Biological Control

Noxious weeds are non-native plant species, most of which originated in Europe and Asia. Many of these weeds were introduced to North America either by accident, possibly as contaminants of crop seed, or deliberately, perhaps as ornamental plants. In their native ecosystems, these plants do not pose a problem because they evolved with natural controls such as insect predators, plant pathogens, fungi, other competing plants, and grazing animals. Without those natural controls in North America, these non-native plants overtake the native plant communities here, decreasing biological diversity, reducing forage for wildlife and livestock, increasing wind and water erosion, and altering nutrient cycling.

Bio-control is the intentional use of living organisms to try to suppress the population of a pest to an acceptable level. In this case, the pest we are attempting to suppress are noxious weeds, and the living organisms that we use are mostly insects.

These insects are natural enemies of the targeted weeds that come from the weeds native ecosystem. Biological agents are discovered and tested by the USDA Agricultural Research Service European Biological Control Laboratory (ARS EBCL).

Insects are tested extensively to be specific to the plant being targeted for biological control. The USDA attempts to insure that certified biological agents will not attack native vegetation or crops, but due to the uncertainties in a biological world, there will always be risks involved.

There are numerous advantages of biological weed suppression. Bio-agents are host specific, self-perpetuating, possess the mobility to spread into areas that are difficult to use other control methods in, and may be an alternative to herbicide use in sensitive areas, such as near waterways.

The limitations of biological control are that it is a long-term method for weed management, bio-agents may be site specific, they may not over-winter, and bio-control agents will not eradicate the weeds.

Once insects are introduced it must be seen if they will become established. If the bio-control agent does establish, then it may take several years (5-7) for the agent to reach a density where it will have an impact on the weed.

Biological agents will not eradicate the weed population because they depend on the weed for their life cycle. Insect species lay their eggs on these weeds and progress through their development while feeding on these weeds.

This project is funded through USDA Water Quality Cooperative Extension Funds, Colville and Okanogan National Forests, Colville Confederated Tribes, and may other partners in the Quad County area.

The Quad County Bio-agent Project is an effort to expand the knowledge and availability of biological agents for the suppression of non-native noxious weeds in our area. The WSU/Ferry County Cooperative Extension Office is leading the Quad County Bio-agent Project. This project uses USDA Water Quality and Forest Service project monies to provide for the education on, collection, redistribution, and monitoring of bio-agents to fight noxious weeds in Ferry, Okanogan, Stevens, Pend Oreille Counties, and the Colville Reservation.

Daro Palmer was hired as the project coordinator. His work is carried out in close cooperation with USDA Animal and Plant Health Inspection Service (APHIS) personnel, WSU Entomologist Gary Piper, as well as representatives of County Extension, County Weed Boards, State Weed Board, National Forest, Washington Department of Fish and Wildlife, Department of Natural Resources, Bureau of Land Management, and private landowners in the Quad County area.

If a release is made on your property, we ask that representatives of the Quad County Bio-agent Project be allowed access to the site for approximately seven years. It will be necessary to monitor the sites to see if the insects are able to establish. If they do establish and the population becomes high enough, then collections will need to be made for further redistributions.

If you have a sizeable weed infestation on your property, one acre or more, it may be possible to use biological agents. Potential areas for bio-agent release should be free of vehicular traffic and insecticide use. The presence of livestock is fine. If you are interested in bio-control for your property please contact our office.


Larinus minutus - This weevil attacks knapweed seed heads, feeding on the actual seeds. A single larva can destroy an entire diffuse knapweed seed head.	Sphenoptera jugoslavica - This beetle prefers diffuse knapweed, but will attack spotted knapweed. The larva mines down into the root and feeds on the root reserves. Feeding stops rosette growth.	Cyphocleonus achates - This large weevil prefers spotted knapweed, but will attack diffuse knapweed. The larva mines down into the root and feeds on the root reserves.


Chrysolina species - Both adults and larvae attack the leaves. Feeding reduces foliage and lowers root reserves, making it difficult for plants to survive harsh conditions.

Mecinus janthinus-

Adults feed on leaves and stems; larvae mine the stems. Larval feeding damages the plant's transport system, leading to premature wilting and suppression of flower formation.

There are three biological control agents available for rush skeletonweed and all three are released in combination.

Galerucella pusilla - Adults and larvae feed on the leaves and buds of purple loosestrife. Feeding on the leaves defoliates the plants so completely that they are often killed. The resulting seed reduction is especially important whereas a single plant can produce up to two million seeds.

Urophora affinis & Urophora quadrifasciata-seed head gall flies-diffuse, spotted squarrose, black, brown & meadow knapweed. Available from lat May - June. Cost: $30/500 adults/acre

Larinus minutus-seed eating beetle-diffuse & spotted knapweed. Available mid-May-June. Cost: $50/100adults/acre

Bangasternus orientalis-seed eating beetle-yellow starthistle. Available June-July. Cost: $40/100 adults/acre.

Eustenopus villosus-seed eating beetle-yellow starthistle. Available June-July. Cost: $50/100 adults/acre

Rhinocullus conicus-seed eating beetle-Canada, musk & plumeless thistle strain. Available May-June. Cost $40/100 adults/acre

Larinus planus-seed eating beetle-Canada thistle. Available mid-June. Cost $40/50 adults/acre

Larinus obtusus- seed eating beetle-meadow & spotted knapweed. Available June-July. Cost $60/100 adults/acre

Agonopterix alstroemeriana-leaf, bud & flower eating moth-poison hemlock. Available in June. Cost $30/250 larvae/acre

Mecinus janthinus-foliage feeding/stem boring beetle-Dalmatian Toadflax. Available May-June. Cost: $50/100 adults/acre

Rhinocyllus conicus-seed eating beetle-musk, plumeless & canada thistle strain. Available in June. Cost: $40/500 adults/acre

Chrysolina hypericil/Chrysolina quadrigemina-leaf and flower eating beetles-St Johnswort. Available May-June. Cost: $35/100 adults/acre.

Gymnetron tetrum-seed eating beetle-common & moth mullein. Available May-June. Cost: $50/100 adults/acre

Cystiphora schmidti-leaf & stem gall fly-rush skeletonweed. Available July-September. Cost: $30/1,000 larvae/acre.

Eriophyes chondrillae-bud gall mite-rush skeletonweed. Available July-September. Cost: $30/ca. 500,000 nymphs or adults/acre

Puccinia chondrillina-leaf, stem & flower rust fungus-rush skeletonweed. Available July-September. Cost: $30/5 lbs of infected plant material/acre

Coleophora klimeschiella-foliage eating moth-Russian thistle. Available June-August. Cost:$65/100 larvae/acre

Galerucella calmriensis/G-pusilla-leaf eating beetles-Purple loosestrife. Available May-June. Cost: $40/400 adults/acre

Exapion fuscirostre-seed eating beetle-Scotch broom. Available late April-mid May. Cost: $55/100 adults/acre

Botanophila seneciella-seed eating fly-Tansy ragwort. Available August-September. Cost:$70/100 adults/acre

Tyria jacobaeae-foliage & flower eating moth-tansy ragwort. Available June-July. Cost: $70/100 adults/acre

Forward Requests to:
Gary L. Piper
Phone: (509) 335-1947
Department of Entomology
Washington State University
Pullman, WA 99163