|MELLBYE, M - Oregon State University
|SILBERSTEIN, T - Oregon State University
|GINGRICH, G - Oregon State University
Submitted to: Seed Production Research at Oregon State University
Publication Type: Experiment Station
Publication Acceptance Date: 2/28/2009
Publication Date: 3/31/2009
Citation: Pfender, W.F., Mellbye, M.E., Silberstein, T.B., Gingrich, G.A. Five year field evaluation summary of the USDA stem rust model for perennial ryegrass. Seed Production Research at Oregon State University. 2009. p. 26-28.
Interpretive Summary: Each year approximately $10 to $20 million is spent on fungicide spray programs for stem rust control in grass seed fields in western Oregon, making stem rust the most costly disease problem in PNW grass seed crops. Timely applications of fungicides are critical in obtaining effective control and keeping application costs to a minimum. A model of stem rust disease based on weather patterns and scouting was developed by researchers at USDA-ARS as a tool to help decide if and when sprays are needed. The objective of this study was to determine the effectiveness of fungicide applications applied according to information provided by the USDA Rust Model in comparison to traditional application programs. Over the 10 site-years shown in Table 1, there were three cases in which the use of the model was no different from the standard treatment, either in fungicide use or yield. In 7 of 10 cases the model provided an economic benefit, ranging from $0 to $143 per acre, through reduced fungicide cost and/or improved yield. The average benefit of using the model, year in and year out, was about $39 per acre per year, and the model did not result in economic loss in any of the cases. So the rust model appears to be a safe addition to existing tools for making rust management decisions.
Technical Abstract: The objective of this study on stem rust of perennial ryegrass was to determine the effectiveness of fungicide applications applied according to information provided by the USDA Rust Model in comparison to traditional application programs. Seed yield and rust control data in this report were obtained from large scale, on-farm yield trials conducted on turf type perennial ryegrass from 2004-2008 as part of an on-going OSU Extension Service testing of fungicide products. A weather station was installed in each test field. Data from the weather stations was used to predict potential rust infection initiation and severity and provide information, by operating the publicly-available stem rust estimator webpage (http://pnwpest.org/cgi-bin/stemrust1.pl), for fungicide applications. Rust infection level in years of “severe” disease pressure ranged from 44% to 85% in unsprayed check plots (late June to early July ratings). Under these condition, the increase in seed yield from fungicide applications, when compared to the non-treated check plot, ranged from 630 to 1245 lb/acre. Over the 10 site-years shown in Table 1, there were three cases in which the use of the model was no different from the standard treatment, either in fungicide use or yield. In five of the cases fungicide use (and therefore cost) was less in the model treatment, with no reduction in yield. In one case the model treatment yielded significantly more seed than the standard treatment even though the number of fungicide treatments was the same, perhaps due to better fungicide timing recommended by the model. And in one case, there was an increase in yield as well as a decrease in fungicide use, again due to better timing of applications. The average benefit of using the model was about $39 per acre per year.