Wheat Disease Update - Late May

Wheat Disease Update - Late May May 26, 2016

leaf rust on triticale
Figure 1. Leaf rust on triticale at Havelock Farm on May 24
wheat-barley-yellow-dwarf
Figure 3. Barley yellow dwarf on wheat in a field in Thayer County on May 25

In research plots at Havelock Farm (Lancaster County) on May 24, there was severe stripe rust in susceptible wheat lines or varieties, low to moderate levels of Fusarium head blight in wheat and barley, and moderate to severe levels of leaf rust in triticale (Figure 1).

On May 25, a survey of growers’ wheat fields was conducted in southeast and south central Nebraska. Most fields looked healthy (Figure 2) with little or no disease. Fungal and virus diseases were found at varying levels in some fields. A field in Saline County was free of foliar diseases but had trace levels of Fusarium head blight.

In Thayer County, one field had low to moderate levels of stripe rust that was severe in several hot spots. This field also had moderate levels of barley yellow dwarf (Figure 3) and trace levels of wheat streak mosaic (Figure 4).

In Nuckolls County, one field had severe stripe rust (Figure 5) that was widespread within the field. In some sections of the field where stripe rust infections started earlier, the entire foliage was dead and stripe rust had moved onto the awns (Figure 6).

Field of healthy wheat in late May
Figure 2. A healthy looking wheat field in Gage County on May 25

wheat streak mosaic
Figure 4. Wheat streak mosaic in a wheat field in Thayer County on May 25
severe stripe rust
Figure 5. Severe stripe rust in a wheat field in Nuckolls County on May 25
Stripe rust on wheat awns
Figure 6. Stripe rust on awns in a wheat field in Nuckolls County on May 25

Management

Wheat in most fields in the southernmost tiers of counties is past the flowering growth stage. It is too late to spray these fields.  Fields that were sprayed earlier have little or no stripe rust.

In the rest of the wheat growing areas in the state, if wheat is headed and is not past the flowering growth stage, it is recommended that a triazole fungicide that will control both stripe rust and Fusarium head blight be sprayed. (See the May 19 CropWatch article with information on triazole and strobilurin fungicides.)

If wheat is not headed, any fungicide labeled for use on wheat can be sprayed to control or prevent stripe rust and other foliar fungal diseases.

Virus diseases cannot be controlled once they occur.