Title Page
 Board of control and station...
 Table of Contents
 Specifications for the station...
 Field performance
 Proper dusting methods
 Historic note

Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 481
Title: The Florida citrus grove duster
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00027436/00001
 Material Information
Title: The Florida citrus grove duster
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 14 p. : ill. ; 23 cm.
Language: English
Creator: Prosser, David S
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1951
Subject: Spraying equipment   ( lcsh )
Citrus fruits -- Fumigation -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by D.S. Prosser ... et al..
General Note: Cover title.
General Note: "A contribution from the Florida Citrus Experiment Station"--T.p.
 Record Information
Bibliographic ID: UF00027436
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000925738
oclc - 18266094
notis - AEN6394

Table of Contents
    Title Page
        Page 1
    Board of control and station staff
        Page 2
        Page 3
    Table of Contents
        Page 4
        Page 5
        Page 6
    Specifications for the station duster
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
    Field performance
        Page 13
    Proper dusting methods
        Page 14
        Page 15
    Historic note
        Page 16
Full Text

Bulletin 481

(A Contribution from the Florida Citrus Experiment Station)

The Florida Citrus Grove Duster


Fig. 1.-The citrus grove duster in field operation.

July 1951


Frank M. Harris, Chairman, St. Petersburg
N. B. Jordan, Quincy
Hollis Rinehart, Miami
Eli H. Fink, Jacksonville
George J. White, Sr., Mount Dora
W. F. Powers, Secretary, Tallahassee

J. Hillis Miller, Ph.D., President3
J. Wayne Reitz, Ph.D., Provost for Agr.3
Willard M. Fifield, M.S., Director
J. R. Beckenbach, Ph.D., Asso. Director
L. O. Gratz, Ph.D., Asst. Dir., Research
Geo. F. Baughman, M.S., Business Mgr.3
Rogers L. Bartley, B.S., Admin. Mgr.8
Claranelle Alderman, Accountant


H. G. Hamilton, Ph.D., Agr. Economist 1
R. E. L. Greene, Ph.D., Agr. Economist
M. A. Brooker, Ph.D., Agr. Economist
Zach Savage. M.S.A., Associate
A. H. Spurlock, M.S.A., Associate
D. E. Alleger, M.S., Associate
D. L. Brooke, M.S.A., Associate'
M. R. Godwin, Ph.D., Associate
H. W. Little, M.S., Assistant
Tallmadge Bergen, B.S., Assistant
D. C. Kimmel, Ph.D., Assistant
A. L. Larson, Ph.D., Agr. Economist
Orlando, Florida (Cooperative USDA)
G. Norman Rose, B.S., Asso. Agr. Economist
J. C. Townsend, Jr., B.S.A., Agr.
Statistician 2
J. B. Owens, B.S.A., Agr. Statistician

Frazier Rogers, M.S.A., Agr. Engineer 1 -
J. M. Johnson, B.S.A.E., Agr. Eng.3
J. M. Myers, B.S., Asso. Agr. Engineer
R. E. Choate, B.S.A.E., Asso. Agr. En_.
A. M. Pettis, B.S.A.E., Asst. Agr. Eng.2

Fred H. Hull, Ph.D., Agronomist
G. B. Killinger, Ph.D., Agronomist 3
H. C. Harris, Ph.D., Agronomist
R. W. Bledsoe, Ph.D., Agronomist
W. A. Carver, Ph.D., Associate
Darrel D. Morey, Ph.D., Associate
Fred A. Clark, B.S., Assistant
Myron C. Grennell, B.S.A.E., Assistant
E. S. Horner, Ph.D., Assistant
A. T. Wallace, Ph.D., Assistant
D. E. McCloud, Ph.D., Assistant

T. J. Cunha, Ph.D., An. Husb.13
R. S. Glasscock, Ph.D., An. Husb.3
G. K. Davis, Ph.D., Animal Nutritionist
R. L. Shirley, Ph.D., Biochemist
J. E. Pace, M.S., Asst. An. Husb.3
S. John Folks, M.S., Asst. An. Husb.4
Katherine Boney, B.S., Asst. Chem.
A. M. Pearson, Ph.D., Asso. An. Husb.3
John D. Feaster, Ph.D., Asst. An. Nutri.
H. D. Wallace, Ph.D., Asst. An. Hush.3
M. Koger, Ph.D., An. Husbandman 3

E. L. Fouts, Ph.D., Dairy Tech. 3
R. B. Becker, Ph.D., Dairy Husb.8
S. P. Marshall, Ph.D., Asso. Dairy Husb.3
W. A. Krienke, M.S., Asso. in Dairy Mfs.3
P. T. Dix Arnold, M.S.A., Asst. Dairy Husb.2
Leon Mull, Ph.D., Asso. Dairy Tech.
H. Wilkowske, Ph.D., Asst. Dairy Tech.
James M. Wing, M.S., Asst. Dairy Husb.


J. Francis Cooper, M.S.A., Editor 3
Clyde Beale, A.B.J., Associate Editor3
L. Odell Griffith, B.A.J., Asst. Editor
J. N. Joiner, B.S.A., Assistant Editor 3 4

A. N. Tissot, Ph.D., Entomologist
L. C. Kuitert, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
F. A. Robinson, M.S., Asst. Apiculturist

Ouida D. Abbott, Ph.D., Home Econ.1
R. B. French, Ph.D., Biochemist

G. H. Blackmon, M.S.A., Horticulturist
F. S. Jamison, Ph.D., Horticulturist 3
Albert P. Lorz, Ph.D., Horticulturist
R. K. Showalter, M.S., Asso. Hort.
R. A. Dennison, Ph.D., Asso. Hort.
R. H. Sharpe, M.S., Asso. Horticulturist
V. F. Nettles, Ph.D., Asso. Horticulturist
F. S. Lagasse, Ph.D., Asso. Hort.2
R. D. Dickey, M.S.A., Asso. Hort.
L. H. Halsey, M.S.A., Asst. Hort.
C. D. Hall, Ph.D., Asst. Horticulturist
S. E. McFadden, Ph.D., Asst. Hort.
Austin Griffiths, Jr., B.S., Asst. Hort.
S. E. McFadden, Jr., Ph.D., Asst. Hort.

Ida Keeling Cresap, Librarian

W. B. Tisdale, Ph.D., Plant Pathologist 3
Phares Decker, Ph.D., Plant Pathologist
Erdman West, M.S., Mycologist and Botanist
Robert W. Earhart, Ph.D., Plant Path.2
Howard N. Miller, Ph.D., Asso. Plant Path.
Lillian E. Arnold, M.S., Asst. Botanist
C. W. Anderson, Ph.D., Asst. Plant Path.

N. R. Mehrhof, M.Agr., Poultry Husb.' 3
J. C. Driggers, Ph.D., Asso. Poultry Hush.

F. B. Smith, Ph.D., Microbiologist 13
GaylorJ M. Volk, Ph.D., Soils Chemist
J. R. Henderson, M.S.A., Soil Technologist 3
J. R. Neller, Ph.D., Soils Chemist
hathan Gammon, Jr., Ph.D., Soils Chemist
R. A. Carrigan. Ph.D., Biochemist3
Falph G. Leighty, B.S., Asst. Soil Surveyor'
G. D. Thornton, Ph.D., Asso. Microbiologist 3 4
Charles F. Eno, Ph.D., Asst. Soils Micro-
H. W. Winsor, B.S.A., Assistant Chemist
R. E. Caldwell, M.S.A.,,Asst. Chemist34
V. W. Carlisle, B.S., Asst. Soil Surveyor
James H. Walker, M.S.A., Asst. Soil
S. N. Edson, M.S., Asst. Microbiologist
William K. Robertson, Ph.D., Asst. Chemist
O. E. Cruz, B.S.A., Asst. Soil Surveyor
W. G. Blue, Ph.D., Asst. Biochemist

D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarian :
C. F. Simpson, D.V.M., Asso. Veterinarian
L. E. Swarson, D.V.M., Parasitologist
Glenn Van Ness, D'.V.M., Asso. Poultry.
G. E. Batte, D.V.M., Asso. Parasitologist



J. D. Warner, M.S., Vice-Director in Charge
R. R. Kincaid, Ph.D., Plant Pathologist
L. G. Thompson, Ph.D., Soils Chemist
W. C. Rhoads, M.S., Entomologist
W. H. Chapman, M.S., Asso. Agronomist
Frank S. Baker, Jr., B.S., Asst. An. Husb.

Mobile Unit, Monticello
R. W. Wallace, B.S., Associate Agronomist

Mobile Unit, Marianna
R. W. Lipscomb, M.S., Associate Agronomist

Mobile Unit, Pensacola
R. L. Smith, M.S., Associate Agronomist

Mobile Unit, Chipley
J. B. White, B.S.A., Associate Agronomist

A. F. Camp, Ph.D., Vice-Director in Charge
W. L. Thompson, B.S., Entomologist
R. F. Suit, Ph.D., Plant Pathologist
E. P. Ducharme, Ph.D., Asso. Plant Path.
C. R. Stearns, Jr., B.S.A., Asso. Chemist
J. W. Sites, Ph.D., Horticulturist
H. O. Sterling, B.S., Asst. Horticulturist
H. J. Reitz, Ph.D., Horticulturist
Francine Fisher, M.S., Asst. Plant Path.
I. W. Wander, Ph.D., Soils Chemist
J. W. Kesterson, M.S., Asso. Chemist
R. Hendrickson, B.S., Asst. Chemist
Ivan Stewart, Ph.D., Asst. Biochemist
D. S. Prosser, Jr., B.S., Asst. Horticulturist
R. W. Olsen, B.S., Biochemist
F. W. Wenzel, Jr., Ph.D., Chemist
Alvin H. Rouse, M.S., Asso. Chemist
H. W. Ford, Ph.D., Asst. Horticulturist
L. W. Faville, Ph.D., Asst. Bacteriologist
L. C. Knorr, Ph.D., Asso. Histologist 4
R. M. Pratt, Ph.D., Asso. Ent.-Pathologist
W. A. Simanton, Ph.D., Entomologist
E. J. Deszyck, Ph.D., Asso. Horticulturist
C. D. Leonard, Ph.D., Asso. Horticulturist
I. Stewart, M.S., Asst. Biochemist
W. T. Long, M.S., Asst. Horticulturist

R. V. Allison, Ph.D., Vice-Director in Charge
Thomas Bregger, Ph.D., Sugar Physiologist
J. W. Randolph, M.S., Agricultural Engr.
W. T. Forsee, Jr., Ph.D., Chemist
R. W. Kidder, M.S., Asso. Animal Hush.
T. C. Erwin, Assistant Chemist
C. C. Seale, Asso. Agronomist
N. C. Hayslip, B.S.A., Asso. Entomologist
E. A. Wolf, M.S., Asst. Horticulturist
W. H. Thames, M.S., Asst. Entomologist
W. N. Stoner, Ph.D., Asst. Plant Path.
W. A. Hills, M.S., Asso. Horticulturist
W. G. Genung, B.S.A., Asst. Entomologist
Frank V. Stevenson, M.S., Asso. Plant Path.
R. H. Webster, Ph.D., Asst. Agronomist
Robert J. Allen, Ph.D., Asst. Agronomist
V. E. Green, Ph.D., Asst. Agronomist
J. F. Darby, M.S.A.. Asst. Plant Path.
H. L. Chapman, M.S.A., Asst. An. Hush.
Thos. G. Bowery, Ph.D., Asst. Entomologist

Geo. D. Ruehle, Ph.D., Vice-Dir. in Charge
D. O. Wolfenbarger, Ph.D., Entomologist
Francis B. Lincoln, Ph.D., Horticulturist
Robert A. Conover, Ph.D., Plant Path.
John L. Malcolm, Ph.D., Asso. Soils Chemist
R. W. Harkness, Ph.D., Asst. Chemist
R. Bruce Sedin, Ph.D., Asst. Hort.

William Jackson, B.S.A., Animal Husband-
man in Charge 2

W. G. Kirk, Ph.D., Vice-Director in Charge
E. M. Hodges, Ph.D., Agronomist
D. W. Jones, M.S., Asst. Soil Technologist

R. W. Ruprecht, Ph.D., Vice-Dir. in Charge
J. W. Wilson, Sc.D., Entomologist
P. J. Westgate, Ph.D., Asso. Hort.
Ben. F. Whitner, Jr., B.S.A., Asst. Hort.
Geo. Swank, Jr., Ph.D., Asst. Plant Path.

C. E. Hutton, Ph.D., Vice-Director in Charge
H. W. Lundy, B.S.A., Associate Agronomist

G. E. Ritchey, M.S., Agronomist in Charge

E. L. Spencer, Ph.D., Soils Chemist in Charge
E. G. Kelsheimer, Ph.D., Entomologist
David G. Kelbert, Asso. Horticulturist
Robert O. Magie, Ph.D., Plant Pathologist
J. M. Walter, Ph.D., Plant Pathologist
Donald S. Burgis, M.S.A., Asst. Hort.
C. M. Geraldson, Ph.D., Asst. Hort.
W. G. Cowperthwaite, Ph.D., Asst. Hort.

Watermelon, Grape, Pasture-Leesburg
C. C. Helms, Jr., B.S., Asst. Agronomist

Strawberry-Plant City
A. N. Brooks, Ph.D., Plant Pathologist

A. H. Eddins, Ph.D., Plant Path. in Charge
E. N. McCubbin, Ph.D., Horticulturist

A. M. Phillips, B.S., Asso. Entomologist2
John R. Large, M.S., Asso. Plant Path.

Frost Forecasting-Lakeland
Warren 0. Johnson, B.S., Meteorologist2

1 Head of Department
2 In cooperation with U. S.
3 Cooperative, other divisions, U. of F.
4 On leave.


INTRODUCTION ......................... .......... .................... 5

SPECIFICATIONS FOR THE STATION DUSTER .......................-. --.. ------------- 7

Dust Storage ...................... ..... ----- ----- --------------- 7

Duster Housing .....................------... ---- ---- ------------- 7

Dust Hopper ................................-- ------- ---- ---------- 9

Blow er ............................ ...................... ..... -- .-- 9

Distributing Fins ............................---......--- -------------- 10

Fan and Engine Drive .....................--- -------- ----------- 10

Fire H azard ..................... ................. ......... ...... 10

Trailer or Truck Mounting ......................--........-....... .. ----- 11

Cost ..............------....----.......-.. --- ---- ----------------. 11

FIELD PERFORMANCE ...................-------------........... ------- 13

PROPER DUSTING METHODS ................-...-....... ..----... --..---. 14

SUM M ARY .......... ---........... ................................................................................... ------- 15

The Florida Citrus Grove Duster

The expense of producing good citrus crops is dependent in
part upon the cost of applying various chemical materials to the
trees to control diseases and insects and to prevent nutritional
deficiencies. Of the tremendous quantities of these chemical
materials applied each year a substantial portion is used in the
form of dusts. These dusts are generally applied by machines
that may be roughly classified into two categories-hand-outlet
dusters and mechanical or fixed-outlet dusters.
Until recent years grove dusting has been carried out almost
entirely with hand-outlet machines, although new types and
designs of fixed-outlet dusters may be found more frequently
today, particularly where large acreages are to be maintained.
The typical hand-outlet duster is usually composed of a small,
high speed, high velocity blower driven either from a tractor
power take-off or by a separate gasoline engine. The dust is
placed in a hopper from which it is fed by a rotating arm through
a metering gate and into the high speed blower. The air and
dust mixture thus obtained is then distributed to one or more
flexible tubes leading out from the blower housing. Operators
standing on the rear of the unit manipulate these tubes from
side to side and up and down in order to apply the air-dust mix-
ture to the trees as the unit progresses through the grove. In
some cases tubes are mounted in multiple and are rigidly fixed
in position, thus giving rise to a simple fixed-outlet machine.
More recent developments include the substitution of a single
distributor head containing vertical fins shaped like a pie wedge
in place of the individual tubes. The blower discharges into
the fins and from there the air and dust mixture is thrown out
in a fan spread. This latter modification further developed into
the large volume machines mounted on truck bodies or trailers
which utilize industrial engines, large volume fans, and huge
distributing fins to throw mixtures over a wide arc.
To overcome some of the obvious disadvantages of previous
1Assistant Horticulturist, Associate Chemist, Entomologist and Asso-
ciate Entomologist, respectively, Florida Citrus Experiment Station, Lake

Florida Agricultural Experiment Stations

dusting equipment, work was started at the Citrus Experiment
Station in 1948 to produce a relatively low cost duster which
could be assembled from standard parts. Two major difficulties
have been noted with hand-operated dusters. In most groves
the operator is subjected to a steady beating from overhanging
branches. This has been so severe in many cases that his major
interest is to dodge limbs and stay on his dusting platform.
Thus, proper attention is not given to the dust distribution job
being performed. Along with this is the fatigue problem in-
volved in manipulating the dust outlet for a period of several
hours. An operator can dust properly for a short while, but
the thoroughness of coverage decreases as he becomes fatigued.
As a result, dust is excessive on certain areas of the trees and
on other areas little or no dust is deposited. This type of dust
job is a common occurrence throughout the citrus-producing
area of Florida.
Other disadvantages have been noted with regular dusters.
In the case of the double-outlet models three laborers are needed,
and with the single-outlet model each tree row requires two
trips with the duster. In either instance labor costs are higher
than would be required with a large double-outlet machine.
Another point is that dust cannot be satisfactorily placed in
the hopper of a regular duster while it is in operation. Some
machines have been poorly constructed and mechanical diffi-
culties have occurred. This was true of only some dusters, but
these few have caused criticism of all.
A large volume double-outlet machine introduced into Florida
in the early 1940's from California eliminated some of these
difficulties. However, it was expensive to build under Florida
conditions and, for practical purposes, was unavailable to Florida
citrus growers in the years following World War II. Its cover-
age is weak in the tops of the trees and the design is such that
the operator is still exposed to a buffeting about by branches
on the trees. Another objection to this duster is that fruit
leaves sometimes drop into the hopper when it is being filled
while it is in operation.
The duster developed by the Citrus Experiment Station and
described here has been termed the Florida citrus grove duster
or "Station duster." In operation it requires only two laborers;
a driver and one man to fill the dust hopper. The latter is com-
pletely protected from all branches." He has a working space
such that he is free to add dust to the hopper as needed and is

The Florida Citrus Grove Duster

also free to regulate the rate of flow of the insecticide. The
duster is built with standard parts and can be assembled at a
reasonable cost in any good machine shop. It may be mounted
on either a trailer or truck bed and can be powered with either
a gasoline engine or a power take-off. Many improvements and
modifications are possible, but any machines built to the specifica-
tions presented here should do a reasonably thorough job.

Specifications for the Station Duster
The completed unit, pictured in field operation in Fig. 1, is
built, on a 6-inch steel channel frame mounted on a second-hand
truck axle, equipped with wheels and tires. The maximum
allowable width of the assembly is approximately 4 feet to in-
sure easy passage through all types of grove. Referring to the
detailed duster assembly (Fig. 2), it is seen that the fan, intake
air duct, hopper and distributing fins are mounted as one unit
on the rear of the chassis, while the engine, engine cover, trans-
mission and driving controls are mounted forward of the axle
and to one side. The engine assembly is covered with a 16-
gauge mild steel hood which is sturdy enough to support many
bags of dust on the flat top.
Dust Storage.-Balancing these two main blocks of machinery
on either side of the axle enables the duster to be easily handled
when unloaded and allows for hitching without the use of jacks.
In operation, the weight of the operator and the dust supply
exerts sufficient leverage forward of the axle to hold the hitch
steady and prevents bucking and jumping on rough terrain.
Dust storage space on the floor immediately forward of the
operator's space holds approximately 700 pounds of dust and
the engine housing cover accommodates up to another 700
pounds, so that the total dust load that may be easily carried
is approximately 1,400 pounds with the hopper empty. The
unloaded trailer, with all necessary machinery and accessories,
weighs 3,100 pounds. The operator's station is between the
dust supply and the hopper and slightly forward of the axle.
This position is not only convenient for filling the hopper but
also promotes steady footing on rough ground.
Duster Housing.-The operator is fully protected from
branches and limbs by the 16-gauge steel front shield and the
16-gauge expanded metal sides and top. The openings in the
expanded metal should be approximately 1/2" x /'", or small

Fig. 2.-Diagram of trailer-mounted duster assembly.

The Florida Citrus Grove Duster

enough to prevent fruit and leaves from falling inside and jam-
ming the dust hopper. The operator may sit on the engine cover
or he may stand on the floor which is kept clean by a stream of
air drawn into the fan intake through a slot cut beneath the
dust hopper for this purpose.
Dust Hopper.-The dust hopper has a capacity of about 11/
bags of standard dusting sulfur and is constructed with a self-
cleaning device and a variable outlet. It may be noted that the
hopper is of smaller capacity than usually found in most dust-
machines. However, due to the facility and comfort with which
the operator may refill the hopper, this is deemed an asset,
since it prevents packing of dust and jamming of the feeding
mechanism by the weight of a large quantity of dust. The
operator may set the size of the hopper outlet by an indicator
lever so that an accurate amount of dust is metered out per
tree, regardless of tractor speed or type of dust.
Blower.-The blower is of the standard centrifugal type
known as backward-curved blade or limit-load, deriving its
name from the shape of the fan blade which is curved back-
wards from the direction of rotation. It is capable of delivering
approximately 20,000 cubic feet of air per minute at five inches
static pressure, with about 25 horsepower required from the
power source. If a tractor power take-off is used in place of a
gasoline engine as the power source it must supply approxi-
mately 30 horsepower to allow for losses in transmission and
in driving the hopper agitator.
The advantages of a fan of this type are high efficiency, quiet
operation and high rotative speed, lending itself well to oper-
ation with gasoline engines. Furthermore, the blades are wide
and their peculiar shape prevents build-up of dust on the blades,
even when the outside temperature is below the dew point.
This is particularly important, inasmuch as most dusting is
done at a time when the air is filled with moisture in order to
have a film of water on the trees to which the dust will stick.
In addition, there have been many breakdowns with various
machines due to the over-weighting of the fan wheel from ac-
cumulated dust, causing the wheel to fly apart from unbalanced
strain or vibration. Maintenance and cleaning expense is
naturally reduced with no build-up and as a result of this char-
acteristic the dust feeding mechanism or hopper can feed directly
into the suction side of the fan through the air duct where the

Florida Agricultural Experiment Stations

dust and incoming air are mixed. However, due to the corrosive
action of some of the dusts on metal, it is advantageous to clean
the machine occasionally with a water hose.
Distributing Fins.-The air-dust mixture from the fan out-
let is distributed to two air-discharge fins, one directed to each
side. Each fin consists essentially of a long, narrow, triangular
box with an outlet slot along one side. The fin is tilted back-
wards slightly at an angle of 10 degrees from the vertical so
that the air and dust mixture is discharged in an upward direc-
tion with a velocity of approximately 70 miles per hour. This
is considered advantageous, since it is difficult to get dust on
the underside of the leaves and this upward motion tends to
correct the difficulty. The slot is 11/4 inches wide and 6 feet
long. Since the bottom of the fins are approximately 5 feet
above ground, some provision must be made to deliver dust to
the portion of the tree below this level. This is accomplished
by cutting a pattern of smaller vertical slots in the fan casing
down to a point where the bottom of the tree is adequately
covered. A satisfactory pattern is shown in the accompanying
Fan and Engine Drive.-The fan is driven by three C section
V-belts from a drive shaft attached to the engine transmission
through a flexible coupling. If an automobile engine is used
for the power source a moderate speed range from about 1,600
to 2,000 RPM is recommended. In this particular case the fan
is turned at 1,500 RPM and the engine at 1,900 RPM. An over-
sized radiator is used to insure that the engine temperature
will not become excessive. In addition, the Z-shaped air-inlet
duct is attached in such a position as to draw fan intake air
through the radiator, across the engine and into the fan. This
serves an additional purpose in that it warms the air before
the dust is mixed with it, thus helping to prevent caking and
sticking of the dust on damp dusting runs. The engine tempera-
ture never rises above 170 F., even under severe operating con-
ditions, while gasoline consumption averages about three gallons
per hour under full load. Auxiliaries include a generator, starter
and electric system for illumination at night, as well as an in-
strument panel for checking the engine in operation.
Fire Hazard.-To reduce the possibility of fire, all parts are
grounded together and a stiff spring is attached to the chassis,
which drags the ground and discharges accumulated static elec-

The Florida Citrus Grove Duster

tricity. A spring is preferred to a chain or wire, since the spring
will dig into the moist soil beneath the surface.
Trailer or Truck Mounting.-The duster is shown as a trailer
mounted unit in Figs. 1 and 2 and in the side view, Fig. 3.
However, if truck mounting is desired a satisfactory assembly
may be seen in Fig. 4. With either mounting the operation is
exactly the same and the outlet fins are maintained in their
identical height and position with respect to the ground.
Cost.-The cost of construction of the machine has been pur-
posely held as low as possible by use of standard parts through-
out and by restricting the design to one that may be easily built
in local shops or garages equipped with an electric welder and
an oxyacteylene torch.
Fig. 3.-Side view of duster, showing position of operator.

fihl I

Florida Agricultural Experiment Stations


The Florida Citrus Grove Duster

Field Performance
The Station duster has undergone extensive field trials. Actual
grove use has indicated that the unit is rugged and easily
maneuverable in the field. The fins have sufficient strength to
withstand severe blows from overhanging limbs. The design
of the shield and housing tends to allow the overhanging tree
limbs to slide along with a minimum of damage to the fruit.
This duster has been compared with commercial dusters as to
general insecticide distribution on the tree and as to efficiency
of insecticides thus applied. It has been used by commercial
growers in large acreage trials and under these conditions has
rendered satisfactory service. Some examples of experimental
results, presented in Tables 1 and 2, are representative of re-
peated trials performed at the Citrus Experiment Station.


Type Ratio of Material per Square Centimeter of Leaf Area
Machine Lower 1% of Lower Upper
S Tree Middle 14 Middle 14 Top 1A
Large blower ....... 5 2.7 2.5 1
Small blower ........ 10 6 4 1
Hand machine ..... 2 4 4 1
Station duster ...... 1 2 2 1


% Leaves Infested with Purple Mites
Type Machine Before 1 Week After 2 Weeks After
Dusting Dusting Dusting
Hand outlet duster ............ 80 2 8
Large blower duster ........... 65 12 5
Station duster ....... ........ 75 2 2

Table 1 is designed to show the general dust distribution pat-
tern on a tree following the use of four different dusters. These
are composite results from a number of different trials. If the
amount of dust in the top is considered as unity, a comparison
can be made with other parts of the tree. For example, the
Station duster applied the same amount of dust to the top as to
the bottom, but applied twice as much in the center of the tree.

Florida Agricultural Experiment Stations

As contrasted with this, the small blower fixed outlet machine
deposited 10 times as much dust in the lower part of the tree
as in the top. In the case of the hand-operated machine, results
were extremely variable and were related to the efficiency with
which the operator handled the outlet tube. The hand-operated
machine is capable of excellent results, but its field perform-
ance is limited by the physical abilities of the operator and
results tend to be erratic. The data in Table 1 demonstrate
that the Station duster tends to give more uniform coverage
than the other models tested. The larger blower fixed-outlet
model appeared to approach the Station duster in overall per-
formance more closely than did the other machines tested.
Table 2 presents typical results obtained in tests at the Citrus
Experiment Station' for the control of purple mites. Experi-
ments for the control of rust mites gave similar results. All
these experiments were on relatively small plots under field
conditions. Because the plots averaged less than two acres in
size, all could be treated in a relatively short period of time.
This made it possible for all dusters to be run at maximum
operating efficiency. A man could readily stand and use a hand-
operated machine with maximum efficiency throughout the
period. Thus, differences were not as large as might be ex-
pected under continuous commercial dusting operations in which
operator fatigue becomes a factor. It has been adequately
demonstrated that the Station duster is as good as or better
than any of the other dusters tested for applying dusts for rust
mite and purple mite control.
The application of copper dusts for melanose control has not
been satisfactory, regardless of the type of duster used.

Proper Dusting Methods
No duster can do a satisfactory job unless operated at the
proper speed and in the proper manner. It has been a common
practice among many citrus growers to apply small amounts of
dust at an excessive rate of travel. This type of application
will not give good results with the duster described here, nor
does it give good results with any duster that is presently avail-
able in the commercial field. For maximum results a duster
should be driven at no higher speed than three miles per hour
and even slower speeds would be desirable. It is absolutely
essential that both sides of the tree be dusted. When only one

The Florida Citrus Grove Duster

side is dusted there is a marked tendency for poor control on
the opposite side of the tree and for more injured fruit to appear
in that area at a later period. Since chemicals applied as dusts
are generally not as efficient as when applied as sprays, it is
very essential that a thorough dust coverage be obtained. If it
requires 11/ pounds of sulfur in a spray to control rust mites
on a given tree, it will require at least 11h pounds of sulfur ap-
plied as a dust, but it has been common practice to apply less
material with a duster than with a sprayer. This is a poor
policy and for satisfactory control growers should apply as much
material per tree with a duster as with a spray machine.

An improved type of duster has been developed for use in
citrus groves in Florida. Specifications for its construction are
shown and field results with it are presented. This duster com-
bines the following advantages:
1. Durable construction from standard parts at reasonable
2. Versatility of power source (power take-off or gasoline
motor) and mounting base (truck or trailer).
3. Complete protection for operator.
4. Minimum labor requirement.
5. Non-clogging dust hopper and fan.
6. Features for improved fire protection.
7. More uniform insecticide distribution than heretofore ob-
8. Insecticide results equal or superior to those obtained with
other dusters.
9. Double-outlet delivery.
10. Economical maintenance.


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

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of Florida

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