Of all the weeds to spot in your garden, for many, Japanese knotweed is considered the worst.
The notoriously hard-to-kill plant can burrow under your home or cling to its walls, creating pricey structural damage. It’s so problematic that people have even been sued for allowing the weed to spread.
And because of its singularly stubborn nature, pros are often called in to remove the plant properly. But non-profit environmental organisation Cabi (formerly Commonwealth Agricultural Bureaux International) thinks salvation could come in the form of a humble insect.
Aphalara itadori (known as jumping plant lice) were the first biological control insect to be allowed in the UK in 2011. Over 150 generations were bred in labs and checked to ensure they wouldn’t harm our native plants, but would damage tricky invasive species like Japanese knotweed.
Though the species caused damage to similar plants, ultimately, they couldn’t survive our cold winters (especially after generations of lab-based institutionalism).
So, a new species of the insect from North Japan began its British trial in 2019 ― and has been found to not only seriously damage Bohemian knotweed, which is a more aggressive version of Japanese knotweed, but also to safely weather our winters.
The bug was released in the Netherlands in 2020 and the UK and Canada in 2021 after its weed-eating skills were observed in Japan in 2019.
Rather than flat-out killing knotweeds, the plant lice significantly impact their ability to spread (which is the characteristic that makes Japanese knotweed so challenging).
Entomologist and senior regional director for CABI, Dr Dick Shaw, said this could make Japanese knotweed “just another annoying weed” rather than the property-devaluing menace it is right now.
The bug still needs some time to evolve
While this variant of psyllid seems to show promise, scientists are struggling to find a bug that loves the specific taste of the types of Japanese knotweed that grow in the UK.
Dr Shaw told The Times: ”I think there’s still the right psyllid out there in Japan that would hit it. We’re not giving up... One of the strategies is to collect the ones that have overwintered successfully and interbreed them. We’re only three years into the new release programme so we’re still hopeful.”
The Welsh government emphasises that natural control of plants “is not a quick fix” and the “benefits can take some time to be fully realised”.
“Experience from around the world has shown that bio-control for most species takes between five and 10 years from the initial release until the time significant control is achieved,” it adds.