26 
Bulletin 71. 
small cheesecloth sack, through which the dust may be sifted lightly 
over the foliage. The best time to apply is in the evening. 
In the wet way use 
White hellebore.1 ounce 
Water.3 gallons 
Apply as a spray in the evening. 
10. BORAX. 
Used chiefly for the destruction of cockroaches. Spread the 
powdered borax upon bread, sweet potato or banana peelings, or 
mix with sweetened chocolate, and place the bait where the cock¬ 
roaches can get at it. 
SUBSTANCES THAT KILL BY EXTERNAL CONTACT. 
Substances in this group are chiefly used against insects that 
take liquid food from beneath the surface of the plant by means of 
a tubular rostrum or beak, but they may be used against many 
other soft-bodied insects with success. Insects having a hard outer 
crust to their bodies resist these substances and are not easily killed 
by them. If insects are covered with a powdery or cottony material, 
the insecticide will have to be applied with considerable force to 
cause it to penetrate to the bod}L Applications must always be 
thorough, because only those insects will be killed that have the 
substances thrown unon them. 
JL 
11. SOAP. 
The ordinary soft soaps and laundry soaps have long been 
used for the purpose of killing vermin on plants and animals, and 
they have considerable insecticidal value, particularly for the 
destruction of very tender insects, like plant lice. There are two 
kinds of soap that are specially useful for the destruction of insects, 
and these are whale-oil soap and fish-oil soap. 
12. WHALE-OIL SOAP. 
For ordinary plant lice one pound of the soap to eight or ten gal¬ 
lons of water is sufficient if the application is thorough. Double 
this strength will not injure most plants and is often required to 
destroy more resistent insects. For scale lice, like the San Jose 
scale for example, it is used as strong as a pound, or even two 
pounds, to a gallon of water. These strongest applications can only 
be used in the winter or early spring when the trees are dormant. 
The soap is more effectual if applied when quite hot. 
13. FISH-OIL SOAP. 
Lodeman in his “ Spraying of Plants ” gives the following for¬ 
mula for the preparation of fish-oil soap: 
