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Winter Wheat Disease Update: Leaf Diseases and FHB on the Increase
Winter wheat fields scouted last week show an increase in fungal leaf diseases and bacterial leaf streak. Among the fungal diseases, the most common leaf diseases are tan spot, Stagonospora leaf blotch, and stripe rust. The risk for Fusarium head blight has also started to increase in a number of areas in the state.
Bacterial Blight Developing in Oats
Oats scouted in a few fields in the Eastern and South Central parts of the state were found with bacterial blight developing on the lower leaves. Plants infected have leaves with water-soaked brown longitudinal lesions in the top-half of the leaf. Severe symptoms can lead to premature leaf death.
Stripe Rust and Leaf Rust Developing in Winter Wheat
Stripe rust and leaf rust were found in winter wheat plots at the SDSU research farm in Aurora. Observation of these two rusts indicates that we have inoculum in our area, therefore winter wheat fields should be scouted until wheat is done flowering.
Aphid Populations Being Observed in Wheat
During the past couple of weeks, reports of aphid populations in wheat fields have slowly been increasing. Typically, the initial aphid populations are observed earlier in the season, but the 2019 spring may have delayed infestations.
Use the Scab and Leaf Disease Forecasting Tools to Decide on Fungicide Application in Wheat
Fungicide application in winter wheat has consistently shown to prevent yield loss caused by fungal diseases. However, in some cases, a fungicide application may not always result in a profitable yield when disease pressure is low. Disease forecasting tools can aid fungicide application decisions and hence improve on the profitability of fungicide application.
Bacterial Leaf Blight Developing in Winter Wheat
Recent winter wheat scouting found bacterial leaf blight developing in some fields. Bacterial leaf blight is caused by the bacteria, Pseudomonas syringae pv. syringae. The disease develops under frequent rains between 59 and 77 degrees Fahrenheit.
2018 Field Plot Summaries for Wheat Disease Management Trials
The wheat disease management field experiments conducted in the 2018 growing season evaluated several experimental and commercially available fungicides for managing foliar, head or root diseases of spring wheat. Foliar and spike/head diseases incidence and severity were assessed. The field experiments were implemented at Volga Research Farm and Northeast Research Farm (NERF) near South Shore, SD. Results of the same experiment may vary between Volga and Northeast due to environmental differences between the two locations.
Wheat Stem Maggots Observed in S.D. Wheat
While scouting wheat fields throughout South Dakota, we have started noticing the presence of bleached heads scattered throughout many different fields. These discolored heads are the result of an infestation of the wheat stem maggot.
Barley yellow dwarf developing in winter wheat.
Barley yellow dwarf is starting to develop in winter wheat. Barley yellow dwarf is caused by the Barley yellow dwarf virus (BYDV). This disease usually becomes more distinct at flag leaf emergence. A typical symptom of Barley yellow dwarf is the purplish-yellow color of infected leaves, especially the flag leaf.
Winter Wheat Breaking Dormancy Early
A threshold indicator for winter wheat emergence is to consider average temperatures over a 14-day period. When that 14-day average temperature is equal to or above 5°C, or 41°F, then hard red winter wheat can break dormancy.