26 MISC. PUB. 526, U. S. DEPT. OF AGRICULTURE 
concentrated nicotine preparation (containing 80 percent of free 
nicotine) into the exhaust pipe of a gasoline engine while the engine 
is running at a comparatively high speed. The vaporized nicotine 
produced is blown out through a boom at the rear of the engine and 
expelled under a gas-proof cloth, or trailer. This cloth trailer is 100 
feet long and is drawn over the field at the rate of 100 feet per minute. 
Caution.—Liquid nicotine and its vapor are both poisonous, and 
great care should be exercised in handling. 
OIL DUSTS 
Oil dusts usually contain about 2 to 5 percent of lubricating oil of 
80 to 110 seconds viscosity (Saybolt, 100° F.) and may include various 
insecticides or fungicides. The oil is added to improve the adhesive 
properties of the dust. | 
An oil dust which may be used for control of the oriental fruit 
moth and brown rot on peach consists of 60 pounds of dusting sulfur, 
35 pounds of dusting talc, and 5 pounds of lubricating oil. This 
should be applied at weekly intervals for a period of 4 to 5 weeks 
before harvest. It has little or no toxicity to the insect but acts as 
a mechanical barrier and irritant. 
A mixture which has been used for the plum curculio on peach 
consists of 80 pounds of dusting sulfur, 30 pounds of dusting tale, 
25 pounds of hydrated lime, 10 pounds of lead arsenate, and 5 pounds 
of lubricating oil. 
Oil dusts containing pulverized rotenone-bearing roots are used to 
control the pea aphid. 
Oil dusts may be prepared in the same manner as nicotine dusts. 
Thorough mixing to break up lumps is necessary. 
PARADICHLOROBENZENE 
Paradichlorobenzene (C,H,Cl,), known to the trade as P. D. B., 
is a white, crystalline compound. It volatilizes slowly at 80° F., has 
a distinctive odor, and the vapor formed is noninflammable and 
penetrating. 
Paradichlorobenzene is employed to a limited extent as a soil fumi- 
gant to kill various insect pests, such as root aphids, wireworms, and 
the sweetpotato weevil. Its principal use as an insecticide, however, 
is for the control of the peachtree borer. The crystals are spread in 
a circle around the base of the peach tree about 1 to'114 inches from the 
trunk and then covered with a mound of soil. This is done in the early 
fall or spring at rates varying from 14 to 2 ounces per tree, depending 
upon age. A solution in cottonseed oil is also applied as a paint in 
the control of the lesser peach borer. An effective mixture consists of 
1 pound of paradichlorobenzene dissolved in 2 quarts of cottonseed 
oil. It is sometimes necessary to warm the cottonseed oil to room 
temperatures to aid in dissolving the paradichlorobenzene. Apply 
only to well-defined infested areas of the trunks or limbs. 
Paradichlorobenzene crystals, at the rate of 1 pound per 100 square 
feet, are spaded into greenhouse soils for the control of the garden 
centipede. This treatment must be appled 3 weeks before replanting 
the beds. 
Caution.—Paradichlorobenzene should be stored in airtight 
containers to avoid loss by evaporation. Do not expose foodstuffs 
to the vapor of this chemical, as they absorb it and are then unfit 
for consumption because of a pronounced odor or taste. 
