BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 43 
Owners of R. nigrum plants have given excellent cooperation in 
this work. Up to the present time 529,043 cultivated black currant 
bushes have been removed in the white pine regions of the United 
States. Half of these plants were found in the North Central States, 
30 percent in the western white and sugar pine regions, 19 percenl 
in the northeastern region, and less than 1 percent in the southern 
Appalachian States. During 1938, 15,935 cultivated black currant 
plants were eradicated, nearly all of which were located in the North 
Central States. The eradication of R. nigrum has retarded the nat- 
ural spread of the disease both within and between white pine regions. 
This work is now nearing completion; although some of these plants 
probably will be found annually for several years, their influence 
in spreading the rust will soon have been reduced to a minimum. 
TREATMENT OF INFECTED PINES OF HIGH VALUE 
White pines have a wide use for recreational, ornamental, and 
esthetic purposes, and many such trees in public parks and around 
homes were attacked by blister rust before the disease-spreading 
currant and gooseberry bushes were removed. Methods have been 
developed for saving these infected pines by cutting out the diseased 
portions and preventing their reinfection by destroying any Ribes 
that may be present within 900 feet of the trees. The removal of the 
diseased parts of infected trees at Federal expense is restricted to 
ornamental and planted pines of high value in publicly owned pine 
stands and is not recommended as a control practice in native forest 
areas. 
The treatment of infected pines was carried on during 1938 to a 
limited extent in the northern white pine regions of the Eastern 
States. In this work 92,358 white pines were saved by the removal 
of 171,731 cankers. In addition, 28,737 trees were destroyed because 
they were so thoroughly infected with blister rust that death was 
inevitable. This work involved the examination of 727,346 white 
pines and provided 5,478 man-days of employment. 
WHITE PINE STANDS MAPPED FOR BLISTER RUST PROTECTION 
White pines grow not only in pure stands but more often in mix- 
ture with other native species, usually of inferior value. In addi- 
tion to forest stands there are numerous white pine wood lots, shelter- 
belts, plantations, recreational areas, and watershed-protection stands. 
Varying degrees of importance and value are placed upon these dif- 
ferent white pine stands as encountered in the field, and good judg- 
ment is required in selecting those that justify blister rust protection. 
Commercial forest stands are selected for protection on the basis of 
their ultimate crop-production capacity at rotation age. and in deter- 
mining this, consideration is given to "forest and disease-control fac- 
tors affecting the future of the crop. White pine shelterbelts, water- 
sheds, and esthetic and recreational stands are considered on the 
basis of their value and practical utility for protective, recreational, 
scenic, and educational purposes. 
During 1938 white pine stands and their protective borders totaling 
2,785,235 acres were mapped for protection from blister rust. This 
LIBRARY 
