190 MANUAL OF GARDENING 
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 cya- 
nide 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 
+ to } oz. potassium cyanide for every 1000 cu. ft. of space, 
leaving the gas in from 4 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 two hours 
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 or 
mixing with similar or weaker solutions. 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 
