Hay imported into Japan in 1995 contained exotic weed seeds

Asai Motoaki, Kurokawa Shunji, Shimizu Norihiro, Enomoto Takashi

doi:10.3719/weed.54.219

Imported agricultural materials are a principal source of exotic weed seed introductions into Japan. Increasing quantities of imported feed unintentionally contaminated with weed seeds have wreaked ecological havoc. We investigated contaminants in imported hay. During 6 months in 1995, all imported hay residue at a dairy corporation in Tochigi prefecture was collected and thoroughly inspected for weed seeds. One hundred fifty hay lots were examined;these included alfalfa, oat, orchard grass, timothy, wheat, fescue and sudangrass imported from Australia, Canada and U.S.A. When the number of seeds belonging to a single taxon was >10 in a lot, we subjected seeds to germination tests. About 60 plant species were identified in hay samples. Grass weed species were the major contaminants. The most abundant was wild oat, found in >50 lots, mostly oat hay from Australia. Ryegrass (Lolium sp.) was the second most abundant. Seeds of wild oat, Hordeum murinum, ryegrass, foxtail species, Vulpia and Portulaca oleracea were found to be viable in germination tests. Wild oat and ryegrass have been recently reported as problematic in the continuous winter cereal cropping system in central Japan, and both species are now also widely found growing on roadsides and riverbanks. Our results indicate that imported hay (as well as feed grains) is the probable source of this infestation.

Hay imported into Japan in 1995 contained exotic weed seeds

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