THE MONTHLY BULLETIN. 



509 



Their most serious injury iu the spread of blight may be largely 

 avoided by removing all sprouts from the crowns and from the main 

 boles of the trees as fast as they appear. A few hours of this sort of 

 work before this infection begins to appear iu the spring will save 

 hundreds of trees where this insect is abundant. 



Fig. 117. — Pear tree treated for pear blight. Showing how the infection started from 

 a single limb, which was removed. The gouge marl^s are plainly visible on tlie 

 healthy limbs. (After Gammon, Monthly Bulletin, Cal. Hort. Com.) 



The Work of Aphids in Spreading Pear Blight. 



Aphis pomi, the apple Aphis: As a rule aphids are capable only of 

 spreading very local infection. These insects are numerous everywhere 

 and more or less infection has been traceable directly to them. Toward 

 the close of the infection period they were especially prominent and 

 caused much damage on the growth in the crowns of the trees. They 



