Application of a New Sdhi Containing Fungicide in Management of Stem Rust in Perennial Ryegrass Seed Crops.

Stem rust caused by Puccinia graminis subsp. graminicola is a serious and widespread disease in perennial ryegrass (Lolium perenne L.) grown for seed in Willamette Valley of western Oregon. Stem rust is known to decrease seed yield, thousand seed weight, and biomass dry weight (seeds and straw) when moderate to severe infections occur. Triazole and strobilurin containing fungicides are currently used by grass seed producers to manage stem rust, and applications are often repeated two or three times in May and June when the disease is active. There has been growing interest in evaluating newly available succinate dehydrogenase inhibitor (SDHI) fungicides for stem rust control and fungicide resistance management in grass seed crops. The objectives of this study were to determine the effect of Trivapro^®, a new SDHI containing fungicide, on stem rust control, seed yield, thousand seed weight, percent cleanout, and biomass dry weight in ‘Accent’ perennial ryegrass, a known susceptible variety. Treatments consisted of an untreated control, 1.0 L/ha Quilt Excel^®, and 0.7, 1.0, and 1.3 L/ha Trivapro^® applied at growth stage BBCH 51, when stem rust was first detected in the plots.  Disease ratings and harvest measurements will be taken in the summer of 2016. This abstract will be modified after harvest (and prior to the annual meeting) to include results of the study.