The red-hot pests of Japan
Biologists have called for urgent nationwide action to prevent venomous fire ants from infesting Japan, after the highly invasive species was spotted at several major ports in the country, including in Tokyo.
“Japan needs to fight the insects as a national project,” Takahiro Murakami, associate professor of behavioural biology at Kyushu University, said. “The government must implement an effective eradication programme with the co-operation of the international community” he said. “If left uncontrolled, the country will go through what the United States and some other countries have experienced.”
Murakami said more than half the residents of some affected areas in the United States have been stung by the pests, which cause some ¥500 billion (149.3 billion baht) worth of economic damage to the country each year.
Koichi Goka, head of the National Institute for Environmental Studies’ Center for Environmental Biology and Ecosystem Studies, said fire ants, native to South America, have already spread to more than 10 countries.
He said the damage is particularly serious in the United States, Australia, China and Taiwan.
The insects made headlines after first being detected in Japan in May in a container that arrived at Kobe port in western Japan from Nansha port in Guangzhou, Guangdong province, in eastern China.
They have since been located at several other ports including Nagoya, Osaka and Tokyo.
Making the situation more serious is the fact queen ants, known to be extremely fertile, were among the insects found in Osaka and Kobe.
Shigeto Dobata, assistant professor of insect ecology at Kyoto University, warned that queen fire ants can lay more than 1,000 eggs a day and that once they build a colony, the number will increase dramatically.
“It is crucial to block them from entering at an early stage. It would be extremely difficult to exterminate the red ants once they take root,” he said.
Eggs or ant mounds of the species have not been found so far in Japan.
An Environment Ministry official said the ants may be breeding in Japan but their settlement is believed to be at an early stage, as the formation of a mound takes about two years.
There have been no reports so far of anyone being stung by fire ants in Japan.
The Land, Infrastructure, Transport and Tourism Ministry urged local governments to carry out intensive extermination measures at 63 ports with regular cargo shipments from China. The ministry also called for similar measures at 870 other ports in the country if they accept container cargo from China.
The Environment Ministry and related ministries discussed steps in early July on fire ant control and underlined the importance of inspection and extermination at ports.
Environment Minister Koichi Yamamoto said last week that his ministry plans to expand its monitoring areas at Kobe, Nagoya, Osaka and Tokyo ports to a 2km radius.
The Environment Ministry has decided to plant poison bait at the four other ports where cargo ships from Nansha port arrive on a regular basis.
Officials of Nagoya port said they examine each cargo container for alien species, but did not rule out the possibility that tiny insects may have escaped notice.
“Many containers are arriving from China and the United States every day. You cannot halt trade to prevent their invasion,” an official of the Nagoya Port Authority said.
“The association does not have a specific department dealing with alien species. We have no other choice than to follow measures of the state and prefectural governments,” the official said.
The reddish-brown ants with a blackish-red belly range from 2.5-6mm in length. Their stings can cause severe allergic reactions such as trouble breathing, pains like burns, and occasionally death.
They build dome-shaped mounds with a diameter as large as 25-60cm in open fields such as parks and farmlands.
Kyushu University’s Murakami said he was once stung by a fire ant during his field research on mounds in Taiwan in 2010.
“About 30 minutes after the sting, I started suffering from nausea, hand tremors and impaired vision,” he said. “After lying down for about half-an-hour, the symptoms thankfully subsided.”
Among affected countries, Australia, where fire-ant colonies were found around 2001, failed to prevent infestation and spent ¥27 billion in 15 years, whereas New Zealand successfully eradicated them in a ¥120 million programme using poison baits, according to Murakami.
New Zealand designated areas of a 1km radius around ant colonies as danger zones, planting poison baits and monitoring them for two years, he said.