PBOTBCTING 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 



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 



216. Gall on a ^ i j 



raspberry root, of these insects may be dispatched by the appli- 



215 The slender tufted growth indicating 

 peach yellows. The cause of this disease 

 is undetermined. 



