CIRCULAR No. 28 JN,11
ALABAMA
Agri tion
icultural 
Experiment 
Sta
OF THE
Alabama Polytechnic Institute
AUBURN
The Oak Scale
AND
Its Control
W. F. TURNER
Assistant Entomologist
Opelika, Ala.
Post Publishing Company
1914
JUNE, 1914
COMMITTEE OF TRUSTEES ON EXPERIMENT STATION.
HON. R. F. KOLB--
HON. H. L. MARTIN-
HON. A. W. BELL
-Montgomery
-- -- - - - Ozark
--- -- - Anniston
STATION STAFF
C. C. THACH, President of the College.
J. F. DUGGAR, Director of Experiment Station.
DEPARTMENTAL ORGANIZATION
AGRICULTURE:
J. F. Duggar, Agriculturist.
E. F. Cauthen, Associate.
M. J. Funchess, Assistant.
J. T. Williamson, Field Agent.
0. H. Sellers, Assistant.
H. B. Tisdale, Assistant.
VETERINARY SCIENCE:
C. A. Cary, Veterinarian.
1. S. McAdory, Assistant.
CHEMISTRY:
B. B. Ross, Chemist, State
Chemist.
J. T. Anderson, Chemist, Soils
and Crops.
C. L. Hare, Phy siological Chemist,
T. Bragg, First Assistant.
S. Adler, Assistant.
EXTENSION :
L. N. Duncan, Superintendent*
J. B. JHobdy, Assistant.*
N. A. Negley, Assistant.*
Mrs. Birdie I. Robinson,
Assistant.*
C. S. Jones, Assistant.*
BOTANY:
J. S. Caidwell, Botanist.
A. B. Massey, Assistant.
PLANT PATHOLOGY:
F. A. Wolf, Pathologist.
HORTICULTURE:
Ernest Walker, Horticulturist.
J. C. C. Price, Associate.
G. V. Stelzenmuller, Field Agent.
ENTOMOLOGY :
W. E. Hinds, Entomologist.
J. E. Buck, Assistant.
G. W. Ells, Field Agent.
ANIMAL INDUSTRY:
G. S. Templeton, Animal Hus-
bandman.
E. S. Girton, Assistant.
S. S. Jerdan, Assistant. *
A. R. Gissendanner, Assistant.
J. A. McLeod, Assistant.
*In co-operation with United States Department of Agr'i-
culture
THE OAK SCALE AND ITS CONTROL.
(Lecanium quercifex Fitch)
By W. F. TURNER, Assistant Entomologist.
The principal street and shade trees of Alabama and
the other Gulf States are the oaks. Of these-the water
oak (Quercus nigra) is by far the most important.
There is probably not a single city in the State in which
a large proportion, if not the majority of the street trees
do not belong to this species. Willow oaks (Q. phel-
los) are occasionally found, and in South Alabama the
live oak (Q. virginiana) is common. Neither of these,
however, is as important as is the water oak.
After the water oak has attained some considerable
size it is, seldom seriously injured by insects. The
young trees, however, are often found to be stunted
and weak without any apparent reason. Such trees
are in most cases being injured by the attack of one of
the soft scales (Lecanium quercifex). The injury is
not confined to the young trees, but is much less appa-
rent on the older trees. The insect which causes this
damage is seldom noticed except in the spring, when
for a few weeks the twigs are covered by the large
scales of the mature females. Nevertheless, the pest
is becoming more and more abundant every year and
constitutes a very serious problem in the care and
maintenance of shade trees.
The oak scale was first described by Fitch, in 1858,
from specimens taken on white oak (Q. alba). It is
found throughout the United States and even in Canada
and has been taken on black oaks (Q. velutina), red
oak, (Q. rubra), scarlet oak (Q. coccinea), willow oak
and live oak. It has also been taken on iron wood,
chinquepin and elm. However, its chief food plant ap-
pears to be the water oak, and its principal damage is
confined to the South Atlantic and Gulf Coast States.
The adult females begin laying eggs in the early part
of April*. In 1911 egg deposition commenced about
April first, in 1912 about April thirteenth. The egg
laying period continues for about three weeks. In 1912
it covered twenty days, ceasing on May third. Only
three actual counts have been made of the number of
eggs laid by one of these females. The first laid 2,245,
the second 5,000, and the third 5,262 eggs. The smallest
*All data given in this circular is for the latitude of Au-
burn. The dates given are probably late for South and early
for North Alabama.
106
number of eggs was laid by a very small female and
the average is undoubtedly as high as. 4,000.
The eggs are oval, slightly tapering at one end and
are very light yellow brown in color when laid. In the
mass they have a rosy hue. The color deepens just
before hatching. The eggs average .29mm. by .16mm.,
and are plainly visible upon the loosening of the moth-
er scale.
Hatching commenced in 1910 about April twenty-
sixth, in 1911 about May fifth, and in 1912 about May
sixth, and continued through a period of about three
weeks in each case, ceasing in 1912 about May twenty-
seventh. Thus the incubation period would be about
twenty-six days for the last, as well as for the first of
the broods. Practically every egg hatches, the un-
hatched probably constituting less than one-tenth of
one per cent of the total number laid. In the majority
of batches examined every egg hatched. In a few in-
stances, the scale of the adult adheres so closely to the
bark that the young are unable to escape, and in such
cases all the young perish. Occasionally a few young
are found dead under the parent scale, although the
majority have escaped. This condition, however, is
exceptional.
The young nymphs are very active and may travel
considerable distances before settling. In one case
several nymphs were found settled on leaves which
were seven feet away from the nearest adult scales.
In another instance a few young scales were found on
the leaves of a small tree which had not been infested
the year before, and which was twenty feet from the
nearest infested tree. It seems quite probable that in
this latter case the scales were carried from one tree
to the other, possibly by birds, or large insects, or per-
haps by the wind. In the first case, however, the
young undoubtedly crawled to the leaves as these were
separated from the parents by a slender, smooth-bark-
ed brandh, over which it would be comparatively easy
to travel. Examinations were made of several heavily
infested trees, and while the branches and twigs were
literally covered with the migrating young, none could
be found on the main trunk more than six inches from
the bases of the branches and perhaps a foot from the
nearest adult. It seems doubtful whether the young
ever crawl to the ground, at least in the case of large
rough-barked trees. The nymphs remain active for a
considerable length of time, even after they reach the
107
leaves. In the laboratory such nymphs were found un-
settled five days after hatching.
All the living young finally settle on the leaves.
There does not seem to be any great difference in the
choice of sides. Of 435 nymphs on ten leaves of the
water oak, 247, or 57.8 per cent were on the upper sur-
face and 188 or 43.2 per cent on the lower. The leaves
of the willow oak are larger and coarser than those
of the water oak, and on them, of 932 nymphs, 394 or
only 42.2 per cent were on the upper surface and 583
or 57.8 per cent on the lower surface. The young settle
principally along the main or larger lateral veins of the
leaf, with the body parallel to the vein. However, if
the infestation is very severe, they settle promiscuously
over the surface. Undoubtedly a large number of
nymphs never settle and of those which do, many prob-
ably die. Laboratory experiments to determine the
percentage of settling were unsuccessful. In one case,
at the end of five days, two out of fifteen young had
settled, two were moving and the remainder were dead.
This experiment was discontinued because the leaves
had become too dry for food.
The nymphs remain on the leaves until fall, appar-
ently not changing in size but remaining in the first
stage throughout the summer. They then migrate
back to the small twigs, seldom going more than an
inch or two from the base of the leaf on which they
were located. This fall migration is a rambling, in-
determinate movement. The first individuals leave
the leaves during the last of September, and the migra-
tion continues throughout the fall and early winter.
In a few cases, in which the trees did not shed their
old leaves until spring, when the new ones pushed them
off, nymphs were found on the old leaves in March.
Probably a large percentage of the nymphs are shed
with the leaves and never reach maturity.
The young remain dormant on the twigs until Feb-
ruary, when as the sap begins to flow again, they begin
to grow slowly. This growth continues until the last
of March, when it becomes very rapid in the case of
the female scales. They soon attain their full adult
size and in this condition are covered by a thick, tough,
scale, which protects them much more fully than the
young were protected. Soon after attaining full size,
the females begin to lay eggs and the life cycle is com-
plete. We have never observed the male, and are un-
certain just when mating occurs.
108
There are several natural enemies which aid in con-
trolling this pest. At least two Hymenopterous para-
sites have been captured, one on the hibernating
nymphs, and one on the eggs. The species have not
been determined. There are also several lady beetles
which feed upon the young stages. The most impor-
tant of these lady beetles at Auburn is the "twice stab-
bed lady beetle" (Chilocorus bivulnerus).
It will be easily seen, from the foregoing sketch of
the life history of this insect, that the only time at
which it can be profitably treated is during the late
winter, preferably just before the leaves start. At this
time the young are collected on the twigs and there are
practically no leaves to interfere in spraying. Also
much stronger spray solutions can be applied at that
time than could be used on the foliage. Lastly, the
insects are still small, and soft, and are not covered
by a toughi impenetrable scale.
We have tested several spraying materials on this
insect. Many of these, which at first thought would be
expected to control the pest, have proven to be abso-
lutely valueless. In the spring of 1910, several trees
were sprayed with lime-sulphur wash. This was a
home-made wash, formula 16-16-50, such as would be
used against the San Jose scale. This was applied af-
ter the trees had begun to leaf out, and while the sca.
were in the fully matured stage. The experiment was
unsuccessful, as the spray had apparently no effect
whatever on the insects.
In 1911, four-materials were tested. These were
crude oil emulsion, 1 to 7 and 1 to 9; kerosene emul-
:ion 1 to 7 and 1 to 9; sulfur-baking-soda wash, and
sulfur-sal soda wash. The two latter were made up
according to formulas given by Prof. H. A. Surface.
We experienced considerable difficulty in preparing
them, and were never able to obtain a perfectly clear
solution. These four materials were applied on May
thirteenth. At that time the leaves were about half
grown, and the Lecaniums had all finished egg laying.
A few of the eggs had hatched. None of these mixtures
gave any apparent control. The sulfur-soda washes
both burned the foliage severely, while the crude oil
emulsion remained as a disagreeable, sticky conating
on the leaves until fall.
In 1912, the spray materials were applied earlier in
the season, on March eighteenth. The insects at that
t Surface. H. A., Zoological Bulletin, Vol. V, No. 11, Div.
Zool., Penn. Dept. Agr., Harrisburg, Penn. p. 334.
109
time were still small and soft. They were, therefore,
in a much more susceptible condition than on either of
the previous years. Three solutions were used;
Schnarr's Insecticide 1 to 20, and emulsions of Junior
Red Engine and Diamond Paraffine Oils. These einul-
sions were prepared according to Yother's formulas.t
They were both used at strengths ot 3 per cent and 4
per cent oil. All of these materials gave about equal
results, killing all of the scales hit.
On April 4th, 1912, other applications were made,.us-
ing Schnarr's Insecticide 1 to 20 and Diamond Paraf-
fine Oil emulsion, 4 per cent oil, made up with Good's
No. 3 Soap. At this time the trees were beginning to
put out leaves. These sprayings 
were not as success-
ful as the earlier ones, since the leaves protected many
of the scales from the liquid. Both sprays burned the
tender foliage rather seveiely. The Diamond Paraf-
fine Emulsion causing the most damage. By mid-sum-
mer, hogver, none of these trees showed any injury to
the foliage while the infestation was perceptibly de-
creased.
We therefore, recommenid a thorough spraying in
March uing any of the tthiee follo6ving formulas:
(A). Schnarr's Insecticide 1 to 20.
(B). Junior Red Engine Oil 2 gals.
Whale Oil Soap . 1 gal.
Water-------------50 gals.
(C). Diamond Paraffine Oil 2 gals.
Whale Oil Soap ---- 1 gal.
Water ------------- 50 gals.
In preparing (B) and (C) the oil should be slowly
added to the soap solution and stirred thoroughly as
added. When the two are thoroughly mixed, about
3 quarts of water should be added, slowly, and the
whole emulsified by stirring. After the enimulsification
is complete the whole may be diluted to 50 gallons aid
is thei ready to apply.
Great care is necessary in applying the spray. The
young are all located on the very small twigs of the
preceding years' growth and it is necessary to soak
the tree thoroughly, wetting these twigs on all sides in
order to hit all the scales. Such careful spraying should
be entirely successful and, as the ,scale spreads very
slowly from tree to tree, one'a plication every four or
five years will probably be sufficient.- AT repetition of
the spraying in February 1913gave very satisfactory
control. Thorough, timely spraying will control this
pest.
t Yothers, W. W. Crossman, S. S., Florida Fruit Grow-
er, April 28, 1911.
iv.
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1
A.
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I Ii rI + . ! ,t 1
Fig. A. Miature ternales oii twsig. M~a; Fig. B, eggs, egg shells and 00ung; Fig. (,
female scale wsith young (raisling 05er it; Fig. I), w~inter stages fromi twig; Fig. F, sum-
mer stage on under side of oak leaf. Fig. A. natulial si/c. It, (' arid F eiilaiged I 0
diameters; D, 20 diameteis. All original.
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