434 F. M. Rolfs 



IMMUNIZATION 



No doubt much can be accomplished in the waj^ of resistance by crossing 

 the less resistant with the more resistant varieties. This is especially- 

 true in the case of plums. 



RECOMMENDATIONS FOR CONTROL 



Since the organism is spread largely in the nursery, great care should be 

 exercised in selecting trees for planting. Stock should be bought only 

 from reliable nurserymen, who should be required to guarantee the trees 

 to be free from the disease. A single diseased tree may cause serious loss 

 after the trees are set out. 



Old, neglected, budded apricot, nectarine, peach, and plum trees, 

 especially plum, usually harbor the organism and become a menace to 

 young orchard trees. All such trees should be cut down before the yomig 

 trees are set out. 



The ground must be thoroughl}' plowed before the young trees are set, 

 and about one pound of a complete fertilizer should be worked into the 

 soil about the tree while it is being set. Too much care cannot be give"n 

 to the cultivation of an orchard, especially during the first two or thi-ee 

 years. 



Where the organism has become thoroughly established, systematic 

 pruning, cutting out, and careful removing of all the diseased tissue from 

 the cankers on the limbs and the trunks of the trees will eliminate the 

 source of infection to a large extent. Complete eradication on old trees 

 (seven or eight j^ears old) , however, can be accomplished only by pruning 

 the trees. Pruning not only tends to eliminate the source of infection, but 

 also serves to stimulate new growth which is more resistant to the disease. 



Where the trees have been heavily prmiecl, a thorough applica- 

 tion of bordeaux mixture (4 pounds of copper sulfate, 4 pounds of lump 

 lime, and 50 gallons of water) just before the buds open will be of 

 considerable assistance in controlling the disease on the fruit, especially 

 if this apphcation is followed by two or three applications of arsenate of 

 lead (2| pounds of arsenate of lead, 4 pounds of lump lime, and 50 gallons 

 of water) to control the curculio and other insects, which aid materially 

 in disseminating the organism. The first application of arsenate of lead 

 should be made just as the shucks slip; the second, two weeks later; and 

 the third, about two weeks after the second. 



