Wheat Disease Update — Levels Still Low

May 30 Nebraska Extension Wheat Field Day in Jefferson County
Figure 1. Attendees viewed more than 30 wheat variety trials at this Nebraska Extension Winter Wheat Field Day northeast of Fairbury May 30. Ten more wheat field days will be held this June. (Photos by Stephen Wegulo)

Wheat Disease Update — Levels Still Low May 31, 2018

Fungal diseases have been absent or at very low levels in Nebraska wheat fields. Recent rains have alleviated stress from lack of moisture in the wheat crop across the state, but the rainfall is still inadequate in some areas in the southeast. During surveys in southeast and south central Nebraska May 29-May 30, most fields looked green with high yield potential. In research plots at the Havelock Research Farm near Lincoln in Lancaster County and at the South Central Ag Lab near Clay Center in Clay County, the predominant disease found at low levels was barley yellow dwarf (Figure 2) caused by aphid-transmitted viruses.

barley yellow dwarf in wheat
Figure 2. Barley yellow dwarf at low levels in research plots at the South Central Ag Lab near Clay Center in Clay County on May 30. Similar levels were observed at the Havelock Research Farm near Lincoln in Lancaster County on May 29
White head of wheat
Figure 3. A white head in a grower’s wheat field in Jefferson County on May 30
Wheat stem maggot damage
Figure 4. Wheat stem maggot

Scattered white heads (Figure 3) resulting from damage by the wheat stem maggot (Figure 4) were observed at low levels in research plots and in a grower’s field in Jefferson County where the first wheat field day this year was held on May 30 (Figure 1).

Fusarium Head Blight Risk

Wheat in eastern, south central, and southwest Nebraska is headed or mostly headed. In the Panhandle, heading is in progress. It is during the heading growth stage and especially during flowering that the Fusarium head blight (scab) fungus infects wheat. Scab is favored by moderate to heavy rainfall before and during flowering. Although the risk of scab is low in most of the wheat growing areas in the state, there is a small area in western Nebraska that is at high risk (Figure 5). Growers in this area should consider applying a fungicide to suppress scab. The recommended fungicides for scab suppression are Prosaro and Caramba. They are also excellent in controlling foliar fungal diseases.

Wheat scab risk map
Figure 5. Fusarium head blight risk map for Nebraska as of May 31. Source: Pennsylvania State University Wheat Scab tracking website at http://www.wheatscab.psu.edu/