42 ANNUAL BEPORTS OF DEPARTMENT OF AGRICULTURE, 1 
One of the most significant finds on Ribes occurred in Shasta 
County, about vn miles south of the Oregon line. In 1937 scouting 
activities in this locality uncovered only two diseased Ribes, each 
with but one leaf infected. A year later 300 infected 50 of 
them R. nevademe. and the remainder R. roezli, were found to be 
heavily infected with blister rust in the same locality. 
Again in Tehama County, west of Mount La— en. 1937 scouting 
showed no infection, while in L938 over LOO infected Ribes n 
R. inerme, and R. nevadensi bushes were found in a small localized 
area. Such discoveries, both in good association with sugar pine, 
have laid the foundation for centers of local infection on pines within 
the next few yen-. 
WHITK PINK MHSKKY STOCK PRODI (FD FREE FROM BLISTER RUST INFECTION 
Ribes eradication was carried on in the environs of 103 nurseries 
during L938. These nurseries contained over 80,000,000 young white 
pines that were being grown for use in reforestation work. For 
several years nurseries producing white pine for forest planting have 
been examined annually to keep their environs free of Ribes by de- 
stroying any that may have developed from seeds or sprouts and 
thus a— mi- (he production of trees free from blister rusl infection. 
Tin- i- important, a- these trees arc distributed widely for planting 
purposes and. if infected, would serve as carriers and spreadei 
the disease. Most of the control areas around these nurseries 
have received from one to several workings, and although their pro- 
tective borders are free of large bushes, in some cases seedlings and 
small bushes continue to make their appearance on portion- of the 
protected areas. 
During 1938 a total of 111,268 Ribes were destroyed <>n 45,346 acres 
in protection work around nurseries, or an average of about '2.4 
bushes per acre. Many of these were seedling plant-. Already the 
environs of some nurseries are so free of Ribes that they require 
only periodic inspections. The young tree- are further safeguarded 
by arranging with planting agencies to have the reforestation sites 
examined for Ribeh and such plant- destroyed before the area- are 
planted with white pines. This assures protection to the new forest 
during the early year- of it- life. Young growth that remains un- 
protected i< often completely destroyed by blister rust. 
ERADICATION OF THF CULTIVATED BLA( K CURRANT 
An important phase of the Department'- program for the control 
of blister rust consists in the eradication of the cultivated Mack 
currant (Ribes nigrum) in regions producing valuable crop- of white 
pine timber. These currant- are being eliminated because of their 
extreme -i i scept i 1 ti I i t y to infection and their importance in distribut- 
ing the rust. Field observations -how that they have been responsible 
for starting new center- of infection and firmly establishing the 
disease over extensive area- that otherwise might have remained U-^c 
of the rust for many year-. "With few exception- these plant- arc 
confined i<> gardens, from which they rarely escape. Hence they have 
not become established in our forests. 
