Wheat Disease Update

Alyssa Koehler, Extension Field Crops Pathologist; akoehler@udel.edu

Wheat is in various stages of heading across the state. In Georgetown, main tillers are fully headed and we are getting close to flowering. If you plan to apply a fungicide for Fusarium Head Blight, the application window is rapidly approaching. On the FHB Prediction Center, http://www.wheatscab.psu.edu/, today’s prediction for eastern Sussex County is medium to high risk. There is a chance of rain all weekend, which will likely maintain medium to high risk levels as more plants reach 10.5.1 and begin to flower (Figure 1) over the weekend and into early next week.

Figure 1. Wheat at Feekes 10.5.1. beginning flowering

Over the past week or two, symptoms of Barley Yellow Dwarf Virus (BYDV) have shown up in barley and wheat fields. Symptoms can include yellow to purple leaf discoloration, curling of the leaves, and stunting (Figure 2). Leaf discoloration begins at the tip and the color and level of symptom development can vary based on variety, weather, fertility, and a number of other factors. In wheat, early infections are typically associated with more stunting and red-purple to yellow leaves, while later infections tend to have yellow flag leaves without stunting. BYDV is transmitted by aphids with most infection occurring in the fall and early winter. Early infection is more damaging than infection of mature plants. Resistant varieties are available in oat, but there is only limited host resistance in barley and wheat. At this point in the season, spraying for aphids will not have an impact on disease levels.

Figure 2. Wheat leaves with purple and yellow symptoms on wheat infected with Barley Yellow Dwarf Virus