Effect of a Strobilurin-Containing Fungicide Applied at Two Timings on Seed Yield in Tall Fescue

Abstract

Field studies were conducted from 2010 through 2012 in Oregon's Willamette Valley to determine the effects of a strobilurin-containing fungicide applied at two growth stages on seed yield in tall fescue [Schedonorus phoenix (Scop.) Holub] crops. Stem rust (caused by Puccinia graminis subsp. graminicola) is the primary disease pest of tall fescue in the region, where seed yield losses can be as severe as 70% when the disease is not managed. Weather conditions were favorable for stem rust development in 2012; however, cool and wet conditions in 2010 and 2011 resulted in low pressure from stem rust. Strobilurin-containing fungicide treatments increased seed yield 17% over the untreated control across sites and years, but the greatest seed yield increases were noted when stem rust pressure was highest in 2012. Seed yield increases were attributable to a combination of increased seed number and weight. Cleanout was reduced by up to 18% with fungicide treatments. While fungicide treatment increased seed yield even with low disease incidence and severity, there were no effects on the plant growth or nitrogen metabolism of tall fescue. Tall fescue seed yield can be increased by application of strobilurin-containing fungicides, but the response is dependent on the incidence and severity of stem rust.