176 PLANT LICE. 
and the destruction of existing aphides, from 2 to 5 pounds of 
the dust should be distributed from the crown outward to a 
distance of 2 feet, first removing the surface soil to a depth of 
from 4 to 6 inches. The tobacco kills the aphides by leaching 
through the soil, and acts as a bar for a year or so to reinfesta- 
tion. The dust is a waste product of tobacco factories, and costs 
about one cent per pound, and possesses the additional value of 
being worth fully its cost as a fertilizer. 
“The use of bisulphide of carbon for the woolly aphis is the 
same as for the grape root-louse. It hould be applied in two 
or three holes about the tree to a depth of 6 to 12 inches and 
not closer than one and one-half feet to the crown. An ounce 
of the chemical should be introduced into each hole, which should 
be immediately closed. The bisulphide evaporates and penetrates 
throughout the soil, and readily and promptly kills the aphides. 
It does not, however, furnish any protection from future attacks, 
and is attended with danger to the tree unless the precautions - 
named are carefully observed. That it is highly inflammable 
should also be constantly borne in mind. If it is to be used at 
all extensively, an automatic injecting device should be secured, 
such as the McGowan injector. The chemical costs ten cents 
per pound in 50-pound cans of the manufacturer, E. R. Taylor, 
Cleveland, Ohio. 
“Badly infested nursery stock should be destroyed, since it 
would be worth little even with the aphides removed. Slightly 
infested stock can easily be freed of the aphides at the time of 
its removal from the nursery rows. The soil should be dislodged 
and the roots pruned, and in batches of a dozen or so the roots 
and lower portions of the trunk should be immersed for a few 
seconds in water kept at a temperature of 130° to 150° F. A 
strong soap solution similarly heated or a fifteen times diluted 
kerosene emulsion will give somewhat greater penetration and be 
more effective, although the water alone at the temperature named 
should destroy the lice. This treatment is so simple and inex- 
pensive that it should always be insisted upon by the purchaser 
if there be any indication of the presence of this insect, and stock 
exhibiting much damage should be refused altogether. 
“After planting, if the trees be kept in vigorous condition 
by careful cultivation and, if necessary, proper fertilizing, damage 
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