The noctuid moths, Archanara geminipuncta and A. neurica, were selected as the most promising candidates for biological control of common reed. Successful larval development was only found on Phragmites spp., but development was also... more
The noctuid moths, Archanara geminipuncta and A. neurica, were selected as the most promising candidates for biological control of common reed. Successful larval development was only found on Phragmites spp., but development was also possible on the native North American subspecies P. australis subsp. americanus. However, open-field oviposition tests showed a strong preference of females for both European and introduced P. australis. Because of the higher egg mortality on native reed, the authors expect any impact of A. neurica and A. geminipuncta on the native reed P. australis subsp. americanus to be negligible, should the noctuids be released in North America. A biological control project for flowering rush was started in spring 2013. According to the authors’ literature survey, the semi-aquatic weevil, Bagous nodulosus, is the most promising potential agent for biological control. During various field surveys in Northern Germany, the Czech and Slovak Republics, Hungary, Poland, ...
Research Interests:
ABSTRACT This study investigated the effect of competition from wheat and below ground herbivory on the growth and reproduction of scentless chamomile, Tripleurospermum perforatum (Mérat) Laínz (Asteraceae), a target plant for classical... more
ABSTRACT This study investigated the effect of competition from wheat and below ground herbivory on the growth and reproduction of scentless chamomile, Tripleurospermum perforatum (Mérat) Laínz (Asteraceae), a target plant for classical biological control. Field cages, in which scentless chamomile was planted, were established in 1994 near Neuenburg (Rhine Valley, Germany), and two weevil species, Diplapion confluens Kirby and Coryssomerus capucinus (Beck), were released alone (40 adults each) or together in a substitutive design (20 adults each). Wheat was sown alone or in combination with both herbivores as an additional stress factor. To test the cage effect on plant growth, an uncaged control was set up. At the end of the experiment, caged control plants were about 20 cm (18%) higher, and allocated more biomass to shoots and less to roots and seeds than uncaged plants. Competition from wheat reduced the number of shoots per T. perforatum plant from 7.6 to 3.2. As a consequence, the biomass of scentless chamomile plants that competed with wheat was reduced by 39% and reproductive output by 49%, compared with plants that were grown without competition. At the end of the experiment, 70–80% of T. perforatum plants had been attacked by an average of two to three D. confluens and 60–70% of plants by one to two C. capucinus. At these densities that were lower than expected, the two herbivores alone or in combination had no significant effect on any of the plant parameters measured. However, in the presence of wheat, herbivory further reduced the number of shoots per plant. We conclude that control of scentless chamomile using insect biocontrol agents will be more likely to be successful if agent densities are high, and agents are released in habitats where scentless chamomile is competing with other plant species.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Development of a biological control program for invasive Phagmites australis australis in North America required 20 years of careful research, and consideration of management alternatives. A recent paper by Kiviat et al. (Biol Invasions... more
Development of a biological control program for invasive Phagmites australis australis in North America required 20 years of careful research, and consideration of management alternatives. A recent paper by Kiviat et al. (Biol Invasions 21:2529–2541, 2019. 10.1007/s10530-019-02014-9) articulates opposition to this biocontrol program and questions the ethics and thoroughness of the researchers. Here we address inaccuracies and misleading statements presented in Kiviat et al. (2019), followed by a brief overview of why biological control targeting Phragmites in North America can be implemented safely with little risk to native species. Similar to our colleagues, we are very concerned about the risks invasive Phragmites represent to North American habitats. But to protect those habitats and the species, including P. australis americanus, we come to a different decision regarding biological control. Current management techniques have not been able to reverse the invasiveness of P. austr...
Research Interests:
During the 1980’s, two agents were released in North America to control field bindweed (Convolvulus arvensis): the gall mite Aceria malherbae and bindweed moth Tyta luctuosa. C. arvensis is a vine native to Eurasia that became invasive... more
During the 1980’s, two agents were released in North America to control field bindweed (Convolvulus arvensis): the gall mite Aceria malherbae and bindweed moth Tyta luctuosa. C. arvensis is a vine native to Eurasia that became invasive after it was introduced in the 18th century. Following the mitigated results of these agents, investigations for new potential biological control agents were reopened in 2009. Our efforts focused on an agromyzid stem-boring fly, Melanagromyza albocilia, and two root-mining flea beetles, Longitarsus pellucidus and L. rubiginosus. We also selected two new potential agents for preliminary testing. Good progress has been made investigating the potential of M. albocilia. Studies on behaviour and attack were conducted under different conditions to overcome early difficulties in obtaining mating, oviposition and development. We tested 12 species, including 8 native North American, as cut shoots in no-choice and single-choice tests. The next step will be host...
Experimental studies can be useful tools to test plant responses to herbivory and to quantify the impact of potential biological control agents prior to their release. We evaluated the per-capita effect of Ceutorhynchus alliariae and C.... more
Experimental studies can be useful tools to test plant responses to herbivory and to quantify the impact of potential biological control agents prior to their release. We evaluated the per-capita effect of Ceutorhynchus alliariae and C. roberti, two stem-boring weevils currently being investigated as potential biological control agents for garlic mustard, Alliaria petiolata, in North America. Weevils were released at
Research Interests:
The biology and host range of the two root-mining weevils Diplapion confluens Kirby and Coryssomerus capucinus (Beck), two potential agents for the biological control of scentless chamomile Tripleurospermum perforatum (Mérat) Laínz, were... more
The biology and host range of the two root-mining weevils Diplapion confluens Kirby and Coryssomerus capucinus (Beck), two potential agents for the biological control of scentless chamomile Tripleurospermum perforatum (Mérat) Laínz, were studied in the field in southern Germany and eastern Austria, and in a common garden and under laboratory conditions in Delémont, Switzerland from 1993 to 1999. Both weevils were univoltine, and females started to lay eggs in early spring. Diplapion confluens had three and C. capucinus five instars. Larvae of both species were found in the field from mid-April until the end of July; later instars preferentially fed in the vascular cylinder of the shoot base, root crown or root. Although larvae of both species occupy the same temporal and spatial niche within their host plants, they occurred at all investigated field sites together, and showed a similar distribution within sites. No negative or positive interspecific association was detected. Host-specificity tests including no-choice, single-choice, and multiple-choice tests under confined conditions, as well as tests under field conditions with natural and augmented insect densities revealed that both herbivores were specific to plant species in the tribe Anthemideae. However, their development to mature larva or adult on several cultivated plants, as well as on one plant species native to North America, rendered them unsuitable for field release in North America. It was concluded that to investigate non-target effects reliably, host-specificity tests with biological control agents should be carried out under a variety of conditions, particularly with augmented insect densities, as are expected to occur naturally after release.
Research Interests:
Abstract: In the context of possible biological control of Eurasian water- milfoil (Myriophyllum spicatum), available information is summarized on
Research Interests:
... a result of C. scrobicollis attack were compensated for by increased production of secondary shoots after loss of apical dominance (see also Cartwright & Kok, 1985; Müller, 1989 ... We are grateful to Gislaine Cortat, Magali... more
... a result of C. scrobicollis attack were compensated for by increased production of secondary shoots after loss of apical dominance (see also Cartwright & Kok, 1985; Müller, 1989 ... We are grateful to Gislaine Cortat, Magali Rohner, and Patrick Jäger for their lab and field assistance ...
Research Interests:
Based on an assessment of 706 fungal isolates obtained from Canada and Europe, a group of Colletotrichum sp. isolates, tentatively identified as C. truncatum, was moderately efficacious for biocontrol of scentless chamomile (Matricaria... more
Based on an assessment of 706 fungal isolates obtained from Canada and Europe, a group of Colletotrichum sp. isolates, tentatively identified as C. truncatum, was moderately efficacious for biocontrol of scentless chamomile (Matricaria perforata). In this study, 19 C. truncatum isolates, 11 from Canada and eight from Europe, were compared for virulence, crop safety, and minimum dew requirement for infection
Research Interests:
Tripleurospermum perforatum is an invasive weedy species which exhibits strong over- compensating density dependence. Interactions between density-dependent survival, probability of flowering and fecundity were modelled and their impact... more
Tripleurospermum perforatum is an invasive weedy species which exhibits strong over- compensating density dependence. Interactions between density-dependent survival, probability of flowering and fecundity were modelled and their impact on the population dynamics were examined. When only fecundity was density-dependent, the dynamics were similar to those observed in the model containing all three density-dependent terms. Density-dependent survival was a stabilizing process
Research Interests:
... Environ. Entomol 3:464474. Grigulis, K., AW Sheppard, JE Ash, and RH Groves. 2001. ... 2001. Are plants really larger in their introduced ranges? Am. Nat 157:231236. CrossRef, PubMed, CSA. Van, TK, MB Rayamajhi, and TD Center. 2001.... more
... Environ. Entomol 3:464474. Grigulis, K., AW Sheppard, JE Ash, and RH Groves. 2001. ... 2001. Are plants really larger in their introduced ranges? Am. Nat 157:231236. CrossRef, PubMed, CSA. Van, TK, MB Rayamajhi, and TD Center. 2001. ...
Research Interests:
The Eurasian plant, perennial pepperweed (Lepidium latifolium) is rapidly invading riparian habitats in the western United States, displacing native plants and altering food webs. Surveys in six countries in its native range, including... more
The Eurasian plant, perennial pepperweed (Lepidium latifolium) is rapidly invading riparian habitats in the western United States, displacing native plants and altering food webs. Surveys in six countries in its native range, including China, Iran, and Turkey, have produced several arthropod biological control candidates. Preliminary host-specificity tests and observations of damage to the host plant indicate that two weevils (Melanobaris semistriata and Ceutorhynchus marginellus), one chloropid fly (Lasiosina deviata), and one eriophyoid mite (Metaculus lepidifolii) have promise as potential biological control agents, pending more intensive evaluations. In addition to continued testing on these candidate agents, we plan more field surveys in Turkey, Kazakhstan, and China to search for more candidates.
In the 1980s, two biological control agents were released for field bindweed (Convolvulus arvensis) management in North America: the bindweed moth Tyta luctuosa (Lepidoptera: Noctuidae), and the gall mite Aceria malherbae (Acari:... more
In the 1980s, two biological control agents were released for field bindweed (Convolvulus arvensis) management in North America: the bindweed moth Tyta luctuosa (Lepidoptera: Noctuidae), and the gall mite Aceria malherbae (Acari: Eriophyidae). While establishment for the moth has not been confirmed, the mite is established in several U.S. states and in Canada, but impact is variable. In 2009, the search for additional potential agents for the US was revived. We currently focus on the stem-boring fly Melanagromyza albocilia (Diptera: Agromyzidae) and the root-mining flea beetle Longitarsus pellucidus (Coleoptera: Chrysomelidae). The agromyzid has two generations per year and field observations revealed that attacked shoots often dry up and die. Unfortunately, we were not able to obtain oviposition of the fly under lab conditions in 2010, and so no host-specificity tests could be conducted.. Adults of the flea beetle readily laid eggs, and we started to conduct no-choice larval transf...
ABSTRACT The Eurasian perennial mustard, hoary cress, Cardaria draba (Brassicaceae), is an invasive weed in western North America that can displace native plants and other desirable forage species in pastures and rangelands. This study... more
ABSTRACT The Eurasian perennial mustard, hoary cress, Cardaria draba (Brassicaceae), is an invasive weed in western North America that can displace native plants and other desirable forage species in pastures and rangelands. This study investigated the competitive ability of 11 grasses representing nine species in the genera Festuca and Poa from either North America (NA) or Europe (EU) against hoary cress. Hoary cress was grown alone and with four different grass densities under controlled conditions with ample water and nutrient supply, typical for riparian and disturbed habitats, in which hoary cress infestations are commonly found. Of the five Festuca grasses tested, only Schedonorus phoenix ( = F. arundinacea) decreased hoary cress biomass. Four of the six Poa grasses tested decreased hoary cress biomass and were ranked by decreasing competitive effects as follows: P. annua > P. compressa (EU) > P. pratensis (EU) > P. compressa (NA). The most competitive grass species also experienced higher intraspecific competition. Within both grass genera, Eurasian species were more competitive against hoary cress than their North American congeners, which suggests that hoary cress establishment may be facilitated by lower biotic resistance in the invaded range. Regardless of origin, sod-forming Poa species were competitive at low densities, while Festuca species only had significant effects at high densities if at all. Based on our results we recommend the use of Poa species for restoration of riparian and disturbed sites following the control of hoary cress infestations to restrict recolonization. Nomenclature: Annual bluegrass, Poa annua L. POAAN; Canada bluegrass, Poa compressa L. POACO; hoary cress, Cardaria draba (L.) Desv. [ = Lepidium draba L.] CADDR; Idaho fescue, Festuca idahoensis Elmer; Kentucky bluegrass, Poa pratensis L. POAPR; red fescue, Festuca rubra L. FESRU; rough fescue, Festuca campestris Rydb.; Sandberg bluegrass, Poa secunda J. Presl.; sheep fescue, Festuca ovina L. FESOV; tall fescue, Schedonorus phoenix (Scop.) Holub [ = Festuca arundinacea Schreb.] FESAR Interpretive Summary: Hoary cress is an exotic clonal perennial mustard that invades disturbed rangeland and riparian areas in the western United States This study compared the competitive ability of 11 native and exotic grass species with regard to hoary cress in a greenhouse experiment that mimicked environmental conditions typically found at habitats highly suitable to hoary cress invasion (abundant nutrients and moisture). We used some of the grass species most commonly used in revegetation and found that three out of six Poa species tested decreased hoary cress plant biomass during its initial establishment phase, whereas only one of five Festuca species tested affected hoary cress growth. European grasses generally were more competitive than grasses of North American origin. The lower competitive ability of North American species suggests that there is a lower level of biotic resistance to hoary cress invasion in our native communities. We recommend planting of Poa species for restoration of nutrient-rich, riparian habitats, following chemical or mechanical control of hoary cress to limit recolonization of these susceptible habitats.
Research Interests:
Research Interests:
Research Interests: Demography, Fertility, Ecology, Seed production, Biological Sciences, and 15 moreEnvironmental Sciences, Brassicaceae, Animals, Ecological, North America, Invasive Plant, Beetles, Germination, Theoretical Models, Host Specificity, Biological Control of Weeds, Long Term Monitoring, Ecological Applications, Matrix Model, and Temperate Forest
We studied the influence of the root-crown weevil Ceutorhynchus scrobicollis on its host plant Alliaria petiolata, a European biennial herb that is currently invading much of temperate North America. Varying timing of attack and herbivore... more
We studied the influence of the root-crown weevil Ceutorhynchus scrobicollis on its host plant Alliaria petiolata, a European biennial herb that is currently invading much of temperate North America. Varying timing of attack and herbivore densities in a common garden allowed to assess seasonality of plant response, density-dependence of impact, and the effect of intraspecific competition on C. scrobicollis recruitment
Research Interests:
Research Interests:
Research Interests:
Abstract Hoary cress (Lepidium draba L.) is an invasive perennial mustard (Brassicaceae) introduced to North America from Eurasia. In 2001 we initiated a program to investigate the potential for classical biological control of this weed... more
Abstract Hoary cress (Lepidium draba L.) is an invasive perennial mustard (Brassicaceae) introduced to North America from Eurasia. In 2001 we initiated a program to investigate the potential for classical biological control of this weed in the US. Literature and field surveys for the ...