The Franklin County Noxious Weed Control Board uses insects to manage noxious weeds as part of our biocontrol program. Insects that are natural enemies of the weed in its native range are introduced to the site with the hopes of suppressing weed populations enough that the native plant community is restored over time.
Insects are appropriate in situations where other control methods are not feasible or on sensitive sites, for example near water. Biocontrol can also be combined with physical, chemical and cultural controls for an integrated weed management approach.
Around the county there are several locations where insects are being used to manage noxious weed infestations through a partnership with Washington State University. Currently bios are being used to manage knapweed, Dalmation toadflax, purple loosestrife, yellow starthistle and field bindweed.
Bugs are released on Russian knapweed near the Columbia River in Pasco.
Adult Aulacidea acroptilonica wasps emerge from the previous year's galls in spring, notice the emergence holes in this Russian knapweed stem!
Hatched larvae feeding on plant tissue will severely damage the plants ability to grow. The swollen area of the stem in this picture shows galls developing from larval feeding.
Damage from the root-feeding weevil Cyphocleonus achates. Adults lay eggs in the root crowns. When larvae hatch they mine the upper portion of the root which destroys the plants energy reserves.
Both the adult and larvae of Galerucella ssp feed on the leaves, stems and buds. These beetles have built up large populations on release sites. Defoliated, skeletonized or large gray areas of dead plants is an indicator of their presence.
Mecinus janthiformus is a stem boring weevil used on Dalmatian toadflax. Adults feeding on stems has limited impact on the plant; it is the larval tunneling within stems where eggs are laid that causes the most damage.
Adult Mecinus janthiformus weevils emerge from the infested stems of a Dalmatian toadflax plant. Can you spot the emergence holes along the stem? After feeding on the plant for a few weeks they lay eggs on new shoots. Larval damage causes wilting and suppressed flowering.
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