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Munching bugs brought in to help control invasive weed

The Wey & Arun Canal Trust is enlisting the help of 1,000 tiny bugs to help control an invasive water fern which can threaten other plants, fish and invertebrae.

An army of weevils has been released into the canal at the Summit Level on the Dunsfold/Alfold border to to eat its way through the fast-growing and non-native Azolla weed, which can form a dense cover on the water and deprive other species of light and oxygen.

The weevils can feed and reproduce only on the Azolla, and usually die out naturally once they have eaten their way through the fern, helping to control the weed without the need for chemicals.

The recent hot weather has provided ideal conditions for the Azolla to thrive, and it can rapidly double in size in warm weather, forming a thick blanket and posing a serious threat to water wildlife.

Wey & Arun Canal Trust’s conservation and ecology director John Reynolds said the Trust was keen to use eco solutions to protect the waterway. He said: “We have invested in buying in the weevils as a safe and environmentally friendly way to control this problematic fern. Our aim in restoring the canal is to increase biodiversity, and keeping on top of the water fern will help to ensure the ecology of the waterway remains healthy.”

Gill Davies
Wednesday, August 7, 2019
  • The weevil provides an eco friendly way of dealing with Azolla. Photo credit: Rob Reeder CABI
  • The tiny bugs eat only the Azolla weed. Photo credit: Rob Reeder CABI