Foster Creek Conservation District
Foster Creek Conservation District

Now that spring has sprung, so have biocontrol bugs!

    For many, spring comes with a laundry list of things to do and checking for biocontrol bugs may not be a high priority. However, if you intend to buy bugs or are concerned about invasive weed spread on your land, a quick check could save you time and money. If you’ve released biocontrols on your land before, you should look at the past release sites, as they tend to propagate and migrate across the landscape. A good rule of thumb is, where there is one, there will be plenty! If you haven’t previously released biocontrols on your land, that doesn’t always mean there won’t be an established population, as they could have migrated from previous releases in nearby fields.

     It’s easy to check - just go to an area with the weeds you want to control and look for biocontrols that may have already found the plants. For instance, to find the Toadflax Weevil, look for plants from last year that may have holes in the leaves or stems. This is a telltale sign that a weevil was nibbling on the plant and possibly laid their eggs within the stalk. When you find bugs, count them for 15 minutes or until you reach the number 100, whichever comes first. If you count 100 weevils, that means you have a healthy enough population to clip and move weed stems with weevils to a new weedy area

    If you do your count in May or June, the bugs will be more active and much easier to see, as they will be outside the stem on the plant looking for a mate. Do your count for 15 minutes and if you see 100 bugs, you can use an aspirator to collect 50 weevils and move them to another area. Foster Creek CD has aspirators to lend! You can also shake the bugs from the plant into a mesh net. Once collected, transfer bugs to a box with some toadflax and a lid, and relocate to your desired area. If you aren’t able to relocate immediately after collection the bugs can be stored in the refrigerator and released the following day. The faster the transfer can happen, the better for the weevil! 

    To see a demonstration of Toadflax Weevil capture techniques, check out Foster Creek’s newest video from the “Friend or Foe? The weeds of Douglas County Docu-Series: Dalmation Toadflax” on Youtube.

Want more information or need to borrow some transfer equipment?

Contact Foster Creek Conservation District at

(509) 888 – 6372 or




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Foster Creek Conservation District 203 S Rainier Waterville, WA 98858 509-888-6372 © Foster Creek CD