PROTECTING PLANTS 181 
certain galls that often appear on the limbs of large apple-trees, 
are also known to be caused by this same bacterium. The 
disease seems to be most 
serious and destructive 
on the raspberry, par- 
ticularly the Cuthbert 
variety. The best thing 
to be done when the rasp- 
berry patch becomes in- 
fested is to root out the 
plants and destroy them, 
planting a new patch 
with clean stock on land 
that has not grown ber- 
ries for some time. Not- 
withstanding the laws 
that have been made 
against the distribution 
of root-gall from nurs- 
eries, the evidence seems 
to show that it is not a 
serious disease of apples 
or peaches, at least not 
215. The slender tufted growth indicating 
peach yellows. The cause of this disease 
is undetermined. 
216. Gall on a 
raspberry root. 
in the northeastern United States. It is not 
determined how far it may injure such trees. 
Of obvious insect injuries, there are two 
general types, — those wrought by insects that 
bite or chew their food, as the ordinary beetles 
and worms, and those wrought by insects that 
puncture the surface of the plant and derive 
their food by sucking the juices, as scale-insects 
and plant-lice. The canker-worm (Fig. 217) is a 
notable example of the former class; and many 
of these insects may be dispatched by the appli- 
