PROTECTING PLANTS FROM THINGS THAT PREY ON THEM - Continued
"Hydrocyanic acid gas is a deadly poison, and the greatest
care is required in its use. Always use 98 to 100 per cent pure
potassium cyanide and a good grade of commercial sulfuric
acid. The chemicals are always combined in the following
proportion: Potassium cyanide, 1 oz.; sulfuric acid, 2 fluid
oz.; water, 4 fluid oz. Always use an earthen dish, pour in
the water first, and add the sulfuric acid to it. Put the required
amount of cyanide in a thin paper bag and when all is ready,
drop it into the liquid and leave the room immediately. For
mills and dwellings, use 1 oz. of cyanide for every 100 cu.
ft. of space. Make the doors and windows as tight as possible
by pasting strips of paper over the cracks. Remove the
silverware and food, and if brass and nickel work cannot be
removed, cover with vaseline. Place the proper amount of the
acid and water for every room in 2-gal. jars. Use two or more
in large rooms or halls. Weigh out the potassium cyanide in
paper bags, and place them near the jars. When all is ready,
drop the cyanide into the jars, beginning on the top floors,
since the fumes are lighter than air. In large buildings, it is
frequently necessary to suspend the bags of cyanide over the
jars by cords running through screw eyes and all leading to a
place near the door. By cutting all the cords at once the
cyanide will be lowered into the jars and the operator may
escape without injury. Let the fumigation continue all
night, locking all outside doors and placing danger signs on
the house."
In greenhouses, the white-fly on cucumbers and tomatoes may
be killed by overnight fumigation with 1 oz. of potassium cyanide
to every 1000 cu. ft. of space; or with a kerosene emulsion
spray or whale-oil soap, on plants not injured by these materials.
The green aphis is dispatched in houses by fumigation with
any of the tobacco preparations; on violets, by fumigation with
1/2 to 3/4 oz. potassium cyanide for every 1000 cu. ft. of space,
leaving the gas in from 1/2 to 1 hr.
The black aphis is more difficult to kill than the green aphis,
but may be controlled by the same methods thoroughly used.
Soaking tubers and seeds.
Potato scab may be prevented, so far as planting infected
"seed" is concerned, by soaking the seed tubers for half an
hour in 30 gal. of water containing 1 pt. of commercial
(about 40 per cent) formalin. Oats and wheat, when attacked
by certain kinds of smut, may be rendered safe to sow
by soaking for ten minutes in a similar solution. It is probable
that some other tubers and seeds can be similarly treated
with good results.
Potatoes may also be soaked (for scab) one and one-half
hours in a solution of corrosive sublimate, 1 oz. to 7 gal. of
water.
Spraying.
The most effective means of destroying insects and fungi
however, in any general or large way, is by the use of various
sprays. The two general types of insecticides have already
been mentioned--those that kill by poisoning, and those that
kill by destroying the body of the insect. Of the former, there
are three materials in common use--Paris green, arsenate of
lead, and hellebore. Of the latter, the most usual at present
are kerosene emulsion, miscible oils, and the lime-sulfur
wash.
Sprays for fungi usually depend for their efficiency on some
form of copper or sulfur, or both. For surface mildews, as
grape mildew, dusting flowers of sulfur on the foliage is a protection.
In most cases, however, it is necessary to apply
materials in liquid form, because they can be more thoroughly
and economically distributed, and they adhere to the foliage
better. The best general fungicide is the bordeaux mixture.
It is generally, however, not advisable to use the bordeaux
mixture on ornamental plants, because it discolors the foliage
and makes the plants look very untidy. In such cases it is best
to use the ammoniacal copper solution, which leaves no stain.
[Illustration: Fig. 233. Cyclone or vermorel type of nozzle, single
and multiple.]
In all spraying operations it is especially important that the
applications be made the very moment the insect or disease is
discovered, or in the case of fungous diseases, if one is expecting
an attack, it is well to make an application of bordeaux mixture
even before the disease appears.When the fungus once
gets inside the plant tissue, it is very difficult to destroy
it, inasmuch as fungicides act on these deep-seated fungi very
largely by preventing their fruiting and their further spread on
the surface of the leaf. For ordinary conditions, from two to
four sprayings are necessary to dispatch the enemy. In spraying
for insects in home gardens, it is often advisable to make a
second application the day following the first one in order to
destroy the remaining insects before they recover from the
first treatment.
There are many kinds of machines and devices for the application of
sprays to plants. For a few individual specimens, the spray may be
applied with a whisk, or with a common garden syringe. If one has a few
trees to treat, however, it is best to have some kind
of bucket pump like those shown in Figs. 221, 222. On a lawn or in a
small garden a tank on wheels (Figs. 223, 224, 225) is handy and
efficient. In such cases, or even for larger areas, some of the knapsack
pumps (Figs. 219, 220) are very desirable. These machines are always
serviceable, because the operator stands so near to his work; but as
they carry a comparatively small quantity of liquid and do not throw it
rapidly, they are expensive when much work is to be done. Yet, in
ordinary home grounds, the knapsack pump or compressed-air pump is one
of the most efficient and practicable of all the spraying devices.
For large areas, as for small orchards and fields, a barrel pump
mounted on a wagon is best. Common types of barrel pumps are shown in
Figs. 226, 227, 228. Commercial plantations are now sprayed by power
machines. There are many good patterns of spraying machines, and the
intending purchaser should send for catalogues to the various
manufacturers. The addresses may be found in the advertising pages of
rural papers.
As to nozzles for spraying it may be said that there is no one
pattern that is best for all purposes. For most uses in home grounds the
cyclone or vermorel type (Fig. 233) will give best satisfaction. The
pump manufacturers supply special nozzles for their machines.
Insecticide spraying formulas.
The two classes of insecticides are here described,--the poisons
(arsenites and white hellebore) for chewing insects, as the beetles and
all kinds of worms; the contact insecticides, as kerosene, oils, soap,
tobacco, lime-sulfur, for plant-lice, scale, and insects in such
position that the material cannot be fed to them (as maggots in the
underground parts).
Paris green.--The standard insecticidal poison. This is used in
varying strengths, depending on the insect to be controlled and the kind
of plant treated. Mix the Paris green into a paste and then add to the
water. Keep the mixture thoroughly agitated while spraying. If for use
on fruit trees, add 1 lb. of quick lime for every pound of Paris green
to prevent burning the foliage. For potatoes it is frequently used
alone, but it is much safer to use the lime. Paris green and bordeaux
mixture may be combined without lessening the value of either, and the
caustic action of the arsenic is prevented. The proportion of the poison
to use is given under the various insects discussed in the succeeding
pages.
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