Stripe Rust: Earlier Than Normal Detection In Wheat Is Concerning

 

Stripe rust was found in a winter wheat field south of Miller in Hand County. The incidence and severity were low (scattered plants and one or two leaves), however, the leaves that were observed with stripe rust had heavy pustules (Fig. 1).

 

 

 

 

 

Stripe rust (Puccinia striitiformis f. sp. tritici) infection and progress is favored by cooler temperatures (45-59° F) and wet conditions (at least 8 hours of leaf wetness). Cold conditions may halt progress of this rust but infection can still take place down to 45° F. This rust usually does not survive winter in South Dakota but since we are seeing this rust early, it may have survived locally as this winter was a mild one. Research done on stripe rust winter survival at freezing temperatures indicates mycelia of this rust could survive on leaves at 14° F under snow cover. The survival is even higher on winter hardy cultivars.

 

The 2015 wheat season had severe outbreak of stripe rust and this might have left high stripe rust inoculum that may have survived the winter. If stripe rust is not controlled early, it can develop in a short period of time and cause severe yield losses (Fig. 2).

 

 

 

 

 

Stripe rust is normally detected in winter wheat in South Dakota towards the end of May/early June. Detection of stripe rust this early indicates the risk for this rust is imminent. Scout fields at the time of herbicide application and assess the level of infection. If the planted cultivar is rated as susceptible or moderately susceptible to stripe rust, an early fungicide treatment may be needed (rating of cultivars can be found in SDSU Extension’s 2015 South Dakota Winter Wheat and Spring Wheat variety trial results.