Contact Sprays

Four compounds are used as contact sprays in

combating sucking insects, namely, lime sulphur, soaps such as whale

oil soap, kerosene emulsion, and tobacco extract. Of these lime

sulphur is the most used and for winter spraying is probably the best.

This preparation is made by boiling together for one hour or until

they unite, twenty pounds of quick lime, fifteen pounds of flower of

sulphur, and fifty gallons of water. Although the home made mixture is

much cheaper than the commercial form which may be purchased on the

market, many people prefer the latter because of the inconvenience and

trouble of preparing the mixture, although there is nothing difficult

about it.



This contact spray is used chiefly for the San Jose scale and the

blister mite, and in order to control these must be applied strong on

the dormant wood. The strength necessary will vary from one part of

the mixture above mentioned or of the commercial preparation, to from

seven to ten parts of water, according to the density test of the

material, which should be around twenty-eight per cent. Beaume (a

scale for measuring the density of a liquid) for home made, and

thirty-two per cent. for the commercial mixture.



Any good soap is effective in destroying soft bodied insects such as

plant lice. The fish oil soaps, although variable in composition, are

often valuable, especially the one known in the trade as whale oil

soap. This soap dissolved in water by boiling at the rate of two

pounds of soap to one gallon of water, makes a good winter spray for

scale but should be applied before it gets cold as it is then apt to

become gelatinous. For a summer contact spray against lice, one pound

of soap to seven gallons of water is strong enough to be effective. It

is objectionable because of its odor and because it is disagreeable to

make and handle. Lime sulphur is to be preferred as a winter spray,

but the soap spray is often necessary and valuable for summer sucking

insects.



Kerosene emulsion was formerly more commonly used than now against the

scale and plant lice. It is a mixture of one-half pound of soap and

two gallons of kerosene in one gallon of water--preferably in hot

water. For dormant trees one gallon of this mixture should be diluted

with six gallons of water. While this spray is effective it is no more

so than lime-sulphur and is quite difficult and disagreeable to

handle. As a summer spray, however, it is often necessary. Several

preparations of petroleum known as the miscible oils are sometimes

used. Their use is the same as that of lime-sulphur and they are not

as good.



Within the last few years a tobacco concoction known as black leaf

tobacco extract (nicotine sulphate) has come into quite common use. It

can be purchased commercially under various brand names, and should be

diluted according to its strength, but usually about one part to fifty

of water. It may be made by boiling one pound of good tobacco stems in

two gallons of water for one-half-hour. Objections to it are that it

evaporates very quickly, although it is supposed to be non-volatile,

and that it is expensive, but it is very convenient to use, can be

readily mixed with other summer sprays, and is very effective against

plant lice and mites.