Azolla Weevils Are Go - releasing weevils to eradicate an invasive

Azolla Weevils Are Go - releasing weevils to eradicate an invasive plant
We have teamed up with some unlikely comrades in the battle against one of the most invasive plants in the UK today. Water fern
(Azolla filiculoides) was introduced to the UK in around 1840. It’s pretty fern-like appearance makes it very attractive for garden ponds.
Unfortunately it is able to cover the surface of still or slow moving water in a matter of days. By blocking out the light and reducing
oxygen availability it can be disastrous for our diverse freshwater wildlife.
This site on the River Bourne in Wiltshire is specially designated for its fabulous wildlife. As soon as we noticed a thick mat of water fern
spreading over the water’s surface we knew we had to call in re-enforcements to help.
The azolla weevil is already present in the wild in the UK but they are not easy to spot! We contacted CABI (, an
organisation that researches biological control of invasive plants. Soon 200 weevils arrived though the post in a little container and we set
out to release them into their new home.
After carefully deploying them out onto the water fern mat we watched them happily disperse. The azolla weevil can reproduce rapidly
and both the adults and larvae will be greedily tucking into the problem over the next few weeks.
We will be returning to the site later in September, so stay tuned for some ‘after’ photos to see how they have coped with the challenge.
For more information click here
Tom Morgan
Source to Sea Field Officer
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