50 ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
the bark. These immediately seek new 
tender bark to feed on and their num- 
bers are reinforced by young lice that 
have hibernated in crevices of the bark 
under the dead bodies of lice of the pre- 
vious year, and by an upward migration 
of lice from the roots. Above ground 
the only lice that survive the winter are 
Fig. 6. 
Aphis. 
Winged and Wingless Female of Woolly 
Much enlarged. 
—Author’s Illustration. 
the very small hibernants of the last sum- 
mer generation and those hatching in 
spring from winter eggs. On the roots 
under a more even temperature the lice 
live through the winter in comfort. At 
maturity the lice of the spring and sum- 
mer generations are all wingless, about 
one-tenth of an inch long, reddish-brown 
covered with a white cottony filamentous 
secretion. The lice are very gregarious 
and when massed together are often en- 
tirely hidden from view by this woolly 
covering. The wingless, forms produce 
parthenogenetically as many as 100 young 
in two weeks. These develop in about 
two weeks. In September a winged gen- 
Fig. 7. Elm Leaf Gall or Curl in Which the 
Winged Aphids Develop Before Flying to the 
Apple. —Photo by Maxted. 
eration makes its appearance and migrates 
to other trees. The winged lice are a lit- 
tle shorter than the wingless, are dark 
brown, covered, all except the wings, with 
woolly secretion. They produce the true 
sexed insects on the trunk of the tree. 
These latter are much smaller than the 
viviparous forms and have no mouth- 
parts. Both sexes are without wings, the 
orange-colored females being a little larger 
than the brown males. The sexes become 
full grown in a week and after mating 
the female lays a single large egg in a 
crevice in the bark. The life history of 
the root form is not fully known. The 
root lice apparently are all wingless. This 
louse seems to be capable of passing sev- 
eral years of continuous agamic genera- 
tions, as the proportion of winged lice 
is generally very small and consequently 
there are but few winter eggs deposited 
each season. 
Injury 
The root form is especially harmful to 
young trees and nursery stock, often 
killing a tree in less than two years from 
the time of original infestation. Large 
trees do not succumb so quickly. Infested 
roots produce knotty swellings and galls 
which subsequently decay and the lice 
move to a fresh part. As a rule the root 
lice work within eight inches of the sur- 
face of the soil, a fact that rather sim- 
plifies their successful treatment. Above 
ground woolly aphids occur on any part 
of the tree except on the fruit. Leaves 
are usually free from attack. The parts 
of the tree most preferred are the apices 
of water sprouts and other young growths; 
on sears, formed by pruning, between the 
outer bark and the central woody portion, 
and at the base of the larger limbs. Limbs 
and twigs badly infested will become knot- 
ted in the same manner as the roots. 
Control 
The aerial lice may be controlled by 
any of the contact insecticides suggested 
for the control of the Green Apple Aphis. 
High pressure is necessary in order to 
penetrate the woolly covering, and for 
this purpose if tobacco extract be em- 
ployed it would be advisable to add two 
pounds of fish-oil soap to each 50 gallons 
of spray. In the spring Tanglefoot bands 
around the tree trunk will catch the lice 
migrating upward from the roots. To 
combat the root form it will be necessary 
to remove the earth around the tree for 
a depth of five or six inches so as to 
uncover a portion of the larger roots 
and then apply a diluted tobacco extract 
