Alyssa K. Betts, Extension Field Crops Pathologist; akoehler@udel.edu
Wheat is just approaching flowering. Conditions have been dry, and we are at low to moderate disease risk in susceptible wheat based on the FHB Risk Model (Figure 1). The forecast has been bouncing around, but chances of rain are present for multiple consecutive days. While we could use some rain, the amounts, and durations of these rain events along with wheat growth stage could impact our FHB risk level. If you are in a dry situation and have been trying to irrigate focus on getting soil moisture as close to field capacity prior to flowering and then pause irrigation for at least 8-10 days depending on the spread of flowering occurring in the field. Water during flowering of primary or secondary tillers carries risk. If you are planning a wheat fungicide application, scout frequently and wait to apply when at least 50% of the wheat heads are flowering. You will be looking for bright yellow anthers in the center of the wheat head to signal the start of flowering (Figure 2). Remember, if you spray too early, heads that have not emerged (secondary tillers) will not be protected by the fungicide application. Additional details on fungicide application can be found in the April 4 article.
Figure 1. FHB Risk Model for susceptible wheat on May 1, 2025 (wheatscab.psu.edu).
Figure 2. Flowering wheat with yellow anthers visible.
Stripe rust appeared in eastern NC on April 8 and has been observed at very low incidence on eastern shore VA. We have not yet seen any stripe rust in DE. The yellow to orange pustules of stripe rust are found in stripes down the leaf (Figure 3). Common rust can also be present, particularly late in the season, but the pustules are randomly scattered over the leaves (Figure 3). Varieties that are resistant and moderately resistant to stripe rust are at low risk, those rated as susceptible or moderately susceptible should be monitored. Early season infections are the most damaging for yield. Last year we saw some stripe rust appear in susceptible varieties around the time of heading, and it was well managed by fungicides applied for head scab.
Figure 3. Wheat leaf with lesions from stripe rust (left) and common rust (right).