144 BULLETIN 623, U. S. DEPARTMENT OF AGRICULTURE. 



The isolation of the valuable strains through bud selection is of 

 vital commercial importance to the entire Washington Navel orange 

 industry. The isolation of the inferior strains is of interest only from 

 the experimental standpoint. The propagation of trees of the valuable 

 strains will result not only in increased production but, what is equally 

 important, in a uniform, improved production of improved crops of 

 fruit of greater commercial value. From this standpoint, the isola- 

 tion of the best strains is of importance, not only to the grower 

 but to the consumer as well. 



TOP- WORKING UNDESIRABLE TREES. 



The elimination from established orchards of trees of undesirable 

 strains has been effected by top-working these trees with select buds 

 from trees of the Washington strain. 



The selection of trees to be top-worked was made before the fruits 

 borne by these trees were picked. While trees of some of the inferior 

 strains can be recognized from their habit of growth or other vegeta-' 

 tive characteristics, it is desirable wherever possible to base the final 

 selection on performance records and the characteristics of the fruits. 



The selection of bud wood for top-working purposes was based on 

 individual-tree performance records, associated with an intimate 

 knowledge of tree characteristics secured from careful observations of 

 the trees. Only fruit-bearing wood was used, and for the most part 

 only that growth immediately back of the oranges. 



In the trees to be top-worked two or three of the main limbs were 

 selected for budding and two buds were inserted in each limb, one on 

 each side, from 12 to 24 inches above the fork of the trunk. After 

 the buds united with the limbs the wraps were removed, the limbs cut 

 off about 6 inches above the buds, and the freshly cut surfaces covered 

 with grafting wax. The trunks and the remainder of the limbs were 

 covered with a heavy coating of whitewash immediately after the 

 tops were removed, in order to prevent injuries from exposure. The 

 sprouts from the limbs and trunk were removed from time to time, 

 in order that the new tops should be made up of the growth from the 

 inserted buds alone. As the buds developed, their growth was con- 

 trolled by pruning, so as to form a well-branched top capable of bear- 

 ing full crops of fruit. 



After a year's growth, the stubs of the original limbs were cut off 

 just above the bud union, making the cuts oblique in order to facili- 

 tate their healing. All cut surfaces were coated with grafting wax 

 or some other suitable covering, in order to prevent decay and to 

 promote the healing processes. Careful attention should be given 

 these trees for the first year or two, to protect the new growth and to 

 guard against undesirable conditions. Afterwards these trees require 



