Take aim at knapweed with this weevil

The long awaited Cypho (pronounced Sifo with a long “i” and “o”) collection season is almost upon us.  These knapweed root boring weevils Cyphocleonus achates, are the best insect for spotted and diffuse knapweed control.  We should have releases available next week.  At this time we have a waiting list for 100+ releases, but are hopeful we can fulfill these and all other requests we might receive.  So, if you want a release of these slow-acting but effective insects, feel free to give us a call and reserve some.  Call Alycia at: 406-565-3993 or Todd at: 406-498-5236 during normal business hours, please.

Cypho adults emerge from within knapweed roots starting in late July through September.  They do not fly (which is why we need to work hard to spread them all over the state) so they crawl around laying eggs one at a time on the root crown (top of the root) just below the soil surface.  Each female can lay more than 100 eggs during the summer.  The larvae hatch in 10-12 days and mine (eat the inside) into the center of the root.  They develop through four instars (i.e. four exoskeleton sheddings) and often cause galling (swelling) of the taproot.  They over-winter as larvae in the root.  The chubby “C” shaped white-ish larvae have a small brown head capsule.  They often severely damage the root and kill the plant.  Pupation occurs in the root in mid-summer.  Starting again in late July, the adults chew their way out of the damaged root and do it all again.  When they chew their way out, their exit hole exposes the damaged, hollowed-out root to soil fungi and bacteria so the damaged plants often dry-up and die suddenly in August.

We collect them by hand-picking or sweep-netting during the hot part of the afternoons when they climb to the top of the plants looking for mates.  Each release will contain about 105 insects in a paper cup much like an ice cream container.  You will need a cooler with an ice pack and some packing to separate them from the ice to keep them from freezing.  They can also be stored for several days in a cooler or refrigerator.  We recommend that you release them in a hot dry area that will not flood and has large knapweed plants.  Spacing of releases should be one every quarter section or every 300-400 yards.  Releases can be closer together if there are barriers such as streams or areas without knapweed.  Cypho disperse by crawling only, so spread slowly.  We find that when well established they spread 70-100 yards per year.