BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 51 
colony strength. This line had also been entirely resistant in 1947 ; the 
other had been 86 percent resistant, although all infected colonies had 
recovered by the end of the season. This is the twelfth season that these 
two lines have been bred and tested in successive generations. Another 
line that had been tested similarly and showed 100 percent resistance 
in 1947 had become so weakened, apparently by inbreeding, that 
tests with it were discontinued in 1948. 
Sulfathiazole for Treating American Foulbrood in 
Experimental Stage 
Six colonies infected experimentally with American foulbrood in 
1946, and treated with sulfathiazole fed in sugar sirup in 1946 and 
1947, remained healthy in 1948 until July 21, when a slight recurrence 
of the disease was noted in two of them. 
Plastic Package-Bee Containers Withstand Shipping Tests 
Six experimental transcontinental shipments of package bees in the 
new plastic containers mentioned in last year's report were made 
from Davis, Calif., to Beltsville, Md., in cooperation with the United 
Air Lines. Two of the shipments made the return trip to Davis. All 
the bees shipped with food in the containers survived well. One such 
package crossed the continent three times with but 5 percent mor- 
tality. A special food consisting of a sugar-sirup-agar jelly was sus- 
pended in a cloth bag. Some bees were shipped without food, but 
they died. A few of the containers were damaged. These plastic con- 
tainers are smaller, lighter, and probably longer lasting than con- 
tainers of wood and screening now in use, but thus far they have been 
more costly to assemble and crate and less convenient to handle, par- 
ticularly to remove hitchhiking bees. 
CONTROL OF PLANT DISEASES 
White-Pine Blister Rust 
Improved methods aid ribes removal 
The control of white-pine blister rust was aided by increased use 
of chemicals, the one-man eradication method, and contract procedure 
for the removal of ribes. Chemical eradication of ribes is speeding 
up the work on areas where hand grubbing is difficult. Methods of 
application are constantly being improved. Power equipment is 
used successfully where it is feasible to broadcast large volumes of 
low-cost sprays. A special back-pack sprayer has given good results 
in areas where selective treatment with small amounts of concentrated 
solution is more practicable. 
The ribes-infested area treated with chemicals in 1948 was about 
twice that treated the previous year. In the sugar-pine section of 
California about 3,000,000 Ribes roezli plants growing on 1,*242 acres 
were destroyed by spraying with 2,4-D. In the western white-pine 
