Wheat (Triticum aestivum ‘Knudson’) S. Halley

Fusarium head blight; Fusarium graminearum Langdon Research Extension Center

Tan spot; Pyrenophora tritici-repentis North Dakota State University

Septoria blotch; Septoria tritici Langdon, ND 58249

‘Knudson’ HRSW Response to JAU 6476 Fungicide Rate, 2003

A new fungicide JAU 6476, prothioconazole, has shown improved efficacy in the control of Fusarium head blight on durum and hard red spring wheat and reductions in deoxynivalenol levels compared to most of the currently labeled fungicides on small grains. Research is needed so growers will know the consequences of different rates under different environmental conditions and infections from different causal organisms. Cultivar ‘Knudson’ HRSW was planted for JAU 6476 fungicide rate 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 with six replicates. 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. Treatments and JAU 6476 rates were: 1) Untreated. 2) 0.125x (0.7 fl. oz/A). 3) 0.25x (1.4 fl oz/A). 4) 0.5x (2.85 fl oz/A). 5) 1x (5.7 oz/A). 6) 2x (11.4 fl oz/A). 7) 3x (22.8 fl oz/A). Treatments were applied by a modified SPRAY-AIR™ tractor sprayer. The sprayer was modified to distribute the solution from orifices angled 30 degrees downward from horizontal and oriented forward and backward to maximize spike coverage. The solution carrier was pressurized CO₂ delivering 19.2 GPA into the air stream through metering orifices on 14 Jul at 9 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 (FHB) incidence and field severity, 20 samples per plot, summation of (spikelet count per individual head multiplied times FHB infected spikes per head) and flag leaf necrosis, 5 samples per plot, were counted on 30 July. A flag leaf necrosis sample was one leaf and a head sample was one spike. 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 and deoxynivalenol determination. 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.

Disease levels were extremely low with Fusarium head blight incidence and field severity on the untreated at 36 and 2.3%, respectively. Fusarium head blight incidence was reduced by a 1x and 3x fungicide application. A 0.5x fungicide application reduced disease levels from the untreated. No differences in Fusarium head blight field severity, yield, and test weight were determined. All fungicide applications reduced deoxynivalenol compared to the untreated. Levels were also reduced by the 0.5x rate compared to smaller rates and a 3x rate compared to 1x and lower rates. Deoxynivalenol levels were significantly correlated with treatment -0.795.

	FHB		Leaf		Test
	Incidence	Field Severity	Disease	Yield	Weight	DON**
Treatment* and rate	(%)	(%)	(%)	(bu/A)	(lb/bu)	(ppm)
Untreated	36	2.3	10.3	64.5	59.3	3.9
0.125x 0.7 fl oz……..	35	4.6	6.2	67.2	59.8	2.0
0.25 x 1.4 fl oz...........	27	2.0	7.9	67.5	59.6	2.1
0.5 x 2.85 fl oz...........	24	1.8	4.2	64.9	59.8	1.4
1.0 x 5.7 fl oz……….	18	2.8	2.9	69.9	60.2	1.3
2.0 x 11.4 fl oz...........	23	1.3	3.5	66.0	60.2	0.9
3.0 x 22.8 fl oz...........	12	0.6	3.8	67.2	60.1	<0.5
LSD	13	NS	4.9***	NS	NS	0.7
C.V. %	46	92	75	8	1	36

*JAU 6476 (480 SC) applied with Induce Adjuvant at 0.125% v/v/A.

**Deoxynivalenol

***P=.0381