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About AzollaControl

How could biological control help you?

Stenopelmus rufinasus Azolla's main natural enemyResearch has shown the tiny 2mm long North American weevil Stenopelmus rufinasus (right) to be one of Azolla's main natural enemies.

The weevil has already been used to control the weed very successfully in South Africa, where after extensive host range testing and climatic matching, it was released as a biocontrol agent.

Even the heaviest infestations were brought under control within a matter of months, without the need for chemicals or further control measures

The weevils can be targeted at very specific sites where the weed is considered a problem.


Why are weevils the best solution for Azolla biocontrol in the UK?

They can only feed on Azolla species, so won't harm other plants. They can also consume large quantities of the weed.

We have developed techniques to overwinter and mass produce large numbers of weevils for release early in the season.

The weevil is already present in parts of the UK (first recorded in 1921), most likely hitching a ride on Azolla plants imported by garden centres and aquarists.

CABI's studies have shown that fairy fern infestations can be brought under complete control using only the weevil in a matter of weeks.

BeforeAfter (approximately 8 weeks)
East sussex - waterway clogged with Azolla East Sussex waterway free of Azolla

What is the CABI AzollaControl project doing?

  • We aim to increase the supply of weevils on demand to control Azolla at a competitive rate. We also want to conduct further research to improve understanding of the weevils' distribution, mobility, population development, survival requirements and potential as natural control agents in the UK. And, carry out releases on water bodies in conjunction with statutory authorities.