Insect and Disease Control 261 



wiry or willowy, yellowish green shoots which become very 

 much branched, forming a sort of brush-like growth. The 

 leaves on this growth are very much smaller and narrower 

 than normal leaves, more pointed, and possess a weak, 

 sickly, greenish-yellow appearance. In the late fall the 

 outermost leaves that develop near the terminal ends of 

 all the current season's growth have some of the character- 

 istics of those borne on the wiry shoots above mentioned. 



"Yellows" trees may go into the winter with their buds 

 more advanced than normal individuals and such trees 

 usually start into growth in the spring in advance of healthy 

 ones. 



From the beginning of the first sjinptoms progressing 

 through the various stages described, the entire course of 

 the disease may be run and the tree killed in three or four 

 years. The tree does not die usually all at once but more 

 or less gradually limb by limb. 



As above stated, the means by which the yellows is spread 

 from a diseased tree in an orchard to healthy trees is un- 

 known. In the past one of the most common means of 

 dissemination into new localities has been by infected nursery 

 stock. However, the danger of spreading the disease 

 through nursery stock is now slight compared with what 

 it was formerly, since all progressive nurserymen are fully 

 aware of the baneful results that follow any carelessness in 

 respect to selecting the buds used in propagation. 



It should be noted that other influences than yellows may 

 cause the development of many of the symptoms of this 

 disease. Premature ripening of the fruit may be caused 

 by girdling a tree or a limb, but the characteristic red mark- 

 ings on and in the fruit are lacking. Weak sickly shoots 

 with narrow leaves may develop also from girdling, as by 



