Photo/Illutration Alligatorweed, originally from Latin America, is designated as an invasive alien species by the Environment Ministry. (Provided by the Environment Ministry)

IWAKI, Fukushima Prefecture—A weed described as “the worst alien species on the planet” has been discovered for the first time in the northeastern Tohoku region, alarming local farmers and officials.

Alligatorweed, originally from South America, has already caused headaches in western Japan, where the rapidly reproducing species has impeded river improvement and farm work.

“We need to rein in the spread,” said an official with the Fukushima prefectural pest control center. “Otherwise, the weed could do tremendous harm.”

Agriculture is the main industry of the prefecture, and local officials are calling on the public to immediately report sightings of suspicious weeds.

Alligatorweed grows to more than 1 meter tall and branches out in large numbers.

The weed’s roots can extend for more than 50 centimeters. It can form dense mats and drive out native species. Clusters of alligatorweed can also block drainage systems.

In Shiga Prefecture, a colony of alligatorweed took root and clogged drainage pipes on Lake Biwako.

If the weed reaches a rice field, it could twine around the rice plants, causing them to fall and resulting in a drop in the harvest.

Alligatorweed was first confirmed in Japan in 1989, when it was found entrenched in Amagasaki, Hyogo Prefecture, according to the Fukushima prefectural government.

Since then, the weed has spread to many regions in western Japan.

In 2005, the Environment Ministry designated alligatorweed as an invasive alien species that poses a threat to local ecology and agricultural produce.

The weed is considered particularly harmful because it not only has strong reproductive power, but it can also thrive both on land and in water.

The weed’s swift spread along the Shin-Tonegawa river in Ibaraki Prefecture forced authorities in the central and local governments, as well as agricultural organizations, to set up a taskforce to fight the harmful plant.

In Iwaki, a resident spotted the suspicious weed in a waterway of a rice paddy and reported it to the prefectural government in June.

Prefectural officials asked the National Agriculture and Food Research Organization to analyze and identify the species.

It was confirmed as alligatorweed in early August.

The weed has not yet been found in other parts of Fukushima Prefecture.

The prefecture’s pest control station swiftly issued an alert, calling for all-out efforts to exterminate the invasive plant.

The prefecture asked farmers to place fine-meshed nets on feed water inlets of rice fields and to thoroughly clean their agricultural equipment.

It also urged them to use herbicides, rather than weed cutters, because use of the machines could disperse the stems and roots of alligatorweed, allowing the plant to further spread.

However, many prefectures are struggling to exterminate the plant due to its ability to quickly replicate.

In Saga Prefecture, local workers go to great lengths to tackle the problem. They remove the weeds with a heavy machinery, dry the plants and then incinerate them.

The Fukushima prefectural government has chosen not to disclose where the alien weed was discovered.

It wants to prevent curious people from visiting the site and unknowingly spreading the species to other regions through tiny alligatorweed pieces attached to their clothes.

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