Stripe rust has significantly increased in all wheat-growing areas in Nebraska. It is recommended that wheat be treated with a fungicide to protect the flag leaf. If the incidence (percentage of flag leaves diseased) or severity (percentage of the flag leaf area diseased) is less than 50%, spraying a fungicide will significantly reduce yield loss due to stripe rust.
A survey of wheat fields in southeast and south central Nebraska this week found most fields looking healthy with little or no disease. Fungal and virus diseases were found at varying levels in some fields. Depending on growth stage and disease present, fungicides may still be beneficial.
With wheat headed or flowering in southeast and south central Nebraska, head diseases are starting to appear, including Fusarium head blight, loose smut, white mold (scab) and barley yellow dwarf. Wheat stem maggots were also causing damage.
Wheat is heading, headed, or flowering in most fields in eastern Nebraska. The Fusarium Head Blight Prediction Center is currently showing a low risk for scab in Nebraska. However, due to the recent rains, there is a possibility that some level of scab may occur in some fields, and the risk will be higher in areas that receive rainfall in the next 10 days. Base the decision to apply a fungicide to suppress scab on the risk level, the cost of application, and the price of wheat.
Report of this week's wheat disease survey: On May 3 stripe rust was observed for the first time at the UNL Havelock Farm in Lincoln, where incidence was low and severity ranged from trace to high. t the Agricultural Research and Development Center near Mead on May 3, infections had spread from small hot spots one to two weeks earlier to larger areas in research plots, and leaf damage was apparent Wheat growth stage at these two locations ranged from flag leaf emergence to heading. On May 5, field surveys found stripe rust to be widespread in the west central and southern Panhandle of Nebraska. The flag leaf had not emerged or was just starting to emerge in these parts of the state. Wheat mosaic virus was identified in Deuel County.
Figure 1. A healthy-looking wheat field in Saline County on April 28. Recent rains boosted wheat growth, but created conditions favorable for wheat disease. Growers are encouraged to scout and treat if necessary to protect the flag leaf. (Photos by Stephen Wegulo)
Wheat field surveys in southeast and south central Nebraska (Lancaster, Saunders, Saline, Filmore, Thayer, Nuckolls, Webster, and Clay counties) on April 27-28 found little disease in growers’ fields. The wheat crop looked healthy and was growing vigorously (Figure 1) thanks to the recent rains.
Following rains across much of the state last week, wheat diseases appear to be increasing, based on field surveys this week. Reported diseases include powdery mildew, stripe rust, and leaf spot.
(From left) Figure 1. A hot spot of stripe rust in a research plot at the ARDC near Mead on April 14. Figure 2. Leaf rust in a research plot at the ARDC near Mead on April 14. Figure 3. A healthy wheat field in Thayer County on April 13. (Figures 1-8 by Stephen Wegulo)
Wheat disease surveys on April 8 and April 12-14 found stripe rust and leaf rust at trace to low levels in south central and southeast Nebraska and in the Panhandle. Given the locations of outbreaks in Banner County this spring are the same as when the disease was identified in seedlings last fall, the two rusts may have overwintered. See more reports and management recommendations.
