BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 37 
A protective dust containing 1.1 percent piperonyl butoxide and 
0.08 percent pyrethrins, when added to newly harvested wheat in 
Kansas at the rate of 75 pounds per 1,000 bushels, provided effective 
protection against insect infestation for a 3-month period following 
harvest. 
Weekly Spraying Reduces Tobacco Storage Losses 
A study was made of actual loss of flue-cured leaf tobacco in stor- 
age. No appreciable damage was found in tobacco in storage one 
year or less. Tobacco in storage 2 years or more did show appreciable 
loss. Where no insect control was practiced this loss was found to 
amount to nearly 2y 2 pounds of tobacco per hogshead. Weekly spray- 
ing with pyrethrum-oil reduced this loss appreciably, the reduction 
ranging from 27 to 37 percent. 
A comparison was made in tobacco warehouses of the relative 
effectiveness of pyrethrum-oil space spray, of HCN fumigation, and 
of fumigation followed by weekly spraying. Against the tobacco 
moth it was again demonstrated that weekly applications of pyreth- 
rum-oil space spray gave almost perfect control, appreciably better 
control than warehouse fumigation. Against the cigarette beetle, 
in a very light infestation, pyrethrum-oil spray gave satisfactory con- 
trol. In a moderate infestation of the beetle, warehouse fumigation 
with HCN followed by weekly spraying was fairly effective, as was 
also a single warehouse fumigation. In a heavy infestation, two 
fumigations failed to give satisfactory control. In a large-scale 
experiment 8 tobacco warehouses were sprayed weekly with 2y 2 per- 
cent of lindane in oil. Control of the tobacco moth was excellent but 
control of the cigarette beetle was unsatisfactory. No difficulty was 
experienced in handling or applying this insecticide. 
Insecticides Show No Repellency to Tobacco Insects 
Studies were made on the repellent action of two insecticides to 
tobacco insects. In one experiment on the repellency of paper hogs- 
head liners impregnated with pyrethrum-piperonyl butoxide, no re- 
pellency was noted after one year in storage. In an additional experi- 
ment, cases and hogsheads of tobacco were sprayed with lindane sprays 
containing up to 2 percent of lindane. Spray was applied to the ex- 
terior and interior of the cases and hogsheads. Sprayed hogsheads 
were as readily infested by the cigarette beetle and the tobacco moth 
as unsprayed ones. 
DDT-Plastic Treatment Protects Animal Hair Padding 
Horsehair treated with DDT in a plastic coating remains undam- 
aged after 18 months. Allyl starch and rubber cement appear to be 
promising adhesives for DDT on animal hair used for insulation or 
padding. 
Low Concentrations of Insecticides Protect Fabrics 
The lowest concentrations of DDT, dieldrin or lindane which gave 
complete protection from insect damage to cloth in laboratory tests 
were determined as 0.05, 0.1, and 1 percent respectively. The 0.5- 
