07/29/2026
Happy Weevil Wednesday! It's nearing spotted knapw**d root weevil (Cyphocleonus achates) collection time, and we CAN'T WAIT! Here's a short video of what some of the collection process looks like for us while we're out in the field.
Spotted knapw**d (Centaurea stoebe) was likely introduced to the US from the transportation of contaminated hay as early on as the 1890s. It can be a biennial or perennial with a deep taproot that releases a toxin in the soil damaging nearby plants. For this reason, and its rapid ability to spread, it has become a nuisance for many native habitats in North America.
Its pink flowers stand out from its spindly limbs and on these flowers is where we typically find the adult weevils. As its name suggests, “root weevil,” when in their larval form, they feed on the taproot limiting the nutrient uptake of the plant. With enough damage, they can effectively kill the plant. As adults, they continue to feed on the leaves, impacting photosynthesis.
When out in the field, we compare this collection to an Easter Egg hunt. You must train your eyes to spot them as their speckled pattern and colors help them blend in with the plants surprisingly well. On top of this, they like to hide from large moving things, so they often play ring-around-the-rosy with us as we reach down to pick them off the flowers or seedheads. We collect 100 weevils per release, and we love every second of it. Unlike most beetles, these ones don’t have functioning wings and elytra, so it’s important that we assist them with spreading to new infestations of knapw**d.
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