Weevils released into Stamford Millstream by East Mercia Rivers Trust and Stamford Town Council

Small bugs have been released into a waterway in Stamford to rid it of an invasive plant.

One thousand weevils, which are part of the beetle family and used as a biological control agent, were introduced into the Millstream on Tuesday (July 18) following an infestation of a type of water fern called azolla.

Martin Ballard, a trustee of the East Mercia Rivers Trust, said: “It has been tremendous to welcome 1,000 new members to the town to help tackle the invasive azolla which grows thick across the surface of slow moving water and prevents life from growing underneath it, devastating the health and ecosystem.”

The American plant was introduced to the UK in the 19th Century but banned in 2014.

As well as the environmental impact it poses a risk to livestock and people when mistaken for solid land, blocks drainage systems and makes water-based leisure activities difficult.

It has been growing in Stamford’s waterways since last autumn and it’s hoped that the weevils’ effect will show in eight to twelve weeks. If it is a success more weevils will be released elsewhere in the River Welland and to the River Witham.

“It is hard to say how the azolla got here,” said Martin. “It is likely it was lifted from another channel.

“A small bit could have been transferred accidentally by someone fishing but it rapidly grows.”

The weevils are one to two millimetres in size so putting them into the Millstream was a tough task.

Dressed in waders a group from the East Mercia Rivers Trust and Stamford town councillor Ed Fancourt stood in the water to release them.

Coun Fancourt said: “It was a lot more difficult as it is deeper than it looks.

“I had to be very careful not to squash any of the weevils.”

They were spread out along a section of the Millstream and will reproduce.

However they only feed off the azolla so once it has all been eaten they will die out.

Coun Fancourt added: “It is positive.

“Most people in Stamford cross the Meadows and the Millstream really regularly but may not pay that much attention.

“Lots of people use the beautiful space so it is a shame it has been left to stagnate.

“As a council we approved funding to buy the weevils.”