| Country or region name |
Japan |
| Organism group |
plant |
| Order name |
Campanulatae |
| Family name |
Compositae |
| Species name |
Ambrosia trifida |
| English common name |
giant ragweed, buffalo weed, horse weed, great ragweed |
| Substantially same species (synonym) |
|
| Year of invasion or detection |
1953 |
| Native region |
North America |
| Situation of establishment |
Category 2: Settled after 1951 |
| Taxonomic description |
| |
| Expansion of distribution area |
| Common ragweed is widespread on arable land and grows in clay, silt,
and sand mixtures in disturbed situations.
Giant ragweed distributed everywhere throughout Japan, especially in the
flood plain of river, abandoned field and roadside.
|
| Environmental impact |
| Giant ragweed is an invasive, allergenic weed in crop fields and
non-crop habitats in Japan. Erect summer annual that may reach up to 4
m in height. Primarily a weed of agronomic crops that thrives in fertile
soils, and invade into the disturbed vegetation to suppress natural vegetation
by shade. Giant ragweed produces much seed, and its seed are short-lived
in the soil. It was discovered that earthworms gather and bury the seeds
in their burrows, presumably as a source of food (Regnier et al., 2002).
Despite its low fecundity and high seed predation, giant ragweed has become
a major weed problem in the upland field and is able to invade and persist
in both disturbed and non-disturbed environments. |
| Economic damage |
| Ragweed infests grain and cultivated fields, open disturbed habitats,
and roadsides. But precise values of losses resulting from the presence
of the weed are difficult. When grazed in large amounts by livestock, giant
ragweed yields considerable amounts of high nutritive value forage, especially
during its seedling stage. However, it competes numerous companion annual
species. Ragweed is the most important cause of hay fever. Both the plant
and its pollen may produce dermatitis in some people who may not suffer
from hay fever. Ragweed oil dermatitis commonly affects male outdoor workers
over 40 yr of age. The large amounts of airborne pollen shed by giant ragweed
also are an important contributor to summer hay fever. |
| Reproduction |
| Giant ragweed produces bounteous seeds, and though the plants are
easily destroyed, the seeds retain their vitality and are readily carried
from place to place by drifting snow or water. The seeds (caryopses) are
6 to 8 mm long and consist of one central beak surrounded by a circle of
five or more marginal points, giving a king's crown appearance, hence the
plant's common names-kinghead and crown-weed. These spines, or tubercles,
give much trouble in cleaning it from other seeds, as they catch in the
screens; also they contain air spaces, which enable the fruits to float
on water. The seeds are scattered far and wide by flood waters in the flood
plane of river. |
| Growth |
| |
| Countermeasure |
| |
| Writer's name and affiliation |
| © Written by Fujii, Y. National Institute for Agro-Environmental
Sciences. (written in Nov. 2003) |
