50 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



the bark. These immediately seelc 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 



-^w. 



Fig. 6. WinRPd and Wingless Female of Wooll.v 

 Aphis. Much enlarj^ed. 



— 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 Lea£ Gall or Curl in Which the 

 Winged Aphids Develop Before Flying to the 

 Apple. — Photo by Masted. 



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 histor.v 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 scars, 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 iish-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 



