Wheat Disease Update – 25 March 2024

On March 19, Tyler Lynch (Agriculturalist Sr, OSU, Department of Plant and Soil Sciences, OSU) brought wheat samples (Figure 1) showing tan spot symptoms from the wheat variety trials at Balko (Beaver County) and Hooker (Texas County), OK. Tyler reported that tan spot incidence was low and mainly observed on lower leaves. Tan spot was reported at Chickasha (Grady County) in my previous update on March 21. On March 14, spot blotch (caused by Bipolaris sorokiniana, Figure 2) was found at low incidence at Chickasha.

 

Figure 1. Tan spot on lower wheat leaves at Chickasha, OK (March 15, 2024).

 

 

Figure 2. Spot blotch on wheat leaves at Chickasha, OK (March 14, 2024).

 

 

On March 19, powdery mildew was reported in a grower’s field at Hominy (Osage county), northeastern Oklahoma (Figure 3, 4). The infected field area showed pale green to yellow patches as shown in Figure 3. White cottony patches (fungal mycelium and spores) were observed on the upper surface of lower leaves (Figure 4). 

 

Figure 3. Light green to yellow patches in a wheat field affected by powdery mildew at Hominy, OK (March 19, 2024). 

 

 

Figure 4. White cottony patches (fungal mycelium and spores) indicative of powdery mildew infection (Hominy, OK; March 19, 2024). 

 

 

Stripe rust (Figure 5) was observed at Altus, Southwestern OK (Jackson County) on March 20, 2024. On March 22, Tyler Lynch reported moderate to high stripe rust pressure in the wheat variety trial at Altus with susceptible varieties showing up to 70% disease severity. The wheat crop at Altus is at flag leaf stage and all wheat plots at the variety trials showed symptoms of stripe rust. The wheat varieties in Altus were rated for their reactions to stripe rust. On March 22, Tyler also found stripe rust at Tipton (Tillman County), OK, however the disease pressure was low.

 

Figure 5. Stripe rust on a susceptible winter wheat variety at Altus, OK (Photo: Mike Schulz, March 20, 2024).