the roots of a young tree to the depth of a foot or so become clubbed 

 and knotted by the growth of hard fibrous enlargements, with the result, 

 in a year or two, of the dying of the rootlets and their ultimate decom- 

 position with attendant disappearance of the galls and also of the aphides, 

 so that after this stage is reached, the cause of the injury is often 

 obscure. On the trunks the presence of the aphides sometimes results in 

 the roughening of the bark or a granulated condition which is particularly 

 noticeable about the collar and at the forks of branches or on the fresh 

 growth around the scars caused by pruning, which latter is a favorite 

 location. On the water shoots the insects collect particularly in the axils 

 of the leaves, often eventually causing them to fall, and on the tender 

 greener side of the stems. The damage above ground, though com- 

 monly insignificant, is useful as an indication of the probable existence 

 of the aphides on the roots. A badly attacked tree assumes a sickly ap- 

 pearance and does not make satisfactory growth and the leaves become 

 dull and yellowish, and even if not killed outright it is so weakened that 

 it becomes especially subject to the attacks of borers and other insect 

 enemies. Injuries from the woolly aphis are almost altogether confined 

 to the apple, even the wild crab not being so liable to attack or at least 

 injury' by it. There is, however, some difference exhibited by different 

 varieties of apple in immunity, and particularly is the Northern Spy 

 proof against it, and it is possible that, as in the case of the grape 

 phylloxera, by emplojdng root stock from seedlings of the more resist- 

 ant varieties or from wild crabs, considerable protection would result. 

 The character of the soil also exerts some influence — that is, loose dry 

 soils are favorable and wet compact ones are unfavorable to the aphis. 



ORIGIN AND DISTRIBUTION. 



There is considerable difference of opinion as to the origin of the 

 woolly aphis of the apple. The belief has fluctuated between a Euro- 

 pean and an American origin for this insect, but the weight of evidence 

 seems to indicate the latter. At any rate, it is an insect which is most 

 readily carried from place to place with nursery stock of the apple, and 

 it has been so transported to practically all the important countries of 

 the world which have been reached by colonization or European settle- 

 ment. The woolly aphis was first noticed in England in 1787, on some 

 stock imported that year from America, and was early called the Ameri- 

 can blight. Hausmann described it in 1801 as infesting apple trees in 

 Germany, and within the next twenty-five years it was recognized as a 

 serious enemy of this fruit tree throughout England, Belgium, northern 

 France, and Germany, but seems never to have been especially notable 

 in the warmer latitudes of Europe. 



It was very early introduced into Australia and New Zealand, and is 

 known in India and Chile, and probably is as widespread as any of the 

 common injurious fruit pests. Notwithstanding the possibility of its 

 being a native American insect, it did not attract attention in this 



