BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 79 
of ribes plants near ground level. These concentrates are either 
oil-2,4-D or oil-2,4,5-T. Dosages, diluent, and markers to show areas 
sprayed were further studied to lower costs and improve the effective- 
ness of this work. 
Of many markers tested, a commercially made scarlet dye used at 
the rate of a tablespoonful of dye per gallon of herbicide proved to 
be the brightest and most light-fast. This indicator speeds the work 
of crews using this method and assures thorough coverage of indi- 
vidual bushes. It proved very effective in treating ribes in remote, 
rugged terrain in both Rocky Mountain and Sequoia National Parks. 
Encouraging results with defoliants 
Continuation of the previous years' ribes-defoliation tests showed 
that three spray applications of 2,4-D at a low dosage of 50 p. p. m., 
using about 3 ounces of the acid per acre, gave nearly complete kill of 
Ribes roezli. 
Encouraging results obtained in destroying ribes and associated 
brush in western pine areas by broadcast spraying with 2,4,5-T 
has renewed interest in the seed tree method of pine management 
whereby certain trees are selected for seed production and regenera- 
tion of the stand. The Bureau therefore expanded its plot studies 
on the selective toxicity of 2.-1, 5-T to white pine as well as associated 
ribes and brush. Further work is contemplated to improve broadcast 
methods for ribes suppression by aircraft, mist blower and power 
sprayer, especially with repeated Ioav dosage applications of herbicides 
that selectively damage ribes. 
Antibiotics tested against blister rust cankers 
Actidione, an antibiotic, in mixture with 2,4,5-T has proved of 
sufficient toxicity to blister rust cankers in infected trees to warrant 
further field tests. 
Additional rust-resistant pines found 
Seven additional white pines that are apparently rust-resistant 
were found during the year, increasing to 66 the number of available 
rust-resistant trees. Several apparently rust-resistant sugar pine 
trees were located in northern California. Scions from these trees 
were successfulh T grafted on seedling stock. 
As part of these studies, five test plantings of grafted ami seedling 
western white pines were established in northern Idaho. Seed was 
also collected and extracted from trees in which pollination was con- 
trolled in 1050. These seeds will be used to produce ¥ t progeny start- 
ing in 1952. Of 93 crosses attempted in 1950, 85 produced normal- 
appearing seed, with 78 crosses yielding seed in quantities adequate 
for progeny testing. 
Blister rust spread determined 
White pines infected with blister rust were observed for the first 
time in Avery County, X. (\; Morgan County, Tenn.; Botetourt, 
Bedford and Warren Counties, Va .; and Raleigh and Morgan Coun- 
ties, W.Va. 
With discovery of blister rust in Calaveras County, Stanislaus 
National Forest, Calif., the known southward range of the rust on 
