38 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE, 1952 
and 1-percent dieldrin and L-percent I > I > T treatments gave protection 
to the cloth after three washings. None of the treatments withstood 
<lrv cleaning. 
Comparative Toxicity of Three Insecticides to Black Carpel 
Beetle Determined 
In comparat ive toxicity studies using lindane, chlordane, and DI )T 
dusts, against black carpet beel le larvae, Lindane at L2.5 mg. per square 
fool was faster acting and produced higher mortalities than chlordane 
ai 30 mg. or DDT at 50 mg. Chlordane acted considerably faster 
than DDT. 
Commercial Mothproofing Sprays Effective 
Studies of three low-pressure gas-propelled mothproofing sprays 
revealed that when they were used as directed by the manufacturer, no 
deposit was visible on the cloth either during or l v hours after treat- 
ment. A 7-day exposure of black carpet beetle larvae on the treated 
cloth showed that the treatments were effective in preventing insect 
damage. 
Treated Rug Still Protected After Eighteen Months 9 Use 
Biological tests showed that a rug treated with 0.5 percent I)D 1 
weight was still protected against damage by fabric insects after being 
subjected to constant walking and weekly vacuum cleaning for L8 
months. I>y chemical analysis, it was determined that walking and 
vacuum cleaning for 18 months had reduced the DDT residue from 
0.41 to 0.17 percent by weight. 
Treatments for Quarantined Plants Tested 
Seedling tomato plants grown in DDT-treated soil 29 months after 
application were retarded in growth. At transplanting time, plants 
in -oil originally t reated at rates of in. 25, and 50 pounds of 1 >I > T | ier 
acre were reduced in height by 0, 27, and 28 percent, respectively, and 
in weight 22, l<». and 53 percent. Previous experience had shown 
that such retarded plant- regain normal condition when transplanted 
into untreated soil. 
Very unsatisfactory distribution of methyl bromide resulted when 
the load was placed directly on the floor in a 65-foot vacuum chamber. 
Forced circulation with a Mower did not correct the poor distribution 
until the load was placed on floor racks o) permit circulation beneath 
t he load. 
Added experimental work permitted the hot water treatment for 
lily of the valley pips contaminated with golden nematode cysts to 
be lowered from 30 minutes at L20 to the same time at 11 s V. An 
attempt to treat the pips in Germany before freezing and storage 
not successful. This procedure caused a serious deterioration of 
the pips. 
A fumigation dosage schedule of ethylene dibromide for the treat- 
ment of Puerto Kican mangoes was developed and recommended. 
The method was approved for use October 1. L951. 
Continued germination tests with tree seeds have failed to show 
any effect from methyl bromide fumigations at normal rate- of 
applicat ion. 
