GAS TREATMENT FOR TOBACCO 3 
to be the difficulty of handling a liquid in tobacco beds, particularly 
if they are more than 3 or 4 yards wide. Very satisfactory blue 
mold control has been obtained with treatments twice a week, using 
benzol at the rate of 5 quarts per 100 square yards of bed; an evapor- 
ating pan surface equal to 1/100 of the bed area, supplemented by 
cloth wicks in cool weather, to insure complete vaporization, the pans 
being placed not more than 8 to 10 feet apart; and heavy muslin 
FicuRreE 1. a arranged for paradichlorbenzene treatment. In this method the 
crystals are scattered on tobacco-cloth strips that are stretched across the bed 15 
feet apart. The strips do not interfere with the growth of the plants beneath. 
cover (60 to 65 thread count) weighing about 414 ounces per square 
yard. 
Gas Treatment With Paradichlorbenzene 
Paradichlorbenzene has the advantage over benzol of being much 
more convenient to use and, furthermore, treatment of the usual 
wide plant bed is not difficult. However, the margin of safety is 
much less with paradichlorbenzene than with benzol, and the problem 
of vaporization is somewhat more complicated. 
Distribution of the Crystals 
Under most conditions, the most practical procedure is to scatter 
the crystals over a 24-thread-per-inch or tighter, regular tobacco cloth. 
As a substitute, when suitable cotton covers are not available, l-yard 
wide strips of tobacco cloth or thin cheesecloth stretched across the 
bed at the rate of one strip to each 5 or 6 running yards can be used 
(fig. 1). Much better vaporization of paradichlorbenzene has been 
secured with the cloth strips than with board shelves or wire baskets, 
though satisfactory results were obtained with these methods except 
during very cool weather. The tobacco cloth, used either as whole 
covers or as strips, should be stretched well above the plants, 1. e., 
12 to 18 inches above the ground surface. If the cloth is down close 
to the plants, injury is likely to occur. 
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