Fusarium head blight (FHB) was described more than a century ago. Since that time the disease has caused severe and repeated epidemics on small grain crops resulting in billions of dollars in crop losses. More specifically, Nganje et al. (2004) estimate the recent 1993-2001 FHB epidemics have caused economic losses of greater than $5.2 billion in Minnesota and North Dakota alone. The disease remains a constant threat to the economic stability of small grain growers in production areas with rain, humidity, or heavy dews during critical fungal infection periods.

Disease development is highly dependent on environmental conditions prior to, and during the period when crops are in susceptible growth stages. Cultural disease management strategies (e.g.: crop rotation, tillage, and field sanitation) have provided producers slight disease suppression, and additional control has been achieved from application of select fungicide products at Feekes 10.5 (early-heading growth stage) for barley and Feekes 10.51 (early-flowering stage) for wheat. Ongoing research into disease control efficacy of experimental fungicides is needed to preserve small grain yield and quality losses in regions most at risk for crop losses caused by FHB.

During 2004, registered and experimental fungicide products were evaluated for Fusarium head blight (FHB, scab) control efficacy when applied on hard red spring wheat and barley in northwest Minnesota. Cooperatively, the yearly multi-state uniform fungicide trial effort determines which fungicide compounds were most effective at reducing FHB severity of small grains across diverse environments in the U.S.

MATERIALS AND METHODS

Hard red spring wheat cultivar ‘Oxen’ and spring barley ‘Robust’ were planted 4 May 2004 into wheat residue at 1.25 million/acre and 1.375 live seed/acre, respectively, in a randomized complete block design with four replicates. Tests were inoculated with Fusarium graminearum infested corn grain five weeks after planting. Night-cycle mist irrigation was initiated after tests were inoculated and was continued until 3 August. Misting was discontinued temporarily during the growing season when weather events caused standing water at the testing site. Treatment applications were made with a CO₂ backpack-type sprayer that was adjusted to 40 psi at 18-20 gpa with forward and backward positioned ‘XR’ Teejet flat fan 8001 VS nozzles. Leaf spotting and FHB disease severities were evaluated. The tests were harvested during August.

Fungicide treatments were applied to barley and wheat at nine and ten weeks after planting, respectively. Experiments consisted of one nontreated control and eight fungicide treatments (Table 1).

Table 1. Eight fungicide treatments evaluated on wheat and barley for the control of Fusarium head blight in Crookston during 2004.

RESULTS AND DISCUSSION

Barley

The cool growing season provided an optimum environment for barley production in the Red River Valley. Four of eight disease response categories (FHB incidence, FHB index, DON, and yield) didn’t have significantly different results (Table 2). Two treatments (‘JAU6476 5 fl oz’ and ‘Headline’) resulted in significantly reduced FHB severity compared with the ‘Folicur’ or ‘Tilt’ treatments. Four treatments (‘JAU6476 5 fl oz’, ‘JAU6476 + Folicur’, ‘Quadris’, and ‘Headline’) resulted in significantly reduced VSKs compared with the ‘Tilt’ treatment.

Table 2. Fusarium head blight and leaf spot disease responses from ‘Robust’ spring barley in Crookston, Minnesota during 2004.

¹Each fungicide treatment included 0.125% Induce. Treatment abbreviations are DS, Fusarium head blight (FHB) severity (number of infected spikelets on each head); DI, FHB incidence (average number of diseased heads in a field); DX, FHB index (severity x incidence/100); VSK, visually scabby kernels; LDS, leaf disease severity (% leaf area with lesions). Different letters within a column indicate that treatments are statistically significant.

Wheat

Overall, the nontreated control had the most severe disease (Table 3). The ‘JAU6476 5 fl oz’, ‘JAU6476 + Folicur’, ‘V-10116 6 fl oz’, and ‘V-10116 4 fl oz’ treatments significantly reduced FHB and leaf disease symptoms and preserved crop yield and grain quality across all categories tested compared with the nontreated control. Two treatments (‘JAU6476 + Folicur’ and ‘V-10116 6 fl oz’) significantly improved control and preserved grain yield and quality compared with the ‘Tilt’ treatment. Application of ‘Tilt’ resulted in the least disease control of all fungicide products with five of eight categories not significantly different from the nontreated control (e.g.: FHB incidence, VSKs, DON, leaf disease severity, and test weight).

Table 3. Fusarium head blight and leaf spot disease responses from ‘Oxen’ hard red spring wheat in Crookston, Minnesota during 2004.

¹Each fungicide treatment included 0.125% Induce. Treatment abbreviations are DS, Fusarium head blight (FHB) severity (number of infected spikelets on each head); DI, FHB incidence (average number of diseased heads in a field); DX, FHB index (severity x incidence/100); VSK, visually scabby kernels; LDS, leaf disease severity (% leaf area with lesions). Different letters within a column indicate that treatments are statistically significant.

ACKNOWLEDGEMENTS

The authors would like to thank the U.S. Wheat and Barley Scab Initiative and the Northwest Research and Outreach Center for supporting this research, BASF Corp., Bayer CropScience, Syngenta Crop Protection, and Valent U.S.A. for supplying fungicide materials, and the University of Minnesota Mycotoxin lab for providing DON results.

Sources for additional information

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McMullen, M., R. Jones and D. Gallenberg. 1997. Scab of wheat and barley: A re-emerging disease of devastating impact. Pl. Dis. 81:1340-1348.

Nganje, W.E., S.Kaitibie, W.W. Wilson, F.L. Leistritz, and D.A. Bangsund. 2004. Economic impacts of fusarium head blight in wheat and barley: 1993-2001. NDSU AES Report No. 538.

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Stack R.W. and M.P. McMullen. 1995. A visual scale to estimate severity of Fusarium head blight in wheat. NDSU Ext. Bulletin 1095. Fargo, North Dakota.

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