INSECTICIDES AND EQUIPMENT FOR CONTROLLING INSECTS 33 
aphids and the younger stages of mealybugs, scale insects, whiteflies, 
and other soft-bodied insects, but should not be used on very young or 
tender plants. For use on hardy plants the amount of soap may be 
increased to kill larger insects. 
The soapy water remaining in the tub after clothes have been 
laundered may also be used for spraying or dipping foliage of infested 
house plants. When potted plants are dipped, they should be inverted 
and submerged only to the soil surface and then laid on their sides to 
drain before being set in an upright position. This will avoid saturat- 
ing the soil with the soap solution. House plants dipped or sprayed 
with concentrated soap solutions should not be placed in full sun for 24 
hours, after which the folage may be syringed with clear water and 
the plants returned to their former locations. 
Soap is used as a wetting and spreading agent with nicotine, pyre- 
thrum, and some other sprays. The amount of soap required in a 
spray mixture is regulated somewhat by water hardness. If used with 
lead arsenate, some soaps may increase arsenical injury to foliage. 
Oleates of monoethanolamine, triethanolamine, and ammonia, as 
well as several other soaps, have been used with mineral oil and lead 
arsenate in making deposit-building mixtures to obtain the heavy 
deposits of lead arsenate often needed for control of the codling moth. 
SODIUM ARSENITE 
Sodium arsenite (essentially NaAsO,), a white crystalline solid, 
is soluble in water and is, therefore, unsuitable for use on living plants. 
In fact, it is probably best known as a weed killer. It is more gen- 
erally available in liquid form containing about 32 percent of arsenic 
trioxide (As,O;), although it can also be purchased as a powder. Its 
chief use in direct control of insects is in poisoned baits (p. 28), 
but it is used as a spray on wild vegetation to control grasshoppers. 
Caution.—Sodium arsenite is a violent poison and must be 
stored in clearly labeled packages. 
SODIUM CYANIDE 
Sodium cyanide (NaCN) isa white, deliquescent, very poisonous salt 
manufactured in this country. When it is mixed with dilute sulfuric 
acid a reaction takes place in which the deadly hydrocyanic acid 
gas (HCN) is liberated. For fumigation purposes sodium cyanide 
should be practically free from chloride and contain not less than 
51 percent of the cyanogen radical. The chemical may be purchased 
in the form of “eggs,” each weighing 1% or 1 ounce. Dosages may, 
therefore, be easily calculated by counting the number of eggs required. 
Hydrocyanic acid gas is used as a fumigant to control such pests 
as scale insects, aphids, whiteflies, mealybugs, and thrips on plants 
and bulbs in fumigation vaults, greenhouses, or tents. The dosages 
range from 1% to 1 ounce of sodium cyanide per 1,000 cubic feet of 
space, with exposure periods of 1 to 5 hours or overnight. The dosage 
and length of exposure depend upon the plants’ tolerance to the gas, 
