8 LEAFLET 209, U. S. DEPARTMENT OF AGRICULTURE 
The treatment of 100 yards of bed will actually give the average 
erower considerable blue mold protection, because at present only 
about 1 acre can be set from each 100 square yards of bed, whereas 
if blue mold is controlled, it is easily possible to set 3 or more acres. 
Cost of Treatment 
The question of the cost of paradichlorbenzene treatment is impor- 
tant. Because labor costs vary, only the cost of the two chief ma- 
terials, muslin and paradichlorbenzene, is given. It will be assumed 
that one muslin cover will be used for two halves of a 100-square-yard 
bed during an average outbreak requiring six treatments. 
Per 100 square yards of bed per year 
Muslin (good for 3 years), 60 square yards at 14 cents=8.40K %________ $2. 80 
Paradichlorbenzene, 18 pounds (6 treatments of 3 pounds each) at 18 cents 
Der POUNCEt a2 See ne ee ee ome 
Totalecostwiw.. 882 esa LL. _ Se a ee ee 6. 04 
If a cheap grade of muslin is used the figures might be: 
Muslin (good for 2 years), 60 square yards at 7 cents=4.20 %_____ 2.10 
Paradichlorbenzene, 24 pounds at 18 cents per pound______________ 4. 32 
Totalicost2 35.208 oe oo. 225 5 Se ee ee ee 6. 42 
The use of cheap muslin would tend to increase the expenditure for 
paradichlorbenzene and would reduce the expected life of the cover, 
but would hardly reduce the cost of treatment if this is considered 
over a period of years. It is to be understood of course that cost 
figures are subject to many variations, and the above merely represent 
estimates based on rather extensive experience. 
Summary of Recommendations for the Use of Paradichlorbenzene 
(1) Use a No. 6 grade of paradichlorbenzene, though a smaller grade 
is somewhat better in very cool weather and a larger one 
entirely satisfactory in warm weather. 
(2) Use 2% to 3 pounds per 100 square yards of bed if the muslin is 
dry or slightly moist; with a water-soaked muslin 1% pounds 
is adequate. 
(3) Distribute the crystals on the regular tobacco cloth that is 
stretched 12 to 18 inches above the ground surface. 
(4) Cover with a 60- to 65-thread muslin weighing about 4% ounces 
per square yard. 
(5) Start treatment just before sundown and open the beds at 8 a. m. 
Treatments should be started earlier in cool weather and later 
in warm. 
(6) The first treatment should be given as soon as mold is observed 
either in the bed or in nearby beds. Applications should be 
made twice a week but not on 2 consecutive nights, so that the 
longest period between treatments is not over 4 days. Increase 
the number of treatments to 3 a week during cold weather. In 
general, 5 to 10 treatments have been required per season. 
U.S. GOVERNMENT PRINTING OFFICE: 1941 
For sale by the Superintendent of Documents, Washington, D.C. - - - - Price 5 cents 
