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Title: Characterizing pathways of invasive plant spread to Alaska: II. propagules from imported hay and straw

Author
item Conn, Jeffery
item Stockdale, Casie
item Werdin Pfisterer, Nancy
item Morgan, Jennifer

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2010
Publication Date: 11/1/2010
Citation: Conn, J.S., Stockdale, C.A., Werdin Pfisterer, N.R., Morgan, J.C. 2010. Characterizing pathways of invasive plant spread to Alaska: II. propagules from imported hay and straw. Journal of Invasive Plant Science and Management. 3(3):276-285.

Interpretive Summary: Hay and straw was studied to determine whether its shipment is a significant pathway for importation and spread of weed seed in Alaska. Vendors were surveyed in 2004 and 2005 to determine the amounts and types of hay and straw sold. Three bales of each type of hay or straw were purchased. The hay and straw types were alfalfa hay, timothy hay, ryegrass straw and wheat straw from Oregon and Washington and barley straw and timothy/brome hay from Alaska. Bales were weighed and one quarter of each bale was shaken over screens and the fine materials that passed through the screens was mixed with sterile potting soil, placed in flats, and kept moist in a heated greenhouse. Seedlings were counted and were identified. Forty-nine plant species were identified from hay/straw including quackgrass , a prohibited weed in Alaska, downy brome, and other species ranked as invasive in Alaska. There was an average of 14418 seeds and an average of 3 species per bale (52 lb). Crop seed (except for alfalfa), comprised a large proportion of the germinated seeds found from hay/straw. Hay-straw from Alaska contained more seeds and species than hay-straw from WA-OR, but there was no difference when only non-crop seed were used in the analysis. Washington/Oregon alfalfa hay and wheat straw and Alaska barley straw contained significantly fewer seed than Alaska timothy/brome hay. The grower or distributor that produced or brokered the hay-straw also affected the number of seeds for alfalfa hay, WA-OR timothy hay, and Alaska timothy/brome hay, both when total seed and non-crop were considered, reflecting differences between sources in weed management and other farming practices. The number of seed species contained in all crops except ryegrass straw and barley straw was also affected by grower-distributor, both for the total and for non-crop seed. Hay and straw are a significant pathway for movement of weed seeds into and within Alaska.

Technical Abstract: To determine the extent and nature of spread of exotic plant species to and within Alaska by shipment of hay and straw we conducted a study to determine the amounts of hay and straw imported into Alaska and the amounts and types of seed contained in hay/straw. Vendors were contacted to determine the amount, type and source of hay and straw sold. We purchased alfalfa hay, wheat straw, ryegrass straw, and grass hay from Washington and Oregon and locally produced barley straw and smooth bromegrass and timothy hay. The hay/straw was shaken over screens and the remaining fines were mixed with sterile potting soil and incubated in the greenhouse. Forty-nine plant species were identified from hay/straw including quackgrass (Elmus repens (L.) Gould), a prohibited weed in Alaska, downy brome (Bromus tectorum L.), and other species ranked as invasive in Alaska. The number of seeds ranged from 0 – 6205 with an average of 610 seeds kg-1 and the number of species from 0 to 10 with an average of 3 species per bale. Crop seed (except for alfalfa), comprised a large proportion of the germinated seeds found from hay/straw. Hay-straw from Alaska contained more seeds and species than hay-straw from WA-OR, but there was no difference when only non-crop seed were used in the analysis. Alfalfa hay and wheat straw from WA-OR and Alaska-grown barley straw contained significantly fewer seed than Alaska-grown timothy/brome hay. The grower or distributor that produced or brokered the hay-straw also affected the number of seeds for alfalfa hay, WA-OR timothy hay, and Alaska timothy/brome hay, both when total seed and non-crop were considered, reflecting differences between sources in weed management and other farming practices. The number of seed species contained in all crops except ryegrass straw and barley straw was also affected by grower-distributor, both for the total and for non-crop seed.