Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu
Across much of the region, barley is approaching or at heading and wheat is ranging from Feekes 7-9. I have heard very few reports of powdery mildew this season and with more warm weather on the way, it is unlikely to develop. We did receive quite a few calls this spring about yellow patches, particularly in malting barley (Figure 1). These patches tested positive for Barley Yellow Dwarf Virus (BYDV) and often had Pythium species recovered from the root system. We do not usually see such early symptoms of BYDV and we will be keeping a close eye on the amount of symptoms in barley and wheat flag leaves as we continue to understand what factors were contributing to these patches. Leaf discoloration from BYDV in flag leaves can be yellow, orange, red, or purple and plants may have shortened internodes resulting in shorter plants (Figure 2).
We are currently at low risk on The Fusarium Risk Tool http://www.wheatscab.psu.edu/, with the eastern part of Sussex County moving to medium/high risk only for very susceptible hybrids in the six day outlook (Figure 3). In barley, flowering begins just before the spike emerges from the boot. While florets are not as susceptible, Fusarium can infect the glumes and produce deoxynivalenol (DON). DON accumulation is the primary concern, especially for malting barley acreage. If making a fungicide application to manage FHB in barley, the optimum stage to protect barley glumes is when the spike is fully emerged from the boot and florets are exposed (Figure 4). Work in North Carolina has shown that application up to 6 days after 100% emergence can reduce infected kernels and DON. In our 2022 malting barley fungicide trials we had moderate FHB pressure and saw DON reduction with anthesis application of Caramba, Miravis Ace, Prosaro Pro or Sphaerex. We also had some two pass treatments, which had the lowest DON and Fusarium damaged kernels (Table 1).
Figure 1. Yellow patches present in multiple malting barley fields this spring that were positive for barley yellow dwarf virus and Pythium species in the root system
Figure 2. Discoloration of flag leaves due to barley yellow dwarf virus
Figure 3. Fusarium Risk Tool Prediction for April 13, 2023
Figure 4. Stages of barley at or near spike emergence, with the two right spikes (100% emergence and 6 days after) at optimum stage for fungicide application.
Table 1: Carvel Research and Education Center Georgetown, DE
2022 Barley Fungicide Timing Trial
| Treatmentz | % Frost Incidencey | % Frost Severity | FHB % Incidencex | FHB % Severityw | DON (PPM) | FDK (%) | Yield (Bu/A)v |
| Control | 52.0 | 8.50 | 26.0 | 2.24 | 2.32 a | 2.08 a | 67.5 c |
|
Prosaro anthesis 6.5 oz/a |
66.0 | 13.46 | 27.0 | 2.43 | 1.72 ab | 1.44 ab | 69.1 bc |
|
Caramba anthesist 13.5 oz/a |
56.0 | 9.11 | 31.0 | 2.29 | 1.51 b | 1.52 ab | 70.7 abc |
| Miravis Ace anthesis 13.7 oz/a | 44.0 | 8.50 | 23.0 | 2.10 | 0.71 cde | 1.00 bc | 80.2 ab |
| Prosaro Pro anthesis 10.3 oz/a | 54.0 | 11.12 | 29.0 | 2.94 | 0.85 cd | 1.16 bc | 75.8 abc |
|
Sphaerex anthesis 7.3 oz/a |
66.0 | 14.39 | 27.0 | 1.96 | 1.28 bc | 0.92 bc | 65.7 c |
|
Miravis Ace anthesis fb Prosaro Pro 5 daa 13.7 oz/a fb 10.3 oz/a |
70.0 | 12.99 | 22.0 | 1.68 | 0.30 e | 0.52 c | 77.6 abc |
|
Miravis Ace anthesis fb Sphaerex 5 daa 13.7 oz/a fb 7.3 oz/a |
52.0 | 10.28 | 26.0 | 2.80 |
0.40 de
|
1.08 bc | 74.8 abc |
|
Miravis Ace anthesis fb Tebuconazole 5 daa 13.7 oz/a fb 4 oz/a |
46.0 | 6.92 | 16.0 | 1.54 | 0.79 cd | 1.08 bc | 81.7 a |
| p-value | 0.58 | 0.31 | 0.85 | 0.90 | 0.0001 | 0.0002 | 0.002 |
| LSD (α=0.05) | ns | ns | ns | ns | 0.6 | 0.5 | 8.15 |
|
Dr. Alyssa Koehler 302-856-2585, ext. 571 akoehler@udel.edu |
z Applications were made at anthesis 4/25/22 and 5 days after anthesis (daa) 4/29/22 using a CO2 pressurized backpack sprayer equipped with Turbo TwinJet 1102 nozzles calibrated to deliver 20 GPA at 40 psi. All treatments included 0.125% non-ionic surfactant, Induce 90SL, fb= followed by.
y Percent of 10 heads showing frost damage. Means followed by the same letter are not significantly different based on Fisher’s Least Significant Difference (LSD; α=0.05), ns= not significant.
x Fusarium Head Blight Incidence was visually assessed as the % of 20 barley heads per plot displaying symptoms.
w Fusarium Head Blight Severity was visually assessed as the average amount of symptoms present on 20 barley heads per plot.
vPlots were harvested 6/21/22 and yield was adjusted to 13.5% Moisture.
Variety: Violetta
Planting Date: 10/20/21
Planting Population: 1.5 mil sd/A