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Issued April 1-1, 1908.

U. S. DEPARTMENT OF AGRICULTURE.

FARMERS' BULLETIN No. 127.

IMPORTANT INSECTICIDES:

DIRECTIONS FOR THEIR PREPARATION AND USE.

[Second Revision.]

C. L. MARLATT, M. S.,

ENTOMOLOGIST AND ASSISTANT CHIEF, BUREAU OP ENTOMOLOGY.

WASHINGTON:

GOVERNMENT PRINTING OFFICE.
I 908.

LETTER OF TRANSMITTAL.

U. S. Department of Agriculture,

Bureau or Entomology,
Washington, D. C, March 2, 190S.
Sir: I have the honor to transmit herewith a second revision of
Farmers' Bulletin No. 127, on insecticides. The five years that have
elapsed since the last revision of this publication have brought some
important additions to our knowledge of insecticides and have neces-
sitated some changes of old formulas. These additions and correc-
tions have been incorporated in this revision. As stated in the letter
of transmittal to the first edition, this bulletin supplants Farmers'
Bulletin No. 19, prepared in 1894 by Mr. C. L. Marlatt, then First
Assistant Entomologist. The latter publication, having gone through
four slightly revised editions, was in large part rewritten by Mr.
Marlatt early in 1901 and issued under the new number to take the
place of the older publication.
Respectfully,

L. O. Howard,
Entomologist and Chief of Bureau,
Hon. James Wilson,

Secretary of Agriculture.

127

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CONTENTS.

Page.

Introductory 5

Relation of food habits to remedies 5

Injury from biting insects 5

Injury from sucking insects 6

Groups subject to special treatment 7

Insecticides for external biting insects (food poisons ) 7

The arsenicals 7

Paris green 8

Copper arsenite 8

Arsenite of lime 9

London purple 9

Arsenate of lead 9

General considerations 10

How to apply arsenicals 10

The wet method 11

The dry method 11

Poisoned bait 12

Time to spray for biting insects 13

Care in the use of arsenicals 14

Insecticides for external sucking insects (contact poisons) 14

Soaps as insecticides 15

Pyrethrum, or insect powder 16

Tobacco decoction 16

Sulphur 16

Petroleum oils 17

Pure kerosene treatment 18

The crude petroleum treatment 19

The oil-water treatment 19

Kerosene emulsion (soap formula) 20

Kerosene emulsion (milk formula) 21

The distillate emulsion 21

How to use the emulsions 22

Cautions regarding use of oil washea 22

Miscible oils 23

The resin wash 23

The lime-sulphur wash 24

Composition and preparation 25

Directions for use 26

Range of usefulness 26

Time to spray for sucking insects 27

127

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Page.

Dusting and spraying apparatus 28

Powder distributers , 28

Liquid sprayers 28

The barrel pump 29

Tank outfits 29

Geared sprayers 29

Gas-pressure sprayers 29

Hose, nozzle, and agitator 30

Selection of spraying outfit 30

Directions for spraying 31

Hydrocyanic-acid gas treatment 31

Fumigation of nursery stock 32

Orchard fumigation 33

Amounts of chemicals to use 33

General directions 35

Construction and handling of tents 36

Bisulpliid of carbon vapor 38

Remedies for subterranean insects 38

Hot water 39

Tobacco dust 39

Kerosene emulsion and resin wash 40

Potash fertilizers 41

Bisulphid of carbon 41

Submersion 42

Remedies for insects affecting grain and other stored products 42

General methods of treatment 42

Bisulphid of carbon 43

Character and method of application 43

Caution 44

Sulphur dioxid 44

General considerations on the control of insects 45

Advantage of prompt treatment 45

Killing insects as a profession 45

Determination of the result of treatment 46

Control of insects by cultural methods 47

The profit in remedial measures 48

ILLUSTRATIONS.

Page.

Fig. 1. Illustrating the different classes of biting insects 6

2. Illustrating the different classes of sucking insects 6

3. Barrel spray jjump 28

4. Power sprayer at work in apple orchard 29

5. Vermorel spray nozzle 30

6. Tenting trees for gas treatment, San Diego, Cal 32

7. Method of hoisting sheet tent 36

127

IMPORTANT INSECTICIDES: DIRECTIONS FOR
THEIR PREPARATION AND USE.

INTRODUCTORY.

Without going minutely into the fiekl of remedies and preventives
for insect depredations it is proposed to give in this bulletin brief
directions concerning a few of the insecticide agents having the widest
range and attended with the greatest usefulness, economy, and ease
of ai^plication. These are not covered by patents, and in general it is
true that the patented articles are inferior, many of the better of them
being in fact mereh-^ more or less close imitations of the standard
substances and compounds hereinafter described. Onl}^ such brief
references to food and other habits of insects will be included as are
necessary to illustrate the principles underlying the use of the several
insecticide agents.

RELATION OF FOOD HABITS TO REMEDIES.

For the intelligent and practical employment of insecticides it is
necessary to comprehend the nature and method of injury commonly
due to insects. Omitting for the present purpose the exceptional
forms of injury which necessitate peculiar methods of treatment, the '
great mass of the harm to growing plants from the attacks of insects
falls under tAvo principal heads based on distinct principles of food
economy, viz, whether the insect is a biting (mandibulate) or a suck-
ing (haustellate) species. Each group involves a special system of
treatment.

INJURY FROM BITING INSECTS.

The biting or gnawing insects are those which actually masticate
and swallow some portion of the solid substance of the plant, as the
wood, bark, leaves, flowers, or fruit. They include the majority of the
injurious larvae, many beetles, and the grasshoppers. (See fig. 1.)

127

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For these insects direct poisons, such as the arsenicals, which may
be safel}^ applied to the leaves or other parts of the plant attacked,

Fig. 1. — niustrating the dififerent classes of biting insects. ^AU
natural size. (Author's illustration.)

and which will be swallowed by the insect with its
food, furnish the surest and simplest remedy, and
should always be employed, except where the parts

treated are themselves to be shortly used for the food of animals or

of man.

INJUHY FROM SUCKING INSECTS.

The sucking insects are those which injure j^lants by the gradual
extraction of the juices from the bark, leaves, or fruit, and include
the plant-bugs, aphides, scale insects, thrips, and plant-feeding mites.
These insects possess, instead of biting jaws, sucking beaks or bristles,
which are thrust down through the outer layers of the bark or leaves

Fia. 2. — Illustrating the different classes of sucking Insects. Natural size and enlarged.

(Author's illustration.)

into the soft, succulent tissues beneath and used to extract the jjlant
juices, with a resulting injury not so noticeable as in the first group,
but not less serious. (See fig. 2.)

127

For this class of insects the application of poisons, which penetrate
little, if at all, into the plant cells, is of trifling value, and it is neces-
sary to use substances which will act externally on the bodies of these
insects as a caustic, or will smother or stifle them by closing their
breathing pores, or will fill the air about them with poisonous fumes.
Of value also as repellents are various deterrent or obnoxious sub-
stances.

Where it is not desirable to use poisons for biting insects some of
the means just enumerated may often be employed.

GROUPS SUBJECT TO SPECIAL TREATMENT.

The two general groups outlined above comprise the species which
live and feed upon the exterior of plants for some portion or all of
their lives, and include the great majority of the injurious species.
Certain insects, however, owing to peculiarities of habit, inaccessi-
bility, or other causes, require special methods of treatment. Of
these, two groups properly come within the scope of this bulletin:
(1) Those working beneath the soil, or subterranean insects, such as
the white grubs, root maggots, root aphides, etc.; and (2) insects
affecting stored products, as various grain and flour pests.

T.hree other groups, which include species requiring very diverse
methods of treatment, and which are not considered in this bulletin,
are (1) such internal feeders as wood, bark, and stem borers, leaf
miners, and gall insects, and species living within fruits; (2) house-
hold pests; and (3) animal parasites.

The classification of insects outlined above, based on mode of nour-
ishment, and indicating groups amenable to similar remedial treat-
ment, simply stated, is as follows:

I. Elxternal feeders : III. Subterranean insects.

(a) Biting insects. IV. Insects affecting stored products.

(&) Sucking insects. V. Household pests.

II. Internal feeders. VI. Animal parasites.

INSECTICIDES FOE EXTERNAL BITING INSECTS (FOOD POISONS) .

THE ARSENICALS.

The arsenical compounds have supplanted practically all other
substances for insects falling under this heading. Of these, Paris
green is the best known and most generally emploj'^ed, and probably
from 2,000 to 3,000 tons of it are used for horticultural purposes
every year. Arsenate of lead is a new arsenical coming into very
general use, and arsenite of copper, a near ally of Paris green, is also
increasingly employed. Arsenite of lime is usually a home prepara-
tion, and London purple, the least uniform in composition of all the
mixtures, is rather going out of use. The powdered white arsenic or

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arsenious oxide can not be employed on account of its scalding action
on the foliage, and in the case of any of the arsenicals the percentage
of soluble arsenic (arsenious oxide) should be at the very minimum,
certainly not in excess of 3 or 4 per cent. With more than 4 per cent
soluble arsenic there is great danger of scalding the foliage, the
danger increasing with the percentage of soluble arsenic."

Paris green. — Paris green is a definite chemical compound of white
arsenic, copper oxide, and acetic acid, and is known as the aceto-
arsenite of copper. Properly compounded and washed, it should be
substantially uniform in composition and nearly free from uncom-
bined soluble white arsenic. It is a rather coarse powder, or, more
properly speaking, crystal, and settles rapidly in water, which is its
gi-eatest fault. To give better suspension in water, it should be re-
duced to such fineness by grinding that it will pass through a 100-mesh
sieve. Its high cost (varying from 20 to 40 cents a pound, following
the market price of copper and arsenic) is further increased by its
being crystallized with acetic acid, making it a more brilliant pigment,
but giving it a coarse grain and rendering it a poorer insecticide. The
standards of purity demanded by various States have led most manu-
facturers to produce a very fair article, but if there is any doubt of
purity a sample should be submitted to the State Experiment Station
or to the United States Department of Agriculture for analysis.

Copper arsenite. — Copper arscnite, often called Scheele's green, is
the simple arsenite of copper, differing from Paris green in lacking
acetic acid. It is a much finer powder than Paris green and therefore
is more easily kept in suspension, and it costs considerably less per
pound. It is dull in color, lacking the brilliancy of Paris green.
When properly prepared and washed by the manufacturers, it is no
more harmful to the foliage than Paris green when the latter is
brought to an equal fineness, and should supplant the latter as an
insecticide. It is used in the same way and at about the same strength
as Paris green.

<^ Hellehore. — The powdered roots of the white hellebore {Veratrum viride)
are often recommended and used as an insecticide, particularly as a substitute
for the arsenites. This substance is useful when a few plants only are to be
sprayed, as in yards and small gardens, but is too expensive for large opera-
tions. It kills insects in the same way as the arsenicals, as an internal poison,
and is less dangerous to man and the higher animals ; but if a sufficient amount
be taken it will cause death. It is particularly effective against the larva; of
sawflies, such as the cherry slug, rose slug, currant worms, and strawberry
worms.

It may be applied as a dry powder, preferably diluted with from 5 to 10 parts
of flour, and dusted on the plants through a muslin bag or with powder bellows.
The application should be made in the morning, when the plants are moist with
dew. Used as a wet application, it should be mixed with water in the propor-
tion of 1 ounce to the gallon of water and applied as a spray.
127

Arsenite of lime. — This is normally a home-made preparation, and
there is no reason for its not being employed wherever one is willing
to take the trouble to compound it carefully. Its preparation, de-
scribed below, following substantially the Kedzie formula, is simple
enough :

White arsenic pounds__ 1

CiTstal sal soda" do 4

y/ater i gallons.- 1

Place the above ingredients in an iron vessel, which is to be kept
exclusively for this purpose, and boil for twenty minutes or until
dissolved. To 40 or 50 gallons of water a pint of this stock solution
and 3 to 4 pounds of freshly slaked lime are added. This excess
of liine not only takes up any free arsenic, but by its distribution on
the foliage enables one to determine how well the spraying has been
done. This formula has been thoroughly tested and used now for
many years, and is fully as efficient as any other arsenical and far
cheaper. Chemically it is arsenite of lime. The soda is used to
hasten the process and to insure the combination of all the arsenic
with the lime. The greatest care should be exercised in preparing
the stock mixture, and afterwards it should be plainly labeled to pre-
vent its being mistaken for some other substance. The only objec-
tion to its use is the necessity of handling the poisons in its home
preparation.

London purple. — London purple is a waste product in the manufac-
ture of aniline dyes and contains a nmnber of substances, the chief
of which are white arsenic and lime. It is not so effective as the
copper arsenites, and contains a much larger percentage of soluble
arsenic, and is very apt to scald foliage unless very carefully mixed
with fresh stone lime. It comes as a very fine powder, and is easily
kept in suspension. It costs about 10 cents a pound. If employed,
the lime should always be added.

Arsenate of lead. — Arsenate of lead may be prepared at home by
combining approximately 3 parts of the crystallized arsenate of soda
with 7 parts of crystallized acetate of lead (sugar of lead) in water.
This gives a slight excess of acetate of lead. Each of the ingredients
should be dissolved separately in water in wooden vessels, and the
two solutions poured together into the spray tank filled with water.
The white, flocculent precipitate of arsenate of lead which im-
mediately results is extremely fine and remains in suspension much
longer than any other arsenical. Furthermore, prepared in this way
and diluted at once, there is secured a mixture that is chemically su-
perior to the combined product sold in paste form and that remains in

<^Two pounds only of the anhydrous sal soda are necessary.
73159— Bui. 127—09 2

10

jiuspension better. Arsenate of soda costs wholesale about 10 cents a
pound, and first-class acetate of lead about 10 cents a j^ound.

Arsenate of lead may be used at any strength from 3 to 15 pounds
to 100 gallons of "svater without injury to the foliage, for the reason
that it contains little, if any, soluble arsenic. It is ordinarily used
at the rate of 4 to G pounds to the 100 gallons of water or Bordeaux
mixture. In later years it has come into general use, especially for
spraying plants sensitive to arsenical poisoning, such as peach, and
also in cases where it is necessary to make heavy applications. Its
safety as regards the burning of foliage and its adhesive quality
offset its greater cost, and it is now much used in the codling moth
•work and general arsenical spraying.

In the home preparation of this arsenical, the number of pounds
of the poison per 100 gallons of water as given in directions for use
should be understood to mean the combined weights of the two
ingredients. In point of fact, the resulting lead arsenate is only
about half the actual weight of the two ingredients, which explains
in part the apparently excessive amounts used as compared with
other arsenicals.

A good many brands of arsenate of lead can be purchased on the
market, usually in the form of heavy pastes. As already indicated,
they have not the same power of remaining in suspension as the
freshly made product, but are otherwise, if properly made, quite
satisfactory. The water content, which is variable, should be spe-
cifically indicated and guaranteed, to make it possible to use the
poison at the strength desired.

Arsenite of lead is a compound very similar to the arsenate of lead,
but it contains a less percentage of arsenic. It is prepared from
sodium arsenite.

General considerations. — In point of solubility and corresponding
danger of scalding the foliage, these arsenicals fall in the following
order, the least soluble first: Arsenate of lead, arsenite of lime, Paris
green, copper arsenite, and London purple. In point of cost the
arsenite of lime is much cheaper than the other arsenicals, and the
arsenate of lead, at the rate at which it is necessary to use it, much the
most expensive. But after all the main cost is in the application,
and it is therefore well worth while to secure a good arsenical and
get the best results.

HOW TO APPLY ABSENICALS.

There are three principal methods of applying arsenicals. The wet
method, which consists in using these poisons in water in the form of
spray, is the standard means, secures uniform results at least expense,
and is the only practical method of protecting fruit and shade trees.

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The dry application of these poisons in the form of a powder, which is
dusted over plants, is more popular as a means against the cotton
worm in the South, where the rapidity of treatment possible by this
method, and its cheapness, give it a value against this insect, in the
practical treatment of which prompt and economical action are the
essentials. This method is also feasible for any low-growing crop,
such as potatoes, young cabbages, or other plants not to be immedi-
ately employed as food. The third method consists in the use of
the arsenicals in the form of poisoned baits, and is particularly avail-
able for such insects as cutworms, wureworms, and grasshoppers in
local invasions.

The wet method.— Either Paris green, arsenite of copper, arsenite of
lime, or London purple may be used at the rate of 1 pound of the
poison to 100 to 250 gallons of water, or 1 ounce to G to 15 gallons.
The stronger mixtures are for such vigorous foliage as that of the
potato, and the greater dilutions for the more tender foliage of the
peach or plum. An average of 1 pound to 150 gallons of water is a
good strength for general purposes. The poison should first be made
into a thin paste in a small quantity of water and quicklime added in
amount equal to the poison used, to take up the free arsenic and
remov^e or lessen the danger of scalding. An excess of lime will do
no injury. The poisons thus mixed should be strained into the spray
tank or reservoir, care being taken that all the poison is pulverized
and washed through the meshes of the strainer. The use of the lime
is especially desirable in the case of the peach and plum, the foliage
of which, particularly the former, is very tender and easily scalded.
To the stronger foliage of the apple and m.ost shade trees Paris green
may be applied without danger at the strength of 1 pound to 150 gal-
lons of water ; with London purple it is always better to use the lime.
The method of preparation of arsenate of lead has already been indi-
cated. Lime is not needed with this arsenical.

If it be desirable to apply a fungicide at the same time, as on the
apple for the codling moth and the apple scab fungus, the Bordeaux
mixture " may be used instead of water, adding the arsenical to it at
the same rate per gallon as when water is used. The lime in this fun-
gicide neutralizes any excess of free arsenic and makes it an excellent
medium for the arsenical, as it removes liability of scalding the foli-
age and permits an application of the arsenical, if necessary, eight or
ten times as strong as it could be employed with water alone.

The arsenicals can not be safely used with most other fungicides,
such as the sulphate of copper, eau celeste, or iron chloride solution,
the scalding effects of these being greatly intensified in the mixture.

The dry method. — The following description applies to the pole-

«* See F. B. 243, Fungicides and Their Use in Preventing Diseases of Fruits.
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and-bag duster commonly used against the cotton worm: A pole 5
to 8 feet long and about 2 inches in diameter is taken, and a three-
fourths-inch hole bored through it within 6 inches of each end.
Near each end is securely tacked a bag of " 8-ounce osnaburg cloth,"
1 foot wide and 18 inches to 2 feet long, so that the powdered poison
may be introduced into the bags with a funnel through the holes at
the ends of the pole. The bags are filled with undiluted Paris green,
which is generall}^ preferred to London purple on account of its
quicker action, and the apparatus is carried on horse or mule back,
through the cotton fields, dusting two or four rows at once. The
shaking induced b}^ the motion of the animal going at a brisk walk
or at a trot is sufficient to dust the plants thoroughly, or the pole may
be jarred by hand. The application is preferably made in early
morning or late evening, when the dew is on, to cause the poison to
adhere better to the foliage.

From 1 to 2 pounds are required to the acre, and from 10 to 20
acres are covered in a day. The occurrence of heavv- rains may neces-
sitate a second application, but frequently one will suflfice. This
simple apparatus, on account of its effectiveness and cheapness, is
employed throughout the cotton belt to the general exclusion of more
complicated and expensive machinery. The cost frequently does not
exceed 25 cents per acre, and the results are so satisfactory that the
leaf worm is no longer considered a serious factor in cotton culture.

With the patented air-blast machines for the dry distribution of
poisons, arsenicals are diluted with 10 parts of flour, lime, or ground
gypsum, and from 60 to 75 acres may be covered in a day by using
relays of men and teams. Greater uniformity is secured with these
machines in distribution of the poisons, but their cost (from $30 to
$60) prevents their general use.

The planter should have a good supply of poison on hand and appa-
ratus for its application prepared in advance, since when the worm
puts in an appearance its progress is very rapid, and a delay of a
single day may result in material damage to the crojo.

If small garden patches are dusted with poison by this or similar
means from bags or with hand bellows, it is advisable always to dilute
the poison with 10 parts of flour, or f)referably lime, and for applica-
tion to vegetables which ultimately will be used for food, as the cab-
bage, 1 ounce of the poison should be mixed with 6 pounds of flour or
10 of lime and dusted merely enough to show evenly over the surface.
Arsenicals should not be applied to lettuce or other vegetables the
free leafage of which is eaten.

Poisoned bait. — It is not always advisable or effective to apply
arsenicals directly to the plants, and this is particularly true in rela-
tion to the attacks of the grasshopper and of the various cutworms

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and wireworms. In such cases the use of poisoned bait has proved
very satisfactory.

For grasshoppers, take 1 part, by weight, of white arsenic, 1 of
sugar, or mohisses, and 6 of bran, to which add water to make a wet
mash. Place a tablespoonfiil of this at the base of each tree or
vine, or apply a line of baits just ahead of the advancing army of
grasshoppers, placing a tablespoonful of the mash every 6 or 8 feet
and following up with another line behind the first.

A cheap grasshopper bait used successfully in parts of the West
is obtained by mixing fresh horse droppings with arsenicals. One
pound of Paris green, or some other convenient arsenical, together
with 2 pounds of salt, are thoroughly mixed with 60 pounds of fresh
horse droppings. The resulting mixture is scattered among the young
" hoppers " or around the edges of fields which it is thought may be
invaded. A very convenient receptacle in which to make this prepa-
ration is a half barrel. A trowel or paddle can be used in scattering
the mixture in the desired places.

Bran and Paris green, on the authority of Prof. J. B. Smith, thor-
oughly mixed and sprinkled dry on cabbage heads, proved a most
successful remedy for cabbage worms, the latter preferring the
poisoned bran tc the cabbage, to their prompt undoing. The same
dry mixture has been successfully employed against cutworms and is
recommended by Smith for the army worm, running it in rows 10
feet apart across the infested field. One pound of jDoison to 10 of
bran is a good proportion. The bran-arsenic bait may also be used
for cutworms.

For sowbugs, or pill bugs, which frequently are injurious pests to
tender flowering plants and vegetables grown under frames or in
glass houses, poisoned slices of potato have proved to be the most
effectual remedy. The freshly sliced potato may be poisoned by dip-
ping in a strong arsenical solution, or by dusting thickly with a dry
arsenical, and should then be distributed over the beds. Pansy beds
have been notably protected in this way, and a Michigan vegetable
grower reports that in two nights he destro3'ed upward of 24,000 of
these bugs by this means in four houses used for lettuce growing.

Another remedy for cutworms and also for wircworn-s is poisoned
green succulent vegetation, such as freshly cut clover, distributed in
small bunches in the infested fields. Dip the bait in a very strong
arsenical solution, and protect it from drying by covering. Renew
the bait as often as it becomes dry, or every three to five days.

TIME TO SPRAY FOR BITING INSECTS.

Specific directions for spraying with arsenicals to control im-
portant insect pests are given in Farmers' Bulletins or in circulars
of this Bureau relating to these different insects. One of the princi-

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pal uses of arsenical poisons is for the control of the codling moth.
Detailed information on the subject is given in Farmers' Bulletins
Nos. 247 and 283. The plum curculio is discussed in Circular No. 73,
and leaf -feeding grape insects in Farmers' Bulletin No. 284. Other
publications relating to special insect problems are also available
giving detailed directions for spraying.

For leaf-feeding insects in general, such as the Colorado potato
beetle, blister beetles, elm leaf-beetle, maple Avorm, and other forest
or shade-tree caterpillars, the application should be mads at the
earliest indication of injury, and repeated as often as necessary.
Fruit trees should never be sprayed when in bloom, on account of
the liability of poisoning honey bees or other insects useful as cross-
fertilizers.

There is no basis for the idea occasionally advanced that the fre-
quent use of Paris green or other arsenicals on potatoes and other
crops is injurious to the foliage or health of the treated plants. This
matter has been fully tested, and the injurious results can always
be accounted for by improper mixtures or applications.

CARE IN THE USE OF AUSENICALS.

It must be remembered that these arsenicals are very poisonous and
should be so labeled. If ordinary precautions are taken, there is no
danger to man or team attending their application. The wetting of
cither, which can not always be avoided, is not at all dangerous, on
account of the great dilution of the mixture, and no ill effects what-
ever have resulted from this source. With some indi\'i duals the arsen-
ate of lead, when in strong mixture, affects the eyes, but this is im-
usual, and, with a little care in spraying, the mist need not strike the
operator at all.

The poison disappears from the plants almost completely within
twenty to twent3'-five days, and even if the plants were consumed
shortly after the application, an impossible quantity would have to be
eaten to get a poisonous dose. To illustrate, in the case of the apple,
if the entire fruit were eaten, core and all, it would take several bar-
rels at a single sitting to make a poisionous dose (Riley), and with the
cabbage, dusted as recommended above, 28 heads would have to be
eaten at one meal to reach this result (Gillette). It is preferable,
however, to use other insecticides in the case of vegetables soon to be
eaten, and thus avoid all appearance of danger.

INSECTICIDES FOR EXTERNAL SUCKING INSECTS (CONTACT

POISONS).

The simple remedies for this class of insects, such as soap, insect
pov.'der, sulphur, tobacco decoction, etc., are frequently of value, but
need little special explanation. Some brief notes will be given, how-

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ever, describing the methods of using some of these substances which
are easily available and will often be of service, particularly where
few plants are to be treated. The standard remedies for this group
of insects, viz, crude petroleum, kerosene, and kerosene emulsions,
resin washes, lime-sulphur wash, hydrocyanic acid gas, and vapor of
bisulphid of carbon, will be treated farther on,

SOAPS AS INSECTICIDES.

Any good soap is effective in destroying soft-bodied insects, such as
aphides and 3'oung or soft-bodied larvae. As winter washes in very
strong solution, they furnish one of the safest and most effective means
against scale insects. The soaps made of fish oil and sold under the
name of whale-oil soaps are often especially valuable, but they are
variable in composition and merits. A soap made with caustic potash
rather than with caustic soda which is commonly used, and not con-
taining more than 30 per cent of water, should be demanded, the jDot-
ash soap yielding a liquid in dilution more readily sprayed and more
effective against insects. The soda soap washes are apt to be gelatin-
ous when cold, and difficult or impossible to spray except when kept
at a very high temperature.

For aphides and delicate larvae, such as the pear slug, a strength
obtained by dissolving half a pound of soap in a gallon of water is
sufficient. For the pea aphis as little as 1 pound of potash fish-oil
soaj) to G gallons has been effective. Soft soap will answer as well
as hard, but at least double quantity should be taken.

As a winter wash for the San Jose and allied scale insects, whale-oil
or fish-oil soap is dissolved in water by boiling at the rate of 2 pounds
of soap to the gallon of water. If applied hot and on a comparatively
warm day in winter, it can be easily put on trees with an ordinar}''
spray pump. On a very cold day, or with a cold solution, the mix-
ture will clog the pump and difficulty will be experienced in getting it
on the trees. Trees should be thoroughly coated with this soap wash.
Pear and apple trees may be sprayed at any time during the winter.
Peach and plum trees are best sprayed in the spring, shortly before
the buds swell. If sprayed in midwinter or earlier, the soap solution
seems to prevent the development of the fruit buds, and a loss of fruit
for one year is apt to be experienced, the trees leafing out and grow-
ing, however, perhaps more vigorously on this account. The soap
treatment is perfectly safe for all kinds of trees, and is very effective
against the scale. With large trees, or badly infested trees, as a pre-
liminary to treatment, it is desirable with this as well as other appli-
cations to i^rune them back very rigorously. This results in an econ-
omy of spray and makes much more thorough and effective work
possible. The soap can be secured in large quantities at from 3^

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16

cents to 4 cents a pound, making the mixture cost, as applied to the
trees, ftx)m 7 cents to 8 cents a gallon.

PYRETHRUM, OR INSECT POWDER.

This insecticide is sold under the names of Buhach, Dalmatian, and
Persian insect powder, or simply insect powder, and is the ground-up
flowers of the Pyrethrum plant. It acts on insects externally through
their breathing pores, and is fatal to many forms both of biting and
sucking insects. It is not poisonous to man or the higher animals,
and hence may be used where poisons would be objectionable. Its
chief value is against household pests, such as roaches, flies, and ants,
and in greenhouses, conservatories, and small gardens, where the use
of arsenical poisons would be inadvisable.

It is used as a dry powder, pure or mixed with flour, in which form
it may be puffed about rooms or over plants. On the latter it is
preferably applied in the evening, so as to be retained by the dew . To
keep out mosquitoes, and also to kill them, burning the powder in a
tent or room w^ill give satisfactory results.

It may also be used as a spray at the rate of 1 ounce to 2 gallons of
water, but in this case should be mixed some twenty-four hours before
being ajjplied. For immediate use, a decoction may be prepared by
boiling in water from five to ten minutes.

TOBACCO DECOCTIOU.

A tobacco decoction sufficiently strong for aphides and other very
delicate insects may be prepared from tobacco stems and other refuse
tobacco by boiling at the rate of 1 pound for each 1 or 2 gallons of
water, sufficient water being added to make up for that lost in boiling.

SULPHUR.

Flowers of sulphur is one of the best remedies for plant mites, such
as the red spider, the six-spotted orange mite, and the rust mite of
citrus fruits. It may be applied in several forms, the simplest of
which is its use as a dry povv'der dusted over the trees with powder
bellows or any broadcasting device, preferably in the early morning
when the foliage is damp with dew, or immediately after a rain. For
the rust mite in very moist climates, such as that of Florida, to keep
the fruit bright it is sufficient merely to sprinkle the sulphur about
under the trees. The flowers of sulphur may be easily ajDplied also
with any other insecticide, such as kerosene emulsion, resin wash, or
a soap w\ash, mixing it up first into a paste and then adding it to the
spray tank at a rate of from 1 to 2 pounds to 50 gallons.

Somewhat more uniform results can be obtained perhaps b}^ getting
the sulphur into solution, either dissolving it with lye or by boiling
it with lime.

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17

In making the lye-sulphiir wash, first mix 20 pounds of flowers of
sulphur into a paste with cold water, then add 10 pounds of pulver-
ized caustic soda (98 per cent). The dissolving lye will boil and
liquefy the sulphur. "Water must be added from time to time to pre-
vent burning, until a concentrated solution of 20 gallons is obtained.
Two gallons of this is sufficient for 50 gallons of spray, giving a
strength of 2 pounds of sulphur and 1 of lye to 50 gallons of water.
An even stronger application can be made without danger to the
foliage. This mixture can also be used in combination with other
insecticides.

The chemical combination of sulphur and lime known as sulphid
of lime is perhaps a better liquid sulphur solution than the last as a
remedy for mites. It may be very cheaply prepared by boiling
together for an hour or more, in a small quantity of water, equal
parts of flowers of sulphur and stone lime. A convenient quantity is
prepared by taking 5 pounds of sulphur and 5 of lime and boiling in
o or 4 gallons of water until the ingredients combine, forming a
brownish liquid. This may be diluted to make 100 gallons of spraj^

Almost any of the insecticides with which the sulphur may be
applied will kill the leaf or rust mites, but the advantage of the
sulphur arises from the fact that it forms an adhering coating on the
leaves and kills the young mites coming from the eggs, which are
very resistant to the action of insecticides.

A strongly intrenched popular fallacy, often exposed but con-
stantly being revived, is that sulphur is a valuable remedy against
insects when put into holes bored into the trunks of trees, t'' .e idea
being that the sulphur, when plugged in, is carried up by the move-
ment of the sap into the branches and distributed in the foliage,
rendering the latter distasteful to insects. In point of fact, the
sulphur remains exactly where it is placed, and is of no possible
advantage from an insecticide standpoint or any other, and further-
more the treatment is mischievous in that it injures to that extent
the soundness of the trunk.

PETROLEUM OILS.

The emulsions of kerosene, or coal oil, with soap or milk have long
been the standard insecticides for external sucking insects, and espe-
cially the aphides and scale insects, and these emulsions still are the
safest and most reliable means of getting these oils upon plants. The
use of kerosene in the pure state as an insecticide was early experi-
mented with by Comstock and Hubbard, and the feasibility of such
applications was demonstrated, but the greater safety in the use of
the emulsions resulted in a discontinuance of the use of the pure oils.
Especially during the last twelve years, however, the use of these
73159— Bui. 127—09 3

18

oils in the pure state has come into very general vogue, more particu-
larly as winter washes for the San Jose scale and allied scale insects,
the value of the crude oil being especially demonstrated by Prof. J. B.
Smith. The petroleum oils may also be mechanically combined with
water by means of especially adapted spray pumps.

In addition to its direct application to plants, kerosene is often used
as a means of destrojdng insects by jarring the latter from plants into
pans of water on which a little of the oil is floating, or by jarring
them upon cloths or screens saturated with kerosene, preferably the
crude oil. The same principle is illustrated in some of the hopper-
dozers, or machines for collecting grasshoppers and leaf -hoppers.

As a remedy for mosquitoes, kerosene has proved very effective.
It is employed to destroy the larvce of the mosquitoes in their favorite
breeding places in small pools, still ponds, or stagnant water; and
where such bodies of water are not sources of drinking supply or of
value for their fish, especially in the case of temporary pools from
rains, which frequently breed very disagreeable local swarms, the use
of oil is strongly recommended. The kerosene is applied at the rate
of 1 ounce to 15 square feet of water surface. It forms a uniform
film over the surface and destroys all forms of aquatic insect life,
including the larvas of the mosquito, and also the adult females coming
to the water to deposit their eggs. The application retains its effi-
cienc}^ for several weeks, even with the occurrence of heavy rains. A
light grade of fuel oil is preferred for this purpose.

The methods of using kerosene in the pure state and as emulsions
with soa]3 and milk folloAv.

Pure-kerosene treatment. — This consists in spraying the trees with
ordinary illuminating oil (coal oil or kerosene). The application is
made at any time during the winter, preferably in the latter part, and
by means of a spray pump making a fine mist spray. The applica-
tion should be made with the greatest care, merely enough spray being
put on the plant to moisten the trunk and branches without causing
the oil to flow down the trunk and collect about the base. With the
use of this substance it must be constantly borne in mind that careless
or excessive application of the oil will be very apt to kill the treated
plant. The application should be made on a bright, dry day, so that
the oil will evaporate as quickly as possible. On a moist, cloudy day
the evaporation is slow, and injury to the plant is more apt to result.
If the kerosene treatment be adopted, therefore, it must be with a full
appreciation of the fact that the death of the tree may follow. This
oil has been used, however, a great many times and very extensively
without consequent injury of any kind. On the other hand, its care-
less use has frequently killed valuable trees. Its advantages are its
effectiveness, its availability, and its cheapness, kerosene spreading

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19

very rapidly and much less of it being required to wet the tree than
of a soap and water spray. Pure kerosene is more apt to be injurious
to peach and plum than to pear and apple trees, and the treatment of
the former, as with the soap wash, should be deferred until spring,
just before the buds swell. With young trees especially it is well to
mound up about the trunk a few inches of earth to catch the overflow
of oil, removing the oil-soaked earth immediately after treatment.

The crude-petroleum treatment. — Crude petroleum is used in exactly
the same way as is the common illuminating oil referred to above.
Its advantages over kerosene are that, as it contains a very large per-
centage of the heavy oils, it does not penetrate the bark so readily,
and, on the other hand, only the light oils evaporate, leaving a coat-
ing of the heavy oils on the bark, which remains in evidence for
months and prevents any young scale, which may come from the
chance individuals not reached by the spray, from getting a foothold.
Crude i)etroleum comes in a great many different forms, depending
upon the locality, the grade successfully experimented with in the
work of this Bureau showing 43° Baume. Crude oil showing a lower
Baume than 43° is unsafe, and more than 45° is unnecessarily high.
The lower specific gravity indicated (43°) is substantially that of the
refined product, the removal of the lighter oils in refining practically
offsetting the removal of the paraffin and vaseline. The same cau-
tions and warnings apply to the crude as to the refined oil.

The oil-water treatment. — Various pump manufacturers have now
placed on the market spraying machines which mechanically mix
kerosene or crude petroleum with water in the act of spraying. The
attempt is made to regulate the proportion of kerosene so that any
desired percentage of oil can be thrown out with the water and be
broken up by the nozzle into a sort of emulsion. Some of these ma-
chines, when everything is in good working order, give fairly satis-
factory results, but absolute reliability is far from assured. The
best outlook for good apparatus of this sort seems to be in carrying
the oil and water in separate lines of hose to the nozzle, uniting them
in the latter, and in maintaining an absolute equality of pressure on
both the oil and the water tanks by emplo3dng compressed air as the
motive force, kept up by an air pump, the air chamber communicat-
ing with both of the liquid receptacles. One or more manufacturers
are now working on apparatus of this general description. A 10-per-
cent-strength kerosene can be used for a summer spray on trees where
the San Jose scale is multiplying rapidly and where it is not desirable
to let it go unchecked until the time for the winter treatment. The
winter treatment with the water-kerosene sprays may be made at a
strength of 20 per cent of the oil. Applications of the oil-water
spray should be attended with the same precautions as with the pure

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20

oil, and there is even somewhat greater risk, owing to the natural
tendency one has to apply the dilute mixture much more freely than
the pure oil The application should be merely enough to wet the
bark and the mixture should not, to any extent at least, run down
the trunk, as it is just as dangerous to the tree as the pure oil.

In the use of the oil sprays noted above, one who has not had expe-
rience with them is advised to make some careful preliminary tests
to fully master the process, preferably waiting two or three weeks to
determine the results before entering on the general treatment of the
orchard. It is well, also, with the oil-water mixtures to test the pump
from time to time, spraying into a glass jar or bottle to determine by
actual measurement whether the correct percentages of oil and water
are being m.aintained.

Kerosene emulsion (soap formula) . — The kerosene-soap emulsion, fol-
lowing chiefl}' the Rilej-Hubbard formula, has been one of the stand-
ard means against scale insects for twenty years. The distillate
emulsion generally employed in California for spraying citrus and
other trees is substantially the same thing, except that it is made with
the California distillate or petroleum oil. Crude petroleum of any
kind, as well as the refined product, may also be used in making this
emulsion. The use of the soap emulsions against the San Jcse scale
in the East has not been very general, on account of the greater facil-
ity with which the pure oil or oil-water mixtures can be applied.
The difficulty of obtaining uniform results with the latter has led to a
return to the use of emulsions to some extent, and there can be no
doubt about their superior merit when it is desired to dilute the pure
oils. Emulsions may be applied at any strength with absolute con-
fidence that there will be no variation. Where the emulsion can be
prepared wholesale by steam power, its employment is attended with
no difficulties. In California it is prepared by oil companies and sold
at very slightly more than the cost of the oil and soap ingredients. It
is made after the following formula :

Petroleum gallons.^ 2

Wliale-oil soap (or 1 quart soft soap) pound — i

Water (soft) Sallou__ 1

The soap, first finely divided, is dissolved in the water by boiling
and immediately added boiling hot, away from the fire, to the oil.
The whole mixture is then agitated violently while hot by being
pumped back upon itself with a force pump and direct-discharge
nozzle throwing a strong stream, preferably one-eighth inch in diam-
eter. After from three to five minutes' pumping the emulsion should
be perfect, and the mixture will have increased from one-third to one-
half in bulk and assume the consistency of cream. Well made, the
emulsion will keep indefinitely and should be diluted only as wanted
for use.

127

In limestone regions, or where the water is very hard, some of the
soap will combine with the lime or magnesia in the water, and more or
less of the oil will be freed, especially when the emulsion is diluted.
Before use, such water should be broken with lye, or rain water
should be emplo3'^ed.

Kerosene emulsion (milk formula). — This formula is as follows:

Kerosene gallons— 2

Milk (sour) gallon— 1

Heating is unnecessary in making the milk emulsion, which other-
wise is churned as in the former case. The change from a watery
liquid to a thick buttery consistency, much thicker than with the soap,
takes place very suddenly after three to five minutes' agitation. With
sweet milk difficulty will frequently be experienced, and if the emul-
sion does not result in five minutes, the addition of a little vinegar will
induce prompt action. It is better to prepare the milk emulsion from
time to time for immediate use, unless it can be stored in quantity in
air-tight jars; otherwise it will ferment and spoil after a week or two.

The distillate emulsion. — This wash was originated by Mr. F. Kahles,
of Santa Barbara, Cal. It has been recommended by the California
State board of horticulture and has found very general use in the
citrus sections of the State. It is substantially an emulsion of crude
petroleum, made in the same way as the kerosene emulsion described
above, except that a greater amount of soap and only half as much oil
proportionately is used. The lessened quantity of oil enables it to be
made comparatively cheaply, and in spite of this reduction in the oil,
the wash is, if anything, stronger than kerosene emulsion, judging
from the experience of the writer with both these washes in southern
California.

It is termed distillate spray, because the oil used is a crude distil-
late of the heavy California petroleum. The product used for pre-
paring the emulsion should have a gravity of about 28° Baume, and
is the crude oil minus the lighter oil, or what distills over at a tem-
perature between 250° and 350° C. In general characteristics it is
very similar to lubricating oil. The emulsion, or, as it is generally
known, " cream," is prepared as follows: Five gallons of 28° gravity
distillate; 5 gallons of water, boiling; 1 to 1-1 pounds of whale-oil
soap. The soap is dissolved in hot water, the distillate added, and the
whole thoroughly emulsified by means of a power pump until a rather
heavy yellowish, creamy emulsion is produced. The product is very
similar to, but rather darker in color than the ordinary kerosene
emulsion. For use on citrus trees it is diluted with from 12 to 15
parts of water, the stronger wash for the lemon and the weaker for
the orange. The " distillate cream " is commonly prepared and sold
by oil companies or individuals at from 10 to 12 cents a gallon,

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22

making the diluted mixture cost in the neighborhood of a cent a
gallon.

The distillate spray has the same range of application as kerosene
emulsion. In California it has been used extensively for the spray-
ing of citrus trees, and when so used has been often charged with
injury to trees and especially resulting in spotting of fruit. If this
spray be applied to citrus plants in spring and summer, there is
danger of the spotting and dropping of the young fruit and leaves.
Where several applications may be necessary each year, gas fumiga-
tion is undoubtedly preferable. Nevertheless it has been fully demon-
strated that any applications made to citrus trees during the com-
paratively dormant season in October and November, with a second
treatment if necessary in January and February, the latter just
before the flower spurs start, results in no injury.

How to use the emulsions. — During the growing period of summer,
for most aphides and other soft-bodied insects, dilute the emulsion
with 15 parts of water; for the red spider and other plant-mites, the
same, with the addition of 1 ounce of floAvers of sulphur to the gallon ;
for scale insects, the larger plant-bugs, larva?, and beetles, dilute with
from 7 to 10 parts of water. Apply with spray pump. The greatest
dilution noted gives 4 per cent of oil and the lesser dilutions approxi-
mately 6 and 8 per cent.

For winter applications to the trunks and limbs of trees in the dor-
mant and leafless condition to destroy scale insects, stronger mixtures
may be used, even to the pure emulsion, which can not be sprayed suc-
cessfully but may be applied with brush or sponge. Diluted with one
or more parts of water it may be applied in spray without difficulty.
The use of the pure emulsion is heroic treatment and only advisable
in cases of excessive infestation.

The winter strengths recommended are the emulsion diluted with
either 3, 4, or 5 parts of water, giving approximately 17, 13, and 11
per cent of oil. These dilutions are equivalent in strength to oil-
water sprays containing 25, 20, and 15 per cent of oil, because rela-
tively more of the emulsion is held by the bark. The two stronger
mixtures may be used on the apple and pear and the weaker one on
peach and plum.

The winter treatment may be followed in June by a use of the sum-
mer wash to destroy any young which may come from female scales
escaping the stronger mixture.

Cautions regarding use of oil washes. — In the use of kerosene washes,
and, in fact, of all oily washes on plants, the application should be
just sufficient to wet the plant without allowing the liquid to run down
the trunk and collect about the root. Usually, in the case of young
trees at least, there is a cavity formed by the swaying of the tree in

127

the wind, and accumulation of the insecticide at this point, unless
precautions be taken, may result in the death or injury of the plant.
Under these conditions it may be advisable to mound up the trees
before spraying and firmly pack the earth about the bases. Care
should be taken in refilling the tank that no free oil is allowed to
accumulate gradually in the residue left at the bottom when spraying
with emulsions or oil-water mixtures.

Miscible oils. — It will be noted that the difficulty to be overcome in
the use of oils is to effect their dilution to render them harmless to
the plant. This dilution is effected with great accuracy b}^ the kero-
sene-soap emulsions, and less accurately by the mechanical emulsions
of oil and water. There have appeared during the last few years
various so-called miscible oils, which readily and permanently mix
with water, and can be applied with the same readiness and accuracy
of strength as the emulsion of kerosene and soap. These oils have
for their principal ingredient some form of petroleum rendered solu-
ble by the addition of a percentage of vegetable oils and cut or sapon-
ified with an alkali, and they are, in fact, a sort of liquid petroleum
soap. They are sold under various trade names. They have the
disadvantage of costing a good deal more than the standard emul-
sions or the lime-sulphur wash (see p. 24), but have the great advan-
tage of being always ready for immediate use without troublesome
preparation. They can not be diluted for winter applications against
scale insects with more than 10 or 15 parts of water to give good re-
sults, and there is some danger of injury to the trees if they are care-
lessly or excessively applied. They have, however, a very useful place,
and especially as furnishing a good insecticide where only a few
trees are to be treated and the owner would probably not go to the
trouble of preparing an emulsion or the lime-sulphur wash. They
have been so far principally used against the San Jose scale as dor-
mant tree washes.

THE RESIN WASH.

The resin wash has proved of greatest value in California, particu-
larly against the red scale {Ghrysomphalus aurantii Mask.) and the
black scale {Sais^etia olecB Bern.) on citrus plants, and the last named
and the San Jose scale (Aspidiotus perniciosus Comst.) on deciduous
plants, and will be of use in all similar climates where the occurrence
of comparatively rainless seasons insures the continuance of the wash
on the trees for a considerable period, and where, owing to the
warmth, the multiplication of the scale insects continues almost with-
out interruption throughout the year. Wliere rains are liable to
occur at short intervals, and in the Northern States, the quicker-
acting and stronger kerosene washes and heavy soap applications are

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preferable. The resin wash acts by contact, having a certain caustic
effect, but i3rincipally by forming an impervious, smothering coating
over the scale insects. The application may be more liberal than with
the kerosene washes, the object being to wet the bark thoroughly.
The wash may be made as follows:

Resin pounds. _ 20

Crude caustic soda (78 per cent) do 5

Fish oil pints__ 2i

Water to make gallons 100

Ordinary commercial resin is used, and the caustic soda is that put
up for soap establishments, in large 200-pound drums. Smaller
quantities may be obtained at soap factories, or the granulated caustic
soda (98 per cent) may be used — 3^ pounds of the latter being the
equivalent of 5 pounds of the crude. Place these substances, with
the oil, in a kettle with water to cover them to a depth of 3 or 4
inches. Boil about two hours, making occasional additions of water,
or until the compound resembles very strong black coffee. Dilute to
one-third the final bulk with hot water, or with cold w^ater added
slowly over the fire, making a stock mixture, to be diluted to the full
amount as used. When spraj^ed the mixture should be perfectly
fluid, without sediment, and should any appear in the stock mixture
reheating should be resorted to ; in fact the wash is preferably applied
hot.

As a winter wash for scale insects, and particularly for the more
resistant San Jose scale {Aspidiotus perniciosus) ^ stronger washes are
necessary. In southern California, for this insect, a dilution one-
third less, or water to make 6G| gallons instead of 100 (see for-
mula), has given good results. In Maryland, with this insect, it has
proved necessary to use the wash at six times the summer strength
to destroy all of the well-protected hibernating scales; and with
other scale insects much stronger mixtures than those used in Cali-
fornia have proved ineffectual in the East. For regions, therefore,
with moderately severe winters the use of the resin wash to destroy
hibernating scale insects seems inadvisable.

THE LIME-SULPHUR WASH.

In California, where the San Jose scale first appeared, the standard
remedy for it is the lime-sulphur-salt wash, a mixture formerly used
as a sheep dip in Australia and employed with little change against
the San Jose scale. This wash was naturally first thought of on the
discovery of the San Jose scale in eastern orchards. The earlier tests,
however, conducted by this office in 1894, gave unfavorable results,
and the experimentation which followed resulted in the demonstra-
tion of several distinct and valuable methods of control noted below.

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25

Later studies of the action of this wash in California led the writer
in 1900 to give it a further careful trial in the East, with most suc-
cessful results, demonstrating that, with favoring conditions, i. e.,
absence of dashing rains for a few days after the application, it would
give just as good results in the Eastern States as on the Pacific coast.
A year later (1901-2) very elaborate tests conducted by Doctor
Forbes in Illinois showed that fairly hard rains will not alwa37s in-
validate spraying with this mixture. A vast amount of experience
of the most practical kind since gained, contributed to by all the
eastern experiment stations and by the big commercial fruit growers
of the Middle and Eastern States, has fully demonstrated the prac-
tical merit of this wash and its superiority to others in point of safety
to trees and in cheapness. Its disadvantages are the difficulty of
preparation and the heavy wear whicn it entails on apparatus — objec-
tions, however, which do not offset its notable advantages, particu-
larly for commercial orchard work or where the number of trees to
be treated is sufficient to warrant the trouble of its preparation. It
is, in fact, the standard spray now used in commercial orchards for
the San Jose scale.

Composition and preparation. — In the matter of composition of the
wash, scarcely any two experimenters agree. Salt was a part of the
original composition of the sheep clip and has long been retained,
with the idea that it added, perhaps, to the caustic qualities, and par-
ticularly to the adhesiveness of the wash. For the latter purpose a
very small amount only, 1 or 2 pounds to the bushel of lime, need be
added, following the custom in the preparation of whitewash mix-
tures. In practical exj^erience, however, the salt seems to have been
of very little benefit and is therefore omitted in the formula now
given. The proportion of lime and sulphur is a matter of some in-
difference. The mixture obtained is sulphide of lime, and if an ex-
cess of lime is used it simply remains undissolved in the mixture and
adds to the whitewashing character of the application. Too much
lime is distinctly objectionable, however, because of the greater diffi-
culty of spraying and harder wear on the pump and nozzles. The
formula here given is substantially the one which has been hitherto
recommended by this Bureau, reduced to the 45 or 50 gallon basis, or
the capacity of the ordinary kerosene barrel commonly used in its
preparation by the steam method.

Unslaked lime _' pounds__ 20

Flowers of sulphur do 15

Water to make gallous__ 45 to 50

The flowers of sulphur, although requiring somewhat longer cook-
ing, seems to make a better wash than ground sulphur, but the latter
may be employed. Stone lim^e of good quality should be secured and

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26

slaked in a small quantity of water, say one-third the full dilution.
The sulphur, previously mixed up into a stiff paste, should be added
at once to the slaking lime. The whole mixture should be boiled for
at least one hour, either in an iron kettle over a fire out of doors or in
barrels by steam. Prolonged boiling increases the percentage of the
higher sulphides, but the practical end is obtained by boiling for the
time indicated. In the process of making, the color changes from
yellow to the clear brown of sulphide of lime, except for the excess
of lime floating in it. After an hour's boiling the full quantity of cold
water can be added, and the mixture should then be promptly applied
in order to get its full strength before the higher sulphides are lost
by cooling and crystallizing out. In transferring to the spray tank
it should be passed through an iron screen or strainer, and the tank
itself should be provided with an effective agitator.

Directions for use. — The wash is a winter application and can not
be applied to trees in leaf. It may be applied at any time after the
falling of foliage in early winter and prior to the swelling of the buds
in spring. The later the application can be made the better the re-
sults, and the best j^eriod is just before the buds swell in March or
April. It will probably be necessary also to make this application
every year, or at least as often as the San Jose scale develops in any
numbers. The wash kills the San Jose scale not only by direct caustic
action, but also by leaving a limy coating on the trees, which remains
in evidence until midsummer or later and kills or prevents the settling
of young scale insects which may come from parents escaping the
winter action.

The wear on pumps and nozzles can be kept to a minimum by care-
fully washing the apparatus promptly after use. The Vennorel
nozzle is the best one for the wash, and additional caps may be se-
cured to replace worn ones. The use of an air or other gas pressure
pump instead of the ordinary liquid pump will save the wear of the
lime on the pump. In spraying with this wash clothing is ruined,
and only the oldest garments should be worn. Care should be taken
also to protect the eyes to avoid unnecessary inflammation.

Range of usefulness. — Tliis wash is distinctively the remedy for the
San Jose scale and is particularly effective in applications to the
smooth-barked fruit trees — such as peach, pear, and f)lum. In the
case of the apple the terminal twigs are often covered with a fuzzy
growth, more pronounced in some varieties than others, which pre-
vents the wash from properly coating the bark. The young from
scale insects which escape destruction at such points, for the reason
indicated or from imperfect spraying, are driven out onto the new
growth, or, in the case of fruit spurs, onto the fruit, so that a tree on
which the scale has been pretty thoroughly exterminated may never-

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27

theless present badly spotted fruit.* In such cases the additional
use of some one of the oil sprays may be necessary.

This wash is of equal value against closely allied scale pests, such
as Forbes's scale and the West Indian peach scale, and late sprayings
are quite effective against the scurfy scale and the oyster-shell scale.

The spring application, just before the buds swell, has been demon-
strated by Prof. J. M. Aldrich to kill most of the eggs of the apple
aphis, and Mr. Fred Johnson, of this Bureau, has found that it is
equally effective in destroying the eggs of the pear-tree Psylla. It
is useful against other pests which hibernate about the leaf buds of
fruit trees, as, for example, the pear-leaf blister-mite and the silvery
mite of the peach, and in California Mr. Clark has shown that it is
an entirely satisfactory remedy for the peach twig borer {Anarsia
lineatella Zell.).

In addition to this range of usefulness against insect pests this
wash has shown itself to be a valuable fungicide, notably for the
peach leaf curl, sprayed trees being practically immune from this
disease, so that the cost of treatment in the case of the peach is often
more than made good by the fungicidal benefit alone. Later experi-
ence indicates its usefulness also as a winter application for apple
scab and possibly for other plant diseases.

TIME TO SPSAY FOR STICKING INSECTS.

For the larger plant-bugs and the aphides, or active plant-lice, and
all other sucking insects which are present on the plants injuriously
for comparatively brief periods, or at most during summer only, the
treatment should be immediate, and if in the form of spray on the
plants, at a strength which will not injure growing vegetation.

For scale insects and some others, as the pear Psylla, which hiber-
nate on the plants, two or more strengths are advised with most of
the liquid insecticides recommended, the weaker for summer applica-
ti>c«is and the more concentrated as winter washes. The summer
washes for scale insects are most effective against the young, and
treatment sliould begin with the first appearance of the larvae in the
spring or any of the later broods, and should be followed at intervals
of seven days with two or three additional applications. The first
brood, for the majority of species in temperate regions, will appear
during the first three weeks in May. Examination from time to
time with a hand lens will enable one to determine when the young
of any brood appear.

The winter washes may be used whenever summer treatment can
not be successfully carried out, and are particularly advantageous in
the case of deciduous plants with dense foliage which renders a thor-

° See Bui. 46, Bur. Eut., p. 54.
127

28

ough wetting difficult in summer, or with scale insects which are so
irregular in the time of disclosing their young that many summer
treatments would be necessary to secure anywhere near complete ex-
termination. In the winter also, with deciduous trees, very much less
liquid is required, and the spraying may be much more expeditiously
and thoroughly done. In the case of badly infested trees, a vigorous
pruning is advisable as a preliminary to treatment.

DUSTING AND SPRAYING APPARATUS.

POWDER DISTRIBUTEBS.

For the application of powders the dusting bags already described
(pp. 11-12) are very satisfactory for field work. Much more expen-
sive and more rapid
machine distributers
have been devised, but
these are rarely used.
For garden work
some of the small
powder bellows and
blowers are excellent.
These cost from $2
to $8.

LIQUID SPBAYEES.

For the application
of poisons in liquid
form the prime essen-
tial is an apparatus
which will break up
the liquid into a fine
mist-like spray that
will coat every leaf
and every other part
of the plant as lightly as is compatible with thoroughness. The
essential features of such an apparatus are the force pump, suitable
hose, and nozzles or spray tips. The leading pump manufacturers
now put out a large variety of spraying apparatus suited for all
ordinary needs, including the small knapsack pumps, barrel and tank
pumps, and geared and power sprayers. For limited indoor opera-
tions a hand atomizer or even a sprinkling can with fine rose tip
may be made to do fair service.

127

Fig. 3. — Barrel spray pump. (From Waite.)

29

The barrel pump. — This is the commonest form of spraying appara-
tus, and is supplied in many different styles; or, a suitable spray
pump can be combined with an empty 50-gallon kerosene barrel "with-
out much difficulty. (See fig. 3.) This apparatus may be hauled
about on a sled or in a -wagon or a two-wheeled cart.

Tank outfits. — For larger operations it is much better to have
a specially constructed rectangular or half-round spray tank of a
caj^acit}^ of 200 or 300 gallons. Such an apparatus enables an ele-
vated platform to be mounted on the wagon and tank, greatly facili-
tating spraying of the higher parts of trees, as indicated in the
accompanying illustration (fig. 4). The ideal sprayer for extensive
work combines such a tank, with platform, with gasoline or steam
power spray pump.

Fig. 4. — Power sprayer at work iu apple orchard. (From Scott and Quaintance.)

Geared sprayers. — For low -growing regidarly planted crops it is
sometimes possible to use spraying apparatus which gets its power
by means of a sprocket wheel from the axle of the Avagon. Several
types of spraying apparatus of this kind are on the market, suited
especially for the treating of crops like potatoes and strawberries,
and the .spraying of vineyards. In orchards it is not often possible to
have the wagon constantly in motion, and geared sprayers are not as a

rule available.

Gas-pressure sprayers. — Some very successful spraying machnies
have been made which have as their motive power gas pressure. This
pressure m.ay be derived from compressed air or carbonic acid gas
cylinders. It is an ideal way of applying liquid sprays, and has a

127

30

special applicability to oil-^Yater mixtures (see p. 19). Ultimately
this principle may come into much more general use.

Hose, nozzle, and agitator. — The hose and nozzle are two very essen-
tial elements of a good spraying apparatus. The verj' best three-
eighths, one-fourth, or one-half inch 3-ply or 4-ply hose should be
bought. A cheap or inferior hose will not stand the pressure and
heavy wear of spraying. For orchard spraying a length of 25 feet
is the least that should be used, and better 35 feet, and longer with
large apparatus where it may be possible to spray more than one row
at a time. Several lines of hose may be operated with a strong spray
pump. Each line of hose should be supplied with an extension rod 8
or 10 feet long. This rod may be an ordinary bamboo pole into which
a small brass tube is fitted carrying the nozzle, or the hose may
terminate in a small gas pipe — a rather heavy device and useful for
short length only.

Of the many types of nozzles which have been devised, the best
is that known as the Vermorel (fig. 5). Where the power is suffi-
cient, a double or even quadruple nozzle may be at-
tached to each line of hose. Most of the nozzles on
the market are inferior, and this special type should
be insisted upon.

A very necessary feature of spray tanks is a device

for keej)ing the liquid constantly agitated to keep up

. a uniform mixture or prevent the settling of the poi-

spray nozzle, son or solid constituents of the wash. This may be

(From waite.) accomplished by constant stirring with a paddle.

Most of the spraying apparatus now on the market are provided

with automatic agitators.

SELECTION OF SPRAYING OUTFIT.

P'or limited garden work or for the treatment of low plants a
simple bucket pump can be used, which will cost about $6, or the
knapsack pump, costing about $14.

For home orchards of small size a barrel pump with one line of
hose will serve every purpose, the complete outfit costing $12 to $18.

For larger operations, with two lines of hose and nozzles, a barrel
outfit, costing from $25 to $30, may be used.

Tank outfits, v>'ith double cylinder pumps suitable for an orchard
of a thousand bearing trees, may be obtained at a cost of from $75
to $90.

The power sprayers are much more expensive, costing $200 to $300

or more.

127

31

DIRECTIONS FOR SPRAYING.

Thorough work in spraying must be done, or failure will result.
To accomplish this, power sufficient to break up the liquid into a fine
mist is essential. This makes it possible for the tree to be thoroughly
and thinly wetted with the spray without waste, and the ideal appli-
cation is to accomplish this without causing the liquid to collect in
drops and fall from the tree. More of the spray is left on the leaves
with a light spray than with a heavy application, which causes the
globules to coalesce and a shower of drops to fall to the ground. To
get a proper spray, it should be possible to produce a pressure of at
least 75 pounds, or, with power outfits, of 125 to 150 pounds.

Fruit trees of average size or, if apple, such as would produce
10 or 15 bushels of fruit, will require from 3 to 7 gallons of spray
to wet them thoroughly. For smaller trees, such as plum and cherry,
1 gallon to the tree may be sufficient. In spraying orchard trees
and other fruit trees it will often be found convenient, especially with
a smaller apparatus, to spray on each side half of each tree in a
row at a time, and finish on the return.

A light rain will remove comparatively little of the poison, but
a dashing rain may necessitate a renewal of the application.

HYDROCYANIC-ACID GAS TREATMENT.

The use of hydrocyanic-acid gas originated in southern California
in work against citrus scale insects, and was perfected by a long
period of experimentation by an agent of this Bureau, Mr. D. W.
Coquillett. It is undoubtedly the most thorough method known of
destroying scale insects and especially is it the best treatment for
citrus trees, the abundance of foliage and nature of growth of
which render thorough spraying difficult, but, on the other hand,
enable the comparatively heayj'- tents employed in fumigation to be
thrown or drawn over the trees rapidl}'' without danger of breaking
the limbs. One good gassing is usually the equivalent of two or
three sprayings, the gas penetrating to every particle of the surface
of the tree and often effecting an almost complete extermination,
rendering another treatment unnecessary for two years or more.
(See fig. G.)

The gas treatment is just as effective against scale insects on decidu-
ous orchard fruit trees, as has been demonstrated by a good deal of
work done in the East, notably in Maryland by Professor Johnson ;
but the difficulty and expense of the treatment as compared with the
value of the crop protected makes it as a rule prohibitive in the case
of deciduous fruits. This does not apply, however, to nursery stock,
which may be brought together compactly and treated in mass in

127

32

fumigating rooms or houses. The general spread of the San Jose
scale in the East has made such fumigation of nursery stock, even
^Yhen infestation is not shown or suspected, a necessary procedure
before shipment or sale, to give the utmost assurance of safety to thp
purchaser. Similarly this gas is the principal agency employed in
disinfecting plant material coming from abroad, and will be the chief
agency for such work wherever quarantine regulations prevail.

Another very important use for hydrocyanic-acid gas is as a means
of controlling insect pests in greenhouses and cold frames. The
process is a special one, however, and entails considerable variation,
owing to the wide range of plants to be considered. The details of
the process are given in a special publication of the Bureau of Ento-
mology (Circular No. 37), which will be supplied to anyone inter-
ested.

Fig. 6. — Tenting trees for gas treatment, San Diego, Cal. (Author's illustration.)

A more recent use for this gas is in disinfecting houses of insect
pests and vermin. The details of this treatment are given in Circular
46, revised edition, of the Bureau of Entomology.

In all work with hydrocyanic-acid gas, its extremely poisonous pm-
ture must he constantly kept in mind and the greatest precautior.s
must he taken to avoid inhaling it.

FUMIGATION OF NURSERY STOCK.

For the fumigation of nursery stock or imported plant material
in a dormant or semidormant condition, a building or room should
be provided, which can be closed practically air-tight, and it should be
fitted with means of ventilation above and at the side, operated from
without, so that the poisonous gas can be allowed to escape without

127

the necessity of anyone entering the chamber. The gas is generated
by combining potassium cyanide, sulpliuric acid, and water. The
proportions of the chemicals are as follows : Refined potassium cyan-
ide (98 per cent), 1 ounce; commercial sulphuric acid, 1 ounce; water,
3 fluid ounces to ever}' hundred cubic feet of space in the fumigating
room. For comparatively green or tender material the same amounts
may be used to 150 cubic feet of space.

The generator of the gas may be any glazed earthenware vessel of
1 or 2 gallons capacity and should be placed on the floor of the fumi-
gating room, and the water and acid necessary to generate the gas
added to it in the order named. The cyanide should be added last,
preferably in lumps the size of a walnut, and the premises promptly
vacated and the door made fast. Treatment should continue forty
minutes.

ORCHARD FUMIGATION.

The methods of fumigating citrus stock in California are now
(1908) being given a thorough investigation by this Bureau. As
already noted, the gas process has been a leading method in Cali-
fornia for more than twenty years, but the results, while normally
good, have not always been satisfactory. The object of the investiga-
tion now under way is to thoroughly standardize the process ; in other
words, (1) to determine the proper strength to be used for the differ-
ent scale pests under different climatic conditions, and also under the
different seasonal conditions of the tree; (2) to determine the phj'si-
ological effect, if any, on the tree and fruit; and (3) to perfect the
mechanical means of handling tents and generating the gas, and de-
termine the proper quantity and quality of chemicals to use. The
results of this investigation will be the basis of a special report on gas
fumigation, and will probably modify somewhat the directions given
below, which are reproduced from the previous edition of this bulletin.

The fumigation for the white fly in Florida is a special problem
and has been under investigation by this Bureau for two years. The
results of this investigation, including general directions for fumiga-
tion, will be given in Bulletin No. 76.

Amounts of chemicals to use. — The amounts of chemicals used var}''
with the size of the tree and, as now employed in California, are con-
siderably in excess of the amounts recommended as recently as 1898.
The gas treatment was first chiefly used against the black scale and at
a season of the jea.r when these scales were all in a young stage and
easily killed. The effort is now made not only to kill the black
scale, but also the red and purple scales, and to do more effective
work than formerly against tlie black scale. The amounts of chem-
icals ordinarily advised and commonly employed in Los Angeles,

127

34

Orange, and some other counties in southern California are indicated
in the subjoined table, published by the horticultural commissioners
of Riverside County, Cal.

Table 1.— Amounts of chemicals and water ordinarily used for trees of different

sises.

Height
of tree.

Diameter
of tree.

Water.

Cyanide,
0. P., 98

per cent.

Sulphuric

acid, 66 per

cent.

Feet.

Feet.

Ounces.

Ounces.

Ounces.

6

4

2

1

1

8

6

3

n

11

19

8

5

2J

2J

12

14

11

SJ

16

16

17

8

9

20

16-20

22

10

12

20-24

18-23

30

14

16

24-30

20-28

34

18

18

30-36

25-30

52

24

■ 28

The proportions here recommended are thoroughly effective for the
black scale at the proper season, and measurably effective also for the
California red scale and the purple scale. AMiere the treatment is
designed to be one of extermination for these latter scale pests,
from one-third to one-half more of cyanide and acid is employed, as
indicated by the subjoined table, furnished by Mr. G. Havens, of
Riverside. The amounts here recommended may be employed also
for compact trees with dense foliage or in moist coast regions where
stronger doses are needed.

Table 2. — Excessive amounts of chemicals used for absolute extermination oj

scale insects.^

Height
of tree.

Diameter
through
foliage.

Water.

Sulphuric
acid.

Cyanide.

Time to

leave tent

on tree.

Feet.

Feet.

Fluid ozs.

Fluid ozs.

Ounces.

Minutes.

6

3- 4

3

n

3-1

20

8

!>- 6

6

2i

2

30

10

7-10

15

5- 6

4 - 5

35-40

12

9-12

20- 30

7- 9

5J- 7J

40

14

12-14

30- 35

9-12

8 -10

40

16

12-15

a5- 40

12-14

10 -12

40

13

14-16

45- 55

15-18

12 -15

40 r)0

20

16-18

60- 70

20-22

16 -20

45-50

23

16-18

70- 75

22-25

20

50

24

18-20

75- 80

25-30

22 -26

50

27

20-24

8.5-100

30-36

28 -32

CO

30

20-28

100-110

30-44

32 -38

60

<*A fumigation of the orangery of the Department, December 3, 1900, demonstrated that
0.15 of a gram of cyanide to the cubic foot, or a little more than half an ounce to the
hundred cubic feet, is completely exterminatiye of scale insects, effectually killing the
eggs, even of the black, purple, and other scales. The strength mentioned is that
ordinarily recommended for violet houses, and the results are scarcely comparable to
the proportions recommended in Tables 1 and 2, for the reason that in these tables the
amount of cyanide Is greatly lessened with larger trees, and, furthermore, that the
orangery probably retained the gas more effectually than would be the case with cloth
tents. Nevertheless, it is interesting to know that a comparatively inconsiderable
strength of cyanide, when applied under the best conditions, will prove thoroughly
effective against the eggs as well as the insects in all stages.
127

35

The duration of the treatment indicated in the second table varies
with the size of the tree, but in general at least forty minutes should
be allowed.

In Florida fumigation for the white fly can be successfully prac-'
ticed only during the short period in winter when the insect does
not occur in the winged stage. This period covers from two and a
half to three months, namely, December, January, and February,'
varying with the climatic conditions of different years. This is the
dry season for Florida, and the trees are in a dormant condition,
with the leafage well matured and hardened, and it is possible to
api)ly a greater strength than Avould be safe under California condi-
tions. The strength recommended is approximately the same as for
deciduous nursery stock, viz, 1 ounce of cj'anide to 100-115 cubic feet
of space, with a duration of 40 minutes.

General directions. — In the fumigation of growing stock, citrus or
other, the treatment consists in inclosing the tree with a tent and
filling the latter with poisonous fumes generated in the same way as
described for nursery stock except that less of the chemicals is used.
The treatment is made at night for trees in foliage, which includes
all work in citrus orchards, to avoid the much greater likelihood of
injury to tender foliage in the sunlight. The vessels for setting off
the charges of cyanide and acid may be, for small doses, any ordinary
earthenware jars. For large trees requiring heavy doses, tall wooden
pails have proved more satisfactory, two generators being employed
for the very largest trees.

It is important that the water he put in the vessel first, then the
acid, and lastly the cyanide. If the water and cj'anide are f)ut in
the vessel first and the acid poured in afterwards, there is danger of an
explosion which Avill scatter the acid and burn the tents and the oper-
ator. In the spring, when the trees are tender with new growth, and
in early fall when the oranges are nearly grown and the skins are
likely to be easily marred, and also with young trees, it is advisable
to add one-third more water than ordinarily used, or to add the
cyanide in larger lumps. This causes the gas to generate more slowly
and with less heat, and, if the tents are left over the trees a third
longer, the effectiveness of the treatment will not be lessened. The
person handling the chemicals should always have an attl^ndant with
a lantern, to hold up the tent and enable the cyanide to be quickly
dropped into the generator, and to facilitate the prompt exit of the
operator.

Trees are fumigated for the black scale in southern California in
October, or preferably in November. The red and other scales may
be treated with gas at any time, but preferably at the season already
indicated. In California most of the work is done by contract, or

127

36

('under the direct supervision of the county horticultural commission-
ers, in some cases the tents and material being furnished at a merely
nominal charge, together with one experienced man to superintend
the work, while a crew of four men oi:)erate the tents, the wages of the
director and men being paid by the owner of the trees.

Construction and handling of tents. — The tents now employed are of

two kinds, the " sheet " tent
of octagonal shape for large
trees, and the " ring *' tent
for trees under 12 feet in
height. The ring tents, or,
as they are also called, the
bell tents, are bell - shaped
and have a hoop of half-inch
gas pipe fastened within a
foot or so of the opening.
Two men can easily throw
one of these tents over a
small tree. An equipment of
3G or 40 ring tents can be
handled by four men. They
are rapidly thrown over the
trees by the crew, and the
director follows closely and
introduces the chemicals. By
the time the last tent has
been adjusted the first one
can be removed and taken
across to the adjoining row.
An experienced crew, with
one director, can treat 350 to
400 5-year-old trees, averag-
ing 10 feet in height, in a
single night of eleven or
twelve hours. The cost un-
der such conditions averages
about 8 cents a tree.

With large trees the large
sheet tents are drawn over them by means of uprights and pulley
blocks. Two of these sheets are necessary for very large trees, the
first being drawn halfway over and the second drawn up and made
to overlap the first. In the case of trees from 24 to 30 years old and
averaging 30 feet in height, about 50 can be treated in a night of ten
or twelve hours Avith an equipment of 12 or 15 tents, the cost being

127

Fig. 7. — Method of hoisting
(After Craw.)

sheet tent.

37

about 75 cents per tree. It is not practicable to treat trees above 30
feet in height.

The handling of the bell tents is simple and needs no further de-
scription, but the large tents are not so easily operated, and the
method of adjusting the great flat octagonal sheets over the trees,
while simple enough when once understood, warrants a description.
The machinery employed consists of two simple uprights, with at-
tached blocks and tackle (fig. 7). The uprights are about 25 feet
high, of strong Oregon pine, 2 by 4 inches, and are provided at the
bottom with a braced crossbar to give them strength and to prevent
their falling to either side while the tent is being raised. A guy
rope is attached to the top of each pole and held to steady it by a mem-
ber of the crev*' stationed at the rear of the tree. The tent is hoisted
by means of two ropes 70 feet long, which pass through blocks, one
fixed at the top of the pole and the other free. The tent is caught
near the edge b}' taking a hitch around some solid object, such as a
green orange, about which the cloth is gathered. By this means the
tent may be caught anywhere without the trouble of reversing and
turning the heavy canvas to get at rings or other fastenings attached
at particular points. The two remaining members of the operating
crew draw the tent up against and over one side of the tree by means
of the pulley ropes sufficiently to cover the other side of the tree when
the tent falls. The poles and tent together are then allowed to fall
forward, leaving the tent in position. Sufficient skill is soon acquired
to carry out rapidly the details of this operation, so that little time
is lost in transferring the tents from tree to tree, even when the trees
approximate the limit in height. A single pair of hoisting poles
answers for all the tents used.

Some of the tents employed are of great size, one described by Mr.
Havens having a diameter of 7G feet. It is constructed of a central
j^iece 50 feet square, of 10-ounce army duck. Four triangular side
pieces or flaps of 8-ounce duck, 10 feet wide in the middle, are strongly
sewed to each side of the central sheet, forming an octagonal sheet 70
feet in diameter. About the whole sheet is then sewed a strip of
G-ounce duck, 1 yard wide. The tent is handled by means of ropes
and pulleys. A l-|-inch manila rope is sewed about the border of the
central piece in an octagonal pattern. Rings are attached to this rope
at each of the eight corners thus formed, and also on either side of
the tent. To these rings the pulley ropes are fastened, and the tent
is elevated over the trees and handled very much as indicated in fig 7.

The canvas for the tents, blue or brown drilling or 8 to 10 ounce
duck, may be rendered comparatively impervious to the gas by
painting lightly with boiled linseed oil. This has the objection, how-
ever, of stiffening the fabric and adding considerably to its weight;
it also frequently leads to its burning by spontaneous combustion
unless carefully watched until the oil is dry. A much better material

127

38

than oil is found in a product obtained from the leaves of the common
prickly pear cactus {Opuntia engelmanni) ,y}\\\ch. grows in abundance
in the Southwest. The liquor is obtained by soaking chopped-iip
leaves in water for twenty- four hours. It is given body and color by
the addition of glue and yellow ocher or Venetian red, and is applied
to both sides of the canvas and rubbed well into the fiber of the cloth
with a brush.

Some practical experience is necessary to fumigate successfully,
and it will therefore rarely be wise for anyone to undertake it on a
large scale without having made preliminary experiments.

BISULPHID OF CAEBON VAPOR.

In line with the use of hydrocyanic-acid gas is the employment of
the vapor of bisulphid of carbon to destroy insects on low-growing
plants, such as the aphides on melon and squash vines. The treat-
ment, as successfully practiced by Professors Garman and Smith,
consists in covering the young vines with small tight boxes 12 to 18
inches in diameter, of either wood or paper, and introducing under
each box a saucer containing one or two teaspoonfuls (1 or 2 drams)
of the very volatile liquid bisulphid of carbon. The vines of older
I^lants may be wrapped about the hill and gathered in under larger
boxes or tubs, and a greater, but proportional, amount of the liquid
used. The covering should be left over the plants from three-quarters
of an hour to an hour, and with 50 to 100 boxes a field may be treated
with comparative rapidity.

Bisulphid of carbon has proved also to be the most effective means
of disinfecting grape cuttings suspected of being infested with
phylloxera." The cuttings arc inclosed in a tight barrel or fumi-
gating box, and the bisulphid of carbon, poured out in a shallow dish,
is put on top of the cuttings. An ordinary saucerful of the chemical
is enough for a box 3 feet cube. The treatment lasts from forty-five
to ninety minutes. This is a pretty strong fumigation, but the dor-
mant condition of the cuttings makes this possible.

REMEDIES FOR SUBTERRANEAN INSECTS.

Almost entire dependence is placed on the caustic washes, or those
that act externall}^, for insects living beneath the soil on the roots of
plants, including both sucking and biting insects, prominent among
which are the white grubs, maggots in roots of cabbage, radishes,
onions, etc., cutworms, wireworms, apple and peach root-aphides, the
grape phylloxera, and many others.

The insecticide must be one that will go into solution and be carried
down by water. Of this sort are the kerosene emulsions and resin

cBul. 192, Cal. Agr. Ezp. Sta., 1907.

39

wash — the former preferable — the potash fertilizers, muriate and
kaiiiit, and bisulphid of carbon. The simple remedies are applica-
tions of strong soap or tobacco washes to the soil about the crown;
or soot, ashes, or. tobacco dust buried about the roots; also similarly
employed are lime and gas lime. Submersion, wherever the practice
of irrigation or the natural conditions make it feasible, has proved of
the greatest service against the phylloxera.

HOT WATER.

As a means of destroying root-aphides, and particularly the woolly
aphis of the apple, the most generally recommended measure hitherto
is the use of hot water, and this, while being both simple and inex-
pensive, is thoroughly effective, as has been demonstrated by practical
experience. Water at nearly the boiling point may be applied about
the base of young trees without the slightest danger of injury to the
trees, and should be used in sufficient quantity to wet the soil thor-
oughly to a depth of several inches, as the aphides may penetrate
nearly a foot below the surface. To facilitate the wetting of the
roots and the extermination of the aphides, as much of the surface
soil as possible should be first removed.

By a hot-water bath slightly infested stock can be easily freed of
the aphides at the time of its removal from the nurserj'^ rows. The
soil should be dislodged and the roots pruned, and in batches of a
dozen or so the roots and lower portion of the trunks should be im-
mCTsed for a few seconds in water kept at a temperature of 130° to
150° F. A strong soap solution similarh' heated or a fifteen times
diluted kerosene emulsion will give somewhat greater penetration and
be more effective, although the water alone at the temperature named
should destroy the aphides.

Badly infested nursery stock should be destroyed, since it would be
worth little even with the aphides removed.

TOBACCO DUST.

Some very successful experiments conducted by Prof. J. M. Sted-
man demonstrated the very satisfactory protective, as well as reme-
dial value of finely ground tobacco dust against the woolly aphis.
The desirability of excluding the aphis altogether from nursery stock
is at once apparent, and this Professor Stedman shoAvs to be possible
by placing tobacco dust freely in the trenches in which the seedlings
or grafts are planted and in the orchard excavations for young trees.
Nursery stock may be continuously protected by laying each spring a
line of the dust in a small furrow on either side of the row and as
close as possible to the tree, and covering loosely with earth. For
large trees, both for protection and the destruction of existing
aphides, from 2 to 5 pounds of the dust should be distributed from
the base outward to a distance of 2 feet, first removing the surface

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soil to a depth of from 4 to 6 inches. The tobacco kills the aphides
by leaching through the soil, and acts for a j^ear or so as a bar to
reinfestation. The dust is a waste product of tobacco factories, costs
about 1 cent per pound, and possesses the additional value of being
worth fully its cost as a fertilizer.

Since its early recommendation marked success has been reported
from the use of tobacco dust. A notable instance is that given by
Mr. M. B. Waite, of the Bureau of Plant Industry, who applied a
ton of tobacco waste, costing $25, in his orchard, with the result of
entirely renewing the vigor of his trees and producing a strong
stubby growth of twigs. A peck of tobacco dust was placed about
each of his larger trees in a circle of 2 or 3 feet around the trunk,
and a slightlv smaller amount about trees from one to three years
old.

KEROSENE EMULSION AND RESIN V/ASH.

Either the kerosene-and-soap emulsion or the resin wash, the
former diluted fifteen times and the latter at the strength of the
winter mixture, are used to saturate the soil about the affected plants
and either left to be carried down by the action of rains or washed
down to greater depths by subsequent waterings.

For the grape phylloxera or the root-aphis of the peach or apple,
make excavations 2 or 3 feet in diameter and 6 inches deep about the
base of the plant and pour in 5 gallons of the wash. If not a rainy
season, a few hours later wash down with 5 gallons of water and
repeat with a like amount the day following. It is better, however,
to make this treatment in the spring, when the more frequent rains
will take the place of the waterings.

For root-maggots enough of the wash is put at the base of the
plant to wet the soil to a depth of 1 to 2 inches, preferably followed
after an hour with a like amount of water.

For white grubs in strawberry beds or in lawns the surface should
be wetted with kerosene emulsion to a depth of 2 or 3 inches, follow-
ing with copious waterings to be repeated for two or three days. The
larva; go to deeper and deeper levels and eventually die.

POTASH FERTILIZERS.

For white grubs, wireworms, cutworms, corn root-worms, and like
insects, on the authority of Prof. J. B. Smith, either kainit or the
muriate of potash — the former being the better — are broadcasted in
fertilizing quantities, preferably before or during a rain, so that the
material is dissolved and carried into the soil at once. These not
only act to destroy the larva in the soil, but are deterrents, and truck
lands constantly fertilized with these substances are noticeably free
from attacks of insects. This, in a measure, results from the in-
creased vigor and greater resisting power of the plants, which of itself

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more than compensates for the cost of the treatment. The value of
these fertilizers against the wireworms is, however, questioned by-
Prof. J. H. Comstock.

For the root-aphis of peach and apple, work the fertilizer into the
general surface of the soil ftbout the trees, or put it into a trench
about the tree 2 feet distant from the trunk.

For cabbage and onion maggots, apply in little trenches along the
rows at the rate of 300 to 500 pounds to the acre, and cover with soil.

These fertilizers (and the nitrate of soda is nearly as good) are also
destructive to the various insects which enter the soil for hibernation
or to undergo transformation.

BISULPHID OF CARBON".

This is the great French remedy for the phylloxera, 150,000 acres
being now subjected to treatment with it, and applies equally well to
all other root-inhabiting aphides. The treatment is made at any
season except the period of ripening of the fruit and consists in mak-'
ing holes about the vines 1 foot to 16 inches deep and pouring into
each about one-half ounce of the bisulphid, and closing the holes with
the foot. The injections are made about 1| feet apart, and not closer
to the vines than 1 foot. It is better to use a large number of small
doses than a few large ones. Hand injectors and injecting plows are
emjDloyed in France to put the bisulphid into the soil about the vines,
but a short stick or iron bar may take the place of these injectors
for limited tracts. i

The use of bisulphid of carbon for the woolly aphis is the same as
for the grape root-aphis or phylloxera. It should be applied in two
or three holes about the tree to a depth of from 6 to 12 inches and not
closer than 1^ feet to the tree. An ounce of the chemical should bo
introduced into each hole, which should be immediately closed.

For root -maggots a teaspoonful is poured into a hole near the base
of the plant, being covered as above.

For ant nests an ounce of the substance is poured into each of sev-
eral holes made in the space occupied by the ants, the openings being
then closed; or the action is made more rapid by covering with a
wet blanket for ten minutes and then exploding the vapor at the
mouth of the holes with a torch, the explosion driving the fumes
more thoroughly through the soil.

SUBMERSION".

This very successful means against the phylloxera is now practiced
over some 75,000 acres of vineyards in France which were once de-
stroyed by the grape root-aphis, and the production and quality of
fruit has been fully restored. In this country it will be particularly
available in California and in all arid districts where irrigation is

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practiced; otherwise it will be too expensive to be profitable. The
best results are secured in soils in which the water will penetrate
rather slowly, or from 6 to 18 inches in twenty-four hours; in loose,
sandy soils it is impracticable on account of the great amount of
water required. Submersion consists in keeping the soil of the vine-
yard flooded for from eight to twenty days after the fruit has been
gathered and active growth of the vine has ceased, or during Sep-
tember or October, but while the phylloxera are still in active devel-
opment. Early in September eight to ten days will suffice ; in October
fifteen to twenty days, and during the winter, forty to sixty days.
Supplementing the short fall submergence a liberal July irrigation,
amounting to a forty-eight hour flooding, is customary to reach any
individuals surviving the fall treatment, and which in midsummer
are very susceptible to the action of water.

To facilitate the operation, vineyards are commonly divided by

embankments of earth into square or rectangular plats, the former for

♦level and the latter for sloping gi'ound, the retaining walls being

protected by coverings of reed grass, etc., during the first year, or

imtil they may be seeded to some forage plant.

This treatment will destroy many other root-attacking insects and
tliose hibernating beneath the soil, and, in fact, is a very ancient prac-
tice in certain oriental countries bordering the Black Sea and the
Grecian Archipelago.

REMEDIES FOR INSECTS AFFECTING GRAIN AND OTHER STORED

PRODUCTS.

GENERAL METHODS OF TREATMENT.

The chief loss from insects of this class is to grains in farmers' bins,
or grain or grain products in stores, mills, and elevators, although
in the warmer latitudes much injury results from infestation in the
field between the ripening of the grain and its storage in bins or
granaries. Fortunately, the several important grain insects arc
amena])le to like treatment. Aside from various important pre-
ventive operations, such as, in the South, prompt thrashing of grain
after harvesting, the thorough cleansing of bins before refilling,
removal of waste harboring insects from all parts of granaries and
mills, and care to prevent the introduction of " woeviled " grain,
there are four valuable remedial measures, viz, agitation of tho
grain, heating, dosing with bisulphid of carbon, and fumigating with
sulphur dioxid.

The value of agitating or handling grain is well known, and when-
ever, as in elevators, grain can be transferred or poured from one bin
into another, grain pests are not likely to trouble. The benefit Avill
depend uj)on the frequency and thoroughness of the agitation. In

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France machines for shaking the grain violently have been used with
success. Winnowing weeviled grain is also an excellent preliminary-
treatment. '
Eaising the temperature of the grain in closed retorts or revolving
cylinders to 130° to 150° F. will kill the inclosed insects if continued
for three to five hours, but is apt to injure the germ, and is not ad-
vised in case of seed stock. The simplest and most effective remedies
are the use of either bisulphid of carbon or sulphur dioxid.

BISULPHID OF CARBON."

Character and method of application. — This is a colorless liquid with
very offensive odor, which, however, passes off completely in a short
time. It readily volatilizes, and the vapor, which is very deadly to
insect life, is heavier than air and settles and fills any compartment
or bin in the top of which the liquid is placed. It may be distributed
in shallow dishes or tins or in saturated waste on the top of grain in
bins, and the gas will settle and permeate throughout the mass of
the grain. In large bins, to hasten and equalize the operation, it is
well to put a quantity of the bisulphid in the center of the grain by
thrusting in balls of cotton or waste tied to a stick and saturated with
the liquid, or by means of a gas pipe loosely plugged at one end, down
which the liquid may be poured and the plug then loosened with a
rod. Prof. H. E. Weed reports that in Mississippi the chemical is
commonly poured directly onto the grain. In moderately tight bins
no further precaution than to close them well need be taken, but in
open bins it will be necessary to cover them over with a blanket to
prevent the too rapid dissipation of the vapor. The bins or buildings
should be kept closed from twenty-four to thirty-six hours, after
which a thorough airing should be given them.

Limited quantities at a time may often be advantageously subjected
to treatment in small bins before being j^laced for long storage in
large masses, and especially whenever there is danger of introducing
infested grain.

The bisulphid is applied at the rate of 1 pound to the ton of grain,
or a pound to a cubic space 10 feet on a side.

In the case of mills, elevators, or larger granaries the application
may be best made on Saturday night, leaving the building closed over
Sunday, with a watchman without to see that no one enters and to
guard against fire. The bisulphid should be first distributed in the
upper story, working downward as rapidly as possible to avoid the
settling vapor, using the substance very freely in waste or dishes at
all points of infestation and over bins throughout the building. If
the building be provided with an exterior means of descent (such as

° See Farmers' Bulletin No, 145, Carbou Bisulphid as au Insecticide.
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a fire escape) it would be preferable to begin with the lower story and
work upAvard.

This insecticide may also be used in other stored products, as peas,
beans, etc., and very satisfactorily where the infested material can be
inclosed in a tight can, chest, or closet for treatment. It may also be
emploA'^ed to renovate and protect wool or similar material stored in
bulk. "

The bisulphid costs, in oO-pound cans, 10 cents per pound, and in
small quantities, of druggists, 25 to 35 cents per pound.

Caution. — The bisulphid may be more freely employed with milling
grain than with that intended for seeding, since, when used excess-
ively, it may injure the germ. It must always be remembered that
the vapor is highly inflammable and explosive, and that no fire or
lighted cigars, etc., should be in the building during its use. If ob-
tained in large quantities it should be kept in tightly closed vessels
and away from fire, preferably in a small outbuilding.

A^Hiile this gas is not especiaih'- dangerous to human beings, care

should be taken to avoid unnecessary inhalation. It has a slight

suffocating effect, and if inhaled for some time produces dizziness,

which should be a Avarning to the operator that it is time to seek fresh,

pure air.

SULPHUR DIOXID.

The fumes of burning sulphur, namely, sulphur dioxid, with some
sulj)hur trioxid, have long been one of the standard insecticide gases
for the destruction of insect pests in rooms or dwellings, and notably
for the bedbug {Cimex Icctularius L.). Doctor Stiles, of the Public
Health and Marine-Hospital Service, reports very successful fumiga-
tion and disinfection of frame cottages at a seaside resort for bedbug
infestation by burning sulphur at the rate of 2 pounds of stick sulphur
for each 1,000 cubic feet of space. Sulphur candles for such fumiga-
tion are a standard supply material to be purchased anywhere. Sul-
phur fumes are also emploj^ed for disinfection from disease germs,
and also in the more recent yellow-fever work for the destruction of
mosquitoes in dwellings. The chief objection to the sulphur fumiga-
tion arises from the strong bleaching action of the fumes in the pres-
ence of moisture and their powerful destructive action on vegetation.
! For the disinfection of ships and ships' cargoes, particularly of
grain, sulphur dioxid, under the name of " Clayton gas," is now being
extensively employed. To determine its efficiency and its effect on
the grains treated, a considerable series of experiments was conducted
by the Bureau." These experiments showed that svdphur dioxid,
under pressure such as can be maintained in an air-tight compartment
or in the hold of a ship, has great penetrating power and is very effi-
cient as a means of destroying all kinds of insects. The germinating

« Bui. 60, Bur. Ent., U. S. Dept. Agric, pp. 139-153. 1906.
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power of seeds is quickly destroyed, but no injury results to the feed-
ing or cooking quality of cereals. It can not be employed in the case
of living plants, nor with moist fruits or products, such as apples or
bananas. The best results in the case of insects infesting grains and
seeds, such as Calandra and Bruchus, Avhich are often inclosed in the
seeds, were obtained by the use of a low percentage (1 to 5 per cent of
gas) for a period of twelve to twenty- four hours. Employed in this
way the gas is a very effective means of disinfecting stored grain or
similar products not intended for planting, and has the additional
advantage of entirely eliminating the danger of explosion and fire.

GENERAL CONSIDERATIONS ON THE CONTROL OF INSECTS.
ADVANTAGE OF PROMPT TREATMENT.

The importance of promptness in the treatment of plants attacked
by insects can not be too strongly insisted upon. The remedy often
becomes useless if long deferred, the injury having already been ac-
complished or gone beyond repair. If, by careful inspection of
plants from time to time, the injury can be detected at the very outset,
treatment is comparatively easy and the result much more satisfac-
tory. Preventive work, therefore, should be depended on as much as
possible, rather than remedial treatment later; the effort being to
forestall any serious injury rather than to patch up damage which
neglect has allowed to become considerable.

KILLING INSECTS AS A PROFESSION.

It may often liappen that the amount of work in a community is
sufficient to induce one or more persons to undertake the treatment
of plants at a given charge per tree or per gallon of the insecticide
employed. Where this is the case, and the contracting parties are
evidently experienced and capable, it is frequently more economical in
the end to emplo}'^ such experienced persons, especially when a guar-
antee is given, rather than attempt to do the work one's self with the
attending difficulty of preparing insecticides and securing apparatus
for work on a comparatively small scale. In California this is a com-
mon practice, and also in some of our Eastern cities, and has worked
excellently.

DETERMINATION OF THE RESULT OF TREATMENT.

It is often of imjjortance to know when and how to determine the
effect of any treatment applied directly to insects exposed on the sur-
face of plants. In the case of scale insects, especially during the dor-
mant condition in winter, the response to insecticides is very slow and
gradual. The scale larvas, or any young scales during the growing
season, are killed in a few minutes, or a few hours at furthest, just
as any other soft-bodied insect, but the mature scale does not usually
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46

exhibit the eflfects of the wash or gas for some time. Little can be
judged, ordinarily, of the ultimate results before two weeks, and itis
often necessaiy to wait one or even two months to get final conclu-
sions. In the case of liquid washes the slow progressive death of the
scales is apparently due to the gradual penetration of the insecticide,
and also to the softening and loosening of the scale itself, enabling
subsequent weather conditions of moisture and cold to be more fatal.

With such biting insects as caterpillars and slug worms, after treat-
ment with arsenicals or other poisons death rapidly follows, the time
being somewhat in proportion to the size of the larvas and their
natural vigor. Soft-bodied larva?, such as the slug worms and very
young larvaj of moths and beetles or other insects, are killed in a day
or two. Large and strong larvge sometimes survive the effect of
poison for eight or ten days, and leaf -feeding beetles will often fly
away and perish from the poison in their places of concealment.

Many larvae or other forms of leaf-feeding insects, after taking one
or tAvo meals of poisoned foliage, wnll remain in a semitorpid and
diseased condition on the plants for several days before they finally
succumb. The protection to the plant, however, is just as great as
though the}^ had died immediately, but misapprehension may often
arise and the poison may be deemed to have been of no service.

The complete extermination of insects on plants is often a very
difficult, if not an impossible undertaking. This is especially true of
scale insects. In California even, where the work against these
enemies of fruits has been most thorough and successful, experience
has shown that the best that can be done is a practical elimination of
the scale for the time being, and it is often necessary to repeat the
treatment every year or two. In exceptional cases once in three years
suffices. With leaf-feeding insects it is often possible to effect com-
plete extermination with the use of arsenical poisons. Such sucking
insects as aphides may also be completely exterminated. But in gen-
eral all applications or methods of treatment must be recognized,
more or less, as a continuous charge on the crop, as much so as are
the ordinary cultural operations.

CONTROL OF INSECTS BY CULTURAL METHODS.

It is much easier to ward off an attack of insects or to make condi-
tions unfavorable for their multiplication than to destroy them after
they are once in possession; and in controlling them, methods and
systems of farm and orchard culture have long been recognized as of
the greatest value, more so even than the employment of insecticides,
which, in most cases, can onl}'^ stop an injury already begun. Insects
thrive on neglect, multiply best in land seldom or never cultivated,
and winter over in rubliish, prunings, or the undisturbed soil about
their food plants, and become, under these conditions, more numerous

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every year. It is a fact of common observation that it is the neglected
farfn, vineyard, or orchard filled with weeds or wild growth which is
certain to be stocked with all the principal insect enemies; and, on the
other hand, thorough and constant culture, with the removal and
burning of prunings, stubble, and other waste, the collection and de-
struction of fallen and diseased fruit, and the practice, where possible,
of fall plowing to disturb the hibernating quarters of field insects,
will almost certainly be accompanied by comparative immunity from
insect pests.

The vigor and healthfulness of plant growth has also much to do
with freedom from insect injury. Strong, healthy j)lants seem to have
a native power of resistance which renders them, in a measure, dis-
tasteful to most insects, or at least able to throw off or withstand their
attacks. A plant already weakened from any cause, however, seems
to be especially sought after, is almost sure to be the first affected,
and furnishes a starting point for general infestation. Anything,
therefore, which aids good culture in keeping plants strong and
vigorous, such as the judicious use of fertilizers, will materially
assist in preventing injury.

The constant cropping of large areas of land year after year to
the same staple is largely responsible for the excessive loss from in-
sects in this country as compared with European countries, because
this practice furnishes the best possible conditions for the multiplica-
tion of the enemies of such crops. A most valuable cultural means,
therefore, is a system of rotation of crops which will prevent the
gradual yearly increase of the enemies of any particular staple by
the substitution every year or two of other cultures not subject to the
attacks of the insect enemies of the first.

With such insects as the Hessian fly, the squash borers, and many
others which have regular times of appearance, much can be done
by the planting of early or late varieties or by deferring seeding
so as to avoid the periods of excessive danger. Wherever possible,
varieties should be selected which experience has shown to be re-
sistant to insect attack. Familiar illustrations of such resistant va-
rieties in all classes of cultivated plants will occur to every practical
man, and a better instance of the benefit to be derived from taking
advantage of this knowledge can not be given than the almost uni-
versal adoption of resistant American vines as stocks for the regenera-
tion of the vineyards of France destroyed by the phylloxera and for
the similarly affected vineyards of European grapes in California.

In the case of stored-grain pests, particularly the Angoumois moth,
or so-called " fly weevil," the chief danger in the South occurs while
the grain is standing in shock or stack, after harvesting, during which
period the insects have easy access to it. This source of infestation
may be avoided by thrashing grain promptly after harvesting and
storing it in bulk. This wall prevent injury to more than the sur-

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face larer, as the insects are not likely to penetrate deeply into the
mass of the grain.

These general notes are by no means new, but their importance jus-
tifies their repetition, as indicating the best preventive measures in
connection with the remedial ones already given.

THE PROFIT IN REMEDIAL MEASURES.

The overwhelming experience of the past twenty years makes it
almost unnecessary to urge, on the ground of pecuniary returns, the
adoption of the" measures re^mmended in the foregoing pages against
insects. To emphasize the value of such practice it is only necessary
to call attention to the fact that the loss to orchard, garden, and farm
crops frequently amounts to from 15 to 75 per cent of the entire
product, and innumerable instances could be pointed out where such
lo^s has been sustained year after year, while now, by the adoption of
remedial measures, large yields are regularly secured with an insig-
nificant expenditure for treatment. It has been established that in
the case of the apple crop spraying will protect from 50 to 75 per
cent of the fruit which would otherwise be wormy, and that in actual
marketing experience the price has been enhanced from $1 to $2.50
per barrel, and this at a cost of only about 10 cents per tree for labor
and material. This is especially true of regions where the codling
moth has but one full brood annually.

In the case of one orchard in Virginia, only one-third of which was
sprayed, the result was an increase in the A'ield of sound fruit in the
portion treated of nearly 50 per cent, and an increase of the value of
this fruit over'tlie rest of 100 per cent. The loss from not having
treated the other two-thirds was estimated at $2,500. The saving to
the plum crop and other small fruits frequently amounts to the secur-
ing of a perfect crop where otherwise no yield whatever of sound
fruit could be secured.

An illustration in the case of field insects may also be given where,
by the' ad;option of a system of rotation, in which oats were made to
alternate with corn, the owner of a large farm in Indiana made a
saving of $10,000 per year, this amount representing the loss pre-
viously sustained annually from the corn rootv.'orm. The cotton crop,
which formerly in years of bad infestation by the leaf worm was
estimated to be injured to the extent of $30,000,000, is now compara-
tively free from such injury, owing to the general use of arsenicals.

Facts of like import could be addu<}ed in regard to many other
leading staples, but the foregoing are sufficient to emj^hasize the
money value of intelligent action against insect enemies, which may
often represent the difference between a profit and a loss in agricul-
tural operations.

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