Effects of human‐mediated processes on weed species composition in internationally traded grain commodities

Abstract

International trade is a major route by which nonindigenous organisms are introduced into new habitats. Various kinds of weed seeds have been introduced through grain trade. The objectives of this study were to understand the factors that affect the initial assemblage of plant species introduced by the international grain trade and to extract their general attributes. We surveyed weed seed contamination of spring wheat imported from Canada to Japan and analysed the effects of the field abundance of each weed and of harvesting and cleaning on the quantity of weed seed included in the imported wheat. The field abundance was positively correlated with the weed seed quantity. Seeds of short weeds and seeds with a pappus were eliminated from the wheat by the harvesting or cleaning process. Many other crop plants contaminated the wheat. Because various transportation vehicles, temporary storage sites and port elevators are used commonly with all exported crops and it is difficult to remove all residues from them, other crops might be carried over into the wheat commodity. These relationships also apply to other grains.

Trade, transport and trouble: managing invasive species pathways in an era of globalization

“…Not surprisingly, island ecosystems are often the most invaded and threatened worldwide (Donlan & Wilcox 2008). Further evidence of the direct role of trade stems from correlations between specific commodity sectors and the subsequent establishment of alien species via horticulture (Lambdon, Lloret & Hulme 2008), the wild‐bird trade (Carrete & Tella 2008), grain shipments (Shimono & Konuma 2008) and aquarium fish commerce (Gertzen, Familiar & Leung 2008). The importance of trade in biological invasions has prompted several authors to extrapolate their findings and predict dire future scenarios for rapidly growing national economies such as China (Jenkins & Mooney 2006; Ding et al .…”

Contamination of internationally traded wheat by herbicide‐resistant Lolium rigidum

“…In another example, herbicide‐resistant biotypes of wild oat were widely found in fields in Canada (Beckie et al . 2004a,b; 2006) and a large number of the seeds of wild oat was present in wheat that was imported from Canada (Shimono & Konuma 2008). Moreover, seeds of the most important herbicide‐resistant weed species, including Amaranthus retroflexus , Chenopodium album , Setaria viridis , Echinochloa crus‐galli , and Kochia scoparia (Heap 2010), were detected in grains that were imported from various countries (Asai et al .…”

“…For example, we found >500 seeds of Raphanus raphanistrum L. (wild radish) in 20 kg of Australian wheat that was imported in both (Shimono Y., 2010.Wild radish is also a problematic weed in WA (Alemseged et al 2001) and over half of the wild radish populations that were collected in fields throughout the wheat belt in WA were found to be herbicide-resistant . In another example, herbicide-resistant biotypes of wild oat were widely found in fields in Canada (Beckie et al 2004a,b; and a large number of the seeds of wild oat was present in wheat that was imported from Canada (Shimono & Konuma 2008 were detected in grains that were imported from various countries (Asai et al 2007).…”

“…1996; Asai et al . 2007; Shimono & Konuma 2008). As the global trade of grain is >100 million t per year (FAO 2009), a very large amount of weed seeds is introduced into grain‐importing countries, even if each shipment contains just a few weed seeds.…”

“…Exotic weeds in agricultural fields are typical cases of unintended introduction. Various kinds of weed seeds have been found in imported grains (Fay 1990;Huelma et al 1996;Asai et al 2007;Shimono & Konuma 2008).As the global trade of grain is >100 million t per year (FAO 2009), a very large amount of weed seeds is introduced into grain-importing countries, even if each shipment contains just a few weed seeds.…”