The San José scale and methods of controlling it

S
i, E. S. Library - GOP. % '

CONNECTICUT ^ ^ ^'

AGRICULTURAL EXPERIMENT STATIOE "

NE^V HAVEN, CONN.

BULLETIN 165, NOVEIVIBER, 1909.

ENTOMOLOGICAL SERIES, No. 15.

The San Jose Scale and Methods of
Controlling It.

Fig. I. — San Jose Scale on apple bark. Natural size.
CONTENTS.

PAGE

Officers and Staff of Station 2

The San Jose Scale and Methods of Controlling It 3

Introduction into the Eastern States 3

Discovery and Spread in Connecticut 3

Nursery Inspection and Legislation 5

General Appearance of the Insect 6

Effect upon Trees 8

How the Scale Spreads from Tree to Tree 8

Life History of the San Jose Scale 10

Food Plants i r

Natural Enemies 13

Control Measures 16

Fumigating Nursery Stock 16

Spraying Orchard Trees ; 17

How to Treat an Infested Orchard 22

Summary 24

The Bulletins of this Station are mailed free to citizens of Con-
necticut "who apply for them, and to others as far as the editions
permit.

CONNECTICUT AGRICULTDRAL EIPERIMENT STATION.

BOARD OF CONTROL.

His Excellency, Frank B. Weeks, Ex officio. President.

Prof. H. W. Conn, Vice President Middletown.

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

George A. Hopson Wallingf ord.

Charles M. Jarvis Berlin.

Frank H. Stadtmueller Elmwood.

J. H. Webb Hamden.

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

STATION STAFF.

Chemists.

Analytical Laboratory.

John P. Street, M.S., Chemist in Charge.

E. Monroe Bailey, M.S. C. B. Morrison, B.S.

R. B. Roe, A.B. C. E. Shepard.

Laboratory for the Study of Proteids.
T. B. Osborne, Ph.D., Chemist in Charge.

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

Entomologist.
W. E. Britton, Ph.D.

Assistant in Entomology.
B. H. Walden, B.Agr.

Forester.
Samuel N. Spring, M.F.

: Seed Testing.

Mary H. Jagger.

Stenographers and Clerks.

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

In charge of Buildings and Grounds.
William Veitch.

Laboratory Helper.
Hugo Lange.

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

THE SAN JOSE SCALE AND METHODS OF CON-
TROLLING IT.*

By W. E. Britton, State Entomologist.

No other insect has caused so much destruction in fruit
orchards throughout the country as the San Jose Scale (Aspidio-
tus perniciosus Comst.). This scale was first noticed by fruit
shippers near San Jose, Cal., and was described by Prof. J. H.
Comstock, in 1880. It was at that time doing much damage in
California, and Prof. Comstock regarded it as the most destruc-
tive scale-insect which he had seen.

Its original home is probably in China.

Introduction into the Eastern States.

The scale was first found in the Eastern States, in August,
1893, at Charlottesburg, Va. In March, 1894, an infested locality
was found at Riverside, Md. In both cases, the introduction of
the insect was traced to New Jersey nurseries, which had
received the scale on nursery stock from California. Another
infested area was discovered in March, 1894, at De Funiak
Springs, Fla. Shortly afterwards Indiana, Pennsylvania, New
Jersey, New York, Georgia, Ohio, Delaware and, in the summer
of 1895, Alabama, Louisiana, Connecticut and Massachusetts
were added to the list of infested states. At the present time, the
San Jose Scale exists in nearly every portion of the United States,
the extreme Northern states alone, perhaps, being exempt.

Discovery and Spread in Connecticut.

About twenty years ago the San Jose or pernicious scale-
insect was introduced into Connecticut on nursery stock from
New Jersey. It escaped notice, however, until June 12th, 1895,

* In 1901, Bulletin 135 was issued on this subject but is now out of
print. As the control methods have changed appreciably since that time,
the present bulletin is a revised and enlarged edition of the old, including
the latest remedies.

4 CONNECTICUT EXPERIMENT STATION BULLETIN 165.

when it was discovered at New London by Dr. W. C. Sturgis,
botanist of this Station. The insect had then been multiplying-
for four years in the orchard and garden of Mr. J. L. Raub,
and several trees had been killed by it. A study of the locality
was made and a bulletin was issued, calHng attention to the
presence of the insect in Connecticut, describing its appearance
and injuries, and giving the best remedies known at that time.
(See Bulletin No. 121, July, 1895.)

Soon after, specimens were received from Hartford and
Bridgeport. During 1896, additional centers of infection were
found at Darien, New Haven, Groton, Mystic, Farmington, New
Britain, Plantsville, and in the following year, Meriden, Walling-
ford, Hamden, Woodbridge and Greenwich were added to the
list. The scale was found in Ivoryton, Nichols, Cheshire, Burn-
side and Rowayton during 1898, and in several new localities in
New Haven, Hartford and Bridgeport. Previous to July ist,
1901, when the Insect Pest Law became operative, the San Jose
Scale had been found in seventy-eight localities in this State.

At the present time it is found practically all over the State
and though some orchards are still uninfested, it is doubtful
if there is a single town or village which does not harbor some
infested trees or shrubs.

In a few of the places, the insect was discovered before it had
infested more than one or two trees. The immediate destruction
of these infested trees has probably wiped out the pest from a
very few localities, but in most cases the scale had spread to a
serious degree before it was discovered, and many trees have
been killed and a still greater number badly injured by its
attacks.

In the cities and larger towns the scale has destroyed many
fruit trees and ornamental shrubs. A number of large peach
orchards were ruined by it. Apple orchards have also been
severely injured, but the principal growers know how to con-
trol it and do not fear it as they did a few years ago. The
annual spraying is a part of their orchard practice and no more
to be neglected than cultivation, pruning or fertilizing; in fact
it is even more important, as actual damage will result if
neglected.

the san jose scale and methods of controlling it. 5

Nursery Inspection and Legislation.

Inasmuch as the San Jose Scale has been distributed chiefly
by means of nursery stock, a system of nursery inspection has
been established in nearly all of the states. Previous to 1896
several states had passed laws requiring that each box or
package of nursery stock shipped into those states should be
accompanied by a certificate of inspection issued by a duly
authorized inspector. States not provided with an inspection

FlG. 2. — Plum Twigs nearly coated over by San Jose Scale. Natural size.

system soon realized the necessity of having one, both for their
own protection and to enable their nurserymen to ship stock into
the. states where laws existed. Twenty-five states had already
passed similar measures when Connecticut, in 1901, enacted an
inspection law, which was amended slightly in 1903. At the
present time forty-five states and territories, including Hawaii
and Porto Rico, have such laws, the only ones without them being
Nevada, New Mexico and North Dakota.

6 CONNECTICUT EXPERIMENT STATION BULLETIN 165.

Though the San Jose Scale has been the exciting cause of most
of the legislation, many other injurious insects as well as fungous
diseases are debarred, and the inspections have prevented the
spread of a number of very serious pests.

General Appearance of the Insect.

Usually the insect appears upon the bark as a greyish, rough
coating, scarcely noticeable to the naked eye. (See Figures i
and 2.) At first there are but few individuals, generally found
clustered around the buds and at the branching of the twigs.
Figure 4 shows how the scales collect in a groove or hollow in
one side of a twig, as if they had sought a sheltered situation.
As the trees become more thoroughly infested, the bark may be
completely covered, and sometimes there are several layers of
scales covering the bark. In such cases leaves and fruit are
usually attacked. The young scales locate upon both sides of
the leaf, along the ribs (see Figure 6), where they cause a red-
dish discoloration. This discoloration also occurs on fruit, and
on the twigs, especially where there are but few individuals, and
it extends through the bark to the wood. Where the insect is
found upon the fruit, it seems to prefer the calyx and the stem
cavities. Upon slightly infested trees the fruit is not attacked,
but on trees which are badly infested the fruit is often so
thoroughly covered as to present a very disgusting appearance.
(See Figures 7 and 8.) If we examine the insect through a
pocket lens, magnifying perhaps ten diameters, we see that it is
distinctly circular in outline, somewhat raised above the bark,
especially in the center, where there is a small nipple, differing
in color from the other portion. If infested twigs are much
handled, the outer layer is rubbed away from the nipple, leaving
it a bright yellow color. Concentric circles are usually apparent
between this nipple and the outside edge. The scaly covering
is formed at the edge in concentric layers or additions. The
covering of the male is different in shape from that of the
female. While that of the female is nearly circular in outline,
the armor of the full-grown male scale is nearly always elon-
gated, with the nipple near one end, and the lines of formation
are eccentric instead of concentric. (See Figure 3.)

THE SAN JOSE SCALE AND METHODS OF CONTROLLING IT. 7

The color of the shell or covering varies greatly, sometimes
being a light grey, sometimes being nearly black. It frequently
turns dark if the insects are killed when half grown. If killed
when fully grown, the shells often assume a light grey color,

Fig. 3. — San Jose Scale on peach twig a. mature female ; b. young
females ; c. immature males. About twice natural size.

and finally drop from the twigs. If we lift this shell or covering
with a pin or point of a knife, we will see underneath a small
yellow object, oval or circular in outline, which appears like a bit
of yellow jelly. This is the insect proper and is shown in the
illustration in Figure 5.

8 connecticut experiment station bulletin 165.

Effect upon Trees.

The effect on the vitality of the tree is not apparent until
the twigs become nearly covered by the insects. Then it may be
noticed that the tree seems unthrifty, but the scale is so incon-
spicuous that frequently the tree loses some of its branches or
dies before the cause of the trouble is discovered. Frequently
we see a peach tree which has been severely injured, and the
branches are dead, but the trunk is still alive and makina^ an
effort to grow a new top. This form of injury is often seen,
and frequently the owner does not discover the cause until his

Fig. 4. — San Jose Scale on peach twig.
Twice natural size.

Fig. 5. — Female with shell raised to show
insect beneath. Much enlarged.

trees reach this condition. The length of time required to
kill a tree depends on various factors. In certain seasons the
species multiplies much more rapidly than in others, depending
undoubtedly upon the weather and the abundance of natural
enemies. The writer has known of several localities where
ornamental plants were attacked and no measures taken to
destroy the scale, yet for two or three years the insect has not
spread to any appreciable extent. On the other hand, in cer-
tain orchards, it has spread with great rapidity in spite of
vigorous combative measures. In Mr. Raub's garden at New
London, large peach trees were killed by the scale in four years.

How THE Scale Spreads from Tree to Tree.

The young scales crawl about for a few hours on the bark,
and if the trees stand so close that the branches interlace, of
course they can readily crawl from one to the other. They are

THE SAN JOSE SCALE AND METHODS OF CONTROLLING IT. 9

scarcely able to crawl long distances from the trunk of one tree
to another over the rough ground, but are often blown about on
fallen leaves and may reach a different section of the orchard
in that way. In cultivating nurseries, the workmen brush against
the young trees, and it is quite possible for some of the young
insects to be carried to other trees along the nursery rows.

In one case, the orchard became infested by hitching a horse
to one of the trees, after the team had been in an infested

Fig. 6. — Infested plum leaves, showing the tendency of the insects to
locate near the veins.

orchard three miles distant.* The throwing about of infested
fruit may aid in distributing the pest. Also where parings of
infested fruit are thrown out into gardens, there is danger that
near-by trees may become infested.

As a rule, however, the insect is carried to distant trees either
by other insects or upon the feet of birds.

* Bulletin No. 3, New Series, Division of Entomology, U. S. Department
of Agriculture, Washington, D. C, p. 50.

lo connecticut experiment station bulletin 165.

Life History of the San Jose Scale.

Both the males and females pass the winter in an immature
state, and do not reproduce until the latter part of June in this
latitude. The female does not lay eggs, but brings forth living
young. The newly-born scales of both sexes crawl about for a
few hours upon the twigs. They are provided with legs, eyes,
antennae and mouth-parts. After they have found a suitable
place, they settle upon the bark, insert their beaks and begin to
suck the juice from it. Legs and antennae now disappear in both
sexes, and the females lose their eyes. At first there is a white

Fig. 7. — Infested plums showing the reddish discoloration caused by the
insects.

waxy substance exuded, which has somewhat the appearance of
wool. A little later this seems to melt down and the insect casts
its skin. The skin, together with the waxy substance, forms the
beginning of the shell or covering. After feeding for about
four weeks, the insect reaches the full-grown stage. If a female,
it then begins to bring forth its young, continuing for a period
of about six weeks. The number of young produced by a single
female varies from less than one hundred in the early part of
the season to nearly six hundred in late summer. The male
feeds until full-grown, passes through the pupa stage, and finally

THE SAN JOSE SCALE AND METHODS OF CONTROLLING IT. I I

the adult comes forth from under the shell, provided with eyes,
wings, legs, antennas and organs of reproduction, but with no
mouth-parts nor digestive system. He can, therefore, eat nothing
after reaching the adult stage. His only mission is to mate with
the female and die. The female, on the other hand, after becom-
ing established upon the twig, loses legs, antennae, and eyes,
never again to be possessed of these organs, while its mouth-parts,
digestive system and reproductive organs become very strongly
developed. It cannot, therefore, move about, but feeds upon the
juices of the plant and reproduces its kind. There are three
complete generations each season in this latitude, and probably
four in favorable seasons.

Food Plants.

Though the San Jose Scale is a pest chiefly of orchards, it
must also be taken into account in the planting of shade and
ornamental trees and shrubs, as the cost of caring for any exten-
sive plantation will be much greater if it has to be treated each
year to destroy the scale.

In 1902 the writer published* a rather extensive list of trees
and shrubs, shoAving their susceptibility to the attacks of the
San Jose Scale. Our experience since then prompts us to make
a few modifications in the hst, it being in the main correct. The
following list is really an abridged edition of the former list,
with common names used in preference to Latin names, and most
of the specific names have been omitted. It is arranged for Con-
necticut, and may not hold good for other sections of the country.

List of Trees and Shrubs and their Susceptibility to the Attacks of
THE San Jose Scale.

Badly Infested.

Akebia. Cherry (all kinds except sour

Apple. ■ cherry).

Apricot. Choke berry.

Basswood or Linden. Cotoncaster sp.

Beech, European (especially purple Currant (all kinds).

.form). Dogwood (Cornus sp. except

Buckthorn (Rhamnus). florida).

* Report of this station for 1902, page 132.

12 CONNECTICUT EXPERIMENT STATION BULLETIN 165.

Elm.

Hawthorn (Crataegus sp.).

Hop tree.

Lilac.

Mountain ash.

Osage Orange.

Peach.

Pear.

Photinia villosa.

Plum (all kinds).

Poplar (Populus sp.).

Quince (including Japanese).

Rose (some hardy species, espe-
cially rugosa).

Shad-bush or June-berry (Amelan-
chier).

Spiraea {opulifolia, sorhifoUa and
Douglasii).

Walnut, Japanese.

Willow, several species.

Occasionally Infested, but not Injured.

Actinidia.
Alder.

Almond, Flowering.
Ash {Fraxinus sp.).
Birch.

Bittersweet (Celastrus).
Blackberry.
Box.

Button Bush (Cephalantus occi-
dentalism.
Catalpa.

Cercidiphyllum laponicuni.
Chestnut.
Dewberry.

Dogwood, Flowering.
Elder (Sambucus).
Euonymus sp.
Gooseberry.
Grape (Vitis).
Hackberry (Celtis).
Honey Locust (Gleditschia).

Honeysuckle (Lonicera, some spe-
cies).

Horsechestnut.

Kieffer pear.

Locust (Robinia).

Maple (Acer sp.) (especially
Striped).

Mulberry.

New Jersey Tea (Ceanothus).

Pecan nut.

Pepperidge or Sour Gum (Nyssa).

Raspberry.

Rose (most species).

Sassafras.

Silver Thorn (Eleagnus) .

Smoke bush (Rhus cotinus).

Sour Cherry.

Sumac.

Viburnum sp.

Virginia Creeper.

Walnut (Black and Persian).

Not Infested.

Ailanthus.

Althea.

Amorpha fruticosa.

Androm.eda sp.

Arbor-vitcB.

Baccharis halimifolia.

Bald Cypress (Taxodium).

Barberry (all species).

Beech (American).

Bladder nut (Staphylea).

Blueberry (Vaccinium sp.).

Boston Ivy (Ampelopsis).

Butternut.

Buttonwood, Sycamore (Platanus).

Cedar.

Daphne sp.

Deutzia.

Dutchman's Pipe (Aristolochia).

English Ivy (Hedera helix).

Filbert or Hazel (Corylus sp.).

THE SAN JOSE SCALE AND METHODS OF CONTROLLING IT.

13

Fir (Abies).

Forsythia sp.

Genista tinctoria.

Golden Chain (Laburnum).

Hemlock (Tsuga).

Hercules Club (Aralia spinosa).

Hickory (except Pecan).

Honeysuckle (most species).

Hop-Hornbeam or Ironwood

(Ostrya).
Hornbeam ( Carpinus) .
Huckleberry (Gaylussacia) .
Hydrangea (all species).
Hypericum Moserianum.
Ilex sp.
Itea virginica.

Japan Pagoda tree (Sophora).
Judas tree or Red bud (Cercis).
Juniper.
Kentucky Cofifee tree (Gymno-

cladus).
Koelreuteria paniculata.
Larch.

Leather leaf (Cassandra).
Leatherwood (Dirca).
Magnolia (all species).
Maidenhair tree (Ginkgo).
Matrimony Vine (Lycium).
Mock Orange or Syringa (Phila-

delphus sp.).
Mountain Laurel (Kalmia).
Oak (all species).
Papaw (Asimina triloba).
Paulownia imperialis.
Pearl bush (Exochorda).

Phellodendron sp.

Pine (all species).

Potentilla frtiticosa.

Prickly Ash (Xanthoxylum ameri-

canum).
Privet (Ligustrum sp.).
Retinospora (all species).
Rhodotypos kerrioides.
Shepherdia sp.

Silvet Bell (Halesia tetraptera) .
Smilax sp.
Spice bush.
Spruce (Picea).
Stephanandra flexuosa.
Styrax japonica.
Sweet Pepper bush (Clethra).
Sweet Gum (Liquidambar) .
Sweet-scented Shrub (Calycanthus

floridus).
Tamarix sp.
Trumpet Creeper (Tecoma radi-

cans) .
Trumpet Vine (Bignonia) .
Tulip tree.
Umbrella pine (Sciadopitys verti-

cillata).
Wax Myrtle (Myrica cerifera).
Weigela.

White Fringe (Chionanthus).
Wistaria.

Witch Hazel (Hamamelis).
Xanthcceras sorbifolia.
Yellow Jasmine.
Yellow Wood (Cladastris).
Yew (Taxus).

Natural Enemies.

The native insect parasites of the San Jose Scale, Anaphes
gracilis How., Aphelinus fuscipennis How., and Aphelinus
mytilaspidis LeB., which have been recorded from Maryland,*
are not very effective in checking the pest in Connecticut, if they
attack it at all here. In fact, at various times we have collected

* Maryland Agricultural Experiment Station Bulletin No. 57, p.

14 CONNECTICUT EXPERIMENT STATION BULLETIN 165.

scale-infested twigs, placed them in glass tubes and stuffed each
end with cotton, to see if any parasites could be reared. None
were obtained. In examining orchard trees and inspecting
nursery stock all over the State we have never observed anything
but slight indications that the San Jose Scale is parasitized in
Connecticut. It is a common occurrence to find old shells of the
oyster shell scale, each with a small round hole where the para-
site had emerged. Not so with the San Jose Scale.

Fig. 8. ^Infested Apples showing the discoloration around the insects.

In the South a fungus-, Sphaerostilhe coccophila, attacks
this as well as other species of scales native to that region.
In Connecticut a fungus, Capnodium, sp., is often found on
trees which are thickly covered with dead scales. This fungus
is evidently a saprophyte, though partially parasitic, and was first
observed in 1902.*

Report of this station for 1902, p. 129.

THE SAN JOSE SCALE AND METHODS OF CONTROLLING IT.

15

In Connecticut the most important natural enemies of the scale
are predaceous and consist of two species of lady beetles known
as the twice-stabbed lady beetle, Chilocorus bivulnerus Muls., and
a much smaller species, Pentilia misella LeC.

Fig. 9. — The Twice-stabbed Lady-Beetle Chilocorus bivulnerus Muls.
Twice natural size.

The twice-stabbed lady beetle is a moderate check on the San
Jose Scale in some orchards in certain seasons. We have
observed it all over the State, where it has been found for many

> IOL:

^

d^ ^•~*^^^ Ji c

Fig. to. — Pentilia misella LeC. a, beetle ; b, larva; c, pupa; d, blossom
end of scale-infested pear, showing beetles and their larvse feeding upon
the scales, all greatl)' enlarged. (After Howard & Marlatt, Bull. 3, N. S.
Div. of Ent., U. S. Department of Agriculture.)

years, and on the whole it cannot be considered as a very import-
ant natural enem}^ of the scale. It is about three-sixteenths of

l6 CONNECTICUT EXPERIMENT STATION BULLETIN 165.

an inch long, and black, with two red spots on the back of the
wing covers. It is shown in Figure 9.

The other lady beetle, Pentilia misella, is all black and less
than one-sixteenth of an inch long. We have also seen this
species in different parts of the State, and sometimes quite
abundantly on a few trees. It is shown in Figure 10.

None of the enemies mentioned above are important checks to
the scale in Connecticut. In fact, all of them together do not
materially lessen the numbers of the scales, of which from 25
to 50 per cent, are killed each winter, the climatic conditions
being a more important check than all insect and fungous enemies
combined.

Control Measures.

After more than twelve years of experimenting in the Eastern
States, the methods commonly practiced at the present time are
fumigating with hydrocyanic acid gas to kill the scales on
nursery stock when dug for shipment and spraying orchard trees
with lime and sulphur mixtures or with oil preparations.

Fumigating Nursery Stock.*

Each well-equipped nursery is now provided with a tight
fumigating house in which hydrocyanic acid gas is generated
from the chemicals named below :

Quantity for Each 100 Cubic Feet of Space —

1 oz. (av.) Potassium cyanide, 98-100% purity.

2 fluid ozs. Sulphuric acid, high grade, 66° Baume test.
4 " " Water.

The fumigating house should be measured carefully, the cubic
contents ascertained, the quantities of chemicals computed and
the figures posted in some place convenient for ready refer-
ence. The house should be as nearly square as possible, with
the stone or earthenware generating jar under the slat floor
and near the center. The loose trees should be packed in hori-
zontally with the roots outside and the tops in the center. It is

* For more complete directions about fumigating nursery stock, see
Bulletin of Immediate Information No. 3 of this station.

THE SAN JOSE SCALE AND METHODS OF CONTROLLING IT. I 7

imperative that the house be suppHed with ventilators and with
a generating jar which can be reached or operated from the
outside. The acid and water should be placed together in the
jar, stirring to prevent a too rapid generation of heat. Cyanide
may be weighed out and placed in cheese cloth bags, and these
kept in tight tin cans or glass jars ready for use. When all is
ready, drop the cyanide into the jar, close everything tight, and
fumigate for a period between thirty and forty-five minutes.
Then ventilate the house thoroughly before entering it.

A house 10 X lo x 8 feet will be large enough for most
nurseries, contains 800 cubic feet, and for each charge requires :

Yi lb. Potassium cyanide.

16 fluid ozs. (i pint) Sulphuric acid.

32 " " (i quart) Water.

CAUTION. — Potassium cyanide is one of the deadliest poisons. Do
not let it come in contact with cuts or bruises, nor inhale the dust or
fumes which rise from it when it is handled.

Spraying Orchard Trees.

Orchard trees in the Eastern States are not commonly fumi-
gated to rid them of insect pests as are the orange trees of Cali-
fornia. The expense would be great on account of their large
size. Considerable fumigating has been done, however, in Mary-
land, and it has been tried experimentally in Connecticut. The
common practice is to spray the trees while dormant with either
some form of the lime and sulphur mixture or one of the oil
preparations. Various sprays have been developed, recommended
and used. At first whale oil soap was advised. Lime and sulphur
was given a trial by the Bureau of Entomology at Washington
in 1894 and pronounced ineffective, and was not again tried until
about 1900. Meantime kerosene and crude oil were used, the
latter tried extensively in New Jersey, with success. Pumps
were devised for mixing oils with water under pressure, the
amounts being determined either by different-sized openings or
by separate cylinders of different size or length of stroke. These
pumps are not used extensively at the present time because they
are not to be depended upon to give the proper proportions. If

1 8 CONNECTICUT EXPERIMENT STATION BULLETIN 165.

the packing wears slightly, the proportions are changed, and in
practice it is not uncommon to find the apparatus throwing at
times almost clear water, which will not kill the scales, and at
other times so much oil that the trees are injured by it.

Various soap emulsions and rosin washes were tested and again
in 1900 the lime, sulphur and salt mixture was investigated and
made the subject of extensive experiments by the Bureau of

Fig. II. — Boiling the lime and sulphur mixture. A portable engine with
boiler is placed near the orchard where water can be obtained. Steam is
conveyed to the barrels through common rubber hose.

Entomology and various agricultural experiment stations in the
Eastern States. This time better results were secured, and the
work was followed through several seasons, resulting in several
modifications of the mixture, and the best methods of preparing
it were worked out. Thus it was found that salt neither adds to
the effectiveness nor the adhesiveness of the mixture. New
York, New Jersey, Maryland, Georgia, Illinois and Connecticut
were some of the states that were foremost in the demonstra-
tion of the practicability of the lime and sulphur mixtures in the

THE SAN JOSE SCALE AND METHODS OF CONTROLLING IT, I 9

East and the development of the formulas for preparing them.
Some of the methods of making' without boiling are not now in
vogue because of the commercially prepared mixtures that are
now on the market. The development and perfecting of the
"soluble" or miscible oil mixtures during the past few years has
enabled us to spray with an ordinary pump oil emulsions which
can be readily diluted with water. These have in part supplanted
the use of the lime and sulphur mixtures, though after using
them many commercial orchardists are now returning to the lime
and sulphur preparations, especially for peach trees, on account
of their great fungicidal value. The home preparation of the
"soluble" or miscible oils has been worked out, but this is too
complicated for general practice, and we do not advise it except
in the large orchard where materials can be purchased in
quantity. Even then it will often be found cheaper to pay the
manufacturer for mixing, and a more uniform product will be
obtained.

Homemade Lime and Sulphur Mixtures.

For making the regular boiled mixture we use fresh white-
wash or finishing lime, nearly free from magnesia, and finely
ground sulphur known as light sulphur flour or the subHmated
product called flowers of sulphur. The boiling may be done in
a kettle over a fire or in an open barrel with steam from a boiler,
as is shown in Figure ii. We advise the following proportions:

20 lbs. Lime.
14 lbs. Sulphur.
40 gals. Water.

The lime should be started slaking, then add the sulphur and
with constant stirring add enough water to cover, and boil for
about one hour. Then strain into the pump barrel and dilute
with cold water to make forty gallons. The mixture should
then be applied at once to the dormant trees. If allowed to stand
over night, crystals form in the bottom of the barrel which clog
pump and nozzles, and it is necessary to heat it up again before
using.

There are several formulas for making the mixture without
boiling, but the space here is too limited to discuss them. In

20 CONNECTICUT EXPERIMENT STATION BULLETIN 165.

general, we advise the orchardist either to make the boiled mix-
ture or to purchase the ready-prepared commercial mixture
which is now sold on the market — a brand being- made by nearly
every manufacturer of insecticides.

Commercial Mixtures of Lime and Sulphur.

For the last two years a number of different makes of lime-
sulphur mixtures have been made and sold. We have not tested

Fig. 12. — An excellent outfit for a rough orchard is shown at the right.

them all, but some of them have been used by us and also in
large quantities by Connecticut orchardists. The results have
been satisfactory. Such preparations are clear liquids of amber
color. The sulphur is all dissolved, no crystals form on standing,
and there is no sediment to clog pumps and nozzles. It is only
necessary to dilute nine or ten times with water, according to
directions. It can be purchased in any quantity from one gallon
up to a car load lot, and is less expensive than most of the oil
preparations and only slightly more so than the homemade lime-
sulphur mixture.

THE SAN JOSE SCALE AND METHODS OF CONTROLLING IT. 21

Lime and sulphur mixtures may be applied to the dormant trees
any time between November ist and April 15th in Connecticut,
and there is no danger whatever of injuring the trees. It is an
excellent fungicide, the best remedy for peach leaf curl, and
by still further dilution, say thirty times, the commercial prepara-
tions are recommended for use as a summer fungicide spray.

"Soluble" or Miscible Oils.

Several preparations of this type are on the market, "Scale-
cide" being one of the oldest and best known. These oil pre-
parations are really emulsions and most of them contain a vege-
table oil and an alkali which when mixed together with mineral
oils in the right proportions will hold the latter as an emulsion
when diluted with water. Some also contain fish oil and carbolic
acid. Those who wish to make up their own miscible oils should
consult the publications of Penny* and Jarvisf and the report
of this station for 1908, page 837, but the average orchardist had
better purchase a ready-made oil mixture than to attempt to
make it himself. With all oil preparations there is more or less
separation of the ingredients on long standing, so that the
entire contents of each original package should be mixed very
thoroughly before any portion is removed to mix with water.
If this is not done, the oil preparation will not mix properly with
water and is liable to injure the tree.
Never use any miscible oil preparation that refuses to mix with, water.

Lime and Sulphur Mixtures vs. Miscible Oils.

The advantages of the lime and sulphur mixtures are the
cheapness, effectiveness in killing scales and excellent fungicidal
quahties. If the bark has been well coated with this mixture
the scales do not become established upon it the following season
as readily as when the oil mixtures are used. There is no injury
to the trees, and the rubber hose is not ruined.

* Bulletins Nos. 75 and 79, Delaware Agricultural Experiment Station,
1907. Bulletin No. 86, Pennsylvania Agricultural Experiment Station,

t Bulletin No. 54, Storrs (Connecticut) Agricultural Experiment
Station, 1908.

2 2 CONNECTICUT EXPERIMENT STATION BULLETIN 165.

The disadvantages are that it is caustic and somewhat unpleas-
ant to handle, and if the spray strikes the light-colored paint
of a fence or building it discolors it, forming black spots, which
disappear after a few weeks. It gives the trees a whitish color,
slightly disfiguring them. Its penetrating qualities are not as
great as in the oil preparations, and on old apple trees having
much rough bark the latter are often preferable. The pubescent
terminal twigs of the apple also can be covered more readily
with the oils than with the lime and sulphur, which tends to
gather in drops and roll off. Where apple trees are sprayed
with the lime and sulphur mixture it is a common experience
to find no scales on the old wood but enough on the new twigs
to infest the fruit and spot it noticeably. The lime and sulphur
mixture corrodes slightly the metal parts of the pumps.

Advantages of the oil preparations are that they are pleasant
and not caustic to handle, and will not disfigure the trees, shrubs,
or painted buildings. They do not clog or corrode pumps or
nozzles, and they penetrate nicely. A gallon will cover more
surface than a gallon of lime and sulphur.

Disadvantages are that the ingredients separate on standing
and evaporation sometimes prevents the proper mixing with
water. Injury has been caused to trees by the use of such prep-
arations not properly mixed. Scales will set more readily on
the bark after the use of the oil mixtures than where lime and
sulphur is used. It is more expensive and is not as valuable
as a fungicide. The oils affect rubber, and the hose is quickly
ruined.

How TO Treat an Infested Orchard.

Suppose we have a badly-infested orchard of peach or apple
trees, how shall we treat it? This is a problem confronting
many commercial fruit-growers in Connecticut to-day, as well
as a large number of persons who have small orchards for the
home supply.

In the light of our present knowledge of what has been accom-
plished in Connecticut and elsewhere the following treatment
seems to be the proper one to apply.

Remove the worthless trees. It will not pay to treat them.

THE SAN JOSE SCALE AND METHODS OF CONTROLLING IT. 23

Cut back severely, especially the branches that have lost a por-
tion of their vitality because infested. This will enable the trees
to make a stronger growth in the spring and reduce the area to
be covered with the spray. The remaining portion being nearer
the ground can be sprayed more economically than the ends of the
twigs. Burn all branches cut off; fire is an effective destroyer
of insects and fungous diseases.

Fig.

-Outfit mounted on waggon.

Spray the pruned trees during the winter months with the
lime and sulphur mixture, or one of the miscible oils, taking
pains to coat thoroughly all portions of the trunk from the
ground to the ends of the branches.

Peach, plum or pear trees, which have smooth bark, should
be sprayed with lime and sulphur, which kills the scale and is
also a good fungicide ; oil preparations are often preferable on
rough-barked apple trees. Badly infested trees sometimes need
to be sprayed twice the first season, in which case the oil may
be applied in November as soon as the leaves fall and lime and
sulphur in the spring. The oil mixtures should be diluted with

24 CONNECTICUT EXPERIMENT STATION BULLETIN 165.

not more than fifteen parts water. Both lime and sulphur
mixtures and oil preparations may be used in the fall.

When growth begins, fertilize liberally, spray apple trees to
preserve the foliage, and cultivate thoroughly to promote the
vigor and health of the trees.

SUMMARY.

The San Jose Scale appeared and caused much destruction of fruit trees
in California thirty years ago. China is probably the country of its
origin.

It was first found in the Eastern States in 1893, and now occurs in
nearly all the states of the Union except, perhaps, the extreme northern
ones.

The scale was brought into Connecticut on nursery stock in the early
nineties, but not discovered until 1895. Seventy-eight infested localities
had been found in this State and twenty-five states had passed inspection
laws up to July ist, 1901, when the present Insect Pest Law went into
effect. Since that time the scale has spread to nearly every portion of
the State and forty-five states and territories now have laws regarding
the inspection and transportation of nursery stock.

The scale is inconspicuous and is seldom noticed until the vitality of
the tree is impaired, at which time the bark is usually coated with a
roughish grey substance. The reddish discoloration may be found around
each individual. Leaves and fruit are also attacked. The female scale
is nearly circular in outline, while the male is somewhat elongated. If
the scale is lifted the insect proper may be seen underneath, by the aid of
a lens, as a yellow object.

The vitality of the tree is gradually lessened by the hordes of insects
sucking its sap. The pest is seldom noticed until some of the twigs die.
Entire trees have been killed in four years in Connecticut by the scale.

Though the young scales crawl short distances, they are usually carried
from one tree to another by other insects, or upon the feet of birds. They
may also be carried upon fallen leaves, fruit, or the clothing of persons, etc.

The full-grown female scale gives birth to living young, w^hich crawl
about for a short time and then settle upon the bark. There are three or
four generations each season. They feed by sucking the juices from the
tree. Each female may produce from less than one hundred to six hundred
young.

Common fruit trees and plants of the rose family are usually preferred
by the insect, but it is liable to attack other kinds that may be growing
near infested trees. A list of food plants may be found on page 11.

Natural enemies are not very effective in holding the scale in check in
Connecticut, the most important being twro species of lady beetles.

In nurseries the stock is fumigated with hydrocyanic acid gas when dug
for shipment. Orchard trees are sprayed while dormant with the lime
and sulphur mixture, or with one of the " soluble " or miscible oils diluted
at the rate of one part in fifteen parts of water.

University of
Connecticut

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