36 Colorado Experiaient Station 
(9) Avoid heavy winter pruning’, as it produces heavy succu¬ 
lent shoots subject to attacks of bacteriiun. 
Crown Gall.—S ee Apple, page 12. 
Rust. —See Apple, page 13. 
PLUM. 
Plum Pockets. —The disease is present on fruit, twigs, and 
leaves. First evidence on the fruit is yellowing. The fruit then 
enlarges rapidly, attaining a size several times the normal. The 
surface becomes deeply wrinkled, and the pit fails to develop, hav¬ 
ing in its place a large air cavity (Plate XL, Fig. 2). The diseased 
Plate XI. Pig. 1. Black knot ou plum. Fig. 2. Plum pocket, showing the enlarged, 
darkened, diseased fruit. 
fruit later turns brown, shrivels, and falls, or in some cases remains 
on the tree. Diseased twigs are enlarged, deformed, and usually 
somewhat curved. In later stages the twig turns brown. Infected 
leaves are abnormally thickened and deformed. Later they shrivel, 
become brown, usually remaining on the tree. 
