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Ground Spray Systems and Spray Parameter Evaluation for Control of Fusarium Head Blight on a Field Scale Basis.

 

S. Halley1*, G. Van Ee2, V. Hofman3, S. Panigrahi3, and H.Gu3

1Langdon Research Extension Center, North Dakota State University, Langdon, ND 58249, 2Dept. of Agricultural Engineering, Michigan State University, East Lansing, MI 48824,

3Dept. of Agricultural & Biosystems Engineering, North Dakota State University, Fargo, ND 58105.

*Corresponding Author: PH: (701) 256-2582, E-mail: shalley@ndsuext.nodak.edu

 

Objectives

 

Evaluate field scale spray systems with differing application technologies for enhanced control of Fusarium head blight (FHB).

Introduction

 

The production industry, growers and commercial pesticide applicators, often question the validity of research using small scale equipment. In the scientific community the validity of research methods receive constant review and revision. Reasons for using small scale equipment include a) parameter control, including reducing variance attributed to soil difference, b) the extensive time necessary to calibrate large spray booms, and c) the cost of the equipment necessary for conducting a research trial. At the request of the chemical and biological committee, and in response to the production industry, a trial was implemented at the Langdon Research Center to compare field scale spray systems and address the research from an interdisciplinary approach with collaboration between the agricultural engineering community and the plant pathology community.

 

Materials and Methods

 

A study was planned as a randomized complete block design (RCBD) arranged as a factorial replicated six times to determine differences between spraying systems with differing application technologies with emphasis on droplet size. Due to limitations among the spray systems and time constraints to equate droplet size parameters necessary for the factorial, the data was analyzed as a RCBD. A foundation seed production field, planted to Alsen, was selected for the suitability of plot layout to the spray systems, soil uniformity (Cavour-Cresbard loam), and the site�s proximity to the mixing and other facilities of the station.Four replicates had previous crop small grains and two replicates were previous crop potatoes. The site was partitioned into 72 plots 35 x 60 feet to accommodate the field scale equipment. All units sprayed each individual replicate and did an end run around the trial to the front to align for the subsequent replicate and to minimize potential of drip contamination to other plots. About 20 ft from the front and backside of each plot was swathed and discarded from all disease assessment and harvest results. Harvest data was collected from the interior 20 feet of the spray area from each respective unit with a Hege small plot combine. Recommended, NDSU Extension Service, HRSW production practices for the northeast North Dakota were followed. A Fusarium spawn was hand broadcast on each individual plot three weeks prior to flowering at about 300 grams per plot. FHB was visually assessed by sampling 20 spikes per plot and counting the spikes per head and the infected kernels per spike 20 days after spray application. Data is reported as incidence and (field) severity. Yield, test weight, and protein were determined on all plots and the percent deoxynivalenol (DON) was determined on three replicates after it was determined from the untreated plots that DON was present. Coverage parameters were assessed by including a Day Glo orange fluorescent dye mixed at 3% v/v with the spray solution. Twenty spikes were collected from the first replicate of each treatment, transported to North Dakota State University in Fargo, photographed under incandescent and UV light on both sides of the spike to determine the area covered by the spray solution from each spraying system. Prior to spraying three sampling stands, with water and oil sensitive paper at grain heading height (1� x 2.75� cards, Spraying Systems Co.), were oriented horizontal and vertical back to back east-west and north-south and spaced to collect spray pattern samples from each spray unit. DropletScan, a product of WRK, Inc. and Devore Systems Inc., was used to analyze the water sensitive cards and generate a report. The field scale sprayers, technical assistance, and operation were provided by AGCO Corporation (Chris Mohning) and Hardi Inc. (Richard Hundt). Technical assistance and operation of a plot scale sprayer previously provided by Spray-Air Technologies Ltd. was provided by Bob Dawes of Degelman Industries. A fourth unit utilized a Proptec system (Ledebuhr Industries Inc.-WWW.PROPTEC.COM) on one boom and a Spraying systems hydraulic flat fan nozzle system mounted on a double swivel with nozzles angled 30 degrees downward from horizontal and oriented forward and backward on the opposite boom. The unit was provided and operated by Dr. Gary Van Ee, Agricultural Engineer from Michigan State University. The five spray units each sprayed two treatments and were compared to two untreated checks for a total of 12 treatments. The technical representatives were encouraged to operate their respective system as close to optimum performance conditions for one spray treatment and readjust the equipment to change droplet size as much as possible within the limitations of each spraying system. Dye and water were provided for testing prior to the trial initiation. A CCD camera was available for visual assessment of the coverage. Sprayers and parameters included:

 

1)      AGCO�s ESP (Energized Spray Process). The spray solution is delivered through a hydraulic spray boom mounted on a Spray-Coupe. The spray solution is energized with a negative electric charge (40,000 volts) that is attracted to the positively charged wheat spike. The charge creates a high-intensity electrostatic field between the nozzle and the plant that increases spray velocity and attracts the solution to the plant. The ESP sprayed fungicide at 10 gpa through XR8003 nozzles operating at 60 psi and XR8002 nozzles operating at 110 psi. No adjuvant was added to the spray solution by recommendation of the company representative.

2)      Hardi Commander Plus 1200 80 ft Twin Force with Mustang 3500 Rate Controller. The spray solution is delivered by hydraulic nozzles, ISO yellow #2 110� tips, which spray into an air stream that delivers the solution to the target. The air stream, generated by a centrifugal fan and dispersed through a bag type manifold, was angled forward 30 degrees. Spray solution was delivered at 15 gpa to both treatments, nozzles spaced 20 inches 22 to 24 inches above the canopy. One treatment was sprayed at 45 psi with fan speed operating at 1750 rpm which would deliver a droplet size of between 160-240 volume mean diameter (VMD). The second treatment sprayed at 100 psi with fan speed of 2300 rpm which would produce a VMD of 160-240 VMD. Greater pressure should produce the droplets in the lower end of the VMD range.

3)      Spray-air Technologies Ltd. The spray solution was delivered by CO2 pressurized system. The solution was dispersed through a metering orifice at 27 psi spaced 10 inches apart angled 15 degrees forward from vertical at 9 gpa. The droplet is formed by wind shear picking the drop off the end of an orifice in the center of the air stream. The speed of the wind stream determines the droplet size with greater wind speed (increased static pressure) producing smaller droplets. The air stream is generated by a centrifugal fan and dispersed by a manifold to individual orifices.

4)      Ledebuhr Industries Proptec. This system produces an air stream generated by hydraulic driven axial fans spaced 48 inches apart. Blade pitch is adjustable. The spray solution is delivered by hydraulic pump through a metering orifice. The droplet is generated by a rotary atomizer spinning at approximately 5400 rpm. The Proptec atomizer was operated at approximately 2000 psi with a 4 gpm hydraulic flow rate delivering spray solution at 10.4 gpa. This system generates an extremely fine droplet (approximately 125 micron VMD) in a 40 to 50 mph air stream.

5)      Conventional F+B. The control system utilizes hydraulic nozzles, XR8001, angle 30 degrees downward and oriented to deliver the spray solution forward and backward to spray both sides of the spike. The nozzles were operated at 40 psi delivering 10.4 gpa spray solution.

 

The spray solution consisted of Bayer�s experimental fungicide JAU 6476, prothiaconazole. This fungicide was selected because of its linear disease reduction as rate increases. A rate of 2.85 oz/acre, half the recommended rate, was used to measure differences between the spraying systems and application technology parameters. Induce adjuvant was mixed with all solutions at 0.125% v/v except the ESP sprayer. A mixing error reduced the fungicide rate in both treatments of the Hardi system by approximately 20% to a rate of approximately 2.3 oz/acre. Data was analyzed with the general linear model (GLM) in SAS. Least significant differences (LSD) were used to compare means at the 5% probability level.

 

Results and Discussion

 

Spray application began at about 1:15 p.m. after the foliage had dried sufficiently to permit data collection. The final treatments were concluded by 6:00 p.m. Average wind speed ranged from 8.3 to 10.2 mph with occasional gusts exceeding 15 mph. Wind direction was WSW. Spray application commenced traveling from east to west minimizing drift between plots. Air temperatures ranged from 72 to 78� F and R.H. decreased from 65 to 55 % over the application period.FHB incidence was reduced by several of the treatments including both Spray-air and conventional treatments, the ESP with XR8003 nozzles with the coarse droplets, the Hardi with the fine droplets, and the Proptec angled at 45egree angle compared to the untreated (Table 1). Field severity and leaf disease was reduced by all fungicide applications compared to the untreated. The recommended conventional system had smaller leaf disease levels than the other conventional treatment. The Spray-air (fine droplet), both Hardi treatments, and the Electrostatic with coarser droplets had smaller leaf disease levels compared to the conventional system 36 inches above target, and the Proptec system angled 45 degrees downward. Both Spray-air systems had increased yield over the untreated, the conventional 36 inches above the target, and the Proptec angled 70 degrees downward. No significant differences were measured in test weight or protein. Deoxynivalenol (DON) levels were reduced below 0.5 ppm by all fungicide applications.

 

Total spike coverage was reduced by about � when the conventional sprayer was operated above recommended height and by � when the angle of the Proptec was increased from 45 to 75 degrees (Table 1). Spike coverage on the front side ranged from a high of 63% with the conventional unit at recommended height to 13% on the Proptec angled 70 degrees downward. The greatest backside coverage was also the conventional at recommended height at 25% and the smallest coverage on the conventional 36 inches above target (3%) and Proptec 70 degrees downward.

 

Conclusion

 

This trial demonstrated the three major spray solution delivery systems, electrostatic, air stream, and hydraulic and further demonstrated three principal methods of spray atomization: hydraulic, wind sheer, and the rotary. The study indicates that operation and adjustment of each of the spray systems can affect one or more disease components and yield parameters. Water sensitive paper analysis indicated less but similar coverage compared to spike measurement (Table 2). The varying VMD indicates a wide range of choices between spraying systems and some variability when parameters of each individual spraying system changed. In most treatments a smaller droplet size was deposited on the back side of the deposition card compared to the front side indicating that a factor other than inertial impact contributed to deposition on the backside of the papers. Each of the spraying systems offers latitude to change application parameters as shown by GPA determinations from the conventional and Proptec systems (Table 2).Similar assessment can be made from the horizontal placed water sensitive paper which would affect leaf coverage and possibly leaf disease control. Proper adjustment and operation is imperative to maximize the efficiency of all the systems. Coverage on the untreated indicates minimal intra plot spray drift.

 

One must conclude that all sprayers in this test successfully delivered the necessary fungicide dose to minimize disease infection. In the future, additional reductions or a range of fungicide rates may be necessary to measure sprayer differences. Measurement of the spray parameters indicates that further study to identify optimal adjustment factors to maximize spray coverage and fungicide efficacy should be undertaken. Evaluation on the appropriate fungicide rate for spray system and spray system parameter study should also be undertaken.

 

The study group wishes to acknowledge funding support of the USWBSI, and the cooperating companies, AGCO Corporation, Hardi Inc., Degelman Industries, Spray-Air Technologies Ltd. and company representatives Chris Mohning, Rich Hundt, and Bob Dawes. "This material is based upon work supported by the U.S. Department of Agriculture, under Agreement Nos. 59-0790-3-079 and 59-0790-9-072.This is a cooperative project with the U.S. Wheat & Barley Scab Initiative." "Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture."

 


Table 1. FHB Incidence and field severity, leaf disease, yield, test weight, protein, and DON by spray systems, Langdon, 2003.

Spray

Spray Parameters

FHB

Leaf

Yield

Test

Protein

DON

System

 

Incidence

Field Severity

Disease

 

Weight

 

 

 

 

%

%

%

bu/acre

lb/bu

%

ppm

 

 

 

 

 

 

 

 

 

Conv. F+B

10� above target

23.3

0.8

10.2

60.6

60.8

14.6

<0.5

Conv. F+B

36� above target

22.5

0.8

15.9

60.0

60.4

14.4

<0.5

Electrostatic

Twinjet XR8003 @ 60 psi

20.0

0.8

5.7

62.1

61.1

14.4

<0.5

Electrostatic

Twinjet XR8002 @ 110 psi

36.7

1.4

10.4

60.4

60.5

14.8

<0.5

Hardi Twin

45 psi 2200 rpm

39.2

1.6

7.0

61.5

60.7

15.2

<0.5

Hardi Twin

95 psi 1800 rpm

23.3

0.8

8.3

62.5

60.6

14.2

<0.5

Proptec

Angled 45� down

28.3

1.0

13.0

63.5

60.7

14.8

<0.5

Proptec

Angled 70� down

32.5

1.2

9.1

59.1

60.5

14.7

<0.5

Spray Air

Static Pressure 15

23.2

0.8

10.1

64.6

60.9

14.5

<0.5

Spray Air

Static Pressure 25

29.2

0.9

6.7

64.0

60.9

15.1

<0.5

Untreated

 

50.8

2.7

23.0

60.3

60.2

14.6

0.8

Untreated

 

45.8

3.0

27.5

57.3

60.1

14.3

1.0

 

 

 

 

 

 

 

 

 

LSD*

 

14.2

1.0

5.6

3.8

NS

NS

0.3

% CV

 

39

64

40

5

1

6

28

* Significant at 0.05 probability level for mean comparisons

 


Table 2. Back, front, and total spike coverage and mean area, VMD, and GPA for front side and backside coverage placed vertically

as measured on water sensitive paper by spray system, Langdon 2003.

Spray

Spray Parameters*

Mean Spike Coverage**

��������������� ��������WS Paper

�������������������� WS Paper

System

 

Back

Front

Total

Front side Mean

Backside Mean

 

 

%

%

%

Area

VMD

GPA

Area

VMD

GPA

 

 

 

 

 

 

 

 

 

 

 

Conv. F+B

10� above target @10.4 gpa

24.91

63.18

44.04

38.7

577

7.9

18.2

481

6.0

Conv. F+B

36� above target @10.4 gpa

3.13

16.98

10.05

2.7

219

1.0

0.4

184

0.1

Electrostatic

Twinjet XR8003 @ 60 psi

@ 10 gpa

12.62

28.02

20.32

15.3

478

5.2

6.7

472

2.6

Electrostatic

Twinjet XR8002 @ 110 psi

@10 gpa

11.35

44.39

27.87

18.3

391

6.5

3.4

300

1.3

Hardi Twin

45 psi 2200 rpm @ 15 gpa

16.14

38.99

27.56

��� 22.5

378

8.3

8.5

439

3.0

Hardi Twin

95 psi 1800 rpm @ 15 gpa

10.02

32.03

21.03

30.5

500

10.2

6.3

285

1.9

Proptec

Angled 45� down @ 10.4 gpa

7.36

21.52

14.44

22.4

270

7.6

2.5

136

0.7

Proptec

Angled 70� down @ 10.4 gpa

1.15

12.55

6.85

5.6

146

1.5

0.9

118

0.2

Spray Air

Static Pressure 15 @ 9 gpa

5.91

36.64

21.27

14.2

353

4.0

4.0

254

1.4

Spray Air

Static Pressure 25 @ 9 gpa

9.3

26.22

17.76

22.2

398

7.0

5.0

170

1.5

Untreated

 

 

 

0.07

 

 

 

0.03

87

.005

Untreated

 

 

 

0.25

 

 

 

0.01

121

.003

*Increased water volumes result in increased coverage parameters when other parameters remain constant.

**20 spike sample

 

Table 3. Mean area, VMD, and GPA for coverage as measured on water sensitive paper placed horizontally by spray system, Langdon 2003.

Spray

Spray Parameters*

�������������������� WS Paper*

System

 

Horizontal Mean

 

 

Area

VMD

GPA

 

 

 

 

 

Conv. F+B

10� above target @10.4 gpa

30.5

474

10.5

Conv. F+B

36� above target @10.4 gpa

19.3

354

7.5

Electrostatic

Twinjet XR8003 @ 60 psi @ 10 gpa

55.4

614

11.7

Electrostatic

Twinjet XR8002 @ 110 psi @10 gpa

46.7

562

11.1

Hardi Twin

45 psi 2200 rpm @ 15 gpa

 

 

 

Hardi Twin

95 psi 1800 rpm @ 15 gpa

73.0

 

 

Proptec

Angled 45� down @ 10.4 gpa

21.6

260

7.6

Proptec

Angled 70� down @ 10.4 gpa

3.8

155

1.0

Spray Air

Static Pressure 15 @ 9 gpa

32.4

448

9.7

Spray Air

Static Pressure 25 @ 9 gpa

37.5

398

11.7

Untreated

 

<0.1

64

<0.1

Untreated

 

<0.1

61

<0.1

*Missing values due to coverage limitations of the water and oil sensitive paper