detection and quantification of nursery spray penetration

detection and quantification of nursery spray penetration
DETECTION AND QUANTIFICATION OF NURSERY SPRAY
PENETRATION AND OFF−TARGET LOSS WITH ELECTRON
BEAM AND CONDUCTIVITY ANALYSIS
C. R. Krause, H. Zhu, R. D. Fox, R. D. Brazee, R. C. Derksen, L. E. Horst, R. H. Zondag
ABSTRACT. Spray penetration and off−target loss from a conventional, air−assist, axial−fan sprayer and a high−clearance,
boom−type sprayer were investigated in Honey Locust (Gleditsia triacanthos) and Canadian Hemlock (Tsuga canadensis) trees
located in two different production nurseries. Aqueous tracer solutions of either Ca(NO3 )2 foliar fertilizer or Cu(OH)2 fungicide
were used in the experiments. Spray deposition distributions within canopies and off−target loss to drift and the ground were
assessed via residues collected on foliage, electron microscope stubs, artificial plates, vertical and ground−level profile plastic
tapes, and high−volume air samplers. Electron beam analysis (EBA) was used to assay residues on stubs, leaves, and needles
placed and collected at several locations and heights in the canopy. Plastic tape samples were evaluated with a laboratory spray
deposit analyzer using a conductivity detector. Both assessment methods used in the present study were useful for detection and
quantification of Ca or Cu spray penetration within nursery canopies. The average spray deposit on upper surfaces of leaves
was three times that deposited on lower surfaces within the Honey Locust trees. Spray deposit at the top of Canadian Hemlock
tree canopies was 14 times higher than that at the middle and bottom of canopies. Spray deposit on ground targets greatly
decreased as the distance from the spray path increased in both nurseries; however, airborne spray deposits did not decrease
as much with increasing downwind distance as ground deposits.
Keywords. Electron beam analysis, Nursery crops, Penetration, Pesticide, Spray drift.
H
orticulture industries generally produce high−value crops, usually on smaller acreage operations
than field crops. Nurseries may range in size from
a few acres to several hundred acres depending on
the varieties of stock grown. While horticultural industries use
less total volume of pest control materials, the variety of those
materials and frequency of use is greater due to the vulnerability of ornamental and food−use crops to many insect pests and
diseases.
The nursery and horticulture industry is one of the fastest
growing enterprises in U.S. agriculture. It produces over 10%
of all income from agricultural products. Many of the products
are attacked by pests and require sprayed chemical or natural
pest control agents. Some research on spraying nursery stock
Article was submitted for review in June 2003; approved for
publication by Power & Machinery Division of ASAE in January 2004.
Presented at the 1997 ASAE Annual Meeting as Paper No. 975006.
Mention of trade names or commercial products in this article is solely
for the purpose of providing specific information and does not imply
recommendation or endorsement by the U. S. Department of Agriculture
and The Ohio State University.
The authors are Charles R. Krause, Plant Pathologist, Research
Leader, Heping Zhu, ASAE Member Engineer, Agricultural Engineer,
Robert D. Fox, ASAE Member Engineer, Agricultural Engineer,
Richard C. Derksen, ASAE Member Engineer, Agricultural Engineer,
Ross D. Brazee, ASAE Member Engineer, Senior Research Scientist, and
Leona E. Horst, Plant Pathologist, USDA−ARS Application Technology
Research Unit, Wooster, Ohio; and Randall H. Zondag, Commercial
Horticultural Agent and Chair, Ohio State University Extension, Lake
County, Ohio. Corresponding author: Heping Zhu, USDA−ARS
Application Technology Research Unit, Agricultural Engineering
Building, 1680 Madison Avenue, Wooster, Ohio 44691; phone:
330−263−3871; fax: 330−263−3670; e−mail: zhu.16@osu.edu.
has been conducted, mainly on Christmas trees (Groszkiewicz
et al., 1991; Groszkiewicz and Hilton, 1991), but widespread
spray trials have not been reported in the literature. Based on
the experience with measuring spray deposit (Hall et al.,
1975), canopy penetration (Franz et al., 1987, Khdair et al.,
1994), drift from spraying fruit trees (Fox et al., 1993), and
electron beam analysis (EBA), a combination of scanning
electron microscopy, energy dispersive x−ray analysis, and
digital image analysis (Krause, 1985; Krause and Powell,
1986; Krause et al., 1996; Krause et al., 1997; Zhu et al., 1997),
experiments were conducted at production nurseries to assess
the performance of two grower application programs.
Bache and Johnstone (1992) have stated that more precise
knowledge of fungicide coverage and plant canopy penetration is required to maximize the effectiveness of chemical and
biological crop management strategies. Many types of collectors have been used to measure deposits in plant canopies and
downwind deposits of spray drift. Salyani and Whitney (1988)
evaluated a fluorescent tracer and copper as tracers for spray
deposit experiments in citrus. They measured similar spray
deposits using both tracers on leaves and on artificial targets,
but the colorimetic results with copper appeared more stable.
Miller et al. (1992) compared the collection efficiencies of
Teflon spheres and flat cards. They conducted still−air studies
and found similar deposition, but greater wind speeds reduced
deposits on flat cards compared to spheres mounted above the
ground. Miller (1993) reviewed several sampling techniques
used to measure the spray drift.
Many nurseries operate in areas close to residential districts
and urban or suburban areas. Due to the circumstance of
nursery crop production, advanced sampling techniques are
needed to efficiently and accurately detect spray distributions
Transactions of the ASAE
Vol. 47(2): 375−384
2004 American Society of Agricultural Engineers ISSN 0001−2351
375
in nursery crop areas. In addition, to obtain the optimum
pesticide spray management, delivery systems must be
operated economically and effectively with minimum canopy
disturbance and minimum spray drift. Many nursery growers
expressed interest in evaluating the effectiveness of their
application programs, including deposit uniformity throughout the canopy, spray loss on the ground, and spray drift from
the sprayed area. The objective of this research was to detect
and quantify spray penetration, off−target loss, and coverage
on two different types of nursery crops by using conductivity
analysis and electron beam analysis as application assessment
methods.
MATERIALS AND METHODS
SPRAY EXPERIMENT IN CANADIAN HEMLOCK NURSERY
The 1.5 m tall Canadian Hemlock (Tsuga canadensis) trees
were sprayed with a high−clearance, boom−type, over−the−
row sprayer (Hagie Manufacturing Company, Clarion, Iowa).
Weather conditions are shown in table 1. A plot map of the site
is shown in figure 1. The hemlock was planted in rows 1.2 m
on center, trees were 0.9 m apart in the rows, and the bottoms
of the canopies were touching within rows. Two rows were
treated with each pass of the sprayer. Sprays were directed
downward toward tree canopies. Five hollow−cone nozzles
(TeeJet D4−25, Spraying Systems Co., Wheaton, Ill.), one
over the top and two on each side, were used to spray each row.
The operating pressure on the nozzles was approximately
1378 kPa. The sprayer traveled along the tree rows with travel
speed of 1.8 m/s. Kocide 101 compound (Griffin Corporation,
Valdosta, Ga.) containing copper hydroxide, Cu(OH)2, was
selected as the tracer and applied at a rate of 1.56 L/ha. Copper
hydroxide is relatively non−phytotoxic and has relatively high
conductivity. Low ambient levels of copper naturally occurring in the background also facilitated electron beam analysis
of spray targets. The spray mixture was applied at a rate of
1403 L/ha. Tests were repeated three times.
Samples of spray deposition at different levels within tree
canopies, beside trees, and on the ground and spray drift in the
Average
wind
direction
N
Row 1
11.4 m
1.2 m
V2
G4
G2
G1
G3
G6
G5
0.9 m
Notes
4.8 m x 5 cm vertical target
V1−Vertical target 1
V2−Vertical target 2
2.4 m x 5 cm ground target
G1−Ground target 1
G2−Ground target 2
G3−Ground target 3
G4−Ground target 4
G5−Ground target 5
G6−Ground target 6
Staplex high−volume sampler
Spray path
V1
Spray
Tree with SEM targets
Tree with plate targets
Canadian Hemlock tree
Drawing is not to scale
Canadian Hemlock
Figure 1. Plan view of Canadian Hemlock nursery spray site showing location of spray collectors.
376
TRANSACTIONS OF THE ASAE
Table 1. Average weather conditions at spray sites.
Spray Site
Temperature (°C)
Relative humidity (%)
Wind speed (m/s)
Wind azimuth (degree)
Honey Locust
Canadian Hemlock
28.1
67
1.6
276.5
27.6
60
1.0
81
air were collected. Sample collector positions relative to the
spray path are shown in figure 1. Inert sample collectors were
used to collect spray deposits at 0.12 m (low), 0.9 m (medium),
and 1.4 m (high) above the ground adjacent to the trunk
(shown as SEM targets in fig. 1). The inert sample collectors
were conductive sticky stubs. Five needles were also sampled
at each level next to the inert sample collectors. The inert stubs
and needles were collected and placed in storage boxes after
each of the three spray trials, which were moved upwind between each pass to ensure that unsprayed canopy was used.
To compare the sampling method with inert stubs, spray
deposits at each of three levels (0.05, 0.51, and 1.30 m above
the ground) within canopies were collected with four sheet−
metal plates (fig. 1). Each plate was 2.5 × 7.6 cm and was
horizontally mounted on a stake. Two sample stakes were
placed in a tree on each sprayed row for each test. One stake
(with collectors) was placed as near to the tree trunk as
possible, and another stake was placed about half way from the
center of the row to the edge of the canopy. The four
simulated−leaf plates at each level and location were put into
a 250 mL bottle after each spray test.
Two vertical plastic tape targets (V1 and V2 in fig. 1) were
used to collect off−target spray and airborne movement from
the sprayer. The vertical target was 4.8 m long and 5 cm wide
and was mounted with two rubber bands in two galvanized,
2.4 m long sheet−metal tape holders. The two holders were
attached to a 5.3 m long and 2.5 cm diameter steel pipe, which
was secured to the ground. The first vertical target was
between the fourth and fifth downwind rows (3.0 m from the
first row centerline), and the second vertical target was 6.6 m
from the first row centerline. After each replication, every tape
was folded with its two holders and stored in a 7.6 cm diameter
and 3.0 m long PVC pipe in order to protect the tape from
contamination during its transportation to the laboratory.
Three 2.4 m × 5 cm plastic tape collectors (G1, G2, G3)
were used to collect ground deposits within the spray area,
with three more (G4, G5, G6) located in downwind rows
(fig. 1). Distances of the ground targets from the first row
centerline were 0, 0.6, 1.2, 3, 6.6, and 11.4 m for G1, G2, G3,
G4, G5, and G6, respectively. Each sample tape was wound
and put into a 400 mL bottle after each spray trial.
To determine airborne spray movement, two Staplex
high−volume samplers (model TFIA, Staplex Company,
Brooklyn, N.Y.) were placed between the fourth and fifth rows
(6.6 m from the first row centerline) and between the eighth
and ninth downwind rows (11.4 m from the first row
centerline) at the 3 m elevation (fig. 1). The Staplex
high−volume sampler used a 10 cm diameter cellulose filter,
while the actual sampling area was within the 9 cm diameter
region. The average air velocity through the filter was about
1.5 m/s. The paper filters were removed from the samplers and
stored in 400 mL bottles after each spray trial.
Vol. 47(2): 375−384
SPRAY EXPERIMENT IN HONEY LOCUST NURSERY
The seven−year old Honey Locust trees (Gleditsia triacanthos) were sprayed with a Durand−Wayland Streamliner 1500,
a conventional, air−assist, axial−fan sprayer. This type of
sprayer was typically used to spray tall trees in the nursery. The
trees were approximately 4 m in height, and branches were not
present on the trunk below 1 m elevation. A plot map of the site
is given in figure 2. The spacing between drive rows was
3.7 m, and row spacing within double rows was 2.7 m. Trees
were 1.8 m apart in the rows. Four TeeJet D5−45 nozzles and
one D8−56 disc/core hollow−cone nozzle (Spraying Systems
Co., Wheaton, Ill.) were used on each side of the sprayer from
bottom to top, respectively. Nozzle operating pressure was
approximately 2,067 kPa. Nozzles only on one side of the
sprayer were used to discharge spray normal to the row. The
sprayer traveled at 2.2 m/s on spray path 1, and then was
returned to the starting line while it sprayed along spray path 2
before the targets, except for two Staplex samplers and two
ground targets (G3 and G4), were collected from the first spray
pass. This was necessary for spray drift measurement because
the wind direction changed in the range of about 270° after the
first spray treatment. Weather conditions are shown in table 1.
The spray mixture was 100 ppm of calcium nitrate, Ca(NO3)2,
and water. Calcium nitrate was used as the tracer because of its
non−phytotoxic nature at this rate and relatively high conductivity. The spray mixture was applied at a rate of 823 L/ha.
The positions of deposition and drift collectors relative to
the spray path are shown in figure 2. Foliar samples for spray
deposition within canopies were collected from 2 m (low), 3 m
(medium), and 4 m (high) elevations in four trees, only after
the first spray pass. The foliage was mounted on 12 mm
diameter, conductive/sticky tabs on stubs that were fastened
onto specimen mounts (Ted Pella, Redding, Cal.). Inert sample
collectors were also placed at 2, 3, and 4 m elevations within
tree canopies on trees 1 and 3 in the first row and on trees 2 and
4 in the second row (shown as SEM targets in fig. 2).
Four 4.8 m × 5 cm vertical plastic tape targets were used
to collect spray distributions from the sprayer in the vertical
direction and to evaluate spray penetration through the trees.
The first vertical target (V1) was located at the middle of two
trees on the first row, the second target (V2) was located
behind the first tree, the third target (V3) was located between
two trees in the second row, and the fourth target (V4) was
located behind a tree in the fourth row.
Four 2.4 m × 5 cm plastic tape collectors were used to
sample ground deposits (fig. 2). The first collector (G1) was
located in the middle of the first and second rows, the second
collector (G2) was located between the third and fourth rows,
and the third (G3) and fourth (G4) ground collectors were
located 19.8 and 32 m downwind from the spray path,
respectively.
To sample airborne spray, two Staplex high−volume
samplers were placed 19.5 and 31.5 m downwind from the
spray path at an elevation of 3 m (fig. 2).
Similar to the tests in the Canadian Hemlock nursery, the
tests in the Honey Locust nursery were repeated three times
with the same trees. Spray samples were collected 15 min after
each trial and then placed in storage boxes for inert stubs and
foliages, in 400 mL bottles for ground targets and paper filters,
and in 3.0 m long PVC pipes for vertical targets.
377
Average wind direction
N
G4
G3
V4
G2
2.7 m
Spray Path 2
3.7 m
4
V2
1
V1
3
24 m
Spray Path 1
Started spraying
V3
2
G1
2.7 m
3.7 m
48 m
Notes
2.4 m x 5 cm ground target
G1−Ground target 1
G2−Ground target 2
G3−Ground target 3
G4−Ground target 4
Staplex high−volume sampler
Tree with SEM targets
Honey Locust tree
Birch tree
Drawing is not to scale
Spray
4.8 m x 5 cm vertical target
V1−Vertical target 1
V2−Vertical target 2
V3−Vertical target 3
V4−Vertical target 4
Honey Locust
Figure 2. Plan view of Honey Locust nursery spray site showing location of spray collectors.
SPRAY SAMPLE ANALYSIS
Spray deposition at different levels within tree canopies,
beside trees, and on the ground and spray drift in the air were
determined with electron beam and conductivity analyses,
respectively.
An EBA system, consisting of a scanning electron microscope (model S−500, Hitachi Instruments, Inc., San Jose, Cal.)
equipped with an energy−dispersive x−ray analyzer and digital
image analysis (model 5504, Thermo Noran, Inc., Middleton,
Wisc.), was used to analyze spray deposits on both leaflets and
inert stub surfaces. The EBA was performed to directly
identify and quantify spray residue, both morphologically and
chemically, and data were recorded as percent residue
coverage on the average of three sample 500 mm2 areas per
378
stub surface, examined at a magnification of 130X, 20 kV with
15 mm working distance.
A laboratory−built spray−deposit conductivity analyzer
(fig. 3) was used to analyze spray deposits on plastic tapes
suspended vertically at various locations near trees. The
analyzer consisted of a tape stand, an 8 cm diameter copper
drum, a 4 cm diameter print roller, an 8002 fan pattern nozzle
(Spraying Systems, Co., Wheaton, Ill.), a conductivity probe
and meter (Engineering Systems and Designs, Newark, Del.),
and a portable computer. The copper drum continuously
pulled the plastic tape at a constant speed of 330 cm/min under
the distilled water jet discharged from the nozzle. The flow
rate of water spray jet was 195 mL/min. Spray deposits on the
plastic tape were washed off and then flowed through a
TRANSACTIONS OF THE ASAE
Plexiglas slot and over a conductivity probe. Preliminary tests
verified that spray deposits on plastic tapes could be completely washed off by the spray jet at a flow rate of 195 mL/min. The
conductivity meter measured conductivity of the solution and
transmitted the results through an A/D converter to a portable
computer. The volume of spray deposit (mL/cm2) on the plastic
tape was calculated from the following formula:
Spray deposit =
C⋅Q
ρ⋅W⋅V
(1)
where
C = tracer concentration (µg/mL or µL/mL) calculated
from conductivity reading
Q = distilled water flow rate from an 8002 flat fan nozzle
(195 mL/min)
ρ = concentration (µg/µL or µL/µL) of field spray
mixture containing water and tracer
W = plastic tape width (5 cm)
V = tape travel speed (330 cm/min).
For the plastic tapes containing the ground deposit and
paper filters containing the airborne spray, 50 mL of distilled
water was added to each bottle to wash spray deposits from
each target for analysis. For the sheet metal plates containing
spray deposits within canopies, 20 mL of distilled water was
added to each bottle. Bottles were shaken well, and a
conductivity probe of the same conductivity meter used in the
deposition analyzer was placed into each bottle to read the
solution conductivity. The volume of spray deposits (mL/cm2)
on the targets was determined from the following equation:
Spray deposit =
C⋅V
ρ⋅A
(2)
where
C = tracer concentration (µg/mL or µL/mL) calculated
from conductivity reading
V = volume (mL) of distilled water to wash the tracer
ρ = concentration (µg/µL or µL/µL) of field spray mixture
containing water and tracer
Plastic tape
A = Target surface area (cm2).
Data were statistically analyzed by one−way ANOVA, and
differences among means were determined with Duncan’s
new multiple−range test using Mac−SAS version 6.12. All
significant differences were determined at the 0.05 level of
significance.
RESULTS AND DISCUSSION
SPRAY PENETRATION DETERMINED WITH EBA
Ca(NO3)2 and Cu(OH)2 residues on targets within tree
canopies were characterized and detected with EBA (figs. 4
and 5). Figure 4a shows typical spray droplets (arrows)
observed in this study as globular deposits and Ca prominent
in the complementary x−ray distribution map (fig. 4b) with a
substantial Ca peak (fig. 4c) on both leaves and stubs.
Similarly, a combination of secondary electron images, x−ray
spectra, and x−ray distribution maps were used to identify
Cu(OH)2 residue as annular−shaped spray droplets on both
needles of Canadian Hemlock and inert stubs (fig. 5). The
percent residue coverage on both leaf and stub surface areas
was then explicitly obtained from the image and energy
spectrum analysis. Comparatively, figure 5d shows that there
was no contamination on needles previously unexposed to
Cu(OH)2 with EBA revealing the surface structure. Apparently, EBA provided both visualized images and explicit amounts
of coverage on both natural and artificial sampling targets.
Statistical analysis indicated no significant differences (p <
0.05) between coverage on leaves and coverage on inert stubs
measured by EBA. Table 2 shows the percent Ca(NO3)2
coverage per Honey Locust tree relative to spray path, surface,
and tree position, measured by EBA. Each value is the mean
of 18 observations. Analysis of variance showed that coverage
on leaves was significantly affected by tree position (p < 0.05)
and leaf surfaces (p < 0.05). The highest coverage on leaves
was at the 3 m elevation on trees 1 and 3 in row 1. Trees 1 and
3 appeared to have quite different coverage of Ca(NO3)2 from
trees 2 and 4. The lowest coverage was at 4 m elevation, which
Copper drum
Flat fan nozzle
Shut off valve
Flow meter
Distilled
water
Pump
Funnel
Print roller
Portable
computer
A/D
convertor
ÎÎÎ
ÎÎÎ
ÎÎÎ
Conductivity probe
Conductivity
meter
Figure 3. Schematic drawing of the conductivity spray deposit analyzer.
Vol. 47(2): 375−384
379
Figure 4. Electron beam analysis of Ca(NO3)2 on Honey Locust leaf and stub: (a) secondary electron image of a typical globular, uniformly
Ca(NO3)2 smooth spray droplet (arrow), bar = 50 mm; (b) x−ray distribution map of Ca(NO3)2 droplet from (a); (c) energy dispersive x−ray analytical spectrum of the Ca(NO3)2 spray droplet in (a), note Ca peak; and (d) Ca(NO3)2 droplets on stub observed in the Honey Locust trees.
Figure 5. Electron beam analysis of Cu(OH)2 droplets on Canadian Hemlock needles: (a) secondary electron image, bar = 50 mm; (b) x−ray distribution map of Cu(OH)2 droplets in (a); (c) x−ray spectrum of droplet in (a), note Cu peak; and (d) Hemlock needle surface before sprayed.
was from the first tree. Overall, the coverage found on lower
surfaces within Honey Locust trees was significantly less than
that found on upper surfaces regardless of elevation above the
ground (p < 0.05, fig. 6). The average spray deposit on upper
surfaces of leaves was three times that deposited on lower sur-
380
faces (table 2). Tree position, elevation, and leaf surface were
all significant factors in percent coverage.
Canadian Hemlock trees varied slightly in shape, foliage
density, and tree size compared to Honey Locust trees. Sprays
were discharged from above the hemlock trees with the
over−the−row sprayer. Results from EBA analysis illustrated
TRANSACTIONS OF THE ASAE
Table 2. Mean percentage of Ca(NO3)2 coverage per Honey Locust
tree relative to spray path, leaf surface, and tree position, as
measured by electron beam analysis. Coefficients of
variation (%) are given in parentheses.
Sample Elevation (m)
Leaf Surface
[a]
[b]
2
Tree
1
2
3
4
20.7 (48)
28.8 (42)
16.7 (32)
29.0 (20)
Avg.
23.8 (36)
Upper[a]
Lower[b]
27.5 (29) 5.7 (36)
10.9 (43) 12.7 (36)
32.4 (40) 13.6 (53)
8.4 (33) 11.0 (42)
30.3 (71)
28.5 (77)
30.3 (189)
20.1 (94)
5.6 (68)
6.4 (61)
11.5 (43)
12.2 (80)
19.8 (36) 10.7 (42)
27.3 (108)
8.9 (63)
3
4
Average spray coverage on upper leaf surfaces across three elevations.
Average spray coverage on lower leaf surfaces across three elevations.
that averaged total percent Cu coverage on needles and stubs
was significantly different (p < 0.05) between the tree locations (table 3). There were no significant differences between
coverage on needles and coverage on inert stubs (p < 0.05).
Coverage versus position within trees averaged from 0.4% on
the lowest needle position (0.12 m) to 52.1% at the highest
position (1.4 m) in the canopy, while coverage averaged from
3.7% to 69.0% on stubs at the lowest and highest positions.
Many of the lowest needles and stubs had no detectable residue. The average coverage in four trees was 60.1% on needles
and 82.6% on stubs. However, statistical tests using Duncan’s
new multiple range test showed that there was no significant
difference in the deposits for the two sampling methods (p <
0.05). Data in tables 2 and 3 illustrate that spray deposition at
different elevations in the Honey Locust trees with the conventional axial−fan sprayer had much less variation than in the Canadian Hemlock trees with the over−the−row sprayer.
Data in table 3 also show the amount of spray deposits on
simulated leaf plates at the top, middle, and bottom of
Canadian Hemlock trees. Results are the average of three
locations in the four tree canopies. Many of the top collectors
were outside the canopy and were directly exposed to spray,
which produced large deposits. Because tree foliage was very
dense, only a small portion of spray droplets penetrated the
foliage. There was no significant difference between deposits
on the targets in the middle and at the bottom of trees (p < 0.05).
Average spray deposit at the top of Canadian Hemlock tree
canopies was 14 times higher than that at the middle and the
bottom of canopies. The coverage determined with metal
plates was similar to that measured by EBA on needles and
stubs; however, EBA provided both visual information on
droplet deposit location and the coverage of spray deposition
on targets.
DEPOSITION ON VERTICAL TARGETS
Figure 7 shows spray deposit distributions discharged with
the axial−fan sprayer on vertical targets at four locations with
Honey Locust trees. The average spray deposit across the
entire vertical target determined with the spray deposit
analyzer was 90.1, 35.7, 38.0, and 2.6 mL/cm2 on V1, V2, V3,
and V4, respectively. For collector V1, most sprays were
deposited on the area from 1.8 to 4.5 m above the ground.
Spray profiles across vertical targets V2 and V3 were very
similar, and most deposition was also in the area from 1.8 to
4.5 m. Conversion of spray deposition on V2 and V3 to percent
total spray indicated that about one−third of the total spray
passed through the first tree. The total spray deposit on the V3
collector was slightly higher than on the V2 collector because
there was no tree in front of the collector. These deposits were
much lower than on the V1 collector, which was located in the
center of the first tree row. This result indicates that about
two−thirds of the spray deposited on the ground and dispersed
before reaching the center of the second tree row. However,
there was very little deposition on the V4 vertical collector
behind the fourth tree.
Figure 8 shows spray deposit distributions discharged from
the over−the−row sprayer on two vertical targets 3.0 m (V1)
and 6.6 m (V2) downwind from the first row centerline in the
Canadian Hemlock nursery. Each point in the graph represents
the average deposit on a section of 30.5 cm long plastic tape.
Although spray droplets were discharged downward toward
trees, there was still some drift collected on both vertical
targets. The highest spray deposition on V1 was 4.1 mL/cm2
from the area about 2.5 m above the ground, while the average
spray deposition on V2 was less than 1.0 mL/cm2 across the
entire target height.
DEPOSITION ON GROUND TARGETS
Figure 9 shows spray deposits on ground collectors 2.1, 7.6,
19.8, and 32 m north of the first spray path in the Honey Locust
Figure 6. Percent Ca(NO3)2 coverage versus surface sampled according to height in Honey Locust trees. Each bar is the mean of 18 observations
(three upper surfaces and three lower surfaces with three replications).
Vol. 47(2): 375−384
381
Table 3. Deposit of Cu(OH)2 on Canadian Hemlock needles, SEM
stubs, and sheet−metal plates on each sample tree as a function
of elevation above the ground. Coefficients of
variation (%) are given in parentheses.
Mean Coverage (%)
Elevation
Mean Deposit
(m)
Needle
Stub
on Plate (µL/cm2)
0.05
0.12
0.51
0.90
1.30
1.40
−−
0.4 (82)
−−
7.6 (40)
−−
52.1 (17)
−−
3.7 (102)
−−
9.9 (60)
−−
69.0 (11)
0.265 (30)
−−
0.247 (12)
−−
3.788 (48)
−−
nursery. Spray deposits on ground targets greatly decreased as
the distance from the spray path increased. The average spray
deposit was 212.9 mL/cm2 on the ground target at 2.1 m north
of the spray path and 0.90 mL/cm2 on the ground target at
19.8 m north of the first spray path. Large amounts of spray
were displaced on the ground near the first and second rows.
Compared to the experiment with Honey Locust trees, the
experiment with Canadian Hemlock trees yielded less spray
on the ground. Figure 10 shows the spray deposit on six ground
targets in the Canadian Hemlock nursery with the over−the−
row sprayer. The spray deposit on the ground target (G2),
which was between first and second rows, was over two times
as great as deposits on targets G1 and G3, which were under
first and second rows. The spray deposit on ground targets
decreased from an average 40.92 to 0.82 mL/cm2 as the
distance from the first row centerline increased from 0.6 to
11.4 m.
AIRBORNE SPRAY
The amount of airborne spray collected by Staplex
high−volume samplers at the 3 m elevation in the Honey
Locust nursery decreased 28.4% as the distance downwind
from the spray path increased from 19.8 to 32.0 m (table 4).
However, the airborne spray deposit in the Canadian Hemlock
nursery was nearly equal at 6.6 and 11.4 m downwind the first
row centerline. Airborne spray deposits did not decrease as
much with increasing downwind distance as ground deposits
in both nurseries. Compared to the axial−fan sprayer used in
the Honey Locust nursery, the over−the−row sprayer used in
Canadian Hemlock nursery had a considerably lower amount
of spray drift because the sprayer discharged material downward.
Figure 7. Profiles of spray deposits on vertical collectors downwind from Honey Locust trees sprayed with an axial−fan sprayer.
Figure 8. Profiles of spray deposits on vertical collectors downwind from Canadian Hemlock trees sprayed with a high−clearance sprayer.
382
TRANSACTIONS OF THE ASAE
Figure 9. Spray deposits on ground collectors downwind from Honey Locust trees sprayed with an axial−fan sprayer.
Figure 10. Spray deposits on ground collectors downwind from Canadian Hemlock trees sprayed with a high−clearance sprayer.
Table 4. Mean airborne spray deposits captured on air volume
sampler filters downwind in the Honey Locust nursery sprayed
with an axial−fan sprayer and in the Canadian Hemlock
nursery sprayed with a high−clearance sprayer.
Distance
Airborne
CV
(m)[a]
(µL/cm2)
(%)
Spray Site
Honey Locust
19.8
32.0
102.38
73.34
12.5
20.5
Canadian Hemlock
6.6
11.4
15.50
16.54
33.7
19.9
[a]
For the Honey Locust site, distance was between the sampler and spray
path 1; for the Canadian Hemlock site, distance was between the sampler
and the centerline of the first row.
CONCLUSIONS
The EBA determined the percent Ca and Cu residue
coverage on both leaf and stub surface areas within tree
canopies and provided an assessment method with both
visualized image and quantification analysis to determine
spray deposition for nursery spray applications.
The coverage on the lower surfaces of Honey Locust trees
was significantly less than that found on the upper surfaces
regardless of elevation above the ground. Average total
Vol. 47(2): 375−384
percentage of Cu coverage on needles and stubs within
Canadian Hemlock trees was significantly different between
the tree locations.
Canopy penetration coverage measured with EBA on
needles and stubs had similar trends to deposits measured on
metal plates with conductivity analysis.
The spray deposit analyzer quantified spray deposition
profile across trees. About one−third of the total spray passed
through the first row of Honey Locust trees with the axial−fan
sprayer.
Ground deposits decreased rapidly with increased distance
from the spray path. Airborne spray deposits did not decrease
as much with increasing downwind distance as ground
deposits.
ACKNOWLEDGEMENTS
The authors wish to thank the following individuals: A. A.
Doklovic, P. T. Keck, and K. A. Williams for technical
assistance; R. S. Lyons, owner, and R. G. Headley, nursery
manager, Sunleaf Nursery, Madison, Ohio; and E. Losely,
owner, and A. Hardy, nursery manager, Herman Losely and
Sons Nursery, Perry, Ohio, for their cooperation in providing
operating facilities, equipment, and experimental field space.
383
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TRANSACTIONS OF THE ASAE
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