Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2000
Publication Date: N/A
Citation: Interpretive Summary: Even moderate levels of two common wheat diseases, powdery mildew and leaf rust, reduced milling flour yield by 0.6% on unsprayed plots compared to plots receiving two fungicide applications, representing an economic loss of $300,000/yr for a mill producing one million lbs of flour/day. That loss was in addition to the significant grain yield loss in unsprayed plots compared to sprayed plots. There was no significant difference in 500-kernel weight due to fungicide application. Disease reduction was associated with a decrease in kernel softness, but the reduction was never below the acceptable range of 50-60% S.E., a measure of the grain texture. Thus the economic benefit in controlling disease would be realized by millers and bakers as well as producers.
Technical Abstract: Changes such as a reduction in milling and baking quality (especially flour yield) of soft red winter wheat can have a large economic impact on the flour mills. To determine the relationship between the control of early-season powdery mildew and late-season leaf rust on flour yield, flour protein, alkaline water retention capacity and kernel texture (softness equivalent), a study was conducted over two years at Kinston and Plymouth, NC. Different levels of powdery mildew and leaf rust developed on three winter wheat cultivars which varied in their level of disease resistance, the presence of seed treatment and the presence and timing of foliar fungicide application. In Kinston and Plymouth in 1989- 990 where leaf rust occurred early, the softness equivalent score was lower in wheat grown from triadimenol treated seed. The following year when the leaf rust epidemic increased later, foliar fungicide application reduced disease and resulted in lower softness equivalent scores at both Plymouth and Kinston for 'Saluda' and in Kinston for 'Coker 983'. A regression model was developed to describe the relationship between the log of the area under the disease progress curves and adjusted flour yield. The flour yield of Saluda was reduced in the presence of powdery mildew such that: %flour yield = 103.96 - 0.92 (1AUMPC).