Two common scale-insects of the orchard : the scurfy bark-louse, the oyster-shell bark-louse

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o. E. F ' r-^^Y. coF, % CONNECTICUT

AGRICULTURAL EXPERIMENT STATION

CoNi .

s

NEW HAVEN, CONN.

BULLETIN 143, MAY, 1903.

ENTOMOLOGICAL SERIES, No. 9-

Two Common Scalc-lnsccts of the Orchard.

The Scurfy Bark-Louse. The Oyster-Shell Bark-Louse.

CONTENTS.

Officers and Staff of Station

Two Common Scale-Insects of the Orchard.

The Scurfy Bark-Louse ....

The 03'ster-Shell Bark-Louse

Remedies

Summary

p C E I V F n

4 1903

U.S. Dep&»tmento1 Agriculture.

Paare.

The Bulletins of this Station are mailed free to all citizens of
Connecticut who apply for them, and to others as far as the limited
editions permit

CONNECTICUT AGRIGDLTURAL EIPERIMENT STATION,

BOARD OF CONTROL.

Ex officio.
His Excellency Abiram Chamberlain, President.

Prof. W. O. Atwater Middletown.

Prof. W. H. Brewer, Secretary New Haven.

B. W. Collins Meriden.

T. S. Gold West Cornwall.

Edwin Hoyt New Canaan.

J. H. Webb Hamden.

E. H. Jenkins, Director and Treasurer New Haven.

STATION STAFF.

Chemists.

Analytical Laboratory.

A. L. WiNTON, Ph.B., Chemist in charge.

A. W. Ogden, Ph.B. M. Silverman, Ph.B.

E. Monroe Bailey, Ph.B.

Laboratory for the Study of Proteids.

T. B. Osborne, Ph.D., Chemist in charge.

I. F. Harris, B.S.

Botanist.
G. P. Clinton, S.D,

Entomologist.
W. E. Brixton, B.S.

Assistant to the Entomologist.
B. H. Walden, B.Agr.

In charge of Forestry Work.
Walter Mulford, F.E.

Grass Gardener.
James B. Olcott, South Manchester.

Stenographers and Clerks.

Miss V. E. Cole.
Miss L. M. Brautlecht.

In charge of Buildings and Grounds.
William Veitch.

Laboratory Helpers.
Hugo Lange. William Pokrob.

Sampling Agent.
V. L. Churchill, New Haven.

TWO COMMON SCALE-INSECTS. 3

TWO COMMON SCALE-INSECTS OF THE ORCHARD.

The Scurfy Bark-Louse Chionaspis furfurus Fitch.
The Oyster-Shell Bark-Louse Mytilaspis poinorum Bouche.
By W. E. Britton, State Entomologist.

Long before Connecticut orchards were attacked by the San
Jose or pernicious scale-insect, the scurfy bark-louse and the
oyster-shell bark-louse were present as parasites upon the trees
and caused considerable damage each year. These orchard
enemies still injure trees, though their work has been some-
what overshadowed by the damage of the San Jose scale dur-
ing the last few years. The two kinds of scale-insects
described in this publication are frequently received at the
Station and the correspondent usually asks if it is the San Jose
scale. This bulletin has been prepared for the purpose of dis-
tributing information about these two common species and the
remedies for them, as well as to point out wherein they differ
in appearance from the San Jose scale. The San Jose scale-
insect has three or four broods each- year, is circular in outline,
and is shown in figure i. The oyster-shell and scurfy bark-
lice are much larger, elongated or pear-shaped, and single
brooded. See figures 2 and 4.

The life histories of the species forming the subject of this
bulletin are so nearly alike that the same remedial treatment
answers for both.

The terms "scale" and 'bark-louse" are both applied to
insects of this group {Coccidce) and may be considered as
synonymous w'ith the compound w'ord "scale-insect."

The Scurfy Bark-Louse.

The scurfy bark-louse is a native of North America, and
was formerly called "Harris' Bark-Louse." It is now found
throughout the United States, and, according to Howard, is
being succeeded by the oyster-shell bark-louse.*

The female scale is about 3 mm. (^ inch) in length,
broadly pear-shaped, with the cast larval skin at the smaller

* Year-book, 1S94, U. S. Department of Agriculture, p. 259, Washing-
ton, D. C.

4 CONNECTICUT EXPERIMENT STATION, BULLETIN I43.

end which usually points upward. The color is light grey or
white. The male scale is much smaller than the female, pure
white, with three parallel ridges along the back, and parallel
sides. Males and females usually occur on separate twigs.
Both sexes are shown in figure 2.

There is only one generation each year in Connecticut. The
eggs hatch during the latter part of May. Our records show

Fig. I. — San Jos6 scale on peach twig : a. mature females : b. young
females : c. immature males. About twice natural size.

that on May 19th, 1902, material was brought to the Station
from North Guilford, and that some of the eggs had hatched.
The writer has made observations on this point for several
years and usually the eggs hatch here between May 20th and
June 1st.

THE SCURFY BARK-LOUSE.

5

The newly-hatched insect (see figure 3, c) crawls about for a
short time, then becomes fixed, forms a shell and sucks the sap
from the tree. The female becomes mature during Septem-
ber, and later dies and shrivels up, leaving the old shell filled
with oval, purple eggs. Usually between thirty and fifty eggs
are produced by each female. In Connecticut the writer found
the eggs as early as October ist in 1900, while they had not
been formed on October 9th, 1901. Usually they are formed
during the first week in October. Howard states that in the
vicinity of Washington the eggs are formed October 15th
and hatch uniformly about the middle of May.* There is
probably more than one brood in the Southern States.

Fig. 2. — Scurf}' bark-louse : a. c. females : b. d. males . a. b. natural
size : c. d. much enlarged. (After Howard, Year-book of U. S. Depart-
ment of Agriculture for 1S94.)

The chief injury caused by this species occurs to young pear
and apple trees either in nursery rows or in newly-set orchards.
Sometimes the bark of the trunk and branches is entirely cov-
ered by the grey shells, thus giving the tree the appearance of
having been whitewashed. Such trees make little growth and
are frequently killed outright. Seldom do we find the insect
abundant on large trees. Currant bushes are often infested
and mountain ash and hawthorn are frequently attacked by the
scurfy bark-louse. The appearance of an infested currant
twig is shown on Plate I.

* Loc. cit.

6 connecticut experiment station, bulletin i43.

The Oyster-Shell Bark-Louse.

This insect is well known and occurs all over the world.
Europe is thought to be its original home, but it has been
known to be present in the United States for over one hundred
years. It is more common at the North, where it is single-
brooded, than in the South, where two generations occur each
year.

Fig. 3. — Scurfy bark-louse : adult male above : b. foot : h. tip of antenna:
c. larva : d. antenna of larva : e. leg of larva : f. pupa : g. adult female
with armor removed. All greatly enlarged. (After Howard, Year-book of
U. S. Department of Agriculture for 1894.)

The armor of the female (shown in figure 4) is about 3 mm.
(}i inch) long, narrow and usually somewhat curved, and nearly
the same color as the bark upon which it is found. The cast
larval skin may be seen at the pointed end. Generally it is darker
in color than the scurfy bark-louse, as well as narrower. The
armor of the male is much smaller and less curved than that
of the female. The male scales are seldom seen upon fruit
trees. The adult male (shown in figure 5) is provided with

THE OYSTER-SHELL BARK-LOUSE.

a pair of wings, legs, antennas and eyes, and resembles the male
of the scurfy bark-louse.

The oyster-shell bark-louse, like the scurfy bark-louse,
passes the winter in the egg stage and the small, oval, white
or pale yellow eggs hatch about the first of June or a few days
later than the eggs of the scurfy bark-louse. The young were
crawling on twigs received at the Station June 9th, 1902. As
many as one hundred eggs are sometimes laid by a single
female.

Fig. 4. — Oj'ster-shell bark-louse : a. female scale from below showing
eggs : b. dorsal view of same : d. male scale — all enlarged : c. females , e.
males — natural size on twigs. (After Howard, Year-book of U. S. Depart-
ment of Agriculture for 1894.)

No observations have been made by the writer regarding the
time when the eggs are laid in the fall, but eggs were formed in
specimens collected in December. According to Smith the
eggs are formed late in August and during September.*

The oyster-shell bark-louse is found on nearly every old
apple tree in Connecticut, and may occur on the small twigs
* Bull. 140, New Jersey Exp. Station, p. 5.

CONNECTICUT EXPERIMENT STATION^ BULLETIN I43,

and on the large branches and trunk in the crevices of the
rough bark. It weakens trees unquestionably, but the writer
has never seen fruit trees killed by the oyster-shell bark-louse
in Connecticut. Many seedlings and sprouts of native trees
in fields and woods are killed each year by it. Ash, poplar,
willow, birch, butternut, black-walnut and maple are the trees
most commonly injured, and are frequently infested to such
an extent that no portion of the bark can be seen.

Fig. 5. — Oyster-shell bark-louse: a. adult male: b. foot: c. larva; d.
antenna of larva : e. adult female with armor removed. All greatly en-
larged. (After Howard, Year-book of U. S. Department of Agriculture
for 1894.)

In nurseries and ornamental plantations lilac, Kilmarnock
willow and some species of Elceagniis are often seriously
infested.

The appearance of twigs and branches infested by the
oyster-shell bark-louse is shown on Plate II.

Remedies.

The eggs of both the scurfy and the oyster-shell bark-lice
are hard to kill, so that winter applications are not effective in

REMEDIES. 9

fighting the species. Some writers advise a winter application
of whitewash to destroy them : this frequently causes the shells
to fall from the bark and the eggs are scattered, and perhaps to
such an extent that the young are not able to reach the tree.
But many eggs remain on the tree and are not injured by the
whitewash. Frequently these eggs withstand applications of
kerosene and crude oil. The most vulnerable point in the life
history of both species is just after the eggs hatch, while the
young are crawling and before they have become protected by
the formation of their shells or armor. In Connecticut this
period occurs during the first half of June, and the newly-
hatched insects may be destroyed readily by spraying with any
of the common contact insecticides. Common soap and water
(i lb. dissolved in 8 gallons) is as convenient as any applica-
tion and is cheap and efifective. Any laundry soap will answer.
It should be cut in thin slices, dissolved in boiling water and
diluted to make the proper proportions. Whale-oil soap in the
same proportions can also be used. Kerosene emulsion is
recommended, and a mechanical mixture of kerosene and
water, containing from lo to 15 per cent, of kerosene, applied
with a " Kerowater" pump is also a cheap and satisfactory
remedy.

Summary.

1. The scurfy bark-louse and the oyster-shell bark-louse
have commonly injured fruit trees for many years in Connecti-
cut by sucking out the sap and are often mistaken for the San
Jose scale-insect, which, on account of a different life-histort,
must receive different treatment.

2. The scurfy bark-louse is a native of North America and
is well distributed over the United States. The female is light
grey and pear-shaped, while the male is much smaller, white
with parallel sides. There is one brood each year at the North.
It winters in the egg stage and the eggs hatch during the latter
part of May. Eggs for the next brood are laid the first week
in October. Small apple and pear trees and currant bushes
are the most seriously infested and are sometimes killed.

3. The oyster-shell bark-louse is found all over the world,
and was probably introduced into this country from Europe
more than a hundred years ago. It is darker in color and

10 CONNECTICUT EXPERIMENT STATION, BULLETIN I43.

narrower than the scurfy bark-louse ; the hfe history is very
similar, but the eggs are a few days later in hatching, and are
formed earlier in the fall. There is one brood each year. It
infests apple, but is common on ash, poplar, willow, butternut
and lilac, often killing them.

4. Spraying the trees during the first two weeks in June, or
while the young are crawling, with soap and water (i lb. in 8
gals.) or with kerosene emulsion will readily destroy the newly-
hatched larvae.

PLATE I.

SCURFY BARK-LOUSE Chiouaspis furfurns Fitch.
Females on currant. Natural size.

PLATE II.

yV^^:,

OYSTER^SHELL BARK-LOUSE Mylilaspis pomorum Bouclie.
Females on poplar. Natural size.

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Connecticut

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