G2 PLANT LICE. 
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 decomposition with 
attendant disappearance of the galls and also of the lice, so that 
after this stage is reached, the cause of the injury is often obscure. 
On the trunks the presence of the lice sometimes results in the 
roughening of the bark or a granulated condition which is par- 
ticularly 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, they 
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 commonly insignifi- 
cant, is useful as an indication of the probable existence of the 
lice on the roots. A badly attacked tree assumes a sickly ap- 
pearance, and does not make satisfactory growth; the leaves 
become dull and yellowish, and even if not killed outright 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 employing root stock from seedlings of the more 
resistant varieties or from wild crabs, considerable protection 
would result. The character of the soil also exerts some in- 
fluence,—that is, loose dry soils are favorable and wet compact 
ones are unfavorable to the aphis.”’ 
The illustration, Fig. 149, will give a good idea of the in- 
sect and its work. On Plate XI another picture of this danger- 
ous pest is given. 
' As far as remedies are concerned it is easy enough to con- 
trol the lice on the bark, where they are readily seen, and where 
they can be reached and exterminated by any of the washes 
recommended for plant-lice, such as kerosene emulsion, a strong 
soap wash, resin wash, etc., which will be described later. All 
of these washes should be applied with sufficient force and 
thoroughness to penetrate the protecting cottony cover, and for 
this purpose it is best to apply them warm. 
