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College of Agriculture
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Western Ag Research Center
> Biocontrol
Western Agricultural Research Center
Knapweed Biocontrol
To date, 12 insect species (eight seed head insects and four root insects) have
been introduced against spotted knapweed in Montana. A root beetle
(Sphenoptera jugoslaica), released against diffuse knapweed, is
associated with spotted knapweed in some areas. Seven insect species
are having an impact on the plant in some areas of western Montana.
These insects include a root weevil, Cyphocleonus achates (Fahraeus)
(Coleoptera: Curculionidae), a root moth, Agapeta zoegana L.
(Lepidoptera: Tortricidae), two seed head flies, Urophora affinis
Frauenfeld and U. quadrifasciata (Meigen) (Diptera: Tephritidae), a
seed head moth, Metzneria paucipunctella Zeller (Lepidoptera: Gelechiidae),
and two seed head weevils, Larinus obtusus Gyllenhal and L. minutus
Gyllenhal (Coleoptera: Curculionidae). The Urophora spp.,
Larinus spp., and M. paucipunctella are causing significant
reductions in spotted knapweed seed production. A. zoegana is
causing reductions in spotted knapweed biomass and C. achates is causing
significant reductions in spotted knapweed density in some areas.
Status of the introduced agents for spotted knapweed follows:
Species |
Type |
Status |
Impact |
Agapeta zoegana |
root moth |
established in good numbers at many locations |
reducing knapweed vigor and biomass in some areas |
Bangasternus fausti |
seed head weevil |
status uncertain |
---- |
Chaetorellia acrolophi |
seed head fly |
established in low numbers |
---- |
Cyphocleonus achates |
root weevil |
established in moderate numbers |
reducing knapweed density in some areas |
Larinus minutus |
seed head weevil |
established in moderate numbers |
causing decline of diffuse knapweed |
Larinus obtusus |
seed head weevil |
established in moderate numbers |
reducing knapweed seed production and seed bank |
Metzneria paucipunctella |
seed head moth |
established in low numbers |
reducing knapweed seed production |
Pelochrista medullana |
root moth |
established in low numbers |
---- |
Pterolonche inspersa |
root moth |
not established |
---- |
Sphenoptera jugoslavica |
root beetle |
established in moderate numbers |
reducing diffuse knapweed vigor and density in some areas |
Terellia virens
|
seed head fly |
established in low numbers |
---- |
Urophora affinis |
seed head fly |
well established |
reducing knapweed seed production, and seed bank |
Urophora quadrifasciata |
seed head fly |
well established |
reducing knapweed seed production |
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