If you live in the US or the UK, you are probably familiar with the scourge of Japanese knotweed, even if you don’t know it. Japanese knotweed is one of the world’s most invasive plants and has colonized many disturbed and undisturbed ecosystems in Massachusetts and at least 38 other states. It has no predators in North America or Europe and is notoriously difficult to remove by force. As the armies of knotweed march ever forward, scientists in the UK are experimenting with a dramatic method of weed-killing: the introduction of a non-native, knotweed-loving insect to munch the stalks down to size.
Commonly known as Japanese knotweed, Fallopia japonica is a plant is so hardy that it grows on the slopes of volcanoes in Japan. 19th century landscape designer Frederick Law Olmstead chose to line the parkways of Boston’s Emerald Necklace with this Eastern Asian native, which he thought would help prevent erosion and provide wind protection for strolling citizens. Unwittingly, Olmstead unleashed a seemingly unstoppable force of nature that is particularly brutal in New England. The plant also has become extremely invasive in the United Kingdom, where it is now illegal to grow Japanese knotweed.
Aphalara itadori, a psyllid insect similar to an aphid, almost exclusively eats knotweed, from which the insect draws sap and drains the health of the plant. Researchers at CABI, a UK research organization focused on agriculture and the environment, have conducted extensive tests on the insect as a bio-control agent for knotweed. The results have been promising. Not only do the psyllids vigorously attack the knotweed, they also seem to have no interest in native plants, even close relatives of knotweed such as rhubarb. Despite contact with other ninety species of native British plants, the psyllids only breed on and consume Japanese Knotweed. The research team’s release of tens of thousands of psyllid eggs in eight locations in the United Kingdom is the first EU-authorized introduction of a non-native species in Europe.
After initial successes, the largest challenge to establishing a psyllid population is their ability to over-winter. Although CABI researchers have noted that some Aphalara colonies could survive the winter, their numbers were too thin to be certain of its hardiness. If colonies were able to survive the winter and go on to suppress knotweed, it would represent an ecological breakthrough. “A more natural equilibrium is restored,” says Kate Constantine, scientist at CABI. “Biological control doesn’t aim to eradicate the target plant, but rather to reduce its vigour and invasiveness. Keeping the invasive plant in check ideally allows native plants to re-establish and flourish.” Concerned citizens would do well to take note of a potentially powerful weapon against the knotweed menace. While the introduction of non-native species can reach comically disastrous levels, the scientists are doing their due diligence to ensure that the psyllid solution is safe and effective.
Via The Independent
Images via Greg Beach, lead image via wikicommons