Wheat Disease Update

Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu
We have had quite a few rain events with more in the forecast for this weekend. The rain and warm temperatures are maintaining another high-risk year for Fusarium Head Blight. If your wheat is close to flowering or, already flowering and you are considering a fungicide application, the optimal window is anthesis until about 5 days after. Once wheat has finished flowering, if your plants were infected, FHB symptoms will be visible in 18-24 days. Next week we will discuss steps for scouting and assessment of FHB damage. We have seen a few lesions caused by Parastagonospora nodorum (formerly Stagonospora nodorum). Symptoms include small brown lesions with a yellow halo (Figure 1). This fungus causes Septoria nodorum blotch, also be referred to as Stagonospora nodorum blotch, and it is the same causal agent of Stagonospora glume blotch. Since leaf blotch precedes glume blotch, lesions high in the canopy and on the flag leaf can indicate an elevated risk for glume blotch.

Figure 1: Septoria nodorum blotch lesions on wheat leaves