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Forests, Lands & Natural Resource Operations
Invasive Plant Program

Target Invasive Plants and Biocontrol Agents Undergoing Screening

The B.C. Ministry of Forests, Lands and Natural Resource Operations (MFLNRO), through contributed funding, enables research into potential new biocontrol agents for the province on an annual basis. Research on these agents is funded by a consortium of interested partners, including Canadian provincial and federal government departments, US county, state and federal agencies, U.S.A. and Canadian Universities and NGOs.
Specific funding and research partners vary with each plant targeted. For prioritization of invasive plants requiring biological control, and an explanation of the process to attain biological control agents, see Priorities for New Biocontrol Agents.

The invasive plants currently targeted, as of April 2016, and their consortia objectives, are:

Common reed

Common reed (Phragmites australis)

Common reed is considered one of the most widespread plant species in the world. Investigation in North America into potential biological control for common reed began in 1998. Participation in the project has mainly involved agencies from eastern Canada and the USA. B.C. joined the project in 2013, to assist with completion of work on two candidate biological control agents as the province has several populations of this invasive plant. Open field tests with the European common reed and the native North American subspecies (Phragmites australis americanus) and two shoot-mining noctuid moths Archanara geminipuncta and A. neurica were conducted to investigate oviposition preference. The moths were confirmed to favour the invasive European common reed. A petition for field release of both moth species is being developed.

Current specific objectives:

  • Maintain rearing colonies of Archanara geminipuncta and A. neurica moths.

Common tansy (Tanacetum vulgare)

The chemical variability of common tansy populations in Europe and North America has been described, particularly with respect to the varying proportions of the toxic compounds, i.e. the essential oil components such as alpha-thujone. This variability may influence host plant acceptance by biocontrol agent candidates. A test plant list for common tansy was developed and accepted by the USDA, APHIS Technical Advisory Group (TAG). A literature review and field surveys resulted in initial focus on six potential agents: the flower-feeding moth Isophrictis striatella; the stem-mining weevil Microplontus millefollii; the root-feeding beetle Longitarsus noricus; the leaf-feeding beetle Cassida stigmatica; the leaf-galling midge Rhopalomyia tanaceticola and the stem-mining longhorn beetle Phytoecia nigricornis. However, tests have indicated that P. nigricornis, all Longitarsus species collected or reared from common tansy, C. stigmata and R. tanaceticola lack host specificity. I. striatella impact is questionable and studies have been suspended. Tests are on-going with M. millefollii, however, the studies will be moved to Russia to better synchronize the collection of weevils and their oviposition period on test plants. An additional candidate, a stem mining moth Platyptilia ochrodactyla has been successfully collected in a survey in Western Germany and appears promising.

Current specific objectives:

  • Additional tests with Microplontus millefolii in Russia;
  • Collections of Platyptilia ochrodactyla in Germany; and
  • Continue host specificity tests with P. ochrodactyla.

yellow toadflax

Dalmatian and yellow toadflax (Linaria dalmatica and vulgaris)

Host range studies for toadflax are continuing. Studies for the Dalmatian toadflax stem-galling weevil R. rara (formerly R. brondelii) are complete as is the petition for approval of release. R. pilosa was successfully released and established on yellow toadflax in B.C. in 2014. However, during the screening studies, additional strains of R. pilosa were also determined. Studies continue on strains that may be more adapted to colder climates for potential release in northern B.C. Four species of the stem-boring Mecinus weevils are currently involved in studies: Mecinus laeviceps and M. janthiniformis for Dalmatian toadflax and M. heydeni and M. janthinus for yellow toadflax. Subsequent to 1991 when the first Mecinus weevils were introduced into B.C., genetic analysis revealed the M. janthinus released in North America and having significant impact on Dalmatian toadflax to be M. janthiniformis while the weevil targeting yellow toadflax in North America, particularly in the U.S.A. and Alberta, is M. janthinus. Molecular work is being conducted to distinguish between some of these closely related species and understand their host preferences. An additional Mecinus species, M. peterharrisi, is being studied for control of L. dalmatica in northern regions.

Current specific objectives:

  • Mass rearing of Rhinusa and Mecinus spp.
  • Submit petition for field release of R. rara
  • Study bio-ecological properties of the northern R. pilosa populations
  • Complete testing of selected Mecinus heydini and M. laeviceps
  • Continue testing M. peterharrisi for L. dalmatica control in northern regions
Flowering rush in flower

Flowering rush (Butomus umbellatus)

Investigation into potential biological control of flowering rush began in 2013. There are currently only three documented infested water bodies in the province, however, the inventory of the plant in B.C. lakes is, to date, not extensive and it may prove to be more widespread. Manual treatments are taking place to control this extremely aggressive and damaging plant yet the effectiveness is not yet known. A literature search was conducted for phytophagous arthropods and fungal pathogens associated with flowering rush in Europe which identified four potential agents, two weevil species and two fly species, all of which feed in the leaves and stems of the host plant. Attempted collections of the flies have not resulted in populations sufficient to conduct testing to date. Quantities of the two weevils have been collected however, the species Bagous nodulosus has thus far resulted in higher populations and so has had additional tests performed compared to the weevil B. validus at this time.

Current specific objectives:

  • Collection of B. nodulosus and B. validus adults; and
  • Improve rearing colony and continue host-specificity tests with B. nodulosus.

Hawkweed complex (Hieracium spp.)

Studies for biocontrol agents of several hawkweed species are on-going. Seven potential biological control candidates have been studied since 2000 of which three were dropped initially due to lack of specificity or effectiveness. The stolon-tip gall wasp Aulacidea subterminalis was approved by CFIA and released in B.C. in 2011. It targets mouse ear hawkweed (H. pilosella), whiplash hawkweed (H. flagellare), a stable hybrid of mouse-ear and orange hawkweed, and the less preferred orange hawkweed (H. aurantiacum). A petition was completed and submitted for approval of the root and rosette-feeding hoverfly Cheilosia urbana. Approval was received in spring of 2016. The fly's release into B.C. is expected in spring 2017. It targets meadow (P. caespitosa) and orange hawkweeds. Work on the rosette-feeding hoverfy C. psilophthalma has been postponed; studies on the stem-galling wasp A. hieracii have been terminated due to rare attack rates found on the target plants; and attempts to maintain a colony of the rust, Puccinia hieracii var. piloselloidarum have proven difficult. Work is still continuing on two genetically divergent forms of the gall-inducing cynipid A. pilosellae.

Current specific objectives:

  • Maintain test and control plants at CABI;
  • Make field collections of A. pilosellae;
  • Continue host-specificity tests with the southern and northern lineages of A. pilosellae; and
  • PSubmit plant material for morphological and molecular analysis.
yellow hawkweed orange hawkweed
yellow hawkweed infestation orange hawkweed infestation

Himalayan balsam (aka: Policman's helmet) (Impatiens glandulifera)

Investigation into potential biological control agents for Himalayan balsam began in the U.K in 2006. B.C. joined the project in 2012 with the compilation of a North American test plant list. A portion of test plants have been shipped to the U.K. for studies involving the macrocyclic, autoecious rust fungus Puccinia komarovii originally observed in the Indian region of the Himalayas. In 2014 the rust was released to field sites in England, the first ever fungal biological control agent in Europe. Of the fifty-one species on the Canadian test plant list, forty-two have been tested and have proven immune to the rust. Efforts are focussed on obtaining and growing the remaining plant species that have proven difficult to collect and maintain. Canadian Himalayan balsam plants will be inoculated with a new strain of the rust.

Current specific objectives:

  • Propagation and maintenance of test plants;
  • Host specificity tests with the Puccinia komarovii rust against critical Canadian test species; and
  • Comparative study of the efficacy of the rust strains from Pakistan and India towards Himalayan balsam from Canada.

Hoary cresses (Lepidium draba, L. chalepense and L. appelianum)

Work on hoary cress (or whitetop) was initiated by the U.S.A. in 2001. The U.S.A. submitted a petition to the USDA, APHIS Technical Advisory Group (TAG) in 2011 to initiate the process of requesting permission to import the gall-forming weevil Ceutorhynchus cardariae. TAG responded with a request for more tests. Studies are continuing on the seed-feeding weevil C. turbatus and recently on the root-galling weevil C. assimilis. B.C. joined the project in 2011.

Current specific objectives:

  • Grow and maintain test plant species at CABI
  • Conduct additional host specificity tests with C. cardariae; and
  • Continue testing with C. turbatus and C. assimilis.
Hoary Cress close-up Hoary Cress infestation

Knotweed (Fallopia/Polygonum)

Screening work of potential biological agents for knotweed involving testing against closely-related North American test-plants is continuing. The potential biocontrol agents are targeting three of the four separate knotweed species in British Columbia: Japanese (Fallopia japonica or Polygonum cuspidatum); Giant (F. sachaliensis or P. sachalinense) and the hybrids between these two species, Bohemian knotweed (F. bohemica, hybrid). Knotweed's ability to hybridize has caused some difficulties in differentiation between the species but also requires consideration for biocontrol agent host range acceptance. Host-range screening of the insect Aphalara itadori, a sap sucking psyllid was conducted by CABI, U.K. while cold tolerance and development studies were conducted by AAFC in their quarantine lab in Lethbridge, AB. A. itadori will establish well within the current knotweed distributions in both the U.S.A. and Canada. A release petition for screened populations of the psyllid was submitted in October 2012 in Canada and the U.S.A. A release permit for a restricted number of releases in Canada was granted in 2014, and establishment field studies by AAFC are underway. Additional screening studies of a knotweed pathogen as a potential biocontrol agent are being conducted by CABI-UK. Current studies are focussed on two strains of the leaf spot fungus Mycosphaerella polygoni-cuspidati. To date North American knotweeds appear to be susceptible to the pathogen. Host-specificity tests to ensure any potential non-target plant species in North America are not affected by the pathogen are ongoing using Canadian test plants.

Current CABI-UK specific objectives:

  • Propagation of test plants;
  • Conduct quarantine studies on mycelial inoculations, to ascertain susceptibility of critical non-target species and, time and budget permitting, the virulence regarding Canadian biotypes of Giant and Bohemian knotweed; and
  • Assess the host specificity of the A. itadori hybrid (Kyushu and Hokkaido strains) against Fallopia cilinodis and Fagopyrum esculentum, depending on budget and seed availability.

Oxeye daisy (Leucanthemum vulgare)

In 2008, B.C. initiated funding on oxeye daisy with CABI and a test plant list was drafted. Studies have also been conducted into oxeye daisy's phylogeny and its potential relationship to other desirable daisies. Neither native North American species nor ornamental daisies are found within the same subtribe Leucantheminae as oxeye daisy with the exception of Shasta daisy. Ploidy analysis has found a diploid and a tetraploid species of oxeye daisy.The tetraploid, Leucanthemum ircutianum is more common in Europe while the diploid L. vulgare is more common in North America. Both are found in B.C. The potential biological control agents investigated to date can be found on both species of oxeye daisy in Europe. The root-feeding tortricid moth Dichrorampha aeratana, the flower head-attacking gall fly Tephritis neesii, the root-feeding weevil Cyphocleonus trisulcatus and recently the root galling tephritid fly Oxyna nebulosi have been prioritized for host-range studies. Unfortunately, studies on C. trisulcatus have been discontinued due to lack of host specificity and overwintering of T. neesii adults has proven difficult. However, D. aeratana looks promising and has shown in an impact study to decrease the below ground biomass of potted oxeye daisy plants by 62%.

Current specific objectives:

  • Grow and maintain test plant species;
  • Continue and if possible complete host range studies with D. aeratana;
  • Collect galls of Oxyna nebulosi in Germany and the Czech Republic, study its biology and start with host-range tests; and
  • Start preparing the petition for field release of D. aeratana.

Russian olive (Elaeagnus angustifolia)

Russian olive is a tree native to south-eastern Europe and Asia. It has been purposefully grown and sold in North America for shade and as a source of nectar for honey bees. It has since spread aggressively, causing particular problems in riparian habitats. This screening project was initiated in 2007 and has been funded by U.S.A. agencies. The focus has been on finding biological control agents that either attack the reproductive capacity of the tree or the subsequent seedlings so as to not disrupt use of existing trees. In 2014, B.C. made a single contribution of funds to the Russian olive screening project while in 2015 B.C. obtained test plant material native to North America and shipped it to Switzerland for use in screening trials. In 2016 B.C. formally joined the consortium. Two potential agents are currently being studied, the shoot-infesting mite Aceria angustifoliae and the fruit-attacking moth Ananarsia eleagnella while a third agent the shoot-feeding mite Aceria eleagnicola has recently been found. All three are believed to be highly specific to Russian olive.

Current Specific objectives:

  • Complete tests with Aceria angustifoliae and prepare petition;
  • Improve experimental designs to assess female host selection behaviour by Ananarsia eleagnella; and
  • Start with investigations on the behaviour, impact and host-range studies with Aceria eleagnicola.