Occurrence and Trends of Weed Seed Contaminants in Fine Fescue Seed Lots in Oregon

摘要

Fine fescues are highly valued cool-season turf species. Nearly all of the fine fescue seed grown in the United States is produced in Oregon, although little is known about the occurrence of weed seed contaminants in these seed lots. This study was conducted to assess the diversity and frequency of occurrence of weed seed in chewings (Festuca rubra subsp. commutata), creeping red (Festuca rubra subsp. rubra), and hard fescue (Festuca trachy-phylla) samples submitted to the Oregon State University Seed Laboratory. The samples represent seed lots from seed production fields. Weed seed data from 1986-1995 and 2002-2006 were collected from the purity analysis reports of certified seed samples of chewings, creeping red and hard fescue. Ninety-five weed seed contaminants were identified to species, with an additional 30 identified to genus. No weed seeds contaminants were found in 30% to 50% of the seed lots, depending on the year. Typically, fewer than three different weed species were detected within asample. The most common contaminants, occurring annually, were rattail fescue (Vulpia myuros), annual bluegrass (Poa annua), and downy brome (Bromus tectorum). Among these, rattail fescue was the most common, occurring in 30% to 61% of seed samples, depending on the year. The number of weed species varied among years and increased as the number of seed lots tested per year increased. During the past decade, the number of new weed species contaminants detected increased at a rate of approximately threeper year.