In an attempt to control the rapid spread of Japanese knotweed in Holland, the Dutch government has issued an exemption to alien species ban.
The once-celebrated plant that has now turned into one of destruction is causing huge problems within Holland, and as a result, five thousand Japanese leaf fleas have been released in a last-ditch attempt to control it. Japanese knotweed within the country has become an increasingly problematic issue, which has begun to threaten local biodiversities, damage water quality and increase risks of floods. As a result, the government took the unusual decision to issue an exemption on a ban on the introduction of alien species as the spiralling costs related to knotweed damage started to mount.
Japanese knotweed is causing huge amounts of damage within the Dutch capital, particularly to pavements, building foundations and dykes, leading to millions of euros in costs each year. According to tests, leaf fleas carry the ability to kill young shoots, preventing the plant from growing by sucking up its sap. This has resulted in an initial 5,000 fleas being released in three distinct locations in hope of combatting the rising problem. It is hoped that the fleas will successfully hibernate over the winter and establish themselves within the new year with further specimens planned to be released next spring.
Knotweed in the Netherlands
Japanese knotweed was introduced and cultivated as an ornamental plant in the Netherlands between 1829 and 1841 by German botanist Phillip Franz von Siebold. Its aggressive root system, which has the ability to grow up to 20cm per day and breakthrough concrete, has caused major issues in many countries across Europe. Previously, the Dutch capital has attempted to control the spread of knotweed through means of hot water, fire and lasers but through no avail. The government is now playing its hopes on the colony of leaf fleas to curb the damage being caused.
One of the leading entomologists at the Institute of Biology in Leiden, Suzanne Lommen who is coordinating the trial, says "All sorts of things have been tried, but complete pest control is extremely difficult and very expensive. We will have to combine various methods to get the Asian knotweed under control. We know from the Japanese knotweed psyllid that it can kill young shoots and slow down or even stop the growth of the plant by sucking up sap – nutrition – from the plant.
“If the psyllid can establish, reproduce and spread, and do the damage we see in the breeding trials, it can hopefully inhibit the growth and spread of Asian knotweed. Then you have a very cheap and environmentally-friendly solution with many years of effect that you can combine with the more expensive methods.”
Lommen continues by stating that the fleas may not take to the Dutch climate, saying "What we do not know yet is how the psyllid will thrive in the Netherlands,” she said. “It comes from an area in Japan where the climate most resembles that of the Netherlands. In the laboratory, it thrives on the interbreed knotweed that grows here. But reality will show whether it can survive in our country.”
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