(Left) Figure 1. Fusarium head blight on wheat varieties 2137 (left) and Overley (middle) in research plots and a field at the ARDC on June 4. (Photos by Stephen Wegulo)
(Right) Figure 2. Risk of Fusarium head blight as displayed by the national Risk Assessment Tool on June 5. Green – low risk; yellow – medium risk; red – high risk.
Figure 3. Black chaff on a wheat head in a field at the ARDC on June 4. To view how this and other wheat varieties performed in the field, attend the June 11 Wheat Tour at the ARDC near Mead.
June 5, 2015
Inspection of wheat research plots and a wheat field at the UNL Agricultural Research and Development Center (ARDC) near Mead on June 4 confirmed Fusarium head blight, also known as scab. Incidence (percentage of diseased heads) was low and severity (percentage of diseased spikelets on a head) ranged from low to high (Figure 1). The disease is in its initial stages of development.
Due to the frequent and heavy rainfall events that occurred before and during flowering, development of Fusarium head blight is expected to progress to severe levels in susceptible varieties within the next two to three weeks in some areas in the state. As of June 5, the Fusarium Head Blight Risk Assessment Tool showed more than half of Nebraska at moderate to high risk (Figure 2).
Most of the Panhandle is at high risk. Although occurrence of Fusarium head blight is rare in the Panhandle, excessively wet weather that coincides with the period before and during flowering can favor development of the disease. This was the case in 2009 when Fusarium head blight occurred at low to moderate levels in some fields in the Panhandle.
Other diseases observed at the ARDC were black chaff (Figure 3) and advanced stages of stripe rust (Figure 4). Black chaff is a bacterial disease; it is also known as bacterial streak when it occurs on leaves.
Management
Figure 4. Advanced stages of stripe rust in a field planted with a susceptible wheat variety at the ARDC on June 4.
An application of Prosaro or Caramba is recommended at early flowering to control Fusarium head blight. Consider the yield potential and other factors such as damage already done by stripe rust when making the decision to apply a fungicide to control Fusarium head blight. The probability of a return on investment from applying a fungicide to control Fusarium head blight increases with increasing yield potential above 40 bu/acre. The preharvest interval for Prosaro and Caramba is 30 days.
It is too late to control stripe rust in the southern part of the state. In northern wheat-growing areas, if wheat is in the early flowering growth stage and stripe rust has not progressed to damaging levels, consider applying Prosaro or Caramba to control both stripe rust and Fusarium head blight.
