
Pecan Rosette ................ ......................... 139
Dieback ............................................. . 141
Diseases Affecting the Nuts only-
Pink Mold ........................................... 144
Kernel Spot ............................................ 144
Diseases Affecting Foliage only-
Brown Leaf Spot ........................................ 145
Nursery Blight ......................................... 146
Leaf Blotch ................. .......................... 146
Minor Troubles-
W inter Kill ............................................. 147
Salamanders ......................................... 148
Mistletoe ........................ ................. 149
PART II.-INSECTS INJURIOUS TO THE PECAN ....................... 150
Pecan Leaf CaseBearer ................................. 150
Pecan Nut Case-Bearer ................. ............ 152
Pecan Shuckworm .................................... 153
Pecan Cigar Case-Bearer ............................. . 154
Fall W e'worm ................. ....................... 155
Walnut Caterpillar .................................... 155
Pecan Bud-Moth ........................................ 157
Flat-Headed Apple-Tree Borer ........................... 157
Hickory Twig-Girdler .................. ............... 159
Shot-H ole Borer ......................................... 160
Oak or Hickory Cossid ................................. 160
Hickory Phylloxera ................... ............... 161











DISEASES AND INSECT PESTS OF THE PECAN
By J. MATZO
A number of diseases and insect pests attack the pecan more
or less seriously. In order to combat them successfully it is
necessary to know their characteristics, to recognize their dif-
ferent stages, and to understand the different methods by which
they develop. By recognizing a disease or insect pest in its in-
cipient stage, a great saving in the year's crop of nuts may be
made and a more likely check be set against the spread of the
disease or insect pest. It often happens that diseases of plants
caused by parasitic, plant-like organisms (fungi) and injuries
caused by insects are mistaken for one another under the popu-
lar but erroneous term, "bugs." Upon close examination one can
distinguish the mechanical and often clean-cut injuries that are
caused by biting and boring insects from the diseases that are
caused by fungi. The latter seldom result in an actual cutting
out of the affected parts. Discoloration, wilting, and a breaking
up of the plant substance, and the ultimate dropping or dying of
the affected parts, are the main characteristics of fungus attacks.
It is essential that these two types of injury as well as the dif-
ferent diseases and insect pests be recognized if the correct
means of control are to be applied. This bulletin describes the
most common pecan troubles and offers methods by which they
can be controlled.
Credit for a part of the information in this bulletin is here
given to publications of the Bureau of Plant Industry, U. S. D.
A., and especially to John B. Gill, Bureau of Entomology, for the
use of data on insects and for some illustrations.

PART I.-DISEASES INJURIOUS TO THE PECAN
SCAB
Fusicladium efusum Wint.
Scab affects the leaves, twigs and nuts of the pecan tree, with
the result that the leaves are distorted and occasionally are shed,
the young twigs are injured and sometimes killed, and the crop
is reduced by many of the young nuts dropping before maturity.
The fungus which causes scab is evidenced by a dark green,
smoky, superficial growth which is usually confined to rounded
spots.







Florida Agricultural Experiment Station


On the leaves (fgs. 46 and 47.), the spots are slightly; raised
and vary in size from small black specks to' 6ne-fouithm inch in
diameter. Both surfaces of the leaves may become infected, in
which case the dark, velvety growth constituting the spore-bear-
ing part of the scab fungus is seen on one side
of the spot only, the opposite side being hard,
more or less smooth, and black. On the nuts,
the first appearance of scab is similar to that
on the leaves, except that owing to the fleshy
nature of the green outer covering of young
nuts the affected areas appear at first more or
less sunken in the green and soft tissue. Under
conditions favorable for the development of the
disease the whole surface of the green nut may
become covered with the
black, fungus growth (fig.
48), arresting development
and preventing maturity of
the kernel. Frequently, the
fungus incrustation causes FIG. 46.-P ec an
the layer of tissue with which suface of le
it is in contact to break (fig.
49), thus forming an entrance for other molds,
and a general decay follows. On the twigs, par-
ticularly the younger ones, the spots are smaller
than on either the leaves or nuts and consist of
a flat, black, round center of fungus growth in
a concave depression in the bark. Affected
twigs become stunted and are more or less
shrunken. (Fig. 50.) This resultant condition
in the nut-bearing stems often causes the im-
mature nuts to drop. The presence of scab fun-
gus on the twigs is a likely source for carrying
S the infection from one growing season to
another.
FIG. 47.-P e c a n CONTROL.-Fallen leaves and husks from
scab on lower
surface of leaf scabby trees should be removed in the fall and
winter and be destroyed. At least one applica-
tion of a standard fungicidal spray, such as lime-sulphur solu-
tion or bordeaux mixture, should be made late in the fall or win-
ter to destroy the fungus spores which may be present in great
abundance on the tree, and particularly on the younger twigs.







Bulletin 147, Pecan Diseases and Insects


FIG. 48.-Pecan s
nearly mature


FIG. 49.-Pecan sc
young nut. Not
cracked hull


FIG. 50.-Pecan
scab on young
twig


Dust, consisting of a mixture of 90
parts finely ground sulphur and 10
parts powdered arsenate of lead, may
be applied with a dusting machine to
the tree as soon as the buds open.
The practicability of spraying
cab on large pecan trees with liquid sprays
nut may be determined chiefly by the de-
gree of susceptibility of the particu-
lar variety to scab, and by atmos-
pheric and climatic conditions. In
some localities one or two applica-
tions of bordeaux mixture will insure
ab a check to the disease, while in others
ab on
e the several applications of the same fun-
gicide at intervals of two weeks may
not give any appreciable results.
There is a marked difference among pecan
varieties in their susceptibility to scab. Many
selected and budded standard varieties are less
susceptible than unselected seedling trees.

ANTHRACNOSE
Glomerella cingulata (Stonem.) S. & V. S.
Anthracnose affects the leaves and nuts of
the pecan. On the leaves it produces somewhat
large, light brown to reddish, irregular
blotches often covering a greater part of the
leaf, and eventually causing the leaves to fall.
At this stage the spores of the fungus are de-
veloped in large numbers. These are carried
over the winter in the dead leaves and are dis-
seminated the following spring, causing, under
conditions of high temperature and humidity,
fresh outbreaks on the leaves and nuts. On
the nuts (fig. 51) the blotches are irregular,
black and slightly sunken in the surrounding
green tissue of the hull. With the advance of
the disease, the whole surface of the nut ma,
become affected and the pink masses of spores
are produced in large numbers. Under condi-
tions favorable to the development of the dis-







138 Florida Agricultural Experiment Station

ease, and especially when a severe attack occurs early in the
growing season, dropping of immature nuts may result. These
nuts, like the leaves, serve to carry over the disease from one
season to another.
The anthracnose fungus is sometimes present in the weakened
tissues of twigs, but there is no record of its causing initial in-


















FIG. 51.-Pecan nuts affected with anthracnose (Jour. Agl. Res., Vol. 1,
No. 4.)
jury to the woody parts of the pecan tree. The attacks of this
fungus are not restricted to the pecan alone. Recent investiga-
tions have shown it to be identical with the fungus which causes
the well known and destructive "bitter-rot" disease of the apple.
CONTROL.-Since the anthracnose fungus reaches greatest de-
velopment and produces spores more frequently and more abun-
dantly on fallen and diseased leaves and fruits, it is essential as
a preventive measure that all dead and infected leaves, hulls, and
nuts be removed and destroyed. This should be followed in the
winter with a dormant spray, using a strong bordeaux-mixture
solution. Another spray should be given soon after the buds
open, and if necessary, two or three sprays be given in the
earlier part of the growing season. The disease should be
checked before the rainy season begins.
MILDEW
Microsphaera alni Wallr.
Pecan mildew is recognized by the superficial, flour-like,
whitish coating which, sometimes covers whole leaves and nuts.








Bulletin 147, Pecan Diseases and Insects


(Fig. 45.) It may be first observed as small flakes on the leaves
and nuts. Later the disease spreads all over the surfaces of the
attacked parts and ultimately causes a yellowing and dropping
cf the leaves. The greatest damage, however, is to the young
nuts. Under humid conditions an excessive dropping of imma-
ture nuts may result. The disease usually starts from the lower
and more or less shaded branches, spreading gradually upward.
The causal fungus is disseminated during the summer by wind
or other carriers, from minutely short and erect fungus branches
which produce at their tips minute spores. in easily detached
chains. Toward the end of the growing season, or at a time
when conditions of humidity and temperature are less conducive
to fungus growth, the white coating becomes less evident, and
minute, black and more or less hard and resistant spore cases
are produced. These contain another form of spores which are
held over on the fallen diseased leaves and hulls of nuts during
the winter until conditions again become favorable for their ger-
mination and for the development of new infections of mildew
in the new pecan growth the following spring or summer. Dur-
ing some seasons mildew may develop into a serious malady and
result in a large loss to the crop.
CONTROL.-All fallen infected leaves, hulls and nuts should
be removed from the vicinity of the pecan trees to prevent fur-
ther infection. Spraying with standard bordeaux mixture and
lime-sulphur solutions at frequent intervals will prove effective
against mildew. Dusting with powdered sulphur is probably the
best and cheapest means for checking this disease.

PECAN ROSETTE
Rosette is widely distributed thruout the pecan-growing terri-
tory from Florida to Virginia and from Texas to the Atlantic
Coast. The disease apparently occurs on all types of soil and at
all seasons; wherever it occurs, however, it is most abundant
late in the summer. It occurs also more frequently on higher
and more exposed soils than on lower and protected territory.
Rosette may be found on seedling and budded trees, on nursery
stock, and on older trees.
While rosette affects the entire tree, it is chiefly evident by the
undersized, crinkled and yellow mottled leaves, which are ab-
normally narrow at the ends of branches. The veins in these
leaves tend to stand out prominently, and light-colored areas
occur between the veins. In these areas the tissues are thinner








Florida Agricultural Experiment Station


and almost transparent. (Fig. 52.) Later in the season the
leaves frequently become dark reddish-brown and die. The dead
leaves do not all drop, and many adhere to the branches during
the winter, unless blown off by strong winds.
The diseased branches usually fail to reach their normal
length, so the leaves are clustered together on a shortened stem
giving the whole group the appearance of a rosette. The ex-
treme and young branches affected with rosette, begin to die in


FIG. 52.-Pecan rosette, showing abnormally narrow leaves, light
areas, and prominent leaf veins

late summer. At first, brown spots appear in the green bark,
which lengthen into streaks until the entire twig turns brown,
takes on a withered aspect, and dies. Numerous succulent shoots
come up from near the base of a dead or partly deadened twig;
at first they are more or less normal in appearance, but they soon
become equally affected with the leaf symptoms and eventually
die. As the disease progresses it seems to affect the tree down-
ward, so that the main trunks of severely affected trees may
send out spindling shoots giving the entire tree a ragged ap-
pearance. This phase occurs also on trunks of pecan trees af-
fected by cold injury.







Bulletin 147, Pecan Diseases and Insects


NATURE AND CAUSE.-Rosette is not of parasitic origin, as no
organism is known to be the cause of it. It is not infectious;
that is, it is not transmitted by contact from diseased to healthy
trees. The disease is not eliminated by careful pruning or even
cutting back the affected tree to a stump. On the other hand,
diseased stocks when budded with healthy buds are known to
have developed rosette in the buds. This can be explained per-
haps on the assumption that the characteristic leaf deformities
most likely result from abnormal root functions of the affected
stock. Certain rosetted trees are known to have recovered when
transplanted to new localities. This would indicate that certain
unfavorable soil conditions affect the development of rosette in
the tree. It is well known that the proper texture of soils is im-
portant in controlling the essential requirements for plant
growth, which are, moisture, humus content, and temperature.
CONTROL.-In its native forest the pecan is protected by shade
from the surrounding forest growth, the soil is rich in humus
and is moist and cool. Pecan trees planted beside houses aid
barns have to some extent an environment not radically different
from their native habitat. But in the orchard, where pecan trees
are planted from twenty to forty feet apart in high and open
sandy soil, and in some cases with a hardpan only a few feet be-
low the surface, the roots lie nearer the surface in the hot, dry,
and sandy soils deficient in humus, and can not supply the re-
mote twigs and leaves with the necessary moisture and food re-
quired for a normal production of plant tissue. Deficiencies in
humus and moisture may be corrected by plowing under green
manures, by shallow cultivation, and by other means that will
improve soil conditions. With young trees which do not furnish
sufficient shade for themselves, some means of protection is
necessary. A rather heavy cover (mulch) of cane pulp, straw,
or compost should be kept around the bases of the trees and ex-
tend for several feet outward, to retain soil moisture and to sup-
ply the humus necessary for rapidly growing trees. A thin
mulch is not sufficient under dry conditions.
DIEBACK
Botryosphaeria berengeriana DeNot.
Dieback is a twig and limb disease. For a time this disease
was not distinctly recognized by pecan growers. It was proba-
bly confused with winter injury, "rosette," and in some cases
was taken for the after effects of insect injury to the leaves and
young twigs which, in instances of severe attack, cause the dying






Florida Agricultural Experiment Station


of twigs and branches. Recent investigations by the writer have
shown this disease to be distinct from any of the other pecan
diseases, and was found to be caused by a specific fungus. How-
ever, dieback may follow in a tree previously weakened either
by rosette, winter injury, or insect attack.
Dieback is a fungus disease and is recognized by the presence
of minute, black fungus crusts embedded in the somewhat
elongated ruptures in the bark of diseased and dead twigs and
limbs. (Fig. 53.) Toward the base of a partly diseased twig,
the bark is often of a water-soaked, waxy appearance, and there
is usually a definite margin between the infected and healthy
tissue. The older diseased portions of the bark of twigs and
branches are dry and sunken, the longitudinal ruptures in these


























FIG. 53.-Broken tark surface of limb affected with
pecan dieback fungus. Twice natural size

being more conspicuous and there the fruiting bodies of the fun-
gus are embedded in a black matrix or stroma. Numerous young
shoots often start out farther back on the branches which have







Bulletin 147, Pecan Diseases and Insects


been partly killed. (Fig. 54.) As the disease spreads these
young shoots may become infected and ultimately die. These
dead clusters of short branches suggest a similar symptom com-
monly observed in rosette. However, this, as in rosette, is a phy-
siological reaction. No deformity or crumpling of leaves is found
to be due directly to dieback, tho it may be associated with it
thru some other cause.
CONTROL.-Pecan dieback may be controlled by pruning out
all the dead wood and burning it. Owing to the difficulty of
recognizing the infected limbs during the dormant season, it is




















FIG. 54.-Pecan tree seriously affected with dieback
best to prune in the fall and again in the spring. By thoroly
pruning in the fall the fungus is prevented from maturing in
the recently infected twigs and the spring pruning eliminates
infections which may come from infected wood not observed in
the fall. It is necessary to cut well beyond the visibly diseased
bark, for the fungus often penetrates into the wood for some
distance beyond its outward manifestations. Trees which show
a tendency toward rosette should be removed as these will form
a harboring place for the dieback fungus. The principal point
in controlling dieback is to keep out dead or weakened wood, and
to eliminate insects or other agencies which tend to weaken the
trees.







Florida Agricultural Experiment Station


PINK MOLD
Cephalothecium sp.

Pink mold sets in and causes rotting of pecan nuts only after
a previous injury by other fungi or insects. This moldy con-
dition is frequently found following scab attack. The mold en-
ters first thru cracks which expose moist and broken tissue in the
green hull of the nut. Under moist conditions the pink mold
grows rapidly and eventually pene-
trates the interior of the nut, in-
fecting and digesting the kernel
and leaving a mass of pink powder
in its place.
CONTROL.-As pink mold is only
a secondary disease following scab
or insect injury, elimination of the
primary causes will also take care
of the mold. (See Scab and Husk
Borer).
KERNEL SPOT
Occasionally different types of
unfilled and partly decayed ker-
nels are found in pecans. These
cannot with the present data at
hand, be classified and attributed
to definite and direct causes or in-
direct agencies, as the case may be.
However, kernel spot, a distinct
disease, occurs on the meat of the
nut and is detected only upon free-
ing the, kernel from the shell, as
there are no external indications
of the infection. The spots are
generally small, rounded, slightly
sunken and darker in color than
FIG. 55.--Brown spot on upper t
surface of pecan leaf the surrounding meat. The dis-
coloration of the meat beneath the
surface of a spot extends considerably toward the interior, and
the kernel is bitter in taste and is more or less dry and pithy.
Th's disease is probably due to a fungus, but it is not certain
thru what channel the fungus makes its way into the meat with
out leaving traces of its entry on the exterior of the nut. It is







Bulletin 147, Pecan Diseases and Insects


doubtful whether different varieties are by nature more or less
susceptible to this disease.
Kernel spot differs from other meat rots of the pecan. The
latter usually produce a general softening, while kernel spot, ex-
cepting when other organisms follow its initial injury, produce
only a dry decay.
CONTROL.-To reduce the chances of further spread of this
disease, and in order to protect the market value of the pecan
it is suggested to gather and destroy
the nuts from badly infected trees.
BROWN LEAF SPOT
Cercospora fusca Rand
The brown leaf spot of the pecan
is found generally distributed thru-
out the pecan-growing area. It affects
young as well as old trees with no
ostensible preference for particular
varieties. As the name implies it af-
fects the leaf blade only. The injury
resulting to the tree from the attack
of this disease is perhaps not obvious
since little defoliation results directly
from its attack. However, it is cer-
tain that a heavy infestation of spots
will greatly interfere with the nor-
i mal functions necessary for vigorous
S\ growth and development of the tree
and fruit.
: This leaf spot which is caused by a
fungus appears on the leaves, first
as a very small dark, reddish-brown
G 56.-Bro spot on low spot that is usually somewhat irregu-
surface of pecan leaf lar in outline. Older spots attain con-
siderable size and may run together
to form large, dark brown blotches, often covering the greater
part of the leaf. Single, old spots have an indefinite margin, are
somewhat lighter in the center and have a darker, brown border.
The appearance of the spot may vary slightly with the different
varieties of trees upon which it occurs. On some narrow-leaf
varieties the spots are more nearly round, they possess a sharper
outline and are somewhat grayish in color. In all instances the







Florida Agricultural Experiment Station


appearance of the spots is similar on both surfaces of the leaf.
(Figs. 55 and 56.)
CONTROL.-Since this disease is confined to the leaves, raking
up and destroying all fallen leaves in the fall is necessary to re-
duce further infection. Wherever practicable, three or more
sprayings with bordeaux mixture should be made in the summer.
NURSERY BLIGHT
Phyllosticta caryae Peck
Nursery blight occurs on the
leaves of young trees and is
particularly injurious to young
nursery trees. With the first
appearance of the disease the
spots are more or less round,
minute, and dark, r e d d i sh-
brown on the upper, and black
on the lower, surface of the
leaf. These spots remain com-
paratively small but become
numerous and in time cover a
considerable portion of the leaf
blade area. In the older red-
dish-brown spots the center be-
comes first gray, then turns
white and later falls out leav-
ing the leaf perforated. (Fig.
57.) Considerable defoliation
takes place in severe attacks
and the young trees have no
chance to make a good growth.
CONTROL.-The first spray
FIG. 57.-Nursery blight; the white with bordeaux mixture should
specks in the leaves are character- be given before the leaflets
istic of this disease have quite matured, and three
to five subsequent sprayings should be made at intervals of three
to four weeks.
LEAF BLOTCH
Gnomonia sp.
Leaf blotch is probably the least established and the least com-
mon disease of the pecan, yet it is capable of doing considerable
damage and this description will help pecan growers to locate
and check it before it gains headway. Leaf blotch attacks only







Bulletin 147, Pecan Diseases and Insects


the leaves of the pecan. The blotches vary from irregular,
smooth, dark and nearly black specks to more or less round,
large, brown areas. (Fig. 58.) The old blotches are grayish
in the center on the upper surface of the leaf and light brown on
the under surface. Small black specks widely scattered may be
detected on the lower side of the old blotches, these specks are
the capsules in which the fungus spores are contained. Appar-
ently, this disease is brought to notice only late in the growing
season.
CONTROL.-It is advisable to gather and destroy all fallen
leaves in the fall.
WINTER KILL SOUR SAP, COLD INJURY, FROST BITE)
Two types of injury have been observed to occur on pecans;
one is an injury to the trunk, taking place usually immediately
above ground and extend-
ing upward, the other is
apparently -a bud injury.
Both types suggest injury
caused by extreme de-
g agrees of temperature
which occur sometimes in
the dormant period of the
tree, and especially by
sudden changes in tem-
perature, when a sharp
cold snap follows a rather
prolonged warm period in
the winter season.
The trunk injury may
be recognized by the some-
what smoky and dark
FIG. 58.-Portion of pecan leaf affected
with leaf blotch gray coloration of the
trunk, the brown inner
layer and cambium of the bark, the soaked condition of the wood,
and the sour odor of the sap. In many cases swollen lenticels
covered with a pinkish, velvety growth are noticeable. Trees
thus affected may send out growth in the spring, and they may
keep on growing for some time, but they often wilt and die. This
injury is probably confined to very young trees. The bud injury
was observed on trees of considerable size and age, where the
trunks were not apparently affected. The only symptom of this
injury is the rounded small leaflets with their outer edges partly







Florida Agricultural Experiment Station


blackened and dried, usually at the edge of the tip. (Fig. 59.)
In color these malformed leaves do not differ from normal ones.
Apparently this injury does not interfere with the growth of the
tree as a whole. It is possible that this type of injury is caused
when a cold snap
suddenly arrests
the swelling of
buds begun dur-
ing a previous
warm period.
The following
suggestions have
been made to
prevent the oc-
currence of win-
ter injury. First,
4 rit is well to ma-
ture the trees

a late crop in the
fall among the
trees to take up
moisture f r o m
the soil; second,
to mound and
wrap the trunks
Sof the trees.
SALAMANDERS
Not infrequent-
v: ly does it happen
FIG. 59.--Pecan leaves. Those at left, normal; those that salamanders
at right from same tree are suggestive of cold ( c k et goph-
injury. (p o c k e t goph-
ers) do a great
deal of damage by cutting the roots off young trees about four
or five inches below the ground. The following described pois-
oned bait is suggested for the control of these animals:
Dissolve 1/2 ounce strychinine sulphate and 1 teaspoonful
saccharin in 21/2 pints water; add 1 pint fine salt and 1/2 pint
starch; beat thoroly with an egg beater. Pour this mixture ove,
8 quarts of whole corn and distribute around the trees.







Bulletin 147, Pecan Diseases and Insects 149

MISTLETOE
Phoradendron flavescens Nutt
Some large seedling pecan trees have been observed to be plen-
tifully inhabited by mistletoe, and while it has not as yet become
a real serious pest, nevertheless this parasite should not be al-
lowed to remain in a tree. It usually attacks the smaller branches
of the tree and causes them to die. In the winter the large
clumps of green mistletoe can be plainly seen, mostly in the tops
of the trees.
CONTRoL.-Infested branches should be cut off and no berries
he allowed to mature, thus preventing the spread of the pest to
other trees.







Florida Agricultural Experiment Station


PART II.-INSECTS INJURIOUS TO THE PECAN

PECAN LEAF CASE-BEARER
Acrobasis nebulella Riley
At present the pecan leaf case-bearer is perhaps the worst
enemy of the pecan in the southern part of the pecan-growing
area. Early in the spring, about the latter part of March or
early in April, the young larvae or "worms" emerge from their
winter cases and begin feeding on the nearest buds and unfold-
ing leaflets, devouring buds, leaves and blossoms. The injury
which this insect causes to the pecan tree is twofold. It is capa-
ble of reducing the nut crop to a considerable extent, and of de-
priving heavily infested trees of their foliage, weakening the
tree materially. In many cases twigs from buds injured by this
insect in the spring were
found late in the sum-
mer to be dead for a con-
siderable distance back-
ward from the tips.
These dead twigs harbor
fungi which may infect
Sthe living parts of the
tree.
All the stages in the
life history of the pecan
FIG. 60.-Injury by newly hatched larva tor of th n
of the pecan leaf case-bearer on pecan leaf case-bearer have
leaf. Part of leaf cut away to show been fully described by
tortuous tube of young larva. (Fla.
Agr. Exp. Sta., Bul. 79) entomologists. For the
purpose of recognizing
the insect and its work it will be sufficient to point out the fol-
lowing characteristics: The adult or mature form of this in-
sect is a moth, measuring about two-thirds of an inch across
the expanded wings, and while it presents a variation in color,
the general color is gray. The head, thorax and base of the fore-
wings and legs are silky-white, in the males, but in the females
these parts are dusky gray. The moths are found in hiding in
trash at the bases of trees and in the thick foliage.
Like most insects of this type, the moth is not directly inju-
rious to the pecan. It lays its eggs in the summer upon the un-
der side of the pecan leaves, usually along the midrib. The
larvae or "worms" hatch from these eggs, emerging during the







Bulletin 147, Pecan Diseases and Insects


period from the middle of May to the first of August. Soon the
larva constructs winding or tortuous tubes or cases which are
at first considerably longer than its body. One end of the tube
is attached to the leaf, while the larva feeds thru the open end.
Later as the larva matures the case becomes quite straight, the
unattached end being larger than the attached end. The larvae
feed sparingly on the leaves during the summer. (Fig. 60.)
From the latter part of September to the middle of October
the larvae migrate from the foliage and take up winter
quarters in small, oval hibernating cases which they attach
loosely around the buds.
(Fig. 61.) They remain
in hibernation during the
winter months and
emerge in the latter part
of March or the first part
of April to begin feeding
on the newly opened buds;
commencing at the tips
or sides of the swelling
buds and devouring the
leaflets as fast as they un-
fold. Consequently, t h e
greatest injury this insect
is likely to cause to the
O i pecan is at this stage in
its life history. During
FIG. 61.-Winter cases of the pecan leaf May and early June most
case-bearer around pecan bud. En-
larged. (Bureau of Ent., U. S. D. A.) of the larvae reach full
growth but some are
ready to pupate by the end of April. Pupation takes place
within the case and lasts from 16 to 23 days, the first adult
moths appearing by the middle of May. The moths continue to
emerge until the first week in August and the life cycle is re-
peated. Only one generation of this insect develops in the course
of a year.
CONTROL.-This insect can be successfully controlled by spray-
ing with arsenate of lead within the period extending from the
first part of August to the middle of September. One thoro
spraying in that period is sufficient. Use the arsenate of lead at
the rate of one pound of the powder, or two pounds of the paste,
to fifty gallons of water, to which should be added the milk of







Florida Agricultural Experiment Station


lime obtained from slaking three pounds of stone lime, to pre-
vent burning the foliage.
PECAN NUT CASE-BEARER
Acrobasis hebescella Hulst.
The pecan nut case-bearer is capable of doing considerable
damage to the pecan nut crop, and if not checked, may become a
serious enemy. In the spring, when the pecan sends out new
growth, the immature larvae or "worms'
S come out of their cocoons, or hibernating
cases, and attack the tender shoots, tunnel-
ing and eating out the interior but leaving
the outside intact. The moths or the mature
adults of the first generation which are the
progeny of the moths from the hibernating
larvae appear during the month of May and
lay their eggs soon after their emergence.
The eggs hatch in from 5 to 7 days, the
larvae coming out of the egg shell crawl to
the base of the young nut, begins feeding
Sand bores into the nut. (Figs. 62 and 63.)
Particles of frass and excrement often web-
bed together in the shape of a tube are com-
monly seen at the base of an infested nut.
The larva matures and pupates in the nut
and the moths of the second generation
ia z emerge from the middle of June to the first
-Y of July. The larvae of this generation are
FIGro. 62.-Young pe-
can nut infested usually not very injurious to the nut crop.
by larva of the A third generation of moths and larvae ap-
pecan nut case-
bearer. (Bureau pears in August but at that time the nuts are
of Ent., U. S. D. more or less hard and the larvae seem to pre-
A.) fer to feed in the leaf petioles and on ten-
der shoots. The larvae of the third generation pass the winter
in hibernation around the buds and these come out the following
spring ready to repeat the life cycle.
CONTROL.-Since this insect has three distinct generations in
the course of a year, it is necessary to spray three times with
arsenate of lead, made up at the rate of 1 pound of the powder
or 2 pounds of the paste to 50 gallons of water to which should
be added milk of lime obtained by slaking 3 pounds of stone
lime. The first application should be made shortly after the nuts
have set; the second a week or ten days after; and the third
spray should follow the second by four or five weeks.







Bulletin 147, Pecan Diseases and Insects


PECAN SHUCKWORM
Laspeyresia caryana Fitch
The pecan shuckworm is primarily a nut-infesting pest, tun-
neling into the shucks of the nearly mature nuts and often eat-
ing out the interior of the younger nuts (fig. 64). Its injury to
the pecan results in the dropping of small and green nuts, in the
discoloration of mature ones, and in preventing the proper devel-


I I
FIG. 63.-Cluster of young pecan nuts infested with the
pecan nut case-bearer. (Bureau of Ent., U. S. D. A.
opment and maturity of half-grown nuts. The larva of this moth
is whitish and very small upon hatching, but reaches a length of
three-eights of an inch and has a creamy-white body and light
brown head. This insect feeds also on the hickory where it
causes a much greater damage to the small green nuts.
The moths begin to appear early and continue to emerge un-
til the latter part of April. Eggs are deposited on the young
nut or foliage. The very small pecan nuts seem to escape much
injury because the first brood of larvae are probably attacking


L_~ __ ~__ ~_~







Florida Agricultural Exepriment Station


earlier host plants, such as the pig nut or white hickory. In
about five days the eggs hatch and the larvae enter the nuts,
mining the shucks of the mature nuts and in some cases boring
into the interior of green
S nuts. The larvae mature and
pupate in the shucks. The
activities of this insect are
most noticeable during the
latter part of June, thru July
and August. The last brood
of "worms" passes the winter
as full-grown larvae in the
shucks on the ground or in
shucks which remain on the
tree.
CONTROL.-The best
method to reduce infestation
by this insect is to destroy all
shucks immediately after
harvesting the cro p. As
moths begin to emerge as
early as February, it is essen-
tial that the shucks should be
removed before the middle of
that month. Hickory trees
in the immediate vicinity of
pecan orchards form a source
of infestation.

PECAN CIGAR CASE-BEARER
Coleophora caryaefoliella Clem.
FIG. 64.-Larva of pecan shuckworm The pecan cigar cas e-
in shuck of nearly matured pecan bearer sometimes becomes a
nut. Enlarged. (Bureau of Ent.,
U. S. D.A.) serious pest on the pecan.
The larva feeds first in the
interior of the leaves, leaving the two epiderinal layers intact,
excepting a small circular opening on one side of the leaf. Later
it constructs a light-brown case, resembling a cigar with a flat-
tened end. This case the insect carries along as it feeds. The
larvae spend the winter in their cases attached to twigs and
limbs. (Fig 65, b, c.) When the pecan buds are opening the
hibernating larvae begin feeding, attacking the buds and the







Bulletin 147, Pecan Diseases and Insects


foliage until they transform into pupae about the middle of May.
In June the moths appear, eggs are deposited on the foliage, and
in a few days the young larvae appear.
CONTROL.-This insect can be controlled by spraying with ar-
senate of lead during the season of its greatest infestation. The
arsenate of lead should be used at the rate of 1 pound of the
powder or 2 pounds of the paste to 50 gallons of water to which
has been added milk of lime obtained by slaking 3 pounds of
stone lime.
FALL WEBWORM
Hyphantria cunea Drury
The fall webworm is the most conspicuous and perhaps most
common insect pest of the pecan. The large webs (fig. 66) em-
bracing large numbers of caterpillars are a common sight on
/ pecan trees late in the
summer and fall, but less
common in the spring.
u The larvae are gregarious
and feed in colonies with-
in the web on the pecan
leaves. When more food is
needed the web is enlarg-
,K ed, taking in new leaves.
SThe caterpillars leave the
S) ^ a web late in the fall,
pass the winter as pupae,
and the moths emerge the
FIG. 65.-The pecan cigar case-bearer: following year in April
a, Moth; b, c, larvae in cases. Enlarged.
(Bureau of Ent., U. S. D. A.) and May. (Fig. 67.) The
eggs are deposited in
masses on the leaves, hatching in a week, each group of larvae
forming a web within which to feed on the leaves. These larvae
mature and pupate and a second brood of moths appears during
the middle of the summer, laying eggs out of which the fall web-
worms hatch.
CONTROL.-Spraying the leaves with arsenate of lead, the
same as for the leaf case-bearers will successfully check the fall
webworm. Where the webs are scattered and can be conven-
iently reached, they should be burned or be removed with a long-
handled pruner and destroyed.
WALNUT CATERPILLAR
Datana integerrima G. & R.
The walnut caterpillar is similar to the fall webworm in that







Florida Agricultural Experiment Station


it feeds in colonies on the pecan foliage, but unlike the webworm
in that it constructs no web. (Fig. 68.) The mature caterpillar is
black, with long whitish hairs, and nearly two inches in length
The caterpillars come down the trunks of the tree or large
branches in a mass to shed their skins. After molting they re-
turn to the upper branches and continue feeding. Afterward
they descend and enter the soil to pupate. The moths emerge
from over-wintering pupae from the middle of April to the mid-


FIG. 66.-Web and caterpillars of the fall webworm. (Bu-
reau of Ent., U. S. D. A.)
,coming out of these eggs feed in colonies. The caterpillars molt
several times and finally when full grown enter the soil, and the
fall generation of moths appears. The second-brood larvae enter
the soil late in the fall and winter over as pupae.
CONTROL.-Egg masses or colonies of caterpillars should be
*destroyed by crushing. Arsenical sprays applied to the leaves
will control this pest.







Bulletin 147, Pecan Diseases and Insects


PECAN BUD-MOTH
Proteopteryx bolliana, Sling.
The pecan bud-moth sometimes causes considerable damage
to pecan nursery stock. The larvae of this insect feed on the
buds, and in attacking terminal buds of young trees excessive
branching and stunted growth result. The larvae may under
certain conditions feed on the foliage. During dry seasons pecan
nursery trees may become
seriously injured by the
larvae of the bud-moth.
At the time pecan buds
begin to open, the moths
which have wintered in
the adult stage, begin to
lay eggs, usually deposit-
ing them on branches
near the buds, but after
the foliage appears the
eggs are laid invariably
on the upper surface of
the leaves. The life-cycle
period of this insect is of
short duration in the sum-
mer, five or six genera-
tions occurring in one sea-
son under favorable con-
ditions of temperature.
CONTROL.-As a nur-
FIG. 67.-Moth and egg mass of the fall sery practice it is recom-
we worm. Enlarged. (Bureau of
Ent., U. S. D. A.) mended that trees be kept
in a vigorous growing
condition. Apparently this insect does not become a. sufficiently
serious pest in the orchard to warrant special spraying.
FLAT-HEADED APPLE-TREE BORER
Chrysobothris femorata Fab.
The flat-headed apple-tree borer attacks certain fruit trees as
well as the pecan and only in recent years has its injury to the
pecan been brought to notice. Generally it is the previously
weakened trees that suffer the most from this insect. For in-
stance, pecan trees that have been affected by winter injury are
very susceptible to the attacks of this borer. In one grove this
borer has girdled and killed a number of good-sized pecan trees;
these trees, however, showed signs of previous mechanical in-







Florida Agricultural Experiment Station


jury. The larva or borer is yellowish-white, without legs, and
measures about one inch long when full grown. One segment
near the head is much broadened, giving the larva the appear-
ance of having a large,
flattened head. ( Fi g.
70.) The borers upon
S6 hatching from the eggs
which are deposited in
cracks or under bark
scales, bore thru the
bark and feed on the
sapwood immediately be-
Sneath, making tortuous
or spiral galleries which
are packed with sawdust
Castings. (Fig 71.) One
can often trace these
galleries by the slightly
depressed condition of
the bark above them.
Owing to a great varia-
tion in the rate of
growth of the larvae,
and in the time of emer-
gence of the beetles, all
sizes of borers may be
found at the same time
under the bark; how-
ever, there is only one
generation of this insect
FIG. 68.-Colony of larvae of the walnut during the course of a
caterpillar, on pecan. (Bureau of Ent.,
U. S. D. A.) year.
CONTROL.-The b e s t
method of destroying the flat-headed borers is to remove the bur-
rowing larvae with a knife, taking care not to injure the
healthy bark unnecessarily. The exposed woody parts should
then be painted cver. The trap-log method is also recommended.
This consists in placing in infested groves, newly cut pecan,
hickory, or oak branches or logs of convenient size at intervals
of about 100 feet in order to attract the egg-laying beetles of the
borer to the dying or dead wood, which it prefers to living trees.
These logs should be placed in the grove in the late winter or







Bulletin 147, Pecan Diseases and Insects


early spring, and must be destroyed the following winter. In-
lection of kerosene oil emulsion into galleries of badly invested
tree trunks have given satisfactory results in one grove.
HICKORY TWIG-GIRDER
Oncideres cingulatus Say.
The hickory
S twig-girdler does
a great dealof
damage by cut-
..* ting off numer-
ous twigs of
young pecan
trees, usually
during late sum-
mer and early
fall. Various
other trees of
economical i m-
portance are at-
tacked by this
FIG. 69.-Egg mass of the walnut caterpillar. En- twig-girdler, but
large. (Bureau of Ent., U. S. D. A.) in the South its
injurious effects
are most conspicuous on the pecan and hickory. The twigs are
cut for the purpose of egg laying. The eggs are inserted singly
beneath the bark near or at the
base of the leaf petioles. The
portion of the twig containing
the eggs is severed by the fe-
male (fig. 72) in order that
the larvae may develop and
subsist on dead wood. The
young are unable to subsist on
wood containing sap. The eggs
hatch in about three weeks and
the larvae which are whitish
and legless begin to tunnel in
the wood, making little growth
during the winter. In the
spring they grow rapidly and
complete their transformation FIG. 70.-Larva of the flat-headed
into adult beetles by the latter apple-tree borer, in its burrow.
Enlarged. (Bureau of Ent., U.
part of August. S. D. A.)






Florida Agricultural Experiment Station


CONTROL.-The simplest and best method for the control
of this insect is to gather the severed twigs during the
fall and winter and burn them. In this way all the eggs and la-
vae which would develop into a new generation the next sum-
mer will be destroyed. If there
are adjacent hickory of persim-
mon trees infested with the
same pest, the cut twigs of
those should also be destroyed.

SHOT-HOLE BORER *
Xylobiops basilaris Say.
The shot-hole borer is at-
tracted to dead or dying trees
and is not a serious pest as it
seldom attacks healthy pecan
trees. It makes a small circular
tunnel in wood which has been
injured by some other agency.
(Fig. 73.) Young pecan trees
about to die from winter injury
have been observed to be in-
fested with this borer.
CONTROL.-To prevent this
insect from becoming estab-
lished in pecan groves it is best
to remove all dead limbs and
dying trees. Trees kept in a
vigorous condition w ill n o t
be liable to attack by this borer.

OAK OR HICKORY COSSID
Cossula magnifica Strecker
This insect tunnels in the
hardwood of the pecan, hickory
and oak. Its work is readily
detected by the castings of wood
.which are pushed out by the
larva from its galleries and
FIG. 71.-Burrow in trunk of young found distributed around the
pecan tree made by larva of the base of the tree on the ground
flat-headed apple-tree borer. (Bu-
reau of Ent., U. S. D. A.) The young larvae first attack the







Bulletin 147, Pecan Diseases and Insects 161

small twigs, tunneling out the central portions.
When the larvae become larger they migrate to the
larger limbs or trunk making their galleries parallel
with the grain of the wood. The larvae pass their
life cycle in the wood of the tree, and they pupate in
their galleries in the spring months. The moths ap-
pear during the early part of the summer and lay
their eggs soon after emergence.
CONTROL.-Locate the openings of the galleries in
the limbs and trunk and inject carbon bisulphid in
them. The holes should be stopped up immediately
after treatment.
HICKORY PHYLLOXERA
Phylloxera caryaecaulis Fitch
Certain pecan trees in orchards are especially sub-
ject to attacks by the hickory phylloxera, an aphid
which causes tumor-like swellings or galls on the
leaves, leafstalks, and succulent shoots. By examin-
ing a newly matured gall both the winged and wing-
less or immature forms of the insect may be found.
Before the maturity of the aphids the gall is closed,
but by the time they have acquired wings the gall
cracks open, allowing the fully developed aphids to
FIG. 72.- escape.
Work of The galls are
the hick-
ory twig- found on both
girdler, a, seedli ng and
egg pune-
ture; b, impr oved va-
larva tun- rieties o f t h e
neling un-
d e r n eath p e c a n, but
the bark; more often, per-
c, twig gir-
dled ready haps, on seed-
to be sev- 1 in g varieties.
ered by
the wind The trouble is
more pronounc-
ed in early spring, yet galls
may be observed thruout
the season. It is not uncom-
mon to find seedling nursery
stock covered with galls
while budded or grafted FIG. 73.-Exit holes of adult beetles of
the shot-hole borer, made in pecan
pecan trees in adjacent rows limb. (Bureau of Ent., U. S. D. A.)






Florida Agricultural Experiment Station


may, and usually do, escape injury. The variation in severity of
attack may extend to the field plantings where certain of the
trees are exceptionally subject to attack while others sustain
little or no injury whatever.
CONTROL-Fortunately, remedial measures are seldom re-
quired to control this insect; natural enemies usually hold it in
check. So far as known, no very satisfactory method of control
can be employed during the growing season on trees that are so
badly affected that the nut crop is seriously interfered with. It
has been recommended that badly affected leaves and shoots be
clipped off with a long-handled pruner before the galls open, and
then destroyed immediately by burning; but this treatment will
not prove feasible for extensive plantings of large trees. Spray-
ing with lime-sulphur solution, kerosene emulsion, or miscible
oil while the trees are dormant might destroy the insect in the
egg stage, but experimental work along this line has not been
done.
In selecting trees for new plantings advantage may be taken
of the fact that certain varieties are more susceptible to infesta-
tion than others. Top-working the more susceptible bearing
trees with resistant sorts would doubtless prove a practicable
means of avoiding injury by this species of aphids.






Bulletin 147, Pecan Diseases and Insects


BOARD OF CONTROL
JOE L. EARMAN, Chairman, Jacksonville, Fla.
E. L. WARTMANN, Citra, Fla.
T. B. KING, Arcadia, Fla.
J. B. HODGES, Lake City, Fla.
J. T. DIAMOND, Milton, Fla.
BRYAN MACK, Secretary, Tallahassee, Fla.
J. G. KELLUM, Auditor, Tallahassee, Fla.


STATION STAFF
P. H. ROLFS, M.S., Director
J. M. SCOTT, B.S., Vice-Director and Animal Industrialist
B. F. FLOYD, A.M., Plant Physiologist
S. E. COLLISION, Chemist
J. R. WATSON, A.M., Entomologist
H. E. STEVENS, M.S., Plant Pathologist
E. G. SHAW, Secretary
J. MATZ, B.S., Laboratory Assistant in Plant Pathology
T. VAN HYNING, Librarian
C. D. SHERBAKOFF, PH.D., Associate Plant Pathologist
R. NEWHALL, Mailing Clerk
F. G. BENDING, Stenographer
O. W. WEAVER, B.S., Agricultural Editor
A. M. SMITH, B.S., Assistant Chemist
M. NOTHNAGEL, PH.D.,Assistant Plant Physiologist
J. B. THOMPSON, B.S., Forage Crop Specialist
G. C. OBERHOLTZER, Farm Foreman
G. UMLAUF, Gardener
H. L. DOZIER, M.S., Assistant to Entomologist
K. H. GRAHAM, Auditor and Bookkeeper




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