Shhh...the bugs are sleeping

knapweed, biocontrol, biocontrol agent

Special insect agents lie waiting to attack invasive plants.

Invasive plants have natural bug enemies and many are fast “asleep” at this time of the year. These bugs are officially called biocontrol and they are one of the “tools” we have in the fight against invasive plant infestations. Before these insects are approved for release, they go through years, sometimes decades, of trials to ensure they don’t attack other plants. BC has a very active biocontrol program and the LRISS region has biocontrol agents on a number of invasive plants: Knapweeds, Toadflax, Hound’s tongue & Canada thistle. There are 2 agents featured below. In the knapweed root on the left, 2 root-feeding weevils can be seen. The larvae of the weevils attack the root and the adults emerge in May feeding on the leaves. The root damage decreases the plant size and shoots. The agent on Dalmatian Toadflax in the right photo below is a stem boring weevil. It attacks the stem and leaves. The larvae mine the stem decreasing water and nutrients available to the plant. Adults also feed on the leaves. Both of these insects can also reduce seed production. Information about these agents and others can be found on the BC Government website: Biological Control Agents & Host Plants.