October 13, 2008

experts comment on CABI’s planned use of biological control against Japanese knotweed

CABI biosciences, a not-for-profit scientific organisation, has advised that biological, rather than chemical, measures should be used to control Japanese knotweed, a highly pervasive plant that costs the UK millions of pounds a year in structural damage to buildings and infrastructure.

Dr Scott Miller, Senior Programme Officer, Office of the Under Secretary for Science, Smithsonian Institution, Washington, said:

“Biocontrol has a long (more than 100 year) history, and the standards for targeting and testing have changed dramatically over the years. Agencies like CABI maintain very high professional standards in pre-release testing, which is very different than what might have been done years ago.

“In Hawaii, where there are extensive data for over 100 years, most individual biocontrol agents have had no impact (positive or negative) because they failed to develop sufficient population sizes. But there have been both great successes and failures – we expect that the improved testing would prevent most of the failures today.

“Each case is different and has to be evaluated on the balance of factors involved with the impact of the target pest, and potential non-target impacts. But there have been some spectacular success stories, such as the control of the cassava mealybug in Africa.”

Bill Overholt, Biological Control Research and Containment Laboratory, University of Florida, said:

“The history of classical biological control (the introduction of host specific natural enemies from an invasive organism’s native range into the invaded area) has a very long track record of success. The key is thorough host range testing prior to release. Admittedly, there are a few examples of negative impacts, but for the most part these can be traced to a change in societal views of the value of native species. In most cases, it was known that certain agents would cause collateral damage, but the agents were approved for release because at the time the inherent value of native species was given less weight that it is today. For example, Rhinocyllus conicus was released in the 1960s in the US for control of musk thistle, with full awareness that it would also attack some native thistles – today, it is very unlikely that the weevil would have been released.”

Click here to read CABI’s advice on the control of Japanese knotweed.