A laboratory apparatus and procedure for testing aqueous spray suspensions as insecticides


Material Information

A laboratory apparatus and procedure for testing aqueous spray suspensions as insecticides
Physical Description:
5, 2 p. : ill. ; 27 cm.
McGovran, E. R
Mayer, E. L
United States -- Bureau of Entomology and Plant Quarantine
U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:


Subjects / Keywords:
Spraying equipment -- Testing   ( lcsh )
Insecticides   ( lcsh )
federal government publication   ( marcgt )
non-fiction   ( marcgt )


General Note:
Caption title.
General Note:
General Note:
"May 1943."
Statement of Responsibility:
by E.R. McGovran and E.L. Mayer.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030352281
oclc - 781865041
System ID:

Full Text

r and Plant Qurantine


and1.L. Mayor
A Investigation

pes of laboratory apparatus for
one type the spray is applied to
,ed plant. In the other type, do-
i applied to a relatively moth
m of a fruit. The spray L even-
aLU drops, to prevent large accu-
ial from fotving in certain areas
a suspension is sprayed to form a
Sthe sane volume closely packed
relatively uniform deposit should
sidered as a unit area. Therefore,
wt is greeter than the area coy-
bable that the insect will ingest
do, This my not be true, how.
wailer area, becausewithin an
osit my not be uniform, owing to
within a drop and other factors-*

m consisted of a cylinder or
feet in diameter. Light ms
Luleid window (B) in the rem'
.The floor o the
top and uas made of half.-
As screen was the settling
of the laboratory (I)* The
the contents of the tower
near the floor. The imer

atomizer ad drew the liquid up through
(I) about 4m. in diameter. The spr
bnd and a .isll chamber in the liquid
by the straight tube because the larga
collected near this beM and also in t
sprayer uas mounted below the acremi I
upwad at about the leve~lof this floc
emitted accurate adjustment of the dire
belew the sprayer was a container (M)
which was held in place by a threaded
tien the liquid was raised verticaUy
and sprayed out sothat settling in th
eliminated. When the air presaurs a
the tube fell back into the container.
per square inch, operated the sprayer.
and off at a valve (0) located outsid.


The agtator used in prelimina
posits. Fer emawple, chemical analysis
fraction of paris green deposited 14,
a coarse fraction 70 inicrogram per eq
equal weights of the three fractions
water. / The agitator adopted gave d
18.2 icrograms per qua"e centimeter
coarse fractions, rospectvely. These
in deposit with increase in particle a
suotie pipe of the sprayer opening ne
ontaner. To obtain umifom deposits
of each fraction used was adjusted to
A mony eope-imel materials that ar
settle or rise rapidly ho_ suspended
demonstrate tkat the efficiecy of the
termite the deposit of insecticide ebt
- w i m _8 od o

The a


The spray suspension was agitated by a rubber blade which
rotated in a horizontal plane near the bottom of the container (M).
This blade was mounted on a vertical shaft (J), which was driven by
a flexible shaft (1) from a variable-speed motor (H) mounted out-
side the spray tower. The agitator speed was adjusted to keep the
materials suspended without forcing air bubbles into the spray sus-


Following prelimnary tests to center the spray discharge,
several applications were made on six pairs of glass slides 8 by
10 cm. arranged in two concentric circles 10 am. apart on the
floor of the chamber. The average deposit on the slides in the
inner circle was 22 percent greater than on those in the outer

To obtain a uniform deposit on leaves, after half the spray
suspension had been applied, the position of the leaves was re-
versed before the other half was applied. The leaves were then
turned over and the other side was treated in a similar manner.

To check further on the uniformity of the deposit at dif-
ferent positions, spray applications were made on six glass
slides arranged on the screen floor in a single circle equidistant
from the center and the outside wall.' After six to nine replica-
tions of each of three fractions of paris green-fine, medium, and
coarse-the average deviation from the mean deposit of all frac-
tions was 7.2 percent, and the average individual variations from
the mean deposit in each application ranged from 1.9 to- 1.42 per-
cent. As these tests varied both in the concentration and the
particle size of the insecticide used, they appear to give some
idea of the variation that might be expected in this method.
Casual observations had shown that near the center of the

spray floor and near the wall the deposits were not uniform.


Flat leaves, such as those of certain varieties of turnips
and beans, were cut and the petioles inserted in vials of water
through one-hole stoppers. The petioles fitted in the stopper
tight enough so that air entered the vials as the leaf withdrew
the water but the water did not leak out (fig. 2, A). The leaves
witl the vials attached were placed on wooden paddles of approx-
imately the same shape and size as a single leaf. The vial was
attached to the paddle with rubber bands, and the leaf blade was
held in a horizontal position by the points of pins that extend-
ed up from the paddle. When the leaf was turned over to spray

Leaves were placed on the screi
tant between the spray nozzle and the
When chemical analyses of a deposit wi
glass slides, 8 by 10 cm., were laid I
was closed and the vent through the e
the blower was not started. The vavi
and the spray stream rose in the chami
leaves on the screen floor. The screo
to pass into the settling chamber bel,
side with little interference, and thi
eddy currents which would tend to disi
of the spray. When half the amount o.
the desired deposit had been sprayed.,
spray allowed to settle for 1 minute.
then raised slightly and the blower r
any spray that might have settled une,
being moved, and also to reduce the hi
The position of the leaves was then r4
spray suspension used was replaced in
tion repeated to finish the spray depj
leaves. The leaves were then turned 4
sprayed, except when one side of the


Either Mexican bean beetles or
as test insects.

When Mexican bean beetles were
with the vial of water on its petiole
dish together with 10 to 20 adults or
by a screen cover, Mortality counts i
hours, and subsequently at 48- or 72-I
tality rate approximated that occurrii
foliage. The treated leaves were rep.
after 48 or 72 hours and subsequently
The leaf surface consumed was measure
meter- ruled paper.

Wha southern arzqworm larvae were used as test insects,
turnip or collard leaves were sprayed. As the southern armyworm
tend to be cannibalistic, especially when poisoned, the larvae
were confined individually (fig. 2, B-F). The blade of a sprayed
leaf was laid on 16-mesh screen tacked to a 12-inch length of 6-
inch board. The vial was fastened to the board with a rubber bani,
A screen cage 2 1/4 by 6 1/4 by 3/4 inches, divided into 5 sections
2 1/4 by 1 1/4 inches, was placed on each side of the midrib of the
leaf. The ends of the screen wires that formed the sides and par-
titions pierced the leaf blade and made close contact with the
screen attached to the board below the leaf. The sides of the
cages had been treated with an acetone solution of celluloid to add
rigidity and also to separate the larvae more completely. One
fifth instar was enclosed in each section of the cage, which was
then placed on the leaf and secured with wooden strips and rubber
bands. Mortality counts were made in the same manner as for Mexi-
can bean beetles.


A laboratory apparatus and a method of applying spray sus-
pensions are described. The spray stream is discharged vertical-
ly upward and the drops of spray fall back on the surface to be
treated. This method gives a relatively uniform deposit of spray
material, and a number of excised leaves can be treated simultan-
eously. A cage for confining a number of larvae individually on
an intact leaf is described.





i .

Figure 2.-Caging larvae individually on a sprayed leaf.
A Leaf in position to be sprayed; B, wooden strips and
rubber bands to hold cage on leaf; C., cage with five
larvae, ventral view, ready to invert and place on leaf
in position D j E. second cage already in place; F base-
board with leaf and one cage in place.


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