Fusarium head blight (FHB) has been known to cause epidemics on small grain crops in Minnesota for decades (Figure 1). The disease is a constant threat to the economic stability of small grain growers in production areas with rain and/or high relative humidities at critical plant growth stages such as early flower for wheat and early heading for barley.

Figure 1. The number of years, by decade, of reported Fusarium head blight (scab) epidemics in Minnesota small grain crops.

FHB control strategies such as crop rotation and residue management are known to help in reducing disease severity. Growing disease-tolerant hard red spring wheat varieties such as Alsen or Hannah has offered an additional level of crop protection. Yearly research activities meant to identify effective, experimental fungicides continue at approximately 24 uniform trial sites across eleven wheat producing states. Researchers continue their efforts in identifying disease control strategies to reduce losses in small grains resulting from FHB.

Uniform fungicide trials were initiated on wheat and barley at the Northwest Research and Outreach Center in Crookston on 28 April 2003. ‘Oxen’ hard red spring wheat and ‘Robust’ spring barley were seeded at 1.25 mil. live seed/acre and 1.375 mil. live seed/acre, respectively. Plots were inoculated with 250 g of Fusarium graminearum infested corn grain five weeks after planting and night-cycle mist irrigation was started. Misting was discontinued temporarily during the growing season when rain caused standing water at the testing sites. Fungicide treatments were applied to wheat nine weeks after planting, at early flowering (Feekes 10.51 growth stage), and to barley eight weeks after planting, at early heading (Feekes 10.4). Foliar applications were made with a CO₂ backpack type sprayer with forward and backward facing nozzles.

Hard Red Spring Wheat (Table 1)

Weather conditions prior to and at early flower supported plant infection and disease progression.

Table 1. Disease responses of Fusarium head blight from fungicide treatments applied to ‘Oxen’ hard red spring wheat in Crookston, MN.

*Severity, the percent of spikelets per head with FHB symptoms; incidence, the percent of heads per plot with at least one infected spikelet.
**Each fungicide treatment included 0.125% Induce. Two experimental products were tested in the trial; JAU6476 from Bayer CropScience and V-10116 from Valent.

Compared to the nontreated control treatment:

• All fungicide treatments significantly reduced disease severity, also known as the percent of spikelets on heads that exhibited symptoms.
• Two fungicide treatments, JAU6476 5.7 fl. oz. and JAU6476 3.6 fl. oz. + Folicur 4 fl. oz., significantly reduced disease incidence, also known as the percent of heads per plot with disease symptoms.
• Each fungicide treatment significantly reduced DON levels with one exception (JAU6476 480SC 5.7 fl. oz.).
• All fungicide treatments significantly increased yield and test weight.

Compared to the Folicur 4 fl. oz. treatment:

• All fungicide treatments significantly reduced disease severity.
• Two fungicide treatments, JAU6476 5.7 fl. oz. and JAU6476 3.6 fl. oz. + Folicur 4 fl. oz., significantly reduced disease incidence.
• Two fungicide treatments, V-10116 6.0 fl. oz. and V-10116 8.0 fl. oz., significantly reduced DON levels.
• No fungicide treatments significantly increased yield.
• Three fungicide treatments, JAU6476 5.7 fl. oz., JAU6476 3.6 fl. oz. + Folicur 4 fl. oz., and V-10116 6.0 fl. oz., significantly increased test weight.

Spring Barley (Table 2)

Severe weather conditions during booting (Feekes 10) caused plants to lodge approximately five days before fungicide treatments were applied. As a result, trial data must be ‘weighed’ against the ‘percent plot lodged’ rating before assessing treatment effectiveness. Nontreated control plots had the least plants lodged (58.8%) which resulted in reduced disease severity compared with Folicur 4 fl. oz. treated plots (81% lodged). Overall, V-10116 8 fl. oz. reduced disease severity by 17% and DON levels by 38% compared with the control, in spite of its 80% lodging score.

Table 2. Disease responses of Fusarium head blight from fungicide treatments applied to ‘Robust’ spring barley in Crookston, MN.

*Severity, the percent of spikelets per head with FHB symptoms; incidence, the percent of heads per plot with at least one infected spikelet.
**Each fungicide treatment included 0.125% Induce. Two experimental products were tested; JAU6476 from Bayer CropScience and V-10116 from Valent.

NOTE: Severe weather caused barley plants to lodge approximately five days before fungicide treatments were applied. Plot lodging assessments were taken six weeks after plants went down.

Acknowledgements
We would like to thank the U.S. Wheat and Barley Scab Initiative and the Northwest Research and Outreach Center for supporting these trials, as well as Bayer CropScience and Valent U.S.A. for providing fungicide materials.