Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 5, 2012
Publication Date: N/A
Interpretive Summary: Seeds of invasive and other non-indigenous plants disperse to new areas via numerous pathways. Study of these pathways helps to focus limited budgets for prevention and early detection. This study examined the pathway of seed contaminants traveling to Alaska via imported crop and grass seed. Crop and grass seed were purchased from 13 retail seed outlets in Alaska and included fourteen seed suppliers. Eighteen crop samples and 100 grass seed samples were collected and sampled using federally-mandated protocols. Seed samples were analyzed for crop and weed contaminants using an approved laboratory. A total of 95 weed and 36 contaminant crop taxa were found. The average number of contaminant taxa was 6.4 for crop seed and 3.5 for grass seed. The average number of contaminant seed per kilogram of seed was 3844 for crop seed and 1250 for grass seed. Two species prohibited from being transported to and sold in Alaska, were found in the samples. Canada thistle was found in a single crop sample, while quackgrass was found in two grass samples. Seed labels of 33% of crop seed samples and 8% of grass seed samples claimed to have 0.00% weed seeds yet contained numerous weed species. Six percent of crop samples and 8% of grass samples did not contain crop or weed contaminants, showing that it is possible to produce clean seed. Statistical analysis showed no differences between seed suppliers or crop species in the number of contaminant taxa or amounts of contaminant seed. Importation of seed into Alaska is a large pathway for movement non-native plants. Contaminant seed utilizing this pathway are likely to establish since they are planted under ideal conditions with the crop seed. Prevention of spread via this pathway would be aided by including the names of all weed and crop species found in seed samples on the label.
Technical Abstract: Invasive plants disperse to new areas via numerous pathways. Study of these pathways helps to focus limited budgets for prevention and early detection. This study examined seed contaminants in imported crop and grass seed as pathway for plant dispersal to Alaska. Crop and grass seed were purchased from 13 Alaska retail outlets and included 14 seed suppliers. Seed bags were sampled using federally-mandated protocols and were analyzed for crop and weed contaminants. Ninety-five weed and 36 contaminant crop taxa were found. Crop seed contained 43 weed taxa and 15 other crop species contaminants, a mean of 6.4 taxa and 3844 contaminant seed kg-1. Grass seed samples contained 73 weed taxa and 21 crop contaminants, a mean of 3.5 contaminant species, and 1250 seeds kg-1. Two species prohibited in Alaska, were found. Canada thistle was found in a single crop sample, while quackgrass was found in two grass samples. There were no significant relationships between either seed type and supplier and the number of number of contaminant species or number of seeds. Labels of 33% of crop samples and 8% of grass samples claimed 0.00 percent weed seeds, but small (0.007% by weight, 2 species) to large (1.18% by weight, 13 species) amounts of weed contaminants were found. Importation of crop seed is a large pathway for seed movement resulting in significant propagule pressure and a high likelihood of establishment of new weed populations. Prevention of spread via this pathway would be aided by including on the label the names of all weed and crop species found in seed samples.