Current Status on Influx and Habitat of Exotic Weeds in Korea

S-M. Oh, B-C. Moon and C-S. Kim Department of Agricultural Biology, National Institute Agricultural Science & Technology, RDA, Suwon City Korea [email protected]

Abstract: For investigation on the present status of exotic weeds in Korea, the number of exotic weed species, their inflow time and native regions were examined with literature. Field surveys were also conducted for seven years from 1995 to 2001. Exotic weeds naturalized in Korea are composed of 315 species in 37 families until 2001. Among the weed flora, 135 exotic weed species have been reported since 1980. The number of exotic weeds by the native regions was 72, 32, 122 and 29 in North America, South America, Europe and Asia, respectively. Many species of exotic weeds are distributed near the ports, roadside for transport of imported cereals, circumference of highway and reclaimed land with wastes. 72 and 56 exotic weeds are found in farmland and pasture, respectively. Also, exotic weed newly found in cultivated area from 1995 to 1999 was reported as 34 species from 13 families.

Key words: Exotic weeds, in-flow time, native regions, habitat.

Introduction

Weeds found in Korea can be discriminated as native weeds and exotic ones. However, all weeds not originating in the country are called foreign weeds. In addition, naturalized weeds are those exotic ones that are completely adapted to the domestic environment. However, because influx time of weeds for naturalization is not determined clearly, all the weeds inhabiting the country from foreign lands are considered proper to be called exotic weeds. A study on inland exotic weeds was initiated first about plants native to the American continent (Lee and Kim, 1961). Lee and Oh (1974) did a research on naturalized plants of Korea and a study on distribution of naturalized plants of the Korean peninsula was carried out (Lim and Jean, 1980). Park reported to the Plant Taxonomy Association of Korea that exotic species had not been recorded inland from 1992 to 2001. Among exotic weeds found in the country, some weeds were adapted completely to the inland environment, and the others were adjusting and found in some regions of Korea. As trade of agricultural products increased with recent liberalization of import, many seeds of exotic plants mixed with import grain were brought in the country. Accordingly, this study was carried out to elucidate the kind of exotic weeds flown in to the country, inflow time, native origin and main places of occurrence and obtain basic information for management of exotic weeds

Materials and Methods

Survey on kinds of exotic weed through different documents In order to survey exotic weeds distributed in the country, weedy plants of alien native origin based on plant picture book published inland and an article, were chosen and summarized by family. Exotic weeds investigated were rearranged by species and only the legitimate name was written using rule of international plant nomenclature after identifying basionym, synonym and misidentified name.

Influx time and native place of exotic weed Date of first entry to the country was surmised based on reference and plant books pre- reported, even if that may not be completely accurate. Depending on references when exotic weeds were reported firstly, influx periods were sorted by 5 periods (before 1910; before the opening of port, 1911∼1945; governing period of Japan, 1946∼1960; the restoration after war,

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Proceedings of the 21st Asian Pacific Weed Science Society Conference (Editors: B. Marambe, U.R. Sangakkara, W.A.J.M. De Costa, and A.S.K. Abeysekara), 2-6 October 2007, Colombo, Sri Lanka. 1961∼1980; growing period of economy, 1981∼1999; period of free trade). We used several references such as Flora Korean (1911 Nakai), Plant name of Josun (1949 Biology Society of Josun), Plant name of Korea (Lee and An, 1963), Plant name of Daehan (Lee, 1982) and Color picture of Naturalized plant of Korea (Lee, 1995) to obtain information on influx time of exotic weeds. Native region by species was investigated through many relevant articles.

Survey on distribution and inhabitation of exotic weeds In order to obtain information on distribution and inhabitation of exotic weeds, we usually surveyed the surroundings of main harbors such as Inchun, Pusan, Gunsan, Mokpoe and Yeosu from which grain is usually imported, near roadside for transport of imported grain and around dairy farms and pasture land. In addition, we surveyed exotic weeds troublesome in cultivated areas including crops like feed corn and grains. Newly found species were identified based on domestic and foreign plant picture books.

Results and Discussion

Exotic weeds found domestically by late 2001 were identified as belonging to 315 species of 37 families and 18 orders (Table 1). Table 8 shows the species by different families and native regions and inflow time to Korea. In Japan, naturalized plants of 403 species were identified in Colored Illustration of Naturalized Plants of Japan (Takemasa, 1992) and 165 species were recorded as exotic weeds of Japan (Livestock Society of Japan, 1994). Park (1995) published picture books including 261 exotic weed species and Kang and Shim (2002) reported 471 exotic weed species. However, it is difficult to compare these with our results because Kang and Shim (2002) includes some flowering grass and cultivated crops in their results.

Table 1. Number of exotic weed species by family.

Family No. of species Family No. of species Poaceae 51 Malvaceae 9 Polygonaceae 12 Convolvulaceae 8 Chenopodiaceae 7 Solanaceae 13 Amaranthaceae 14 Scrophulariaceae 9 Caryophyllaceae 13 Asteraceae 65 Brassicaceae 31 Others 25 Family 63 Fabaceae 20 Total 37 Family 315

When 315 exotic weeds inhabiting domestically were categorized according to plant families, the family Asteraceae 65 had species, Poaceae 51 species, Brassicaceae 31 species and Fabaceae 20 species. These families formed 53% of total exotic weeds and the rest were Polygonaceae, Amaranthaceae, Solanaceae and Caryophyllaceae having 12 to 14 species.

Influx time and native region of exotic weeds The species number by influx periods of exotic weeds is shown in Table 2. Before 1910, even if that time is very long ago, 54 species were reported as exotic weeds.

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Introduction ~’10 ’11~’45 ’46~’60 ’61~’80 ’81~’01 Total Period

No. of Species 54 46 16 64 135 315 (％) (17) (15) (5) (20) (43) (100)

If we are to determine the period before 1910 to be least 200 years, this period conforms to about 1711∼1910 during which some trade to foreign countries was carried out. Most of 55 exotic weeds are considered as be flown at that time. After this period, 46 species and 16 species were introduced during 1911∼1945 (the period of Japanese annexation of Korea to independence of Korea) and 1946∼1960 (early period after the independence), respectively. Influx of exotic weeds during the latter period is reported as little even though much American agricultural products were coming in. This is considered as due to the low interest about new plant species and exotic weeds considering the situation at that time. With the advent of real industrialization from 1961 to 1980, 64 exotic weed species are reported. Since 1980, as a lot of alien agricultural products have been imported with opening of importation, many exotic weeds have flown during this period, with 135 species being identified amounting to 43% of total exotic weeds. Increase of exotic weeds was because of the influx of seeds of exotic weeds coming as contaminations of imported grains.

Native region of exotic weeds Because exotic weeds were not only confined to the native region, the native region of exotic weeds was not the country from which they were flown to Korea. However, native regions provide important information on ecological characters of the species. Table 3 shows the division of exotic weeds based on native regions and introduction period.

Table 3. Number of exotic weed species by native regions and introduction period.

Division As.* Eu. Eu-As nA sA Others Total Before 1960 19 45 17 14 10 10 115 1961~2001 10 77 18 58 21 16 200 Total 29 122 35 72 31 23 315 * As.; Asia, Af.; Africa, Aus.; Australia, Eu.; Europe, nA.; north America, sA.; south America, tA.; tropical America, Chi.; China, Ind.; india, cAs.; central Asia, sEu.; south Europe, Tro.; Tropical, wAs.; west Asia, Mex.; Mexico, Jap.; Japan)

Weed species native to Europe consisted for 122 species forming 39% of the total followed by South America (31 species and 10%), Asia (29 species and 9%) and Eurasia (35 species and 11%) and Australia and Africa (9 species). Considering adjacency and native region of exotic weeds, weeds native to Asia, Europe and Eurasia for 56% and 176 weed species followed by North and South America (33% and 103 species). The results implied that influx of exotic weeds have much connection to these native regions. If comparing native regions of exotic weeds before and after 1960 (Table 3), weeds native to Asia were identified as 19 and 10 species before and after 1960, respectively, followed by North and South America and Europe with 24 and 79 and 45 and 77 species during corresponding periods. Though the native region of weeds is not always the nation from which exotic weeds were introduced, kinds of exotic weed surveyed were greatly influenced by the change of nation for agricultural trade. Since

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Proceedings of the 21st Asian Pacific Weed Science Society Conference (Editors: B. Marambe, U.R. Sangakkara, W.A.J.M. De Costa, and A.S.K. Abeysekara), 2-6 October 2007, Colombo, Sri Lanka. 1960, exotic weeds were judged to be introduced through imported agricultural products considering increased trade of agricultural products from North and South America and Europe.

Distribution and habitation situation of exotic weeds Results of the survey carried out near the habours in terms of distribution and species of domestic exotic weeds are shown in Table 4.

Table 4. Number of exotic weed species distributed near different ports.

Inchun Pusan Ulsan Kunsan Mokpo Yeosu

38 32 35 27 23 23

Near Incheon harbor forming over 60% of total domestic import grains 38 exotic weed species were found followed by Ulsan and Pusan harbors (35 and 32 species respectively). The main reason for many exotic weeds to be found near harbor was the close relation with diffusion of weed seeds when imported grains were loaded and unloaded. In the future, as import of agricultural products is continuously increased, new exotic weeds are predicted to be found more and more around harbors. Imported grain is unloaded to the harbor, stored in storage house and then transported to a processing plant. Accordingly, the region of first occurrence of a new exotic weed is apt determined depending on transferring roads and destination of imported grains. Many new exotic weeds are found along the roads towards industries and express highways (Table 5).

Table 5. Number of exotic weed species by major distribution site.

Reclaimed land with Near by ports Roadside highway Pasture wastes 54 98 56 31

Much of the grain dropped by roadside is often observed on the way to transfer of imported grains. Weed seeds are dropped together with falling grains and new exotic weeds come into existence and spread rapidly. In addition, much exotic weeds are found around cultivated areas of forage crops and pasture of dairy farms. 31 weed species were found in reclaimed and wasteland near Seoul. Main habitation area of exotic weed is greatly related to the imported grain. For example, forage grain used for feed in dairy farms entirely depends on imported one. Accordingly, weed seeds mixed in imported forage grain were a main reason for the increased occurrence of new exotic weeds around dairy farms. Reclaimed and waste land near Seoul also becomes the main occurrence region of exotic weeds because waste after selecting carefully imported forage grain and sweepings of cleaning roadside were put in to reclaimed land. In the future, it is necessary to continuously survey the regions in which new exotic weeds are likely to occur. If new weeds are discovered, management counter measures to prevent a spread of these noxious weeds should be prepared rapidly.

Current aspects of exotic weeds occurring in domestic cultivated area There were 72 species occurring in cultivated areas among total exotic weeds. Classification of weeds found by crops is shown in Table 6.

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Class Weed species

Paddy filed (8) Diplachne fusca, Alopecurus japonicus, Panicum dichotomiflorum, Paspalum distichum, Paspalum distichum var indutum, Lindernia attenuata, Lindernia dubia var. anagallidea, Bidens frondosa

Corn (31) Panicum dichotomiflorum, Lolium perenne ssp. multiflorum, Dactylis glomerata, Polygonum convolvulus, Polygonum orientale, Rumex crispus, Rumex obtusifolius, Chenopodium album var. album, Chenopodium ficifolium, Chenopodium glaucum, Amaranthus hybridus, Amaranthus blitum, Amaranthus viridis, Thlaspi arvense, Abutilon theophrasti, Malva neglecta, Ipomoea hederacea, Ipomoea purpurea, Datura stramonium, Solanum carolinense, Solanum americanun, Ambrosia artemisiifolia var. elatior, Ambrosia trifida, Bidens frondosa, Galinsoga parviflora, Galinsoga quadriradiata, Senecio Upland vulgaris, Sonchus asper, Sonchus oleraceus, Xanthium strumarium var. canadense, Xanthium strumarium var. glabratum

Soybean Panicum dichotomiflorum, Polygonum orientale, Chenopodium album var. (12) album, Chenopodium ficifolium, Amaranthus hybridus, Amaranthus blitum, Abutilon theophrasti, Ambrosia artemisiifolia var. elatior, Bidens frondosa, Senecio vulgaris, Xanthium strumarium var. canadense, Xanthium strumarium var. glabratum

Pasture land (59) Panicum dichotomiflorum, Bromus tectorum, Polygonum orientale, Rumex acetosella, Rumex crispus, Rumex obtusifolius, Rumex conglomeratus, Chenopodium album var. album, Chenopodium ficifolium, Chenopodium glaucum, Amaranthus hybridus, Amaranthus blitum, Amaranthus spinosus, Amaranthus viridis, Phytolacca americana, Cerastium glomeratum, Spergula arvense, Silene latifolia ssp.alba, Ranunculus muricatus, Barbarea vulgaris, Thlaspi arvense, Descurainia pinnata, Descurainia sophia, Trifolium pratense, Trifolium repens, Abutilon theophrasti, Malva parviflora, Malva neglecta, Lamium purpureum, Datura stramonium, Solanum carolinense, Solanum americanun, Veronica didyma var. lilacina, Veronica persica, Ambrosia artemisiifolia var. elatior, Anthemis arvensis, Anthemis cotula, Aster pilosus, Aster subulatus, Aster subulatus var. ligulatus, Carduus crispus, Conyza bonariensis var. leiotheca, Conyza canadensis var. canadensis, Erigeron annuus, Erigeron strigosus, Crassocephalum crepidioides, Erechtites hieracifolia, Senecio vulgaris, Galinsoga parviflora, Galinsoga quadriradiata, Sonchus asper, Sonchus oleraceus, Tagetes minuta, Taraxacum officinale, Hypochaeris radicata, Taraxacum laevigatum, Xanthium strumarium, Xanthium strumarium var. canadense, Xanthium strumarium var. glabratum

Number of weeds occurring in cultivated areas was found to be 8 species including Diplachne fusca in paddy field, 12 species including Amaranthus hybridus in soybean upland field, 31 species containing Abutilon theophrasti in forage corn upland paddy field and 59 species such as Rumex acetosella, Rumex obtusifolius and Solanum carolinense in pasture. These weeds, which occurred in cultivated areas were not always noxious to crops. Kinds of exotic weeds greatly troublesome to crops are shown in Table 7. These weeds have rapid growth characteristics and cause great damage to crops. Because some species also have offensive odor and livestock was reluctant to eat them, occurrence of these species became the main reason for the declining quality of feed for livestock.

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Crops Weed species Soybean (4) Amaranthus hybridus, Chenopodium album var. album, Polygonum orientale, Bidens frondosa Corn (10) Abutilon theophrasti, Amaranthus hybridus, Rumex obtusifolius, Polygonum orientale, Chenopodium album var. album, Datura stramonium, Xanthium strumarium var. canadense, Xanthium strumarium var. glabratum, Solanum carolinense, Ambrosia trifida

Pasture land (19) Rumex acetosella, Rumex obtusifolius, Solanum carolinense, Malva neglecta, Amaranthus spinosus, Lamium purpureum, Datura stramonium, Xanthium strumarium var. canadense, Xanthium strumarium var. glabratum, Abutilon theophrasti, Anthemis arvensis, Veronica persica, Carduus crispus, Erechtites hieracifolia, Crassocephalum crepidioides, Hypochaeris radicata, Sonchus asper, Sonchus oleraceus, Tagetes minuta Paddy filed (2) Diplachne fusca(reclaimed paddy), Bidens frondosa

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