DISEASES OF PLANTS 



245 



trunks and branches (figure 145). It also attacks 

 branches, twigs, and leaf -stalks. To check its spread, 

 cut out and burn as in pear blight; also avoid wound- 

 ing the trees and prune each tree a little at a time 

 rather than all at once. 

 Buds or cuttings should 

 not be taken from in- 

 fected orchards. (Califor- 

 nia Experiment Station, 

 Bulletin 120.) 



The same disease attacks 

 the~oleander. 



Crown gall. This dis- 

 ease, which is probably 

 caused by bacteria, attacks 

 woody plants near the sur- 

 face of the ground. It 

 causes swellings somewhat 

 like those of the olive knot. 

 It seems to enter the plant 

 especially through wounds 

 made in plowing or in 

 transplanting. By pre- 

 venting such wounds we help to keep it out. The galls 

 may be removed from time to time. The bacteria 

 seem to live in the soil, and are very hard to get rid 

 of. (Arizona Experiment Station, Bulletin 33; New 

 Mexico, 58; Utah, 55, 65; Washington, 83.) 



FIG. 145. Olive knot. 



