Starting template used for provisioning Oregon agency sites

Biological Control

Oregon is a US leader in implementing biocontrol as part of its integrated pest management approach to managing noxious weeds. The Oregon Department of Agriculture (ODA) Noxious Weed Program has adopted the International Code of Best Practices for biological control of weeds. Only safe, effective, and approved natural enemies will be used for biocontrol.

What are biocontrol agents?

ODA works with USDA and other scientists who visit the original location of the weed to find natural enemies that can be tested as candidates for introduction as biocontrol agents in the US.

Before release in Oregon, agents are rigorously tested to ensure they are the following:

Safe and will not become pests of crops and native plants
Clean from disease and parasites

How do they work?

Biocontrol agents destroy plant tissues and cause stress to the weeds, making them less competitive against desirable flora.
Once the agents are released and established in Oregon, ODA staff and cooperators collect and redistribute biocontrol agents to other infested areas throughout the state.
It may take 10-20 years for a biocontrol project to successfully control a weed at the regional scale.
Field Guide for the Biological Control of Weeds in the Northwest
Tansy Ragwort Factsheet on Biological Control

Oregon noxious weed biocontrol agents

Basic Info: St. Johnswort Root Borer
Agrilus hyperici
Target Weed(s): St Johnswort
Profiles: St. Johnswort Root Borer Profile 1
Impact on Target: The larvae bore into the root and lower stems of St Johnswort and often cause plant mortality. Larval feeding within a root may completely consume the tissue. Any stems produced from an infested root crown are stunted and flower production is reduced. Pupal population occurs within the damaged root during early May to June. The pupal period lasts 9 to 15 days under laboratory conditions. Pupae are creamy white initially.
Collection/Release: Collect adults with a sweep net during the cool of the morning in the late-flowering period (late June-July) is the most productive. Sort adults from debris using an aspirator. Numbers are usually few, making this a difficult insect to work with. Release 50 – 100 adults per site. Store collected adults in a cooler. It is best to release the adults collected as soon as possible.
Distribution: This beetle has been released in eight counties and has established in four, primarily in northeastern Oregon.
History: The root-boring beetle Agrilus hyperici was introduced in Marion County in 1986, but failed to establish. It occurs in the eastern half of Wallowa County where it spread naturally from populations in Idaho and Washington. The first release of adults collected in Oregon was made in Umatilla County in 1992, which were recovered in 1994, and is now widespread in northeastern Oregon. The beetle has been released in other counties, and was recovered in Jackson County in 2005. An extended effort was made in 2011 with APHIS to collect beetles in northeast Oregon for redistribution into the central and southwest parts of the state.
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Basic Info: Toadflax Defoliating Moth
Calophasia lunula
Target Weed(s): Dalmatian and Yellow Toadflax
Profiles: Toadflax Defoliating Moth Profile 1
Toadflax Defoliating Moth Profile 2
Impact on Target: The moth has two generations per year, and larvae cause minor defoliation.
Collection/Release: Larvae can be hand picked from plants in the summer when plants are in early bloom. Releases should be made with 100-200 larvae, placed 1-2 per plant.
Distribution: The moth has been released in eight Oregon counties and is established in one.
History: Calophasia lunula was released in Deschutes County in 1983 and failed to establish. Larvae have been collected in Washington and reintroduced in several counties until its establishment was confirmed in 2005 in Wallowa County, where it may have spread naturally from Washington and Idaho. Due to the minimal impact of this moth and difficulty in getting them established, further redistribution has been curtailed.
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Basic Info: Tansy Ragwort Seed Head Fly
Botanophila seneciella
Target Weed(s): Tansy Ragwort
Profiles: Tansy Ragwort Seed Head Fly Profile 1
Impact on Target: Larvae feed on the seed head and often create a visible cap of spittle on the flower disc.
Collection/Release: No need for further distribution of this widespread insect.
Distribution: Occurs in 26 Oregon counties, wherever tansy ragwort is found in abundance.
History: Botanophila seneciella (= Hylemyia & Pegohylemyia) was introduced in 1968 and is widespread at most ragwort infestations. It is the primary biocontrol agent at infestations in eastern Oregon. Generally, 5-10% (max. 40%) of the seed heads are attacked, mostly the early developing buds. The fly is more common in shady areas when it occurs with the cinnabar moth.
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Basic Info: Toadflax Seed Capsule Beetle
Brachypterolus pulicarius
Target Weed(s): Dalmatian and Yellow Toadflax
Profiles: Toadflax Seed Capsule Beetle Profile 1
Toadflax Seed Capsule Beetle Profile 2
Impact on Target: Adults feed on shoots and larvae feed on reproductive tissues.
Collection/Release: Little need for distribution as the beetle is widespread.
Distribution: Occurs at most infestations in 17 Oregon counties.
History: Brachypterolus pulicarius was approved for use in 1992, and has been found at numerous locations in eastern Oregon. Seed reduction can occur when beetle densities are high.
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Basic Info: Spotted Knapweed Seed Head Fly
Chaetorellia acrolophi
Target Weed(s): Spotted knapweed
Profiles: Spotted Knapweed Seed Head Fly Profile 1
Impact on Target: Larvae tunnel through seed head, destroying seeds. Adults are nectar feeders.
Collection/Release: Adult flies collected in late bud-early flowering period by sweeping tops of plants with an aerial net. Releases of 100 adults. Moving infested heads may spread parasitoids and is discouraged.
Distribution: Released and established in three Oregon counties.
History: Chaetorellia acrolophi was first released in small numbers in Hood River, Lane, and Deschutes Counties in 1993 while releasing Terellia virens. In 1994, they were released again in Hood River and Deschutes Counties. The fly is becoming more abundant in the Hood River area and below Cougar Reservoir in Lane County. It is also known to attack diffuse knapweed.
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Basic Info: Field Bindweed Gall Mite
Aceria malherbae
Target Weed(s): Field Bindweed
Profiles: Field Bindweed Gall Mite Profile 1
Impact on Target: Adult and nymphal mites suck plant juices that deforms leaves and developing buds, which interferes with seed production, and reduces plant biomass.
Collection/Release: Hand pick infested plant material in summer when mite attack is evident. Place or intertwine pieces of infested material onto uninfested plants. One sandwich bag of infested material should contain about 1000 mites to treat one site.
Distribution: The mite has been released in 25 Oregon counties and recovered in 8. It is most abundant in the Columbia Basin counties. Attempts to establish the mite west of the Cascades has been unsuccessful. Field bindweed gall mite is native to central and southern Europe and northern Africa.
History: The leaf gall mite Aceria malherbae was released in 1999 in Polk County, at the Baskett Slough National Wildlife Refuge, but failed to establish. Mites were recovered in Tygh Valley in Wasco County in 2006. The mites caused reductions in plant biomass, flowering, and cover by over 90% by 2007. Redistribution began in 2008. A population of this mite was also reported from the Hells Canyon area. A 2010 survey of the general Columbia River counties in central Oregon, revealed mites were present at 80% of the bindweed infestations. A cooperative research project is underway in conjunction with Dr. Ed Peachy (OSU) and his staff to establish the gall mite in western Oregon, especially in crop fields. The long cool, wet season in 2011 and 2012, allowed plants to generally out-grow damage from the mites, therefore redistribution efforts were sparse. Scanning electron microscopy images of the mite indicated that the correct genus for this mite might be Aculops.
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Basic Info: Thistle Stem Mining Fly
Cheilosia grossa ( = corydon)
Target Weed(s): Musk, Italian and Slender Flower Thistles
Profiles: Thistle Stem Mining Fly Profile 1
Thistle Stem Mining Fly Profile 2
Thistle Stem Mining Fly Profile 3
Impact on Target: Larvae bore in stems of musk, slenderflower, and Italian thistles, reducing the number of flowers produced and making the stem more vulnerable to opportunistic pathogens.
Collection/Release: Infested stems containing pupae can be collected in mid-summer and placed at new sites. Adults hatch very early in the spring and are difficult to find and catch.
Distribution: Released in five Oregon counties and established in four.
History: In 1991, Cheilosia corydon was released in Malheur County, near Vale. The fly was re-released again in 1993 and failed to establish. An experimental release was made in Douglas County, in 1993. The fly was recovered in 1999. It requires stems >10 mm in diameter, but is found more commonly on slenderflower thistle. The fly has spread throughout the entire infested area in Douglas County and is established on slenderflower and Italian thistle.
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Basic Info: Scotch Broom Seed Beetle
Bruchidius villosus
Target Weed(s): Scotch Broom
Profiles: Scotch Broom Seed Beetle Profile 1
Impact on Target: Larvae feed on seeds within pods. Adults feed on pollen.
Collection/Release: Collect adults in spring during flowering. Can be sweep-netted or beat onto a beating sheet and aspirated. Release 100-200 adults per site. Widespread at most sites, redistribution as needed.
Distribution: Released in 19 Oregon counties and recovered in 16.
History: Bruchidius villosus was first released in Oregon in 1998, in Marion and Lane counties. It was an accidental introduction to the East Coast, but went through TAG testing protocol for safety to be introduced into Oregon. The beetle has been introduced at numerous sites since 2000. Populations are increasing and out-competing the seed weevil, Exapion fuscirostre (Coombs et al. 2008a). Limited redistribution began in 2004. Surveys in 2009, and 2014, showed the beetle is widely established throughout western Oregon and at elevations up to 3,000 feet.
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Basic Info: Russian Knapweed Gall Wasp
Aulacidea acroptilonica
Target Weed(s): Russian knapweed
Profiles: Russian Knapweed Gall Wasp Profile 1
Impact on Target: Female wasps lay eggs into tender growing stems. Larvae cause galls in the stems, acting as a nutrient sink. The nutrient diversion stunts plant growth and seed production. Adults do not feed on the plant.
Collection/Release: Collect mature galls, release in bouquets, sweep net adults when active. Release 50-100 galls or adults.
Distribution: The gall wasp has been released in eight Oregon counties and established in four.
History: In 2014, the stem gall wasp, Aulacidea acroptilonica, was released at three sites, two in Morrow County and one in Jefferson County. This is the first wasp used as a weed biocontrol agent in the U.S. Due to one-generation-per-year life cycle, overgrazing or mowing can destroy the host plant habitat. The wasp has now been released in numerous Counties on the East side of Oregon.
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Basic Info: Yellow Starthistle Peacock Fly
Chaetorellia australis
Target Weed(s): Yellow Starthistle
Profiles: Yellow Starthistle Peacock Fly Profile 1
Impact on Target: Larvae tunnel through seed head, damaging seeds.
Collection/Release: Collect adults from late budding plants with an aerial net in early summer. Releases of 100 adults. Widespread; further releases are unnecessary.
Distribution: Occurring in 18 Oregon counties.
History: Chaetorellia australis was released in Douglas County in 1989 and in Josephine County in 1991. Establishment was verified in 1993 in Josephine County, where it was released with its alternate host, bachelor’s button. In western Oregon, the fly generally uses bachelor’s button for the first generation, then moves to yellow starthistle. Experimental releases were made in several counties without bachelor’s button in eastern Oregon. Chaetorellia australis is present at most sites in eastern Oregon, few of which have bachelor’s button.
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Basic Info: Knapweed Root Sulfur Moth
Agapeta zoegana
Target Weed(s): Spotted Knapweed and Diffuse Knapweed
Profiles: Knapweed Root Sulfur Moth Profile 1
Knapweed Root Sulfur Moth Profile 2
Impact on Target: The larvae girdle and bore into the roots, causing severe damage and some plant mortality. Adults are nectar feeders.
Collection/Release: Adult moths can be collected using light traps during the summer when plants are in bloom. They can also be flushed from their hiding places in the vegetation and caught with a light aerial net. Ideal release size is 50 – 100 adults. This moth is difficult to collect in sufficient numbers in the wild.
Distribution: The moth has been released in 15 Oregon counties and established in 10.
History: In 1987, the root-boring moth Agapeta zoegana was released near Hood River. The moth is well established in several counties and is collectible in Hood River, Bend, and Enterprise. This insect is also known to attack diffuse knapweed. Several larvae may occur together in the same plant. At release sites where the root beetle Sphenoptera jugoslavica also occurs, the abundance of Agapeta larvae appears to have declined.
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Basic Info: Leafy Spurge Black Dot Flea Beetle
Aphthona nigriscutis
Target Weed(s): Leafy spurge
Profiles: Leafy Spurge Black Dot Flea Beetle Profile 1
Impact on Target: Larvae of the flea beetles feed on roots and buds causing plant mortality. Adults feed on leaves and flowers, and can cause severe defoliation during outbreaks.
Collection/Release: Collect adults with sweep net in June-July. Release 500+.
Distribution: Released in nine Oregon counties and recovered in eight.
History: Three flea beetles, A. cyparissiae, A. flava, and A. nigriscutis were introduced in 1989. A. nigriscutis and A. cyparissiae are well established, but have been slow to increase and spread. A. cyparissiae is usually a small portion mixed in with the other more common species, and has not been much of a contribution to leafy spurge control. It is quite difficult to tell apart from the more common A. nigriscutis. Since 1994, several release sites in central and eastern Oregon have shown significant depression of leafy spurge density by A. nigriscutis, A. cyparissiae, and A. lacertosa. These beetles have provided some limited control but not like the spectacular widespread results that were observed in Montana, North Dakota, and Wyoming. The heavier clay soils may limit the efficacy of the flea beetles in Oregon. Several populations have been harvested for redistribution. The impact of A. nigriscutis which works best in drier, sandy soils, may be compounded by a Wolbachia bacterium.
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Basic Info: Russian Thistle Leaf Mining Moth
Coleophora klimeschiella
Target Weed(s): Russian Thistle
Profiles: None Available
Impact on Target: Damage to leaves appears to have little impact on the plant.
Collection/Release: Widespread, no need for further distribution.
Distribution: Found in 17 Oregon counties, mostly eastern Oregon.
History: Coleophora klimeschiella was first detected in 1998 in Wheeler County, and subsequently found throughout most of eastern Oregon. The larvae mine the lower leaves and later use the leaf sheath as a pupal case.
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Basic Info: Leafy Spurge Brown Dot Flea Beetle
Aphthona cyparissiae
Target Weed(s): Leafy spurge
Profiles: Leafy Spurge Brown Dot Flea Beetle Profile 1
Impact on Target: The larvae of the flea beetles feed on the roots and buds causing plant mortality. Adults feed on leaves and flowers, and can cause severe defoliation during outbreaks.
Collection/Release: Collect adults with sweep net in June-July. Release 500+.
Distribution: This flea beetle has been released in nine Oregon counties and recovered in six.
History: Three flea beetles, Aphthona cyparissiae, A. flava, and A. nigriscutis were introduced in 1989. A. nigriscutis and A. cyparissiae are well established, but have been slow to increase and spread. A. cyparissiae is usually a small portion mixed in with the other more common species, and has not been much of a contribution to leafy spurge control. It is quite difficult to tell apart from the more common A. nigriscutis. Since 1994, several release sites in central and eastern Oregon have shown significant depression of leafy spurge density by A. nigriscutis, A. cyparissiae, and A. lacertosa. These beetles have provided some limited control but not like the spectacular widespread results that were observed in Montana, North Dakota, and Wyoming. The heavier clay soils may limit the efficacy of the flea beetles in Oregon. Several populations have been harvested for redistribution.
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Basic Info: Russian Thistle Stem Mining Moth
Coleophora parthenica
Target Weed(s): Russian Thistle
Profiles: None Available
Impact on Target: The larvae mine pith in stems; little impact.
Collection/Release: Widespread, no need for further distribution.
Distribution: Found in 17 Oregon counties, mostly in eastern Oregon.
History: Coleophora parthenica was first detected in 1998 in Wheeler County, and subsequently found throughout most of eastern Oregon. Often heavily parasitized throughout most of their present range.
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Basic Info: Yellow Starthistle Bud Weevil
Bangasternus orientalis
Target Weed(s): Yellow Starthistle
Profiles: Yellow Starthistle Bud Weevil Profile 1
Impact on Target: Larvae feed in the seed head, reducing the number of seeds produced. Adults can cause minor defoliation. Low efficacy.
Collection/Release: Sweep net plants from budding up to 5% bloom. Releases are 100 to 200 adults.
Distribution: The weevil has been released in 17 Oregon counties and is established in 15.
History: Bangasternus orientalis, was released in 1985. The weevil became widespread at most major infestations. This weevil has become rare, due to competition with the seed head weevil Eustenopus villosus.
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Basic Info: Leafy Spurge Black Flea Beetle
Aphthona czwalinae
Target Weed(s): Leafy spurge
Profiles: Leafy Spurge Black Flea Beetle Profile 1
Impact on Target: The larvae of the flea beetles feed on the roots and buds causing plant mortality. Adults feed on leaves and flowers, and can cause severe defoliation during outbreaks.
Collection/Release: Collect adults with sweep net in June-July. Release 500+.
Distribution: This beetle has been released and established in nine Oregon counties.
History: In 1993, two black species, A. czwalinae and A. lacertosa were released. Both were recovered in 1994. These two species seem to prefer more moist sites and have reduced leafy spurge at a number of sites in eastern Oregon. Both species, particularly A. lacertosa, which usually accounts for >90% of most releases, have been heavily redistributed in eastern and central Oregon.
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Basic Info: Rush Skeletonweed Gall Midge
Cystiphora schmidti
Target Weed(s): Rush skeletonweed
Profiles: Rush Skeletonweed Gall Midge Profile 1
Impact on Target: Larvae cause purplish galls to form on leaves and stems, which reduces photosynthesis and stresses the plant.
Collection/Release: Collect infested plant material in mid-summer, combine into bouquets and place at new site. Does best at large host patches.
Distribution: Released in 5 Oregon counties and is established in 4.
History: Cystiphora schmidti was released in 1978. Populations of the midge remain low due to heavy parasitism and the low density of host plant infestations, many of which are under intensive chemical control. The midge has several generations per year; the latter are often heavily parasitized.
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Basic Info: Knapweed Root Boring Weevil
Cyphocleonus achates
Target Weed(s): Spotted knapweed and Diffuse knapweed
Profiles: Knapweed Root Boring Weevil Profile 1
Knapweed Root Boring Weevil Profile 2
Impact on Target: Larvae are root borers and adults feed on leaves.
Collection/Release: Adults handpicked in late summer from under the rosettes. Release 50 to 100 adults; place two per large rosette.
Distribution: Released in 16 Oregon counties and established in 6.
History: Cyphocleonus achates was first released near Hood River in 1993. Several additional releases were made in other counties the following year. Adults were recovered in 1995 in Bend and are spreading throughout the area. Redistribution began in 1997. The weevil does best at sites with sparse vegetation. At several release sites in Hood River, Deschutes and Crook Counties, plant densities have declined. This weevil also attacks diffuse knapweed and have become abundant on diffuse knapweed in Washington.
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Basic Info: Leafy Spurge Brown-Legged Flea Beetle
Aphthona lacertosa
Target Weed(s): Leafy spurge
Profiles: Leafy Spurge Brown-Legged Flea Beetle Profile 1
Impact on Target: Larvae of the flea beetle feed on the roots and buds causing plant mortality. Adults feed on leaves and flowers, and can cause severe defoliation during outbreaks.
Collection/Release: Collect adults with sweep net in June-July. Release 500+.
Distribution: This beetle has been released and established in nine Oregon counties.
History: In 1993, two black species, A. czwalinae and A. lacertosa were released. Both were recovered in 1994. These two species seem to prefer more moist sites and have reduced leafy spurge at a number of sites in eastern Oregon. Both species, particularly A. lacertosa, which usually accounts for >90% of most releases, have been heavily redistributed in eastern and central Oregon.
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Basic Info: Saltcedar Leaf Beetle
Diorhabda carinulata ( = elongata)
Target Weed(s): Saltcedar - Tamarisk
Profiles: Saltcedar Leaf Beetle Profile 1
Impact on Target: Both adults and larvae are defoliators and can cause complete defoliation of affected trees.
Collection/Release: Adults collected into a sweep net by beating vegetation of infested trees where beetles congregate. Releases made with 500+ adults; the more the better.
Distribution: Released in two Oregon counties and is established in one.
History: Diorhabda carinulata was originally released in Malheur County in various drainages of the Owyhee River in 2003. For several years, they were difficult to establish. In 2007, Gary Brown, USDA-APHIS, provided over 50,000 adult beetles from Lovelock, Nevada for release at several sites in Malheur County. By August, the beetles had defoliated a strip 30 meters long at the Haystack Rock site. Beetles were recovered at this site in May of 2008, and additional releases were made. Later that summer, the beetle population exploded causing significant damage to trees in a 1.3 mile radius with some evidence of tree mortality. In 2009, beetle damage was detected over 4.5 miles from the Owyhee Reservoir release site. Monitoring at two previous release sites (Acton Gulch and Huffman Island), showed beetles were present, but in low numbers. Over 35,000 beetles were released in SE Oregon. Also in 2009, USDA-APHIS withdrew permits for the interstate movement of the saltcedar beetle. Intrastate movement within Oregon was not affected, other than APHIS employees were restricted to monitoring activities. Beetle production in 2010 and 2011 was very low due to a cool wet summer and late flooding. This insect has two generations per year in Oregon.
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Basic Info: Leafy Spurge Copper Flea Beetle
Aphthona flava
Target Weed(s): Leafy spurge
Profiles: Leafy Spurge Copper Flea Beetle Profile 1
Impact on Target: Larvae of the flea beetles feed on the roots and buds causing plant mortality. Adults feed on leaves and flowers, and can cause severe defoliation during outbreaks.
Collection/Release: Collect adults with sweep net in June-July. Release 500+.
Distribution: This beetle has been released in nine Oregon counties and established in six.
History: Three flea beetles, A. cyparissiae, A. flava, and A. nigriscutis were introduced in 1989. A. nigriscutis and A. cyparissiae are well established, but have been slow to increase and spread. A. flava established, but only occurs in low numbers at several sites. This species seems to do better in mountain infestations where sagebrush also occurs.
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Basic Info: Knapweed Broad-Nosed Seed Head Weevil
Bangasternus fausti
Target Weed(s): Diffuse, Spotted and Squarrose Knapweed
Profiles: Knapweed Broad-Nosed Seed Head Weevil Profile 1
Knapweed Broad-Nosed Seed Head Weevil Profile 2
Knapweed Broad-Nosed Seed Head Weevil Profile 3
Impact on Target: Larvae feed in developing seeds, adults cause minor defoliation and chaffing of stems. Limited impact.
Collection/Release: Sweep net adults while plants are in bud stage to 10% bloom.
Distribution: Released in 22 Oregon counties and established in 19.
History: The seed head weevil, Bangasternus fausti, was first introduced in Jackson County in 1989. It is now widespread and abundant in most infested counties in eastern Oregon. The weevil attacks the early buds, and appears to contribute to the impacts of Larinus minutus.
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Basic Info: St. Johnswort Large Klamathweed Beetle
Chrysolina quadrigemina
Target Weed(s): St Johnswort
Profiles: St. Johnswort Large Klamathweed Beetle Profile 1
Impact on Target: Both adults and larvae can cause significant defoliation.
Collection/Release: Collect adults with a sweep net during the early flowering period. Releases of 100 – 200.
Distribution: Released and established in 36 Oregon counties.
History: Defoliation by the Klamath weed beetles Chrysolina hyperici and Chrysolina quadrigemina resulted in spectacular control several years after their respective releases in 1947 and 1948. Chrysolina hyperici is adapted to wetter sites while C. quadrigemina is more effective in drier sites and is widespread throughout Oregon. The two beetles are hard to tell apart in the field. Population declines of both beetles in recent years have allowed the host plant to recover in various areas throughout the state, especially in the mountains where summer rains allow plants to recover from insect damage. In 2014, extensive outbreaks of C. quadrigemina in northeastern Oregon controlled large infestations of St. Johnswort that had been a problematic for several years.
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Basic Info: St. Johnswort Small Klamathweed Beetle
Chrysolina hyperici
Target Weed(s): St Johnswort
Profiles: St. Johnswort Small Klamathweed Beetle Profile 1
Impact on Target: Both adults and larvae can cause significant defoliation. High impact.
Collection/Release: Collect adults with sweep net during early flowering period. Releases of 100 – 200 adults.
Distribution: The beetle has been released and established in 19 counties.
History: Defoliation by the Klamath weed beetles Chrysolina hyperici and Chrysolina quadrigemina resulted in spectacular control several years after their respective releases in 1947 and 1948. Chrysolina hyperici is adapted to wetter sites while C. quadrigemina is more effective in drier sites and is widespread throughout Oregon. The two species are hard to tell apart in the field. Population declines of both beetles in recent years have allowed the host plant to rebound in various areas throughout the state, especially in the mountains where summer rains allow plants to recover. In 2014, extensive outbreaks of C. quadrigemina in northeastern Oregon controlled large infestations of St. Johnswort that had been a problematic for several years.
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Basic Info: Yellow Starthistle Hairy Weevil
Eustenopus villosus
Target Weed(s): Yellow Starthistle
Profiles: Yellow Starthistle Hairy Weevil Profile 1
Impact on Target: Larvae feed on developing seeds in the larger seed heads, reducing seed production by 70% or more. Adults feed on young developing buds, causing the buds to die, causing a characteristic grayish-white hook.
Collection/Release: Adults can be sweep-netted from plants at 10% bloom. Releases of 100 to 200 adults recommended.
Distribution: Released in 17 Oregon counties and is established in 16.
History: Eustenopus villosus was released in Douglas County in 1990 and established in 1991. The Myrtle Creek site, served as the main nursery site for collection. Feeding can significantly reduce seed production of the plant. In 1996, collections of E. villosus at the Myrtle Creek site were difficult because of the low density of yellow starthistle. Reduced grazing and increased plant competition in combination with the biocontrol agents contributed to the decline. This weevil is the largest contributor to control of this weed, and now occurs at most infestations. Adults have been found to occasionally feed on the seed-heads of other knapweeds that grow in proximity to yellow starthistle.
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Basic Info: Rush Skeletonweed Root Boring Moth
Bradyrrhoa gilveolella
Target Weed(s): Rush skeletonweed
Profiles: Rush Skeletonweed Root Boring Moth Profile 1
Impact on Target: Larvae are root miners that decrease root reserves and plant vigor. Adults are nectar feeders.
Collection/Release: Collecting adults during the early bud stage is recommended. Use an aerial net to collect flushed out adults while walking through infested areas. Release are 100 adults. Egg transfers are laborious, but have been successful at some sites.
Distribution: Released in four Oregon counties and recovered in two.
History: Experimental releases of Bradyrrhoa gilveolella were made in Multnomah County (’05, ’07, ’09) and Douglas County (’08). Eggs from colonies in Idaho were supplied for the release. A cooperative release strategy study using cages in the Port of Portland area in Multnomah County was conducted by the staff of Dr. Mark Schwarzländer (U of ID) and Gary Brown (OR USDA-APHIS). Limited larval recovery was reported in 2010 and 2011. By 2012, the Portland site had a thriving population. The moth is active into September. An additional recovery was made in 2012 in the Cow Creek area of Douglas County where the moth had been released in 2008, but was not observed in 2013.
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Basic Info: Gorse Seed Weevil
Exapion ulicis ( = Apion)
Target Weed(s): Gorse
Profiles: Gorse Seed Weevil Profile 1
Impact on Target: Adults lay eggs in the seedpods and larvae feed on developing seeds.
Collection/Release: Adults can be dislodged from plants with green seedpods by hitting the plant with a racquet onto a beating sheet, where they can be aspirated into a vial. Releases of 100 recommended. Widespread; further redistribution unnecessary.
Distribution: Released and established in six Oregon counties.
History: Exapion ulicis was released in 1956 and is widespread at all major gorse infestations. Larvae may attack up to 90% of seedpods, but rarely reduce seed production by more than 50%. Plants may receive heavy damage on branch tips and spines from adult feeding when flowers are not present. Although the density of established plants is not reduced, the spread of gorse seedlings appears to be less. In 1997 a parasitic wasp, identified as Pteromalus sequester, was discovered that parasitizes the weevil.
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Basic Info: Rush Skeletonweed Gall Mite
Aceria chondrillae ( = Eriophyes)
Target Weed(s): Rush skeletonweed
Profiles: Rush Skeletonweed Gall Mite Profile 1
Impact on Target: Mites cause galls to form in the developing flower buds and growing tips, which restrict seed production and stunt growth.
Collection/Release: Collect infested plant material in mid-summer, combine into bouquets and place at new site.
Distribution: Released and established in eight counties in Oregon.
History: Aceria chondrillae was released in 1978 and is now widespread at most infestations. It is often found at newly detected infestations, and seems to be the most effective agent.
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Basic Info: Scotch Broom Seed Weevil
Exapion fuscirostre ( = Apion)
Target Weed(s): Scotch Broom
Profiles: Scotch Broom Seed Weevil Profile 1
Impact on Target: Larvae consume seeds, which may slow the spread of the plant. Adult feeding on the tips of small branches can cause minor twig mortality.
Collection/Release: Adults can be dislodged from plants with green seedpods by hitting the plant with a racquet onto a beating sheet, where they can be aspirated into a vial. Releases of 100 recommended. Widespread; further redistribution unnecessary.
Distribution: Released in 20 Oregon counties and established in 18.
History: Exapion fuscirostre was introduced in 1983 and is now widespread in Western Oregon. During 1996, a cooperative project with USFS was started. Seedpods were checked for weevil infestation from numerous areas throughout Western Oregon. Weevils were found at 46% of checked sites. At sites with weevils, an average of 66% of pods were attacked. In most areas, the seed beetle Bruchidius villosus is out-competing the weevil. A natural enemy of the weevil, Pteromalus sequester, a pteromalid wasp, was found in several samples reared from seedpods.
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Basic Info: Eurasian Watermilfoil Stem Mining Weevil
Euhrychiopsis lecontei
Target Weed(s): Eurasian Watermilfoil
Profiles: Eurasian Watermilfoil Stem Mining Weevil Profile 1
Impact on Target: Larvae are stem-miners and heavy attack can cause stems to die back and sink. Adults feed on leaves.
Collection/Release: Adult weevils reared from infested material in cages and collected with aspirators. Release 500+ per site.
Distribution: Naturally occurs in Oregon. Released into two counties and recovered in one.
History: Euhrychiopsis lecontei was released near Troutdale at Blue Lake in August 2010 from colonies collected in Ohio. The weevil is suspected to occur in Oregon, however this is the first recorded introduction of the insect as a biological control agent. Weevils do not do well in ponds stocked with small fish.
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Basic Info: Purple Loosestrife Golden Leaf Beetle
Galerucella pusilla
Target Weed(s): Purple Loosestrife
Profiles: Purple Loosestrife Golden Leaf Beetle Profile 1
Impact on Target: Young larvae feed on developing buds, often destroying them, which may stunt plants and prevent flowering. Adults and older larvae feed on leaves and cause defoliation.
Collection/Release: Adults collected with sweep net in May and June when they are laying eggs. First generation adults collected in July. Release 250 to 500 adults.
Distribution: Released in 21 Oregon counties and is established in 17.
History: Two leaf beetles, Galerucella calmariensis and G. pusilla were released at several locations in 1992. At the Baskett Slough National Wildlife Refuge in Polk County, spectacular control occurred in 1997 reducing plant density and flowering spikes by more than 90%. In 1999, plant density had increased about 10%, following the crash of the beetle population. In 2000, beetle numbers increased, leading to severe damage again. Spectacular outbreaks and defoliation have become more common. Cooperative studies with OSU and USFWS were conducted to determine the cyclic nature of the plant-insect relationship. Nontarget impacts on crape myrtle during outbreak numbers were shown to be minor and transitory (Schooler et al. 2003). Regional redistribution began in 1997. In 2005 and again in 2008 and 2009, outbreaks of beetles totally defoliated purple loosestrife at the Horseshoe Lake site in Marion County, where purple loosestrife biomass and density have declined and native vegetation has significantly increased. Since 1998, hundreds of thousands of adult beetles have been collected and distributed to numerous locations throughout Oregon and to other states. Off-site management is important near release sites to ensure that flooding or farming does not disturb adults overwintering within 100 feet of the high-water level. The beetles produce two generations per year.
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Basic Info: Purple Loosestrife Root Boring Weevil
Hylobius transversovittatus
Target Weed(s): Purple Loosestrife
Profiles: Purple Loosestrife Root Boring Weevil Profile 1
Impact on Target: Weevil larvae mine roots and stems, adults feed on leaf edges.
Collection/Release: Rearing is more economical because adults are nocturnal and difficult to collect in the wild, falling onto the ground at the slightest disturbance. Release 100 adults.
Distribution: Released in 18 Oregon counties and is established in 13.
History: Hylobius transversovittatus adults were released in Marion and Polk counties in 1993. Weevils were recovered at both sites in 1994 and 1995. Adults may live two to three years. Larvae can withstand flooding for several months. The weevil may help dampen the boom/bust cycle caused by the PLS leaf beetles. In 2005, a cooperative weevil-rearing project was initiated with the Army Corps of Engineers (later with Earth Designs Inc.) to provide adults for areas along the lower Columbia River, where tides make establishment of the leaf beetles tenuous. In 2007, adults and larvae in infested plants were relocated to sites along the Columbia River. In 2012, a colony was established in the ODA greenhouse in Salem to provide weevils for field release.
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Basic Info: Purple Loosestrife Black-Margined Leaf Beetle
Galerucella calmariensis
Target Weed(s): Purple Loosestrife
Profiles: Purple Loosestrife Black-Margined Leaf Beetle Profile 1
Impact on Target: Young larvae feed in and on developing buds, often destroying them, which may stunt plants and delay or prevent flowering. Adults and older larvae feed on leaves and cause severe defoliation.
Collection/Release: Adults can be collected with a sweep net in May and June when they are laying eggs. First generation adults can be collected in July. Release 250 to 500 adults.
Distribution: Released in 21Oregon counties and established in 17.
History: Two leaf beetles, Galerucella calmariensis and G. pusilla were released at several locations in 1992. At the Baskett Slough National Wildlife Refuge, significant loosestrife control occurred in 1997 reducing plant density and flowering spikes by more than 90%. In 1999, plant density had increased about 10%, following the crash of the beetle population. In 2000, beetle numbers increased, leading to severe damage again. Beetle outbreaks and defoliation have become more common. Cooperative studies with OSU and USFWS were conducted to determine the cyclic nature of the plant-insect relationship. Non-target impacts on crape myrtle during outbreak numbers were shown to be minor and transitory (Schooler et al. 2003).
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Basic Info: Knapweed Lesser Flower Weevil
Larinus minutus
Target Weed(s): Diffuse, Meadow, Spotted and Squarrose Knapweeds
Profiles: Knapweed Lesser Flower Weevil Profile 1
Knapweed Lesser Flower Weevil Profile 2
Knapweed Lesser Flower Weevil Profile 3
Impact on Target: Larvae feed on developing seeds and adults can cause severe defoliation during population outbreaks, killing many rosettes.
Collection/Release: Collect adults with a sweep net from plants in 10% bloom or later. Release 100 adults per site.
Distribution: Widespread; released in 24 Oregon counties and is established in 11.
History: Larinus minutus was released in Morrow County in 1992. The weevil is now widespread and abundant at most infestations in eastern Oregon. Attack rates at many sites exceed 95% of the seed heads. This insect also attacks spotted and meadow knapweeds. Heavy attack by adults can stunt or kill plants, delay flowering, and cause stand density reductions at numerous sites in eastern Oregon. In 2012, after two consecutive wet years, a strong resurgence of diffuse knapweed occurred at several sites in eastern Oregon, but by fall, damage on rosettes was severe at most sites. White-footed deer mice, Peromyscus maniculatus, can be a major predator of weevil pupae in late summer. Rosettes may recover from extensive late summer defoliation after fall rains and produce multi-stemmed plants in the next growing season.
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Basic Info: Knapweed Blunt Flower Weevil
Larinus obtusus
Target Weed(s): Spotted and Meadow Knapweed
Profiles: Knapweed Blunt Flower Weevil Profile 1
Knapweed Blunt Flower Weevil Profile 2
Impact on Target: Larvae feed on developing seeds. Adults feed in the open flowers and cause minor defoliation of leaves.
Collection/Release: Collect adults with a sweep net from plants in 10% bloom or later. Release 100 adults per site.
Distribution: Widespread; released in 21 Oregon counties and established in 17.
History: Larinus obtusus was released in 1994 near Hood River and Bend. The original source of the weevils from Europe was from another species of Centaurea. This weevil prefers knapweeds with large seed heads and can exist at wetter sites than other seed head weevils. It is difficult to separate the two weevils when they co-occur. L. obtusus is slightly larger, darker with checkered spots on the elytra, less hairy, and has dark vs. the reddish tibia of L. minutus. The weevil is collectible in the Hood River area. At some sites, predation of adult weevils by house finches may be a significant factor in reducing control. The seed head weevil L. obtusus was recovered in Hood River and Douglas Counties on meadow knapweed for the first time in Oregon in 1999. L. obtusus shows a distinct preference for the larger and earlier available seed heads of meadow knapweed and eventually displaces the smaller weevil L. minutus. It is now found throughout most infested areas of the state and easily collectible in Hood River and Douglas Counties. Several adults (up to 4) can be produced in a single seed head. Adult weevils emerging from this weed are significantly larger than those from diffuse and spotted knapweeds.
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Basic Info: Tansy Ragwort Flea Beetle
Longitarsus jacobaeae
Target Weed(s): Tansy Ragwort
Profiles: Tansy Ragwort Flea Beetle Profile 1
Impact on Target: Adults feed on foliage and cause significant mortality of rosettes during winter months. Larvae feed in the roots and leaf petioles.
Collection/Release: Use a motorized vacuum unit to suck adults from rosettes in fall. Release 100 to 500 adults per site. Widespread, redistribution in western Oregon is unnecessary.
Distribution: Released in 24 Oregon counties and established in 21.
History: Longitarsus jacobaeae, introduced in 1971, has reduced ragwort density by 95% in western Oregon. The combination of the cinnabar moth and flea beetle has nearly eliminated large ragwort patches in many areas of western Oregon. Occasional flare-ups of ragwort occur, but the insects usually control the plants within a couple of years. Plant competition is an important factor in maintaining control of ragwort. In 2007 a cooperative research project with University of Idaho utilized the Swiss biotype flea beetle to control infestations in eastern Oregon, where the Italian biotype is ineffective. Releases of the Swiss biotype were made in Umatilla County in 2007 and in Umatilla and Union Counties in 2008. The insect readily established in similar habitats in Idaho and Montana. Monitoring in 2010 and 2011 for the Swiss biotype did not show that that beetles established in eastern Oregon. Flea beetle populations can exist where host densities are low.
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Basic Info: Yellow Starthistle Flower Weevil
Larinus curtis
Target Weed(s): Yellow Starthistle
Profiles: Yellow Starthistle Flower Weevil Profile 1
Impact on Target: Adults feed on the florets and the larvae in the seed head, reducing seed production.
Collection/Release: Collect adults with sweep net during mid-flowering (July). Release 100 per site.
Distribution: Released in 13 Oregon counties and established in 11.
History: The seed head weevil Larinus curtus was released in Douglas and Baker counties in 1992. An additional release was made in Wasco County in 1993. Collections for redistribution from the Baker and Wasco County sites have provided large numbers of weevils for other locations in Oregon and California. The weevil is widespread in eastern Oregon, occurring at most infestations. This weevil does not appear to do well in southwest Oregon. The weevil attacks flowers later in the growing season than other weevils. USDA-APHIS revoked permits in 2009 for the interstate transportation of this weevil due to concerns of spreading Nosema, an internal parasite.
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Basic Info: Scotch Broom Twig Mining Moth
Leucoptera spartifoliella
Target Weed(s): Scotch Broom
Profiles: Scotch Broom Twig Mining Moth Profile 1
Impact on Target: Larvae mine the epidermis of small twigs, reducing photosynthesis.
Collection/Release: Widespread; no further redistribution necessary.
Distribution: Released and established in 20 Oregon counties.
History: Leucoptera spartifoliella was introduced in 1970, but was later found to have been accidentally introduced prior to its release. The moth occurs throughout Western Oregon. Pupae are often parasitized by small wasps. Large numbers of larvae can cause plant mortality, especially in dry areas.
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Basic Info: Knapweed Sead Head Moth
Metzneria paucipunctella
Target Weed(s): Diffuse, Meadow, Spotted and Knapweeds
Profiles: Knapweed Sead Head Moth Profile 1
Knapweed Sead Head Moth Profile 2
Knapweed Sead Head Moth Profile 3
Impact on Target: Larvae feed in seed-heads. May consume seed fly larvae and pupae.
Collection/Release: Due to heavy parasitism and predation by deer mice, it is not recommended for further redistribution in Oregon.
Distribution: Released in 14 Oregon counties and is established in 10.
History: Metzneria paucipunctella, released in 1981 near Hood River, is now widely established. The moth does not overwinter well in cold areas were seed-heads remain exposed above snow during winter and are consumed by deer, mice, and birds. Facultative carnivory from seed weevil larvae has also drastically reduced the numbers of this insect. It has accumulated several native parasites, which attack up to 10% of the larvae. The moth also attacks diffuse knapweed and to a lesser extent, meadow knapweed.
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Basic Info: Dalmatian Toadflax Stem Boring Beetle
Mecinus janthiniformis
Target Weed(s): Dalmatian Toadflax
Profiles: Dalmatian Toadflax Stem Boring Beetle Profile 1
Impact on Target: Larvae are stem miners. Adult feeding causes stunted stems, reduced flowering, and shot-holes in leaves.
Collection/Release: Use sweep net to collect adults during bud stage (June). Release 100 to 200 per site.
Distribution: Released in 16 Oregon counties and established in 15.
History: Mecinus janthiniformis was introduced into seven counties in 2001. This insect has been widely redistributed in the state. This agent is above average in effectiveness. Over 60 sites in eastern Oregon were inventoried in 2013; weevils were present at almost every site (Park et al. 2014). Observations at previous release sites indicate plant density is less than half of the original density at over 90% of sites. Plant density at some sites rebounds following heavy control, but weevil populations are quick to build up and re-suppress infestations. The weevil originally introduced as M. janthinus (yellow toadflax agent) is actually M. janthiniformis.
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Basic Info: Puncturevine Seed Weevil
Microlarinus lareynii
Target Weed(s): Puncturevine
Profiles: Puncturevine Seed Weevil Profile 1
Impact on Target: Larvae feed on developing seeds within spiny “goat-heads”. Adults cause minor pitting on stem undersides.
Collection/Release: Infested plant materials harvested mid to late summer. One grocery bag is equivalent to approximately 150 adults. Alternately, adults can be collected from under plants by lifting stems and aspirating weevils.
Distribution: Released in 10 Oregon counties and recovered in 4.
History: Two weevils were introduced in 1983 to control puncturevine. The seed weevil, Microlarinus lareynii, and the stem-boring weevil, M. lypriformis, were established in Jackson County. Seed weevils were found to be widely established throughout the Rogue Valley in Jackson County in 2015. The seed weevil is established in Umatilla County, but changes in plant density have not been documented. The stem weevil has not been documented in Oregon since the mid 1980s and may no longer occur. The weevils do not readily overwinter in other areas in Oregon, despite numerous introductions. In warmer regions in the southwest U.S., these insects have been successful in controlling puncturevine. Numerous releases were made using infested plant material collected in Irrigon in 2009. Because of the cool wet summers of 2010 and 2011, weevil populations in the Irrigon area were minimal, but returned in good numbers in 2012 and crashed again in 2014. Also, rearing of adults from infested materials from the Irrigon area by USDA-APHIS showed that the weevil is heavily parasitized by a small wasp, therefore only adult weevils should be used for redistribution.
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Basic Info: Puncturevine Stem Weevil
Microlarinus lypriformis
Target Weed(s): Puncturevine
Profiles: Puncturevine Stem Weevil Profile 1
Impact on Target: Microlarinus lypriformis larvae feed on pith in the stems. Adults cause minor pitting of stem undersides.
Collection/Release: Infested plant material harvested mid- to late summer. One grocery bag is equivalent to approximately 150 adults. Adults can also be collected from under plants by lifting stems and aspirating them.
Distribution: Released in 10 Oregon counties and recovered in 4.
History: Microlarinus lypriformis was released in several counties in Oregon, but has never established. Monitoring of the seed weevil sites may reveal its presence in the future.
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Basic Info: Purple Loosestrife Seed Capsule Weevil
Nanophyes marmoratus
Target Weed(s): Purple Loosestrife
Profiles: Purple Loosestrife Seed Capsule Weevil Profile 1
Impact on Target: Larvae feed on seeds. Adults feed on young growing leaves, causing shot holes.
Collection/Release: Collect adult weevils with a sweep net or beating sheet during the bud stage in July. Release 100 adults.
Distribution: Released in 15 Oregon counties and is established in 12.
History: In 1994, Nanophyes marmoratus was released in several counties in western and eastern Oregon. Adult weevils were recovered at all release sites. Limited redistribution began in 1997. In 1999, the weevil became collectible in Malheur County and have since been distributed to many other infestations throughout the state. This weevil may be most effective in areas where the Galerucella beetles have little impact, especially at sites with low plant densities.
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Basic Info: Mediterranean Sage Crown Root Weevil
Phrydiuchus tau
Target Weed(s): Mediterranean Sage
Profiles: Mediterranean Sage Crown Root Weevil Profile 1
Impact on Target: Adults feed on leaves and larvae feed in the root crown and petioles of large leaves. Adult feeding in late fall and late winter can cause significant mortality of smaller rosettes.
Collection/Release: Adults collected during mating period by aspirating from rosettes in the fall; or by sweep netting adults in summer at mid-bloom. Release 100 adults.
Distribution: Released and established in four Oregon counties.
History: Phrydiuchus tau was released in 1972 and is widely established throughout Lake and Klamath Counties. Successful control has occurred at many Lake County sites (primarily Goose Lake basin) that have competitive vegetation. Sites with salt desert scrub or dominated by annual grasses show little control, especially in the Abert Lake Basin that has been burned by frequent wildfires. Control less effective at higher elevations in Hart Mountain area. An outbreak of Mediterranean sage occurred in the Summer Lake area following a major fire. Within four years, weevil populations responded and caused extensive damage to plants.
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Basic Info: Rush Skeletonweed Rust Fungus
Puccinia chondrillina
Target Weed(s): Rush skeletonweed
Profiles: Rush Skeletonweed Rust Fungus Profile 1
Impact on Target: Affected plants become covered with rust-colored spores, which can stunt plants and cause some mortality.
Collection/Release: Occurs at most infestations; redistribution is as needed. Infected plant material can be placed on plants at new site.
Distribution: Released and established in 13 Oregon counties.
History: Puccinia chondrillina is one of only a few approved pathogens for weed biocontrol in Oregon. It is present in most infested counties. The fungus is most effective on the early flowering biotype, but the late flowering biotype is predominant in Oregon, therefore the rust has had limited impact. During wet summers, rust may become abundant. A cooperative research project with Oregon State University was conducted to determine susceptibility of various strains of rush skeletonweed.
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Basic Info: Knapweed Root Boring Grey-Winged Moth
Pterolonche inspersa
Target Weed(s): Diffuse and Spotted Knapweed
Profiles: Knapweed Root Boring Grey-Winged Moth Profile 1
Knapweed Root Boring Grey-Winged Moth Profile 2
Impact on Target: Larvae mine roots of diffuse and spotted knapweeds, causing swollen galls to form. Prefers diffuse knapweed.
Collection/Release: Adults black-lighted in summer but do not occur in enough numbers to justify. Release 50 to100 adults, or transfer eggs onto rosette leaves.
Distribution: Released in eight Oregon counties and established in two.
History: Pterolonche inspersa was introduced in 1986. After numerous releases, it was recovered in 1997 near Mosier in Wasco County. This insect spreads slowly; therefore it only plays a minor role in knapweed biocontrol. The larvae can coexist below galls caused by Sphenoptera jugoslavica. Larvae have been found associated with an unnamed species of Agrobacterium which causes root crown galls at the Mosier rock pit site.
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Basic Info: Dalmatian and Yellow Toadflax Seed Capsule Weevil
Rhinusa antirrhini ( = Gymnetron)
Target Weed(s): Dalmatian and Yellow Toadflax
Profiles: Dalmatian and Yellow Toadflax Seed Capsule Weevil Profile 1
Dalmatian and Yellow Toadflax Seed Capsule Weevil Profile 2
Impact on Target: Larvae feed in the seed capsule, destroying seeds and adults cause minor defoliation.
Collection/Release: Adults sweep netted during early bloom. Release 100 adults.
Distribution: Weevil occurs at most sites in Oregon; little need for redistribution. Found in 3 Oregon counties; probably occurs in 15 others.
History: Rhinusa antirrhini, an adventive species, was approved in 1996 for use as a biocontrol agent. The weevil is commonly found on yellow toadflax, and some strains attack Dalmatian toadflax. Overall impact to the weed has not been documented. Infestation rates have averaged about 30-40% on yellow toadflax.
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Basic Info: Knapweed Root Bronze Borer
Sphenoptera jugoslavica
Target Weed(s): Diffuse and Spotted Knapweed
Profiles: Knapweed Root Bronze Borer Profile 1
Knapweed Root Bronze Borer Profile 2
Impact on Target: Larvae feed in roots causing galls and plant stress.
Collection/Release: Adults sweep-netted from plants in evenings during early July. Releases 50 to100 adults.
Distribution: Released in 19 Oregon counties and established in 18. It occurs at most infestations, releases made as needed.
History: Sphenoptera jugoslavica was introduced in 1980 in Wasco County. It is now widely distributed and often infests over 95% of rosettes. Major reductions in plant density have been observed, especially in Wasco and Morrow Counties where it occurs with Larinus minutus. It was found in spotted knapweed near Hood River in 1994 where it spread from diffuse knapweed. Releases were made on spotted knapweed and recovered at most sites in 1997. Larvae, up to several per plant, may co-occur with C. achates which also mine roots. This agent may be more damaging and displacing the larvae of Agapeta zoegana at some sites.
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Basic Info: Russian Knapweed Gall Nematode
Subanguina picridis
Target Weed(s): Russian knapweed
Profiles: Russian Knapweed Gall Nematode Profile 1
Impact on Target: Attack shoots as they grow through the soil. Galls look like tiny tennis balls, on stems and leaves, stunting some plants and killing others.
Collection/Release: Collect infested plant material and place bouquets out at new sites. Allow plants to deteriorate, releasing nematodes into the soil. This is a difficult organism to work with. Because of its slow dispersal and lack of availability, it is low priority.
Distribution: Released in six Oregon counties and is established in three.
History: In 1990, a release Subanguina picridis was made in Crook County, which failed to establish. Additional releases were made in several counties in 1993 and 1994, and were later recovered, but in small numbers. In 1998, only two release sites, in Jefferson and Wheeler Counties, showed symptoms of nematode attack. They can survive several years in the soil without showing any signs of attack, then cause significant impacts on plants when soil moisture is adequate. Experimental releases of nematode infested soil have been made at several other locations, but have not yet been recovered. Control appeared to be promising at Springer’s Spring in the Crooked River National Grassland in 2005, where there was an 80% reduction causing a 20 foot wide hole in the knapweed stand. Unfortunately, the control was short-lived, and the site was reinfested by September by from surrounding plants.
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Basic Info: Gorse Spider Mite
Tetranychus lintearius
Target Weed(s): Gorse
Profiles: Gorse Spider Mite Profile 1
Impact on Target: Mites damage plants by sucking juices from leaves, causing yellowing and desiccation. Heavily attacked plants produced 90% fewer flowers the following year. Mites make extensive webbing, which can enshroud entire plants.
Collection/Release: Collect infested plant material, inoculate by tossing infested material into bushes. Ten infested branches per release are usually adequate. Avoid releasing mites from sites with predatory mites.
Distribution: Released and established in six counties.
History: Tetranychus lintearius was released in 1994. It is the first spider mite introduced into the U.S. as a biological control agent for a weed. It is widely established, though rare, at gorse sites in Oregon. Mites were imported from New Zealand, and represent populations collected from Great Britain, Portugal, and Spain. An intensive interagency redistribution project was conducted in 1996. Over 270 releases of mites were redistributed throughout southern Oregon coastal infestations. Cooperative studies to monitor impacts of the mite on gorse and predatory mites that attack the gorse spider mite were conducted in conjunction with USFS and OSU. Several species of predatory mites have been found to attack the gorse spider mite, the most serious being Phytoseiulus persimilis, which was first found in the Bandon area (Pratt et al. 2002 and 2003). This predator reduced the gorse mite impact by more than 90% during 1998. Very few colonies were found after 1999, and most were infested with the predator. The predatory mite is not known to be established elsewhere in Oregon outside of greenhouses. Also, a predatory ladybird beetle (Coccinellidae), Stethorus punctillum, was found attacking gorse spider mites in the Sutherlin and Florence areas. A species of Scymnus was also found at Baker Beach; appears to deplete mite colonies during the summer months.
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Basic Info: Thistle Crown-Root Weevil
Trichosirocalus horridus
Target Weed(s): Musk, Italian and Slender Flower Thistles
Profiles: Thistle Crown-Root Weevil Profile 1
Thistle Crown-Root Weevil Profile 2
Thistle Crown-Root Weevil Profile 3
Impact on Target: Adult weevils emerge in late winter and oviposit into the central stem. Adults feed on leaves and cause pitting of stems. Larvae feed in root/crowns. The central stem often dies after severe larval damage, causing the development of several smaller stems to arise.
Collection/Release: Adults collected in early spring by aspirating them from the rosettes, or sweep net adults in early flowering stage. Release 100+ adults per site.
Distribution: Released in six counties and established in two.
History: Trichosirocalus horridus was released in Malheur, Klamath, and Umatilla Counties in 1994. Research indicates the weevil released in Oregon is probably T. mortadelo. The weevil was recovered in Klamath County at the Devils Garden site, where stand density declined by 95%. This weevil has naturally spread more than 20 miles from the Devil’s Garden. It does not do well in moist pastures. In 1994, an experimental release of the weevil was made in Douglas County. It was recovered in 2008 on Italian and slender-flower thistles and found to be widely established.
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Basic Info: Knapweed Green Clearwing Fly
Terellia virens
Target Weed(s): Spotted and Diffuse knapweed
Profiles: Knapweed Green Clearwing Fly Profile 1
Knapweed Green Clearwing Fly Profile 2
Impact on Target: Mobile larvae feed on developing seeds.
Collection/Release: Adults gently sweep netted from budding plants with an aerial net, or infested seed heads can be transferred as bouquets to new area, however parasitoids may be moved with them. To exclude other seed head insects and parasitoids, adults should be recovered in a sleeve cage. Release 100 + adults per site. The fly prefers cooler and wetter sites than the seed-head weevils.
Distribution: Released in seven Oregon counties and established in four.
History: Terellia virens was released in Hood River, Lane, and Deschutes Counties in 1993. Adults were recovered at all sites. The flies are collectible in Lane County at the Cougar Reservoir site. The fly is known to attack diffuse knapweed. The mobile larvae are less vulnerable to predation by Metzneria larvae than Urophora larvae.
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Basic Info: Tansy Ragwort Cinnabar Moth
Tyria jacobaeae
Target Weed(s): Tansy Ragwort
Profiles: Tansy Ragwort Cinnabar Moth Profile 1
Impact on Target: Does best on dense stands of ragwort where larvae cause severe defoliation in late spring and summer.
Collection/Release: Collect by picking tops of plants with late stage larvae and placing them in paper bags or buckets. Release 10 larvae per plant. Make releases with 250 to 500 larvae.
Distribution: Released in 25 counties and established in 22.
History: The cinnabar moth, Tyria jacobaeae, was introduced in 1960. It is the symbol of the ODA Weed Control Program. The moth can attack tansy ragwort at elevations up to 3,000 feet. Ragwort can grow back after defoliation by cinnabar larvae and survive as a short lived perennial. Attempts to establish the moth east of the Cascades have been mostly unsuccessful. Investigations are being conducted to determine the impact of the cinnabar moth larvae feeding on native Senecio species, especially S. triangularis and Packera pseudaurea (=Senecio pseudaureus). Cooperative studies with Dr. P. McEvoy and staff (OSU) will continue to determine the extent of attack on non-target plants and impact of predators and parasites. Moth larvae were abundant at infestations observed in 2011, and heavily defoliated stands by the end of summer.
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Basic Info: Field Bindweed Defoliating Moth
Tyta luctuosa
Target Weed(s): Field Bindweed
Profiles: Field Bindweed Defoliating Moth Profile 1
Impact on Target: Larvae are defoliators. Adults are nectar feeders and are commonly seen during the day.
Collection/Release: Adults sweep netted in early morning from June to August. Release 50+ adults per site. Larvae are almost impossible to find in the wild, and are best raised in a greenhouse. Release 100+ larvae, at a rate of no more than two to three per square yard.
Distribution: Released in 10 counties and established in 3.
History: Tyta luctuosa was released in 1998 and 1999 at the Baskett Slough National Wildlife Refuge in Polk County and in 1999 in Douglas County. August 2009 it was recovered for the first time in Oregon in a light trap. The recovery was about 10 miles south of the Baskett Slough area, where it had been released several times. Light traps in Polk County revealed a strong population of the moth. Initial collection and redistribution occurred in 2011 in conjunction with Dr. Ed Peachy (OSU). Redistribution of larvae reared by Colorado Department of Agriculture was made in eastern Oregon in 2010 and 2011, however pheromone traps placed out in 2013 and 2014 did not reveal establishment. An additional release of adults was made near Heppner in Morrow County.
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Basic Info: Knapweed Banded Gall Fly
Urophora affinis
Target Weed(s): Diffuse, meadow, spotted and squarrose knapweeds
Profiles: Knapweed Banded Gall Fly Profile 1
Knapweed Banded Gall Fly Profile 2
Knapweed Banded Gall Fly Profile 3
Knapweed Banded Gall Fly Profile 4
Impact on Target: Larvae cause a hard seed-like gall that acts as a nutrient sink, reducing seed production.
Collection/Release: Widespread; no need to redistribute. Adults can be sweep netted during bud-stage with an aerial net. Release 100+ per site.
Distribution: Released in 23 counties and established in 22.
History: Urophora affinis was released in 1975 and is widely distributed throughout Oregon. There are generally two generations per year. It usually emerges two weeks after U. quadrifasciata. Seed head infestation rates average 40% to 60%.
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Basic Info: Canada Thistle Gall Fly
Urophora cardui
Target Weed(s): Canada Thistle
Profiles: Canada Thistle Gall Fly Profile 1
Impact on Target: Larvae gall stems. Galls act as nutrient sinks, occasionally reducing seed production or plant height.
Collection/Release: Collect galls in fall after first killing frost. Scatter 100 galls at new site. Due to widespread status and no significant effects, it is low priority.
Distribution: Released in 36 counties and is established in 28.
History: Urophora cardui introduced in 1980 is prevalent throughout the Willamette Valley. It is well established west of the Cascades, and has become more abundant in eastern Oregon along riparian areas. Releases can be collected from the cold hardy population at Ladd Marsh Wildlife Refuge in Union County. Recent research indicates galls generally have no significant effects on Canada thistle at the individual or population level (Price et al., unpublished data).
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Basic Info: Knapweed UV Seed Head Fly
Urophora quadrifasciata
Target Weed(s): Diffuse, Meadow, Spotted, and Squarrose Knapweeds and Bachelors Button
Profiles: Knapweed UV Seed Head Fly Profile 1
Knapweed UV Seed Head Fly Profile 2
Knapweed UV Seed Head Fly Profile 3
Knapweed UV Seed Head Fly Profile 4
Impact on Target: Larvae attack developing flower heads and cause minor galls that act as nutrient sinks, reducing seed production.
Collection/Release: Found at nearly every infestation, additional redistribution unnecessary.
Distribution: Released and established in 31 counties. Larvae-infested seed-heads collected in early spring and transported to release sites prior to adult emergence, or collected in the fall and stored at 39° F to 46° F. Adults can be reared from caged seed-heads.
History: Urophora quadrifasciata was released in 1979. It was probably brought in as a contaminant of knapweed seed-heads infested with U. affinis, but was later approved by TAG for general use. This insect attacks most species of introduced knapweeds. U. quadrifasciata makes a thin soft gall and has several generations per year. Seed-head infestation rates average 40% to 60%.
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Basic Info: Yellow Starthistle Seed Head Gall Fly
Urophora sirunaseva
Target Weed(s): Yellow Starthistle
Profiles: Yellow Starthistle Seed Head Gall Fly Profile 1
Impact on Target: Larvae cause development of lignified galls in seed-heads, which act as nutrient sinks and reduce the viability and number of seeds produced.
Collection/Release: Adults sweep netted during plant bud stage. Release 100+ adults per site. Infested bouquets of seed heads can be collected in early spring and placed at new sites.
Distribution: Released in 15 counties and established in 13.
History: Urophora sirunaseva was released in 1985 in Jackson County and not recovered until 1989. The fly is well established throughout western Oregon. It has been extensively redistributed, but is less common in eastern Oregon. The fly has several generations per year. Infestation rates averaged about 30%, but have declined due to competition with other seed-head agents.
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Basic Info: Bull Thistle Seed Head Gall Fly
Urophora stylata
Target Weed(s): Bull Thistle
Profiles: Bull Thistle Seed Head Gall Fly Profile 1
Impact on Target: Larvae form hard multi-chambered galls in flower receptacles, interfering with seed production and dispersal. Many seeds become lodged in the gall tissues, rendering them incapable of dissemination. Adults are nectar feeders.
Collection/Release: Harvest infested seed-heads in fall after killing frost. Disseminate 50 to100 galls per site by scattering them.
Distribution: Released in 34 counties and established in 14. More monitoring is needed to fill in gaps in redistribution.
History: Urophora stylata was introduced in 1988. It is collectible in Benton and Douglas Counties. It has been widely introduced throughout Oregon, but has only established east of the Cascades in northern Morrow County. A survey in Morrow County in 2009 found that bull thistle at the original release site was difficult to find. Additional studies are needed to show effectiveness. The fly is available for mass redistribution in western Oregon, though the populations are somewhat cyclical. During the past several years, fly populations have declined, for unknown reasons.
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Basic Info: St. Johnswort Defoliating Moth
Aplocera plagiata
Target Weed(s): St Johnswort
Profiles: St. Johnswort Defoliating Moth Profile 1
Impact on Target: Larvae are minor defoliators; adults feed on nectar.
Collection/Release: Sweep net larvae from plants during bloom. Release two larvae per plant over a large area. Releases should be 100+ larvae.
Distribution: Released in 19 Oregon counties and established in 14.
History: In 1989, Aplocera plagiata was released in several counties. Greenhouse reared colonies at the ODA Salem facility supplied releases for several more counties. The moth was first recovered in Jefferson County in 1993. The moth is widespread in northeastern Oregon, in the Cascades south to Douglas County, and recently in the Willamette Valley. There may be several generations per year. It does not occur in large enough numbers to cause significant damage to plants.
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Basic Info: Canada Thistle Crown-Stem Weevil
Hadroplontus litura ( = Ceutorhynchus)
Target Weed(s): Canada Thistle
Profiles: Canada Thistle Crown-Stem Weevil Profile 1
Impact on Target: Larvae mine the pith (non-essential tissue) in stems of bolting plants. The adults feed on leaves causing minor damage.
Collection/Release: Adults aspirated from rosettes in early spring when plants are less than four inches in height. New adults can be collected with sweep nets in mid-summer. Release 100 adults per site, best using spring collected weevils.
Distribution: Released in 22 Oregon counties and recovered in 7.
History: Hadroplontus litura was first introduced in 1981. It was reintroduced in 1988 and is now established in most eastern Oregon counties. The weevil is becoming more widespread but is still difficult to collect. Experiments in 2010 were made to determine if releases of late season collected adults would establish in central Oregon. The weevil does not seem to thrive in western Oregon.
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Basic Info: Leafy Spurge Defoliating Hawk Moth
Hyles euphorbiae
Target Weed(s): Leafy spurge
Profiles: Leafy Spurge Defoliating Hawk Moth Profile 1
Impact on Target: Larvae are defoliators.
Collection/Release: Collect larvae in early summer. Release 200+ over a large area, apart from each other.
Distribution: Released in 4 Oregon counties. An unverified establishment has been reported in Grant County.
History: Hyles euphorbiae was released in Klamath County in 1974, Baker County in 1980 and in Wallowa County in 1984. The moth failed to establish at all three sites. Problems with pathogens have plagued this moth in other states. No additional attempts to reintroduce it into Oregon are planned. A similar native moth is frequently confused with the leafy spurge hawk moth.
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Basic Info: Russian Knapweed Gall Midge
Jaapiella ivannikovi
Target Weed(s): Russian knapweed
Profiles: Russian Knapweed Gall Midge Profile 1
Impact on Target: Larvae cause leafy 'rosette' galls on growing plant tips, acting as a nutrient sink and interfering with seed production. There are several generations per year.
Collection/Release: Mature galls can be cut with a few inches of stem, made into boquetes in water, and placed in new RKW stands during plant bolting (early spring).
Distribution: Released in seven Oregon counties, established in five.
History: In 2011, Jaapiella ivannikovi was released in Morrow and Wheeler Counties by APHIS and ODA. Minor galling was observed in fall, however no recovery was made in 2012. Greenhouse colonies were reared to increase release numbers for 2012 field season. A number of current season galls were observed in 2013 at the Rimrock Springs Wildlife Refuge site in Jefferson County. Recoveries were also made at release sites in Gilliam and Morrow counties. Midge galls were extensively collected and redistributed in 2014 throughout Oregon from the original Rhea Road site in the Willow Creek area in Morrow County in cooperation with USDA APHIS. An extensive statewide redistribution program continued into 2017.
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Basic Info: Yellow Starthistle Rust Fungus
Puccinia jaceae var. solstitialis
Target Weed(s): Yellow Starthistle
Profiles: Yellow Starthistle Rust Fungus Profile 1
Impact on Target: Rust fungus grows in leaves and on stems, affecting photosynthesis and nutrient transport.
Collection/Release: Spores are collected from infested plants reared in greenhouses and sprayed onto plants in the field.
Distribution: Released in five Oregon counties, established in one.
History: Puccinia jaceae var. solstitialis was first released in California. In 2008, a permit for release in Oregon was approved. In cooperation with California Department of Food and Agriculture, releases were made in Josephine, Jackson, Douglas and Umatilla Counties. Recovery of infected plants was made in all but Jackson County. Oregon Department of Agriculture conducted a greenhouse-rearing project in Salem to produce rust spores for releases in 2009. None of the release sites showed any signs of the pathogens in 2009. Release sites were monitored in 2010, 2011, and 2013; there was no recovery of the rust. Field releases in California have also appeared less than promising. In 2014, the rust fungus was recovered for the first time in Oregon in the Myrtle Creek area in Douglas County.
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Basic Info: Leafy Spurge Stem Borer
Oberea erythrocephala
Target Weed(s): Leafy spurge
Profiles: Leafy Spurge Stem Borer Profile 1
Impact on Target: Larvae bore in stems and roots. Adults girdle the top of a stalk before laying eggs in the stem; they also do minimal feeding on leaves.
Collection/Release: Sweep net adults in early morning when plants are in bloom (July). Release 100 adults.
Distribution: Released in 10 Oregon counties and established in 8.
History: In 1982, Oberea erythrocephala was released in Klamath County but failed to establish. It was re-released in 1994 and established in several counties. The beetle now occurs at most sites in Crook County. The population at Smith Rock State Park in Deschutes County provides releases for other counties. This beetle is widespread and has lead to a decline of larger plants at many infestations in eastern Oregon.
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Basic Info: Canada Thistle Rust Fungus
Puccinia punctiformis
Target Weed(s): Canada thistle
Profiles: Canada Thistle Rust Fungus Profile 1
Impact on Target: Spores germinate on leaves, travel down stems, and systemically infect the root system as a cryptic root parasitic fungus. The rust fungus often limits an infestations ability to increase and, in some cases, causes infestations based on one or two mother plants to experience colony collapse.
Collection/Release: Sites with known infection can be collected from in September. Yellowing basal leaves with dark spots underneath (ruptured spore pustules) can be clipped off. Leaves are then dried, crushed, and sprinkled on fall emergent rosettes at a new release site (0.5 grams per rosette). Best applied with high likelihood of dew. Late fall mowing can increase rust abundance locally.
Distribution: Naturalized in North America and present at low levels throughout Canada thistle's range. Likely to be present statewide.
History: Puccinia punctiformis was likely introduced at the same time as Canada thistle and has since naturalized throughout all temperate regions of the globe. The USDA-ARS plant pathology labs in Maryland developed methods of utilizing the rust and transferred that knowledge to the Colorado Department of Agriculture in 2013. Using Colorado's expertise and source material for initial releases, Oregon added Canada thistle rust to the biocontrol program in 2018.
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Basic Info: Yellow Toadflax Stem Weevil
Mecinus janthinus
Target Weed(s): Yellow Toadflax
Profiles: Yellow Toadflax Stem Weevil Profile 1
Impact on Target: Larvae are stem miners. Mining causes plant desiccation. Often attack over 30% of stems resulting in some noticable change in infestation.
Collection/Release: Limited adult collectablility during May-June using a sweep net. Releases should be 100 or more adults.
Distribution: Released in four counties and established in two.
History: Introduced in Klamath and Jefferson counties in 2011. Has since been recovered in both counties.
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Basic Info: Whitetop gall mite
Aceria drabae
Target Weed(s): Whitetop Lepidium draba
Profiles: Whitetop gall mite Profile 1
Impact on Target: Several hundred to a few thousand mites are found per infested plant. Mites feed on developing plant tissue that induces bud galls, fuzzy leaves, and thick curled leaves/stems. Damage results in stunting of the plant and reduces seed production. Infestation rates are variable from 1-3% in park settings to 60-95% in cultivated/disturbed sites.
Collection/Release: Collect infested stems with galls late spring and place in direct contact with uninfested stems at new sites. Be careful not to move seed on gathered plants to new sites. As the old galls dry out, mites will migrate to fresh material. A softball sized clump of galled tissue is enough for a release.
Distribution: Currently waiting on collectible Montana populations for first Oregon release. First field release was in Montana, 2019.
History: Petitioned for release in 2013 and permitted for release in 2018. Mites are tubular, white to orange, and microscopic. Mites are wind dispersed and sometimes carried on insects. Mites are widespread across Europe and Eurasia. Life cycle is 10 to 14 days. Mites goes through several generations per year. Mites migrate down to the roots as plants senesce during summer. Mites overwinter on root buds.
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Basic Info: yellow starthistle root-crown weevil
Ceratapion basicorne
Target Weed(s): Yellow starthistle
Profiles: yellow starthistle root-crown weevil Profile 1
Impact on Target: Adults feed on and lay in leaves. Larvae mine down the leaf and feed in root crown. In lab setting, feeding could decrease plant size by 23%. Impact may be greater once introduced in the field where plants experience environmental stressors. 3-4 agents per plant on average. In the field, agents reduced seed fertility by 15%.
Collection/Release: Overwintering adults emerge early spring and are collectable April-May. Adults can be aspirated from rosettes. Releases of 50 adults minimum. Current year adults emerge in June and spend mid-summer through winter in dormant state hiding in secluded places.
Distribution: Native to Europe and SW Asia. Releases expecting in California in 2020 and Oregon in 2021.
History: Petitioned for release in 2006 and approved for release in 2019. Wide tolerance to climate. Spring adults lay a few eggs per day for 1-2 months before dying.
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Basic Info: yellow toadflax shoot-galling weevil
Rhinusa pilosa
Target Weed(s): yellow toadflax
Profiles: yellow toadflax shoot-galling weevil Profile 1
Impact on Target: In experimental tests, galled plants produced 16% less above-ground biomass, 41% less below-ground biomass, 39% less flowering stems, and 58% fewer new stems, compared to control plants. Field observations concur on stunted shoots and flower prevention. Impacts in Oregon are not known.
Collection/Release: Collecting adult weevils can be conducted in April-May when they can be sweep netted or aspirated from stems. Move in groups of 100 adults-200 adults.
Distribution: Currently waiting on collectable Montana populations for first Oregon release.
History: Agents were first petitioned for release in 2013 and approved in 2018. The weevil is becoming rare in its native range (Serbia, Hungary, Romania) due to parasitism, lacking here in Oregon, so biocontrol releases may be important for the preservation of the species globally. Galls average 1x2 cm in size, 2.4 adults per gall and occur between middle and tip of stems. Adults overwinter in soil with one generation per year.
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Basic Info: Gorse thrip
Sericothrips staphylinus
Target Weed(s): Gorse
Profiles: Gorse thrip Profile 1
Impact on Target: Thrips puncture plant cells and suck up contents. Feeding results in mottled white leaf spots. Thrips target new growth and can reduce flowering. In lab settings, thrips could stop seedling growth and kill it within 65 days, even at low thrip density. Small gorse bushes (1 ft) attacked were 25% smaller than healthy plants. Does not attack broom species.
Collection/Release: Collectable year-round but best when warm weather brings fresh gorse growth and moved thrips will have time to recover before winter. Adult thrips can be knocked off branches and onto beating sheets with a stick, then aspirated into vials. Thrip covered branches can also be clipped, paper bagged sealed during transport, and infested branches tucked securely into new gorse site bushes. Be careful not to move predatory arthropods or seeds when collecting thrips. 300 thrips is the minimum release size.
Distribution: Established as a biocontrol in New Zealand, Australia, and Hawaii. Native range throughout NW Europe. First releases in Oregon in 2020.
History: Adults are 1-2 mm long. Easily confused with flower thrips. Eggs laid in tender new stem growth. 76 eggs per female with 32-day life span as adults. Two generations per year are expected with peaks in June and August. Slow to spread, as winged forms are only produced at high thrip density and typically spread by walking or being blown onto neighboring plants.
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Basic Info: Knotweed sap-sucking psyllid
Aphalara itadori
Target Weed(s): Knotweeds
Profiles: Knotweed sap-sucking psyllid Profile 1
Knotweed sap-sucking psyllid Profile 2
Knotweed sap-sucking psyllid Profile 3
Impact on Target: Larvae and adults suck sap from phloem cells of leaves and stems. In lab settings, psyllids reduced attacked plant and root biomass by 50%. Feeding damages meristems and causes leaf curl where psyllids hide from predation. This depletes plant energy supply and reduces leaf area for photosynthesis.
Collection/Release: Agents can be released in mid-April.
Distribution: Native to Japan and Korea. Released in Canada (2015) and the U.K. (2010). First releases in Oregon in 2020.
History: Petitioned for release in 2013 and permitted for release expected in 2020. One agent biotype from N. Japan prefers giant knotweed and another biotype from S. Japan prefers Japanese knotweed. 700 eggs per female laid on leaf surface. 33-day life cycle. One to three generations per year. Adults can fly and likely overwinter by seeking shelter in coniferous tree bark.
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Resources

Biological control of noxious weeds in Oregon

Biological control agent guide to common biological control agents found in Oregon.
Biological control release form