Japanese bugs vs. weeds in U.K.

by William Hollingworth

Kyodo

Britain is expected to release hundreds of bugs imported from Japan in an attempt to reduce the impact of a fast-growing weed that has blighted large parts of the country.

Scientists are hoping to get government approval to introduce the insects into areas affected by Japanese knotweed.

This would be the first time a foreign insect has deliberately been released in the European Union to check the spread of a weed, according to those behind the project.

The knotweed was originally introduced to Britain in the mid-19th century from Japan and was much sought after, given its exotic origins.

But knotweed has now spread across the country and is a particular problem on railway lines and is known to push up through pavements.

Authorities have tried to use weedkiller, but this has had a limited effect and can be expensive. It also tends not to get to the roots.

Scientists at CABI, a nonprofit organization that provides firms with scientific expertise, have spent the last few years in Britain looking at using a natural way of reducing the knotweed’s advance and have gone back to Japan — the home of the weed — to find its natural enemies. The knotweed in Britain is similar to that found in Omura, Nagasaki Prefecture.

Working with colleagues at Kyushu University in Fukuoka, scientists went to 140 different sites and observed 186 different species that attack the plant. Looking at the range of insects on similar plants to the knotweed, the experts were able to establish that the bug — Aphalara itadori — is only found on the knotweed.

It sucks sap from the plant, thereby containing its growth. This can result in damaged stems and defoliation. In Japan, it is noticeable that the weed grows less extensively than the knotweed in Britain.

Scientists decided to take the bug back to Britain for further tests. They had to reject other insects that do much more damage because the risk to native species in Britain would be too high.

Dick Shaw, from CABI, said bugs were taken from knotweed on Mount Aso, near Kumamoto, and are now in quarantine in Britain, pending a decision by the government.

In the laboratories, scientists have been testing the bugs on other plants common in Britain to see if the insects also attack them. It has been found, however, that they do not have a negative effect on other plants, which means it will be much easier to win government approval for a controlled release of the insects.

Shaw hopes a decision will come soon so the bugs can be released in about a year.

“We have seen the bugs limit the plant’s growth and destroy leaves,” he said. “We have gone through a thorough licensing process and the data will go to the government and ministers for a final decision.”

Japanese knotweed was originally brought into Britain by Philipp Franz von Siebold, the first European to teach Western medicine in Japan. He was also passionate about plants and brought back many specimens on his return to Europe.

Originally it was planted in the large gardens of the rich who had their own staff to maintain the plant. But as time passed, and fewer people had gardeners, the weed has grown unchecked.