Biocontrol Evaluation Research

Information contained herein is intended to be a compendium of research papers or technical notes on the topic of biocontrol evaluation research, i.e. studies to evaluate the handling, management and effectiveness of biocontrol agents once they have been applied to a target plant or plant population.  This compendium will expand in data and structure over time.

A global review of risk-benefit-cost analysis for the introduction of classical biological control agents against weeds: a crisis in the making?

Farming weed biocontrol agents: A Canadian test case in insect mass-production.

Cattle as dispersers of hound's-tongue on rangeland in Southeastern British Columbia

Early establishment and dispersal of the weevil, Mogulones cruciger...

Overwintering mortality of and host attack by the stem-boring weevil Mecinus janthinus...

Host Specificity of Mogulones cruciger (Coleoptera:Curculionidae), a Biocontrol Agent for ...

Agronomic Practices for Growing Hound’s-tongue (Cynoglossum officinale) as a Crop for ...

Is two company or a crowd: How does conspecific density affect the small-scale dispersal ...

Interspecific interactions between the gall-fly Urophora affinis Frfld. (Diptera: Tephritidae) and the weevil Larinus minutus Gyll...

Influence of dispersal, stochasticity, and an Allee effect on the persistence of weed...

Post hoc assessment of an operational biocontrol program: efficacy of the flea beetle Aphthona lacertosa Rosenhauer...

Temperature and host-plant effects on development and population growth of Mecinus janthinus ...


BiocontrolNews and Information 2003 Vol. 24 No. 4 91N . 108N

Review Article
A global review of risk-benefit-cost analysis for the introduction of classical biological control agents against weeds: a crisis in the making?

A. W. Sheppard1, R. Hill2, R. A. DeClerck-Floate3, A. McClay4,T. Olckers5, P. C. Quimby Jr.6 and H. G. Zimmermann5

1Cooperative Research Centre for Australian Weed Management/CSIRO
Entomology European Laboratory, Campus International de Baillarguet,
34980 Montferrier-sur-Lez, France
2Richard Hill and Associates Ltd, Private Bag 4704,
Christchurch, New Zealand
3Agriculture & Agri-Food Canada, PO Box 3000, Lethbridge,
AB T1J 4B1, Canada
4Alberta Research Council, Bag 4000, Vegreville, AB T9C 1T4, Canada
5Plant Protection Research Institute, Agricultural Research Council,
Private Bag X6006, Hilton 3245, South Africa
6USDA-ARS European Biological Control Laboratory, Campus International
de Baillarguet, 34980 Montferrier-sur-Lez, France


Risks of non-target effects resulting from releases of exotic organisms for the biological control of alien pests are a growing major concern because: (a) previous releases (<1%) are having significant negative impacts on rare native species, (b) alien organisms are a recognized global threat to sustainable agriculture and biodiversity, (c) risk analysis, as applied to environmental threats of species invasions and harmful effects of releases of genetically modified organisms, is a burgeoning field, and (d) biological control is increasingly being used in complex natural ecosystems where indirect impacts are harder to predict. As a result, governments are adopting a more risk-averse attitude to biological control as they assess such releases from an environmental and an economic standpoint. This is leading to more expensive and fewer successful release applications. In this paper we review the processes of risk analysis used by regulatory bodies around the world to pre-judge biological control releases against weeds. The aim is to publicize both strengths and weaknesses and to help encourage existing assessments to be fair to all without blunting the value of biological control as an effective tool against invasive alien weeds. The review, based around the five components of formal risk analysis (comparative analysis, risk assessment, risk management, risk evaluation, and risk communication), also focuses on how well the benefits and costs of biological control releases are evaluated in addition to the traditional analysis of the hazards. Currently only the New Zealand approach closely matches a full ecological risk-benefit-cost analysis of biological control releases with a precautionary approach, open consultation, a broad hazard/benefit definition in the release application and a judicial basis to the decision, but it comes at a high cost. Improving the analytical approaches used by countries runs a high risk of grinding biological control releases to a halt in a world where the precautionary approach has been adopted with respect to threats from exotic organisms on biodiversity (in line with the .precautionary approach. set forth in principle 15 of the 1992 Rio Declaration on Environment and Development). The benefits of biological control remain poorly understood by the public, allowing the risks to attain disproportionate attention. We make recommendations to address this crisis in the making and discuss the outcomes of the review with respect to the inherent social risks of making analysis of biological control releases an overly protracted process.

For information: R. A. DeClerck-Floate , A. McClay

Farming weed biocontrol agents: A Canadiantest case in insect mass-production.

Rosemarie A. De Clerck-Floate1

Agriculture and Agri-Food Canada, Lethbridge Research Centre, P.O. Box 3000,
Lethbridge, AB T1J 4B1
Jim R. Moyer, Brian H. Van Hezewijk, Elwin G. Smith
Agriculture and Agri-Food Canada, Lethbridge Research Centre, P.O. Box 3000,
Lethbridge, AB T1J 4B1


Recent research has shown that the European weevil, Mogulones cruciger, is effective in the biological control of the invasive rangeland weed, hound’s-tongue (Cynoglossum officinale). Because the weevil is difficult to collect en masse from field sites, requests for the insect quickly outstrip supply. A research project was initiated to develop a cost-effective method of mass-producing the weevil to help meet this demand. The unique method, developed over 4 years, involved growing hound’s-tongue as a crop, ‘seeding’ the weevil into the crop for multiple generations of propagation, and harvesting the weevil for distribution. The main project objectives were to: 1) develop best management practices for growing hound’s-tongue as a crop while maximizing root growth for weevil propagation; 2) determine which of the agronomic practices increased weevil production; 3) develop a method for weevil harvest; and, 4) determine the cost of weevil production using the best management method. The project also was designed to test the general feasibility of a farming approach for the mass-production of weed biocontrol insects. Hound’s-tongue can be consistently grown as a crop for biocontrol agent propagation by: sowing the weed in October at a row spacing of 67 cm (i.e., seeding rate of 13 seeds m-2); applying fertilizer in the following spring at a rate recommended for cereal crop production; applying glyphosate at about 1.25 l ha-1 in late fall or early spring before hound’s-tongue seedlings emerge to control winter annual weeds; applying either imazamox + imazethapyr or nicosulfuron and using inter-row cultivation to control annual weeds that emerge after hound’stongue emergence; and regularly applying propiconazole for powdery mildew control. Hound’s-tongue plants survived in drought conditions and did not require irrigation. Any agronomic practice that increased hound’s-tongue root size increased weevil production because the weevil prefers large plants for feeding and egg-laying. In particular, the addition of nitrogen fertilizer increased both root size and larval numbers per root in some site-years, and increased weevil egg production by 25% when adult females were fed nitrogen rich leaves in a laboratory experiment. Fall versus spring planting of hound’s-tongue also increased weevil production. Herbicide applications did not appear to affect larval numbers per root.
Wet-dry vacuum cleaners were used to harvest the weevils from hound’s-tongue trap plants and cardboard box ‘separators’ were used to sort the weevils from vacuumed debris. The harvest of adult weevils may be improved by planting additional hound’s-tongue around and within the crop 1−1.5 yrs prior to weevil harvest to ensure that sufficient trap plants are available. Once all fixed and variable costs of producing M. cruciger within a best management system for growing hound’s-tongue are considered, the total cost of production was $0.10−0.12 per weevil. The costs are considerably lower than those estimated for the production of other weed biocontrol insects reared in a manipulated outdoor setting.

For information: R. A. DeClerck-Floate

J. Range Manage.5O:239-243
Cattle as dispersers of hound's-tongue on rangeland in Southeastern British Columbia


The author is a research scientist in classical weed biocontrol, Agriculture and Agri.-Food Canada, Research Centre, Lethbridge, Alberta, T1J 4BI, Canada.


Hound's-tongue (Cynoglossum officinale L.) is a noxious weed on forested range of western North America (N.A), which produces barbed nutlets (burrs) that attach to animals. There is
anecdotal evidence that cattle are important dispersers of hound's-tongue in N.A., although European studies suggest  animal dispersal of hound's-tongue burrs is minimal. The objectives of this research were to examine the role of cattle as hound’s-tongue ispersers, and to develop a method of estimating hound's-tongue burr and plant density on rangeland that may be useful to researchers and range managers. To determine the movement of burrs onto cattle, the number of burrs on marked stalks, before and after grazing, were counted. In 1993 and 1994. whereas, only l4% of the burrs stalk-1 were lost in a paddock ungrazed by cattle in 1994. Individual cows were monitored for burr gains and losses during monthly moves between paddocks by photographing their faces, and counting the burrs face-1 from projected slides. Cattle also were photographed every 2 weeks while in-situ on paddocks. Within 2 to 4 weeks, cows acquired and then lost burrs as they moved within and between paddocks. These experiments suggest that cattle are major dispersers of hound's-tongue on rangelands. There was a positive, linear relationship (R2 =0.77; p<0.001, N=13) between the mean number of burrs face-1 and the number of burr stalks ha-1 of paddock. A relationship between the percent of photographed cattle with burrs and stalk density was best described by a hyperbolic model
(R2 = 0.83). With refinement, these relationships between burrs on cattle and hound’s-tongue density on paddocks may be useful in monitoring hound's-tongue populations.

Key Words: adhesive fruits, burrs, monitoring weed populations, noxious range weed, seed dispersal, weed biocontrol

For information: R. A. DeClerck-Floate

Biocontrol Science and Technology, March 2005; 15(2): 173_/190
Early establishment and dispersal of the weevil, Mogulones cruciger (Coleoptera: Curculionidae) for biological control of houndstongue (Cynoglossum officinale) in British Columbia, Canada


1Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada ,
and 2Solterra Resources Inc., Kamloops, British Columbia, Canada
(Received 15 January 2004; revised 18 March 2004; accepted 23 July 2004)


First released in Canada in 1997 to control the invasive rangeland weed, hound’s-tongue
(Cynoglossum officinale ), the European root weevil, Mogulones cruciger , is showing early potential as a successful biocontrol agent. Out of 22 experimental releases in southeastern British Columbia, Canada, 100% established, regardless of initial release size (range 100_/400). These founding populations persisted beyond 2 years, and quickly dispersed through a treed and variable landscape to colonise new hound’s-tongue patches surrounding the original release patches. Within 3 years, the weevil had moved 1.42 km. Both initial, within-patch and later, between-patch dispersal followed a similar pattern, with M. cruciger adults and/or their feeding/ oviposition damage being more concentrated nearest the original points of release and declining with distance. Within-patch, this pattern of distribution and also the rate of spread of weevils were similar regardless of initial release size; suggesting density-independence in dispersal behaviour at this scale. Closer investigation of the sequence of invasion at a larger spatial scale suggested that the weevil arrived at, colonized and increased in number on the closest host patches first. Three years post release, both distance from release patch and the number of M. cruciger released, were significant predictors of the amount of feeding/oviposition damage, and presumably weevil population size, within newly colonized hound’s-tongue patches surrounding the original releases. These data, and the finding that more weevils were retrieved from patches where higher numbers of weevils were released in the previous year (i.e., 300 or 400 vs 100 or 200), suggest that release number and placement of releases within a landscape can be manipulated for effective hound’s-tongue control.

Keywords: Biological control, colonization, Cynoglossum officinale, dispersal, establishment, hound’s-tongue, Mogulones cruciger, release strategies

For information: R. A. DeClerck-Floate, R. S. Bourchier

Biological Control 24 (2002) 65–74
Overwintering mortality of and host attack by the stem-boring weevil, Mecinus janthinus Germar, on Dalmatian toadflax (Linaria dalmatica (L.) Mill.) in western Canada

R. De Clerck-Floatea,* and V. Millerb

a Agriculture and Agri-Food Canada, Lethbridge Research Centre, 5403-1 Avenue South, PO Box 3000, Lethbridge, AB, Canada T1J 4B1
b British Columbia Ministry of Forests, 518 Lake St., Nelson, BC, Canada V1L 4C6
Received 6 June 2001; accepted 6 December 2001


Populations of the weevil Mecinus janthinus Germar (Coleoptera: Curculionidae) were monitored at 13 sites in western Canada during the period 1994–1999 to assess the role of overwintering mortality on the establishment of this biocontrol agent introduced against the weed Dalmatian toadflax, Linaria dalmatica (L.) Mill. (Scrophulariaceae). Results indicated that M. janthinus is intolerant of freezing, as evidenced by adult mortalities of 75–100% occurring in about 30% of the site-years examined and whenever winter temperatures reached 6)28 _C. Exposure to low sub-zero winter temperatures explained 70% of the  variation in adult mortality for sites in British Columbia. An 8-fold increase in adult mortality occurred in winter 1997/98 at one Alberta site monitored soon after temperatures dropped to 6)30 _C. Some inconsistencies in the relationship between winter temperatures and adult mortality at the Alberta site may be explained by the presence of insulating snow cover during the coldest temperatures of winters 1993/94 and 1996/97 and unseasonably cold temperatures during the spring of 1995. Despite the high periodic mortalities suffered by M. janthinus at most sites, the incidence and intensity of weevil attack on its host generally increased with time, thus demonstrating the resiliency of weevil populations.
© 2002 Elsevier Science (USA). All rights reserved.

Keywords: Cold climates; Dalmatian toadflax; Establishment; Freezing intolerance; Host plant attack; Linaria dalmatica; Overwintering mortality; Weed biological control

For information: R. A. DeClerck-Floate, V. Miller

Downloaded By: [Agriculture & Agri Food Canada] At: 22:09 23 May 2007
Biocontrol Science and Technology (2002) 12, 293± 306

Host Specificity of Mogulones cruciger (Coleoptera:Curculionidae), a Biocontrol Agent for Houndstongue(Cynoglossum officinale), with Emphasis on Testing of Native North American Boraginaceae


1Agriculture and Agri-Food Canada, Lethbridge Research Centre, P.O. Box 3000,
Lethbridge, Alberta, Canada, T1J 4B1; 2 CABI Bioscience Centre Switzerland,
CH-2800 DeleÂmont, Switzerland
(Received for publication 14 August 2001; revised manuscript accepted 1 November 2001)


Recent concerns over the safety of native North American plant species in the family
Boraginaceae, especially those of endangered status in the USA, prompted additional host
specificity testing of the European root weevil Mogulones cruciger, a proposed agent for the biocontrol of hound’s-tongue in the USA. M. cruciger can complete full development on species within closely-related genera in the Boraginaceae, but prefers hound’s-tongue as a host. Of the 22 species of native North American Boraginaceae that were tested in this study, nine species from four genera within the tribe Eritrichieae (Cryptantha, Hackelia, Mertensia and Lappula) clearly supported development of M. cruciger. However, generally these non-target species experienced less attack by M. cruciger relative to hound’s-tongue . There were diVerences in the incidence and degree of attack depending on the test type, which included the use of potted test plants in laboratory no-choice and open-Weld choice situations. The least non-target attack occurred on rangeland in British Columbia, Canada, where potted test plants were introduced into sites where the insect had been previously released on hound’s-tongue. These results suggest that M. cruciger has a narrow ecological host range. Special emphasis was placed on testing species of Cryptantha because C. crassipes is listed as endangered in the USA. Six of 12 Cryptantha species tested supported full development, but generally, the incidence and intensity of attack were less for these species relative to hound’s-tongue . There was no, or incomplete development, on tested species of Plagiobothrys, a genus that contains two species listed as endangered in the USA.

Keywords: biological control, Boraginaceae, Cynoglossum officinale, hound’s-tongue, host-specificity testing, Mogulones cruciger, non-target attack

Correspondence to: R. De Clerck-Floate. Tel: 403 317 2270; Fax: 403 382 3156; E-mail:
Current address for M. Schwarzlaender: Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow, ID 83844± 2339, USA.
ISSN0958-3157 (print)/ISSN1360-047 8 (online)/02/030293-14 ©Minister of Public Works and
DOI: 10.1080/0958315022012809 5 Government Services Canada 2002

R. A. DeClerck-Floate

Weed Science 2007 55:273–280
Agronomic Practices for Growing Hound’s-tongue (Cynoglossum officinale) as a Crop for Mass-Producing a Weed Biocontrol Agent

James R. Moyer, Rosemarie A. DeClerck-Floate, Brian H. Van Hezewijk, and Louis J. Molnar*


Hound’s-tongue is a troublesome weed of pasture, rangeland, and open forest in British Columbia, Canada. Recently, a rootfeeding weevil was released in Canada that successfully controls hound’s-tongue patches, but it has been difficult to propagate this weevil in sufficient numbers for widespread release. The goal of the current study was to develop methods for growing hound’s-tongue as a crop in a farm-field setting for weevil propagation. Field experiments were conducted to determine optimum seeding dates, depths, and rates for hound’s-tongue. The effects of straw-residue cover and nitrogen application rates were also examined. More than 90% of the seed used was viable, and about 50% of the planted seed emerged. The most consistent plant densities occurred when hound’s-tongue was seeded in October and had a winter and early spring moist chilling period to break seed dormancy. For fall seeded hound’s-tongue, plants emerged equally well from 2- and 5-cm depths. Hound’s-tongue is moderately responsive to nitrogen fertilizer but usually did not benefit from additional straw cover on the soil before emergence. Hound’s-tongue plants also survived in drought conditions. In conclusion, this weed can be consistently grown as a crop for the propagation of a root-feeding weevil for hound’s-tongue control.

Nomenclature: Hound’s-tongue, Cynoglossum officinale L. CYWOF; root-feeding weevil, Mogulones cruciger (Coleoptera: Curculionidae).
Key words: Biological control, insect propagation, insect rearing, nitrogen fertilizer, seed dormancy, seeding method.

For information: R. A. DeClerck-Floate

Biocontrol Science and Technology, March 2005; 15(2): 191_/205
Is two company or a crowd: How does conspecificdensity affect the small-scale dispersal of a weed biocontrol agent?


Environmental Health Program, Agriculture and Agri-Food Canada Research Centre,
Lethbridge, Alberta, Canada
(Received 11 June 2004; revised 8 July 2004; accepted 23 July 2004)


To predict the growth and spread of an insect population introduced for the biological control of weeds, one must first understand the factors affecting the movement of individuals in the population. The purpose of this study was to determine how the dispersal rate of Aphthona lacertosa (Rosenhauer) (Chrysomelidae) was affected by conspecific density and by the characteristics of leafy spurge (Euphorbia esula L.: Euphorbiaceae) in patches where these beetles feed. In 2002 in Manitoba and in 2003 in Alberta, Canada, between 200 and 2500 insects were released in small patches (B/10 m2) of spurge. The number and location of beetles within patches was monitored over subsequent days. In 1 m2 plots within patches, spurge ramet density, the proportions of vegetative and reproductive ramets, and ramet height were measured. In both years, beetle movement within patches and emigration from patches, was not affected by conspecific density. In Manitoba in 2002, beetles aggregated nonrandomly on either vegetative or reproductive ramets within plots, but plot characteristics were not related to the formation of aggregations. In Alberta in 2003, plots in which beetles aggregated had significantly higher spurge density but did not differ in either the proportion of vegetative ramets or in the amount of non-spurge vegetation. These results suggest that density-dependent dispersal does not limit the population’s ability to reach densities up to 2500 beetles/m2.

Keywords: Aggregation, Aphthona lacertosa, biological control , density-dependence, diffusion, dispersal , Euphorbia esula

For information: R. S. Bourchier

Biocontrol Science and Technology, 2006; 16(4): 417_/430
Interspecific interactions between the gall-fly Urophora affinis Frfld. (Diptera: Tephritidae) and the weevil Larinus minutus Gyll. (Coleoptera: Curculionidae), two biological control agents released against spotted knapweed, Centaurea stobe L. ssp. Micranthos


Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, Alberta, Canada
(Accepted 20 September 2005)


Interspecific competition has been suggested as an explanation for the failure of some insects as biological control agents for weeds. Enclosure and exclusion cages were used, in southern British Columbia, Canada to evaluate the importance of interspecific competition between a seedhead weevil, Larinus minutus, and a gall-inducing fly, Urophora affinis , two biocontrol agents released against spotted knapweed in North America. At the seedhead scale, U. affinis , which is an inferior biological control agent based on knapweed seed mortality, was the superior competitor. Larinus minutus attack rates were significantly lower in the presence of U. affinis compared to release treatments where L. minutus was attacking alone. Reduced L. minutus attack rates were apparent in seed heads expected to contain both species, assuming insect distributions were random, but instead only contained U. affinis . L. minutus did not significantly affect U. affinis density. Although overall attack rates on knapweed seedheads were higher when both species were together at a site, the consequence of the antagonistic interaction is that overall seed destruction was not as high as it could have been if the weevil were attacking on its own. These results support minimizing the number of biocontrol agents released that use similar resources on the target weed, to avoid negative interactions between control agents and potential reductions in biocontrol efficacy resulting from competitive exclusion.

Keywords: Biological control, herbivore, interspecific competition, weed, Centaurea stobe ssp. micranthos, Centaurea maculosa

For information: R. S. Bourchier

ecological modelling 2 0 3 ( 2 0 0 7 ) 521–526
Short communication
Influence of dispersal, stochasticity, and an Allee effect on the persistence of weed biocontrol introductions.

Ian D. Jonsena,*, Robert S. Bourchier, Jens Roland

a Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9
b Agriculture & Agri-Food Canada, Research Centre, Lethbridge, AB, Canada T1J 4B1
Article history: Received 14 November 2005,Received in revised form 30 November 2006,
Accepted 11 December 2006, Published on line 12 February 2007


An important problem encountered in biocontrol is the failure of introduced populations to
establish and persist. Recent biocontrol studies focus on the roles of environmental stochasticity and Allee effects in determining introduction persistence but few studies consider the role of dispersal. We use a spatially explicit simulation model that incorporates dispersal and spatio-temporally random population growth to show that elevated emigration rates can exacerbate the negative influences of environmental stochasticity and Allee effects on introduction persistence. However, successful immigration can compensate partly for the otherwise reduced persistence that occurs when environmental stochasticity is high. These results illustrate that dispersal can have antagonistic effects on the persistence of biocontrol introductions and failure to consider the dispersal ability and typical emigration rates of biocontrol agents may yield misleading predictions regarding successful establishment.
© 2006 Elsevier B.V. All rights reserved.

Keywords: Emigration, Immigration, Invasion, Landscape, Simulation, Weed biocontrol

For information: ScienceDirect, R. S. Bourchier

Biological Control 29 (2004) 418–426
Post hoc assessment of an operational biocontrol program: efficacy of the flea beetle Aphthona lacertosa Rosenhauer (Chrysomelidae: Coleoptera), an introduced biocontrol agent for leafy spurge

A.R. Kalischuk,a,* R.S. Bourchiera, and A.S. McClayb

a Agriculture and Agri-Food Canada, 5403 – 1 Avenue South, P.O. Box 3000 Lethbridge, Alberta, Canada T1J 4B1
b Alberta Research Council, Bag 4000, Vegreville, Alberta, Canada T9C 1T4
Received 9 January 2003; accepted 4 August 2003


Mixed populations of Aphthona lacertosa and Aphthona czwalinae were released at more than 50 locations in Alberta in 1997. Two and 3 years post-release, beetle populations were primarily A. lacertosa, with A. czwalinae forming less than 0.5% of the sampled populations. Beetle densities were moderate (10–70 beetles per m2) or high (>70 beetles per m2) at 14% and more than 60% of the sampled sites in 1999 and 2000, respectively. Larger beetles had greater instantaneous egg loads (r2 ¼ 0:424; P ¼ 0:003). In 2000, the largest beetles were found at moderate density sites and there was a significant negative relationship  between beetle size and the time taken to accumulate a degree day threshold of 1230 (for females: r2 ¼ 0:678; P ¼ 0:001). Sites with the most rapid accumulation of degree days have the greatest potential for beetle population growth based on potential fecundity. Changes in leafy spurge percent cover, stem density, and canopy height from 1997 to 2000 were assessed across sites with low (<10 beetles per m2), moderate, and high beetle densities in 2000. Sites with high beetle densities had significantly greater eductions of leafy spurge within 5m of the release point than sites with low beetle ensities (P < 0:017). Damage caused by the beetles at high-density sites was often visible as a halo-shaped patch of dead leafy spurge stems. The significant overall reduction of leafy spurge within release patches makes A. lacertosa a promising biocontrol agent for leafy spurge in Alberta. © 2003 Elsevier Inc. All rights reserved.

Keywords: Leafy spurge; Flea beetles; Aphthona lacertosa; Euphorbia esula; Biological control; Biocontrol

For information: ScienceDirect, R. S. Bourchier , A. McClay

Biological Control 40 (2007) 405–410
Temperature and host-plant effects on development and population growth of Mecinus janthinus (Coleoptera: Curculionidae), a biological control agent for invasive Linaria spp.

A.S. McClay ,*, R.B. Hughes

a McClay Ecoscience, 15 Greenbriar Crescent, Sherwood Park, Alta., Canada T8H 1H8
b 5510 61 Street, Vegreville, Alta., Canada T9C 1N5
Received 7 October 2006; accepted 19 December 2006
Available online 27 December 2006


Mecinus janthinus Germar is a European stem-mining weevil that has been established in North America as a biological control agent against the invasive European weeds Linaria vulgaris P. Mill. and Linaria dalmatica (L.) P. Mill. (Scrophulariaceae). Establishment success and impact of the weevil have varied widely among sites. We investigated the hypothesis that some of this variation may be due to a lack of sufficient time for M. janthinus to develop to the adult (overwintering) stage in less favorable climates. Development time of M. janthinus was measured in L. vulgaris and L. dalmatica at four constant temperatures, and logistic regression was used to derive a model for the effect of temperature on development. Development rates were simulated using historic climate data for a site in central Alberta (where establishment was marginal on L. vulgaris) and one in southern British Columbia (where outbreaks occurred, resulting in heavy damage to L. dalmatica). The model showed that, on average, the British Columbia site had 50 more days available for the weevil to lay eggs that could reach the adult stage in time for overwintering than did the Alberta site. This may explain the more rapid population buildup at the British Columbia site. This model could be used to predict the climatic suitability of other areas for establishment of M. janthinus. An unexplained result was the very low survival rate of eggs laid in L. dalmatica under the same experimental conditions. © 2007 Elsevier Inc. All rights reserved.

Keywords: Mecinus janthinus; Linaria vulgaris; Linaria dalmatica; Climate; Development; Host plants; Oviposition deadline

For information: ScienceDirect , A. McClay