Wheat (Triticum aestivum ‘Knudson’) S. Halley, Langdon Research Extension Center, NDSU, Langdon ND, 58249

Fusarium head blight; Fusarium graminearum G. Van Ee, Dept. of Agricultural Engineering, Michigan State University, East Lansing, MI 48824 and V. Hofman, Dept. of Agricultural & Biosystems Engineering, NDSU, Fargo, ND 58105

Spray Volumes, Spray Systems, and Orifice Orientation to improve efficacy of JAU 6476 Fungicide to ‘Knudson’ HRSW, 2003

One of the most often asked questions from producers is, ‘what spray volume should I apply fungicide for control of FHB (Fusarium head blight)’? Results reported from research trials on small grain suggest increasing volume increases coverage and infers increased coverage improves fungicide efficacy. While this has been shown on many crops, data on the improved fungicide efficacy based on increasing spray volume is limited on small grains. A research study was conducted to evaluate spray volume, sprayer systems, and orifice orientation to improve the efficacy of fungicide for control of FHB. Cultivar ‘Knudson’ HRSW was planted for evaluation in a field at the Langdon Research Extension Center in spring 2003. An area was planted with a Melroe double-disk grain drill, disks spaced 6-inches apart, on 3 May. The area was divided to plots 12 ft. wide by 20 ft. long in a randomized complete block design arranged as a 2 x 2 x 2 factorial with eight replicates. Factors included spray volumes of 5.2 and 19.2 gpa, a conventional nozzle and a modified Spray-Air™ spray system, and orifice orientations, down and forward and backward (F +B).

A conventional nozzle system uses pressure through a nozzle orifice to determine the drop size and pressure, typically pressure pump, to deliver the drop to the target after passing through a spray nozzle. The conventional system was equipped with spraying systems XR8001 or XR8002 nozzles spaced 20 inches on center spraying at 40 psi. The modified Spray-Air uses wind shear and wind speed technology to determine the drop size and an air stream to deliver the spray solution to the target. The air stream is generated by a centrifugal fan powered by a hydraulic pump. Speed is increased or reduced by a flow control value and measured by a static pressure gauge on the distribution tube. Static pressure was maintained at 25 psi. The advantage of this system is that the air stream speed can be increased and the fine drops can be carried a greater distance to the target. Wind does not affect the delivery when the air stream speed exceeds wind speed. The Spray-Air system was modified by adding a second set of orifices (.0424 gpm) spaced 10 inches on center and oriented to spray the back side of the spike. The orifices were angled 30° downward from horizontal. A Spray-Air system typically has one row of orifices angled 12° forward from vertical. Nozzle orientations were F + B (forward + backward) both systems, forward (Spray-Air system), or vertical (conventional system).

The spray volume was adjusted by nozzle size on the conventional system and/or tractor speed. Recommended production practices for Northeast North Dakota, NDSU Extension, were followed. Wheat grains colonized by F. graminearum were hand broadcast on 19 Jun on individual plots at 3.5 oz per plot to increase chance of infection to Fusarium head blight. Fungicide was applied by a pressurized CO₂ delivery system on 12 Jul at 8 a.m. The tractor traveled on the left half of the plot area. This area also provided border to reduce off target drift between treatment areas. Visual estimation of Fusarium head blight incidence and field severity, 20 samples per plot, summation of (spikelet count per individual head multiplied times FHB infected spikes per plot) were counted on 2 Aug on the untreated. The fungicide, Bayer experimental JAU 6476 at 5.7 oz/A, reduced disease to negligible levels so incidence and field severity were not recorded on the treated plots. Each plot was harvested with a Hege plot combine on 19 Aug and the grain sample cleaned and processed for yield and test weight measurement. 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.

The untreated had FHB incidence and field severity levels of 53 and 5.8%, respectively. DON, deoxynivalenol, levels on the untreated were 1.6 ppm. Visible FHB on treated plots was negligible, < 0.5%, so levels were not recorded. Yield was increased with the conventional spray system compared to the modified spray-air system, 65.5 to 62.8 bu/A. This is in contrast to a field trial conducted in 2003 at the Langdon Research Extension Center in which a regular spray-air system increased yield over the untreated and one configuration of a conventional system. Further research into application technologies is needed particularly into the applicable air stream speed under differing environmental conditions. Too great an air speed stream may negate any positive effect of orifice orientation and reduction in drop size.

Spray Volume	Nozzle Orientation*	Spray System	Yield	Test Weight
(gpa)			(bu/A)	(lb/bu)
5.2	Down	Conventional	67.0	60.7
5.2	Down	Spray-Air	61.0	60.7
5.2	F + B	Conventional	63.4	60.9
5.2	F + B	Spray-Air	61.2	60.6
19.2	Down	Conventional	66.2	60.8
19.2	Down	Spray-Air	65.7	60.5
19.2	F + B	Conventional	65.5	60.7
19.2	F + B	Spray-Air	63.4	60.5
Spray volumes by orifice orientations averaged across spray systems
5.2	Down		64.0	60.6
5.2	F + B		62.3	60.8
19.2	Down		66.0	60.6
19.2	F + B		64.4	60.6
Spray volumes by spray systems averaged across nozzle orientations
5.2		Conventional	65.2	60.8
5.2		Spray-Air	61.1	60.6
19.2		Conventional	65.8	60.7
19.2		Spray-Air	64.5	60.5
Nozzle orientations by spray systems averaged across spray volumes
	Down	Conventional	66.6	60.7
	Down	Spray-Air	63.4	60.5
	F + B	Conventional	64.4	60.8
	F + B	Spray-Air	62.3	60.6
Spray volumes averaged across nozzle orientations and spray systems
5.2			63.1	60.7
19.2			65.2	60.6
Nozzle orientations averaged across spray volumes and spray systems
	Down		65.5	60.6
	F + B		63.3	60.7
Spray systems averaged across spray volumes and spray orientations
		Conventional	65.5	60.8
		Spray-Air	62.8	60.5
Untreated			61.1	60.2

*Nozzle orientations were F + B (forward + backward) both systems, forward (Spray-Air system), or vertical (conventional system)

Spray Volume	Nozzle Orientation	Spray System	Yield	Test Weight
gpa			bu/A	lb/bu
GPA			NS	NS
Orientation			NS	NS
GPA*orient			NS	NS
Sprayer			2.4* ^z	NS
GPA*spray			NS	NS
Dir*spray			NS	NS
GPA*dir*spray			NS	NS
C.V. %			8	1

*Significant at 0.0308 probability level for mean comparisons