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Knapweed root-boring insects available to landowners

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The cypho is a knapweed root-boring weevil.

Landowners can reserve a release of weevils that control knapweed.

The releases are free and are provided by the Whitehall Project.

Contact Todd at 406-498-5236 or Bryce at 406-533-5672 to reserve a release of the weevil, called Cyphocleonus achates or "Cypho."

The cypho is a knapweed root-boring weevil. It is the best biological weed control species of insect available for spotted and diffuse knapweed at this time. The adults emerge from mid-July to September and lay their eggs on the roots of larger knapweed plants.  The eggs soon hatch and then the small larvae eat their way into the root.  They stay in the root feeding and growing all fall, winter, spring and early summer. In midsummer they pupate within the root and emerge as adults the following summer to do it all again. It is this larval root feeding that can kill the plant.

"We often see good results within five to eight years after a release,'' a spokesman said.

The release site needs to be in a dry area that will not flood. The site should have a number of plants where the tap root has the diameter of a dime or larger as these weevils prefer to lay their eggs on larger plants.

The project is funded by the Montana Noxious Weed Trust Fund, the Montana Department of Transportation, other agencies, and many voluntary donations by local land owners. The insects may not be transported out of state.


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