Learn About Whitehall Bio Control: 8/9/2023

We are finished with leafy spurge insects and most of the crew will be finished working this week for the summer as they start school and sports. We have now collected about 60 releases of spotted knapweed root boring weevils Cyphocleonus Achates and have requests for 100+. Hopefully, we can meet these requests. These neat beetles (weevils are long-nosed beetles) are collected one at a time by hand, 100 per release. The insects are only up and out of the soil in collectible numbers when the afternoon temperatures are in the high eighties or above. They are also very camouflaged and drop off the plant to the ground when jostled, so it takes a sharp eye and a quick, steady hand to gather them. The crew is doing a great job!

Some of the crew members may be able to collect a few more releases on Fridays or after school on hot afternoons during the rest of August so if you still want a release, please call Todd Breitenfeldt the project coordinator at 406-498-5236 during normal business hours. We will do our best to get you a release.

You can monitor your land for the presence of these very good bioagents by pulling up larger spotted knapweed plants (wear gloves) and tearing or cutting the tap roots in half the long way. Uninfected roots will be a plain whiteish inside. Infected roots will have brown or black tunneling and damage inside and often break apart when pulled. You may also find the larvae (which are white and "C" shaped) or pupae of the beetle in the roots during late spring, summer, and up to about now. During fall and winter, the larvae are too small to easily see.

Cypho (with an "S" sound at the beginning), are out as adults now laying eggs on the root crown (top of the root) one at a time. These eggs soon hatch and mine (dig/eat) their way down into the root. They feed inside the root all fall, winter, spring, and early summer developing into a robust "C" shaped white grub with a brown head. In summer they pupate and then become adults. The new adult weevils eat their way out of the root and dig their way to the surface. These adult exit holes let soil bacteria and fungus into the root so the plants often die in August or September.

Once emerged, the weevils start the cycle again. They have one generation a year and do not fly so spread slowly, about 70 meters (yards) a year. Therefore, we must be "Johnny weevil-seed" and spread them all over the state. We try to make a release every quarter section or quarter mile wherever there are dry sites with larger spotted knapweed plants present in large enough quantities to support a release. Standing water on the site for more than a day or so will drown the larvae in the roots.

Cypho works slowly. They often start killing the larger knapweed plants in 2-3 years after a release. This then allows many of the knapweed seeds in the soil seed bank (knapweed seeds can stay viable for up to 12 years in the soil) to sprout. You will sometimes get more plants per square meter but they are smaller plants that produce fewer seeds. The seed-feeding insects that are also well established all throughout our area will then kill most of the seeds and over the course of the next 4-10 years, most of the knapweed plants die out. It is often a good idea to seed an approved mixture of native or grazing plants to help revegetate the site to what you want.

Remember, biological control insects will never completely eliminate the plant, just hopefully control knapweed to below the economic or environmental damage threshold. We hope to make spotted knapweed just "another pretty little flower" scattered about the land not causing many problems. That is how things are in Eurasia where the plant and the biological control agents come from and evolved together over time. The insects did not cause the extinction of knapweed there, just kept it in check as our native insects do with our native plants. Remember, many of the native insects (moths, beetles, and such) you see around now eat our native plants and help keep them in check/balance within the ecosystem.

Keep to your noxious weed management plan for your land and be patient!