PROTECTING PLANTS FROM THINGS THAT PREY ON THEM - Continued
Arsenate of lead.--This can be applied in a stronger mixture than
other arsenical poisons without injuring the foliage. It is, therefore,
much used against beetles and other insects that are hard to poison,
as elm-leaf beetle and canker-worm. It comes in the form of a paste
and should be mixed thoroughly with a small quantity of water before
placing in the sprayer, else the nozzles will clog. Arsenate of lead and
bordeaux mixture can be combined without lessening the value of
either. It is used in strengths varying from 4 to 10 lb. per 100 gal.,
depending on the kind of insect to be killed.
Arsenite of soda and arsenite of lime are sometimes used with bordeaux
mixture.
White Hellebore.--For wet application, use fresh white hellebore,
4 oz.; water, 2 or 3 gal. For dry application, use hellebore, 1 lb.;
flour or air-slaked lime, 5 lb. This is a white, yellowish powder made
from the roots of the white hellebore plant. It loses its strength after
a time and should be used fresh. It is used as a substitute for the
arsenical poisons on plants or fruits soon to be eaten, as on currants
and gooseberries for the currant-worm.
Tobacco.--This is a valuable insecticide and is used in several
forms. As a dust it is used extensively in greenhouses for plant-lice,
and in nurseries and about apple trees for the woolly aphis. Tobacco
decoction is made by steeping or soaking the stems in water. It is
often used as a spray against plant-lice. Tobacco in the form of extracts,
punks, and powders is sold under various trade names for use in
fumigating greenhouses. (See page 188.)
Kerosene emulsion.--Hard, soft, or whale-oil soap, 1/2 lb.; water,
1 gal.; kerosene, 2 gal. Dissolve the soap in hot water; remove from
the fire and while still hot add the kerosene. Pump the liquid back
into itself for five or ten minutes or until it becomes a creamy mass.
If properly made, the oil will not separate out on cooling.
For use on dormant trees, dilute with 5 to 7 parts of water. For
killing plant-lice on foliage dilute with 10 to 15 parts of water. Crude
oil emulsion is made in the same way by substituting crude oil in
place of kerosene. The strength of oil emulsions is frequently indicated
by the percentage of oil in the diluted liquid:--
For a 10% emulsion add 17 gal. of water to 3 gal. stock emulsion.
For a 15% emulsion add 10 1/3 gal. of water to 3 gal. stock emulsion.
For a 20% emulsion add 7 gal. of water to 3 gal. stock emulsion.
For a 25% emulsion add 5 gal. of water to 3 gal. stock emulsion.
Carbolic acid emulsion.--Soap, 1 lb.; water, 1 gal.; crude carbolic
acid, 1 pt. Dissolve the soap in hot water, add the carbolic acid, and
agitate into an emulsion. For use against root-maggots, dilute with 30
parts of water.
Soaps.--An effective insecticide for plant-lice is whale-oil soap.
Dissolve in hot water and dilute so as to obtain one pound of soap to
every five or seven gallons of water. This strength is effective against
plant-lice. It should be applied in stronger solutions, however, for
scale insects. Home-made soaps and good laundry soaps, like Ivory soap,
are often as effective as whale-oil soap.
Miscible oils.--There are now on the market a number of preparations
of petroleum and other oils intended primarily for use against the San
José scale. They mix readily with cold water and are immediately ready
for use. While quickly prepared, easily applied, and generally
effective, they cost considerably more than lime-sulfur wash. They are,
however, less corrosive to the pumps and more agreeable to use. They are
especially valuable to the man with only a few trees or shrubs who would
not care to go to the trouble and expense to make up the lime-sulfur
wash. They should be diluted with not more than 10 or 12 parts of water.
Use only on dormant trees.
Lime and sulfur wash.--Quicklime, 20 lb.; flowers of sulfur, 15 lb.;
water, 50 gal. The lime and sulfur must be thoroughly boiled. An iron
kettle is often convenient for the work. Proceed as follows: Place the
lime in the kettle. Add hot water gradually in sufficient quantity to
produce the most rapid slaking of the lime. When the lime begins to
slake, add the sulfur and stir together. If convenient, keep the mixture
covered with burlap to save the heat. After slaking has ceased, add more
water and boil the mixture one hour. As the sulfur goes into solution, a
rich orange-red or dark green color will appear. After boiling
sufficiently, add water to the required amount and strain into the spray
tank. The wash is most effective when applied warm, but may be applied
cold. If one has access to a steam boiler, boiling with steam is more
convenient and satisfactory. Barrels may be used for holding the
mixture, and the steam applied by running a pipe or rubber hose into the
mixture. Proceed in the same way until the lime is slaked, when the
steam may be turned on. Continue boiling for 45 min. to an hour, or
until sulfur is dissolved.
This strength can be applied safely only when the trees are dormant. It
is mainly an insecticide for San José scale, although it has
considerable value as a fungicide.
Lime-sulfur mixtures and solutions for summer spraying are now coming
to take the place of bordeaux in many cases. Scott's self-boiled
lime-sulfur mixture, described in U. S. D. A. Bureau Plant Industry
Circ. 27 is now a standard fungicide for brown-rot and black-spot or
scab of the peach. Concentrated lime-sulfur solutions, either home
boiled or commercial, are effective against apple scab and have the
advantage of not russeting the fruit. Such concentrates, testing 32°
Baume, should be diluted at about 1 gal. to 30 of water. Apply at same
time as with bordeaux. Add arsenate of lead as with bordeaux.
Fungicide spraying formulas.
The standard fungicide is bordeaux mixture, made in several forms. The
second most important fungicide for the home gardener is ammoniacal
copper carbonate. Sulfur dust (flowers of sulfur) and liver of sulfur
(potassium sulfide) are also useful in dry or wet sprays for surface
mildews. The lime-sulfur wash, primarily an insecticide, also has
fungicidal property.
Bordeaux mixture.--Copper sulfate, 5 lb.; stone lime or quicklime
(unslaked), 5 lb.; water, 50 gal. This formula is the strength usually
recommended. Stock mixtures of copper sulfate and lime are desirable.
They are prepared in the following way:--
(1) Dissolve the required amount of copper sulfate in water in the
proportion of one pound to one gallon several hours before the solution
is needed, the copper sulfate crystals being suspended in a sack near
the top of the water. A solution of copper sulfate is heavier than
water. As soon then, as the crystals begin to dissolve the solution will
sink, keeping water in contact with the crystals. In this way, the
crystals will dissolve much sooner than if placed in the bottom of the
barrel of water. In case large quantities of stock solution are needed,
two pounds of copper sulfate may be dissolved in one gallon of water.
(2) Slake the required amount of lime in a tub or trough. Add the water
slowly at first, so that the lime crumbles into a fine powder. If small
quantities of lime are used, hot water is preferred. When completely
slaked, or entirely powdered, add more water. When the lime has slaked
sufficiently, add water to bring it to a thick milk, or to a certain
number of gallons. The amount required for each tank of spray mixture
can be secured approximately from this stock mixture, which should not
be allowed to dry out.
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