DNR releases weevils to control invasive knapweed
Weevils released in General Andrews State Forest will help combat invasive spotted knapweed (Minnesota DNR).
On Wednesday, the Minnesota DNR released around 1,000 spotted knapweed weevils in the General Andrews State Forest. The goal is to help control invasive species without using herbicides or mowing.
In Minnesota, biological control uses two seedhead weevil species, Larinus minutus and L. obtusus, as well as a root-boring weevil species, Cyphocleonus achates. Seedhead weevils are widely distributed in Minnesota, and their larvae will eat developing spotted knapweed seeds. Root-boring weevils are not as widely distributed in Minnesota and have larvae that weaken or kill the plants by eating its roots.
Root-boring weevils were the ones released in the General Andrews State Forest. These spotted knapweed weevils eat the roots of the invasive spotted knapweed, acting as a biological control. Spotted knapweed is poisonous to other plants and threatens prairies, dunes, and other environments.
The DNR says that hopefully, the weevils will reproduce at this location, and future populations could be used to control knapweed at other Minnesota DNR sites. Unlike seedhead weevils, root-boring weevils cannot fly, so they are expected to not go far from where they were released.