Clippings

New bioweapons fight alien invaders

A tiny mite, visible only under a microscope, could be about to beat back the tide of invasive non-native water weeds from the UK’s rivers. Scientists have gained permission to release the mite, Aculus crassulae, into the wild to tackle rafts of Australian swamp stonecrop (Crassula helmsii), a superweed currently choking rivers across the country.

Until recently, swamp stonecrop was a popular garden pond plant but it is such a thug that it’s now banned from sale in garden centres. It can reproduce from tiny fragments, spreading easily into nearby waterways and devastating native biodiversity.

Scientists from bioscience research institute CABI travelled to Australia to collect the plant’s natural enemies, then tested their effect on all kinds of plants, from house plants to wildflowers. This mite was the only one that fed just on swamp stonecrop. “ is very picky,” says lead scientist Dr Sonal Varia. Although the mite won’t eliminate swamp stonecrop, it severely weakens it. “We’re aiming to redress the balance so it’s not so dominant,” she