Wheat Disease Update
Figure 1. Wheat field in the Hemingford area with heads still green on July 9.
|Figure 2. Wheat field in the Hemingford area which was drying down on July 9.|
July 10, 2009
|Figure 3. Leaf rust on the flag leaf of a susceptible variety.|
|Figure 4. (Left) The flag leaf of a wheat variety co-infected with leaf rust and stripe rust.|
A July 9 survey of wheat fields in the Hemingford area showed varying levels of crop maturity. In some fields, wheat heads were still green (Figure 1) and in others, the wheat crop had turned color and was drying down (Figure 2).
Leaf rust was the predominant disease in all surveyed fields (Figure 3) with an incidence of 100% and severity ranging from low (less than 10%) in resistant varieties to high (greater than 50%) in susceptible varieties. (Incidence is the percentage of affected plants and severity relates the percentage of leaf area affected.) This year leaf rust started late in the growing season (late June) and progressed rapidly due to wet weather. It is not expected to impact yields as much as if it had started in May or early June.
Stripe rust was observed on one variety in the State Variety Trial. This variety was co-infected by stripe rust and leaf rust (Figure 4).
Fusarium head blight (scab, Figure 5) was observed at a very low level in an irrigated field. The level of scab observed is not expected to impact the yield or quality of grain.
Extension Plant Pathologist