LIBRARY 
 3TATE PLANT BOARD 
 , September 19^3 ET-2U 
 
 1 UNITED STATES DEPARTMENT OF AGRICULTURE 
 
 i Agricultural Research Administration 
 
 Bureau of Entoaology and Plant Quarantine 
 
 A DUSTER FOR LABORATORY EXPERIMENTS WITH INSECTICIDES 
 
 By F. H. Harries 
 Division of Truck Crop and Garden Insect Investigations 
 
 The apparatus shown in figure 1,A, was designed to apply snail 
 weighed charges of dusts evenly to plants and leaves in laboratory ex- 
 perinents with insecticides and for use in dusting the pea aphid under 
 controlled temperature and humidity conditions while in a natural or 
 undisturbed condition on the plants. The duster (fig. 1,A) consisted 
 of a bell Jar, an electric mixer with a variable speed transmission, 
 and the specially constructed parts shown in figure 1,B and C. The 
 funnel, or hopper (fig. 1>B), was attached rigidly to the frame of the 
 mixer, and the shaft (fig. 1,C) was mounted in a chuck on the vertical 
 drive shaft of the motor so that tfie metal disc would spin freely in 
 close contact with the lower edge of the funnel. The duster operated 
 by driving a dust charge from the hopper by centrifugal force through 
 a slight clearance space between the revolving disc and the lower edge 
 of the funnel, where it was finely dispersed under the bell Jar and 
 swirled about the plant and among the leaves by the action of a small 
 fan. 
 
 The base for mounting the motor was made by sawing a short 2" 
 by A" piece of lumber in half longitudinally and fitting and bolting 
 the two pieces of wood tl^tly together around the neck of the bell 
 Jar* The motor was placed over a pad of sponge rubber to prevent ex- 
 cessive vibration and was held in place by bands cut from the inner 
 tube of an automobile tire. The funnel, or hopper (fig. 1,B), was 
 made from a bakelite spark plug cover by cutting out the closed end 
 and was cemented inside a metal collar and attached to the frame of 
 the mixer by small metal brackets. The shaft (fig. 1,C) was made by 
 machining and cutting threads on a short piece of brazing rod. The 
 disc was made of sheet copper about 0.04. inch in thickness. The fan 
 was constructed froa. a disc of the same material by cutting in f ran 
 the edge toward the center at 45*'degree intervals and twisting the 
 sections at a 45-degree angle with the original plane. The disc and 
 fan were mounted in the desired position on the shaft by means of thin 
 lock nuts. Rubber washers were used on each side of the disc to give 
 some flexibility in its mounting on the shaft. When the shaft was 
 fastened in the chuck of the mixer, emery powder was used to grind the 
 lower edge of the funnel smoothly in the same plane as that of the disc 
 so that the latter part would revolve freely in close contact with the 
 hopper. To prevent dust from collecting in the neck of the bell Jar, 
 
2 - 
 
 this space was closed off by a gasket of cork or sponge rubber fitted 
 around the lower part of the fxinnel (fig. 1,A). Tufts from a camel' s- 
 hair brush were cemented to the lower side of the disc to sweep the op- 
 posite surface of the glass and prevent dust from collecting at this 
 point as it was tiirown from the lower edge of the dust hopper. 
 
 The speed of the disc and fan was regulated near the maximum rat« 
 of 3,500 r,p,m. by raising the horizontal wheel of the transmission to a 
 level near the outer edge of the vertical wheel (fig. 1,A). The rate of 
 distribution of the dust was controlled by moving the adjustment screw 
 very slightly to regulate the amount of clearance space between the disc 
 and lower edge of the dust hopper. 
 
 In use the duster was placed over an infested plant, and a weighed 
 charge, usually of 50 or 100 mg. of dust, was transferred to the hopper 
 and brushed cleanly to the bottom with a small camel* s-hair brush. With 
 the aid of a stop watch and an interval timer the duster was operated for 
 30 seconds to distribute the dust and then was left in position for an 
 additional period of 3 minutes to pen&it most of the dust to settle down. 
 
A 
 
 MOTOR 
 
 PONGE-RUBBER PAD 
 
 WOODEN 
 BLOCK 
 RUBBER BANDS 
 
 GLASS BELL JAR 
 
 h. 
 
 B 
 
 
 RUBBER WASHER 
 
 WOODEN 
 PANEL 
 
 Figure !• — Diagram of duster showing details of construction. 
 

 UNIVERSITY 
 
 OF 
 
 -LORIDA 
 
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