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Wheat Disease Update – 21 March 2024

Late February-early March 2024, symptoms of wheat soilborne mosaic virus (SBWMV)/wheat spindle streak mosaic virus (WSSMV) were observed at Oklahoma State University (OSU) Entomology and Plant Pathology farm in Stillwater. The susceptible wheat check ‘Vona’ and other susceptible hard winter wheat breeding lines showed stunting and yellowing (Figure 1, 2). Most wheat varieties grown in Oklahoma and the U.S. Central Plains are resistant to these virus diseases.

 

Two different wheat lines of early stage of growing. The right line is a darker green and a little taller.

Figure 1. Resistant vs. susceptible hard winter wheat lines to wheat soilborne mosaic virus /wheat spindle streak mosaic (Stillwater, OK; February 29, 2024).

 

 

Two wheat blades next to each other. The top wheat blade is more yellow and has a view lines of green. The bottom wheat blade looks all green and normal.

A copper penny on top with a green wheat blade with a view lines of yellow.

Figure 2. Wheat showing reactions to the wheat soil-borne mosaic (WSBM)/wheat spindle streak mosaic (WSSM) complex.
Top: Symptoms typical of WSBM.
Bottom:  Symptoms typical of WSSM.

 

 

On March 15, 2024, Septoria tritici blotch (Figure 3, 4) was observed in Dr. Amanda Silva’s variety trial at the OSU North Central Research Station in Lahoma, OK (Garfield County). Septoria tritici blotch was observed on all wheat varieties, however symptoms were limited to the lower canopy. On March 15, 2024, we also observed symptoms of tan spot (Figure 5) at the OSU South Central Research Station in Chickasha, OK (Grady County). Tan spot incidence was low to moderate at Chickasha and symptoms were observed on lower leaves.

 

Showing big brown circles with yellow around the brown in the middle of a green wheat leave.

Figure 3. Wheat showing reaction to Septoria tritici blotch (Lahoma, OK; March 15, 2024).

 

 

Showing three big brown circles with black dots in the brown circle on a yellow wheat leave.

Figure 4. Septoria tritici blotch on wheat leaf. Black specks on the lesions indicate pycnidia (Lahoma, OK; March 15, 2024). 

 

 

Yellow and brown areas on green wheat leave.

Figure 5. Symptoms of tan spot on lower wheat leaves (Chickasha, OK; March 15, 2024).

 

 

Stripe rust (Figure 6) and leaf rust (Figure 7) have not yet been observed in Oklahoma. However, there were reports of stripe rust in wheat fields in both Louisiana and Texas as early as January 31. On March 7-8, 2024, Dr. Shuyu Liu (Wheat Breeder, Texas A&M University) reported high incidence and severity of stripe rust at McGregor, Chillicothe, and Castroville TX. The early appearance of stripe rust in Texas indicates a potential stripe rust epidemic in Oklahoma if the weather conditions continue to be favorable. Leaf rust was also observed at lower incidence/severity at Castroville, TX on March 8, 2024 and it can develop further with rising temperature.

 

A hand holding a wheat leave with yellow and brown areas.

Figure 6. Stripe rust on a susceptible winter wheat variety in Castroville, TX (Photo: Dr. Shuyu Liu, March 8, 2024).

 

 

A close up of four wheat leaves with yellow and brown spots.

Figure 7. Leaf rust on a susceptible winter wheat variety in Castroville, TX (Photo: Dr. Shuyu Liu, March 8, 2024).

 

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