- F.J.J.A. Bianchi (2)
- F. Bigler (2)
- L.H.M. Blommers (1)
- S. Bogya (1)
- P.M. Brakefield (1)
- G. Burgio (1)
- P. Clercq de (1)
- S.A. Cunningham (1)
- A. Estoup (1)
- S. Farrokhi (1)
- G. Gbehounou (1)
- I. Goryacheva (1)
- T. Guillemaud (1)
- L.J.L. Handley (1)
- Th. Heijerman (1)
- H.M.T. Hokkanen (1)
- M.E. Huigens (1)
- A. Huis van (1)
- W. Jones (1)
- P.W. Jong de (3)
- E. Jousselin (1)
- E. Kondorosy (1)
- K.G. Koops (1)
- D. Kossou (1)
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- S. Kuske (1)
- J.C. Lenteren van (4)
- J. Li (1)
- A. Linden van der (1)
- E. Lombaert (1)
- S.T.E. Lommen (2)
- S. Lommen (1)
- A. Loomans (1)
- A.J.M. Loomans (2)
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- I. Menzler-Hokkanen (1)
- Gerben Messelink (1)
- A. Migeon (1)
- P.G. Milonas (1)
- H. Pang (1)
- N.E. Papanikolaou (1)
- R.L. Poland (1)
- J. Poutsma (1)
- C.L. Raak-van den Berg (1)
- P.C.J. Rijn van (1)
- N.A. Schellhorn (2)
- J. Shirazi (1)
- M.B. Thomas (1)
- C.E. Thomas (1)
- C.E. Togbe (1)
- M.G. Tommasini (1)
- S. Wang (1)
- W. Werf van der (1)
- I.A. Zakharov (1)
- E. Zannou (1)
- Q.Q. Zeng (1)
Conservation of predaceous Coccinellidae species in greenhouse ecosystems
Papanikolaou, N.E. ; Milonas, P.G. ; Meijer, R.J.M. - \ 2016
BioGreenhouse (Fact sheet BioGreenhouse 7) - 2 p.
organic farming - horticulture - greenhouse horticulture - plant health - natural enemies - habitats - coccinellidae - agroecosystems - biological control - pesticides - biologische landbouw - tuinbouw - glastuinbouw - plantgezondheid - natuurlijke vijanden - agro-ecosystemen - biologische bestrijding - pesticiden
Conservation of natural enemies is an important component of pest management, which can improve their efficacy against target pests. Conserving predaceous Coccinelidae species in agricultural ecosystems is used to enhance their biocontrol contribution. Favourable conditions in these habitats can contribute to a more efficient population regulation of several pests. Conservation efforts focus on discouraging emigration from a crop system and enhance retention time of coccinelids in periods with low prey availability. Thus, the management of agroecosystems should focus on providing resources in such temporal and spatial scale that may prevent their emigration or attract them in habitats. In addition, in a greenhouse ecosystem, another conservation action is to reduce mortality and sublethal effects caused by insecticides.
Field evaluation of the synergistic effects of neem oil with Beauveria bassiana (Hypocreales: Clavicipitaceae) and Bacillus thuringiensis var. kurstaki (Bacillales: Bacillaceae)
Togbe, C.E. ; Zannou, E. ; Gbehounou, G. ; Kossou, D. ; Huis, A. van - \ 2014
International Journal of Tropical Insect Science 34 (2014)4. - ISSN 1742-7584 - p. 248 - 259.
metarhizium-anisopliae - azadirachta-indica - natural enemies - cotton bollworm - compatibility - insecticides - coleoptera - curculionidae - coccinellidae - lepidoptera
In the present study, the synergistic effects of Beauveria bassiana (Bals.-Criv. Vuill.) (isolate Bb11) and Bacillus thuringiensis var. kurstaki (Berliner) with neem oil were evaluated in three agroecological zones in Be´nin. Four bioinsecticide treatments (neem oil, neem oil and B. bassiana used separately for different target pests, neem oil mixed with B. bassiana and neem oil mixed with B. thuringiensis) were compared with a calendar-based treatment using synthetic insecticides and a control without insecticides. The bioinsecticide treatments were less effective than the calendar-based treatment at controlling cotton pests. There was no difference in yields and the number of damaged bolls in plots under treatments with the four bioinsecticide formulations, suggesting an absence of synergy between neem oil and B. bassiana and neem oil and B. thuringiensis. The numbers of natural enemies in all the bioinsecticide treatment plots and the control plots were similar and higher than those in the calendar-based treatment plots. The highest yield and profitability were obtained with the calendar-based treatment. Screening the compatibility of plant-based products and biopesticides through bioassays is essential for a successful application of their combinations in any integrated pest management strategy.
Habitat functionality for the ecosystem service of pest control: reproduction and feeding sites of pests and natural enemies
Bianchi, F.J.J.A. ; Schellhorn, N.A. ; Cunningham, S.A. - \ 2013
Agricultural and Forest Entomology 15 (2013)1. - ISSN 1461-9555 - p. 12 - 23.
agricultural landscapes - coccinellidae - agroecosystems - biodiversity - assemblages - coleoptera - density - aphids - sinks
1 Landscape management for enhanced natural pest control requires knowledge of the ecological function of the habitats present in the landscape mosaic. However, little is known about which habitat types in agricultural landscapes function as reproduction habitats for arthropod pests and predators during different times of the year. 2 We studied the arthropod assemblage on six crops and on the seven most abundant native plant species in two landscapes over 1 year in Australia. Densities of immature and adult stages of pests and their predators were assessed using beat sheet sampling. 3 The native plants supported a significantly different arthropod assemblage than crops. Native plants had higher predator densities than crops over the course of the year, whereas crops supported higher pest densities than the native plants in two out of four seasonal sampling periods. Crops had higher densities of immature stages of pests than native plants in three of four seasonal sampling periods, implying that crops are more strongly associated with pest reproduction than native plants. Densities of immature predators, excluding spiders, were not different between native plants and crops. Spiders were, however, generally abundant and densities were higher on native plants than on crops but, because some species disperse when immature, there is less certainty in identifying their reproduction habitat. 4 Because the predator to pest ratio on native plant species showed little variation, and spatial variation in arthropod assemblages was limited, the predator support function of native vegetation may be a general phenomenon. Incentives that maintain and restore native remnant vegetation can increase the predator to pest ratio at the landscape scale, which could enhance pest suppression in crops.
Comment on "Invasive Harlequin Ladybird Carries Biological Weapons Against Native Competitors"
Jong, P.W. de; Lenteren, J.C. van; Raak-van den Berg, C.L. - \ 2013
Science 341 (2013)6152. - ISSN 0036-8075
intraguild predation - harmonia-axyridis - coccinellidae - coleoptera
We comment on the implications that Vilcinskas et al. (Reports, 17 May 2013, p. 862) attach to the finding that the exotic, invasive ladybird Harmonia axyridis carries microsporidia to which this species is insensitive but that is lethal to species that are native to the invaded areas. The authors suggest that these microsporidia might serve as “biological weapons” against the native competitors, but we cast doubt on the importance of this suggestion in the field.
Exploring and exploiting natural variation in the wings of a predatory ladybird beetle for biological control
Lommen, S.T.E. - \ 2013
Leiden University. Promotor(en): P.M. Brakefield, co-promotor(en): Peter de Jong. - S.l. : s.n. - ISBN 9789053356821 - 176
adalia - adalia bipunctata - coccinellidae - organismen ingezet bij biologische bestrijding - vleugels - roofinsecten - morfologie - biological control agents - wings - predatory insects - morphology
The central theme of this PhD thesis is natural variation in the wing length of the predatory two-spot ladybird beetle, Adalia bipunctata. ‘Wingless’ individuals of this species occur occasionally. They possess truncated wing covers and flight wings and cannot fly, but the extent of the reduction is highly variable between individuals. At one hand, I take a multidisciplinary experimental approach to study the causes and consequences of this variation in an evolutionary context. Genetic and developmental studies show that it is regulated by several polymorphic genes, and results from gene-environment interactions affecting the growth of the larval wing discs. Studies on life-history traits and mating behaviour provide no evidence that winglessness is an adaptive trait in this ladybird. However, they reveal a function of the wing covers in survival and mating behaviour. On the other hand, I examine the use of wingless ladybirds in the biological control of aphids, since winged ladybirds are not effective when flying away soon after release. I show that wingless morphs have the potential to improve biocontrol efficacy. I then suggest that mass-rearing of this less fit morph could be improve by manipulation of the wing length. Altogether, this thesis interlinks the fields of fundamental (evolutionary) biology and applied biological control.
Banker plant systeem voor Delphastus catalinae tegen wittevlieg
Linden, A. van der - \ 2013
Bleiswijk : Wageningen UR Glastuinbouw (Rapporten WUR GTB 1266) - 18
sierteelt - plagenbestrijding - trialeurodes vaporariorum - biologische bestrijding - encarsia formosa - coccinellidae - glastuinbouw - organismen ingezet bij biologische bestrijding - predatoren - ornamental horticulture - pest control - biological control - greenhouse horticulture - biological control agents - predators
Kaswittevlieg Trialeurodes vaporariorum is voor verscheidene sierteeltgewassen een belangrijke plaag. Naast de inzet van de sluipwesp Encarsia formosa is het lieveheersbeestje Delphasitus catalinae erg geschikt om haarden van kaswittevlieg op te ruimen. Omdat het lieveheersbeestje veel wittevlieg nodig heeft om zich te kunnen ontwikkelen, wordt nagegaan of een andere soort dan kaswittevlieg geschikt is om Delphastus catalinae in grotere aantallen in kassen met sierteelten in stand te houden. De wittevlieg Aleyrodes lonicerae blijkt geschikt als prooi voor Delphastus catalinae. Aleyrodes lonicerae werd gekweekt op zevenblad Aegopodium podagraria en aardbei Fragaria ‘Ellsanta’ maar vestigde zich niet op gerbera, hibiscus. Wel werden eieren gelegd op roos. In roos zou een andere soort wittevlieg kunnen worden toegepast.
Lommen, S. ; Kuik, A.J. van - \ 2012
Bomen, het vakblad voor de boomverzorging (2012)21. - p. 14 - 17.
straatbomen - aphidoidea - plantenplagen - organismen ingezet bij biologische bestrijding - coccinellidae - adalia - honingdauw - secreties - bestrijdingsmethoden - onderzoek - street trees - plant pests - biological control agents - honeydew - secretions - control methods - research
Bladluizen in stadsbomen zorgen soms voor grote overlast. Vooral onder lindebomen is er jaarlijks wel een periode van honingdauwoverlast. Sommige steden gaan het probleem te lijf met het uitzetten van tweestippelige lieveheersbeestjes in de lindebomen. Het resultaat is niet altijd bevredigend. Nu is het effect van deze maatregel voor het eerst onderzocht. Voor dit onderzoek is echter speciaal gebruikgemaakt van een in de natuur voorkomend ongevleugeld type van dit lieveheersbeestje. De verwachting is dat dit langer in de boom blijft en daardoor beter is in bladluisbestrijding.
Genetic linkage between melanism and winglessness in the ladybird beetle Adalia bipunctata
Lommen, S.T.E. ; Jong, P.W. de; Koops, K.G. ; Brakefield, P.M. - \ 2012
Genetica 140 (2012)4-6. - ISSN 0016-6707 - p. 229 - 233.
2-spot ladybird - phenotypic plasticity - thermal melanism - geographical variation - harmonia-axyridis - coleoptera - coccinellidae - consequences - polymorphism - evolution
We report a case of genetic linkage between the two major loci underlying different wing traits in the two-spot ladybird beetle, Adalia bipunctata (L.) (Coleoptera: Coccinellidae): melanism and winglessness. The loci are estimated to be 38.8 cM apart on one of the nine autosomes. This linkage is likely to facilitate the unravelling of the genetics of these traits. These traits are of interest in the context of the evolution of intraspecific morphological diversity, and for the application of ladybird beetles in biological control programs.
Inferring the origin of populations introduced from a genetically structured native range by approximate Bayesian computation: case study of the invasive ladybird Harmonia axyridis
Lombaert, E. ; Guillemaud, T. ; Thomas, C.E. ; Handley, L.J.L. ; Li, J. ; Wang, S. ; Pang, H. ; Goryacheva, I. ; Zakharov, I.A. ; Jousselin, E. ; Poland, R.L. ; Migeon, A. ; Lenteren, J.C. van; Clercq, P. de; Berkvens, N. ; Jones, W. ; Estoup, A. - \ 2011
Molecular Ecology 20 (2011)22. - ISSN 0962-1083 - p. 4654 - 4670.
multiple transatlantic introductions - western corn-rootworm - microsatellite loci - harlequin ladybird - biological invasion - pallas coleoptera - united-states - f-statistics - gene flow - coccinellidae
Correct identification of the source population of an invasive species is a prerequisite for testing hypotheses concerning the factors responsible for biological invasions. The native area of invasive species may be large, poorly known and/or genetically structured. Because the actual source population may not have been sampled, studies based on molecular markers may generate incorrect conclusions about the origin of introduced populations. In this study, we characterized the genetic structure of the invasive ladybird Harmonia axyridis in its native area using various population genetic statistics and methods. We found that native area of H. axyridis most probably consisted of two geographically distinct genetic clusters located in eastern and western Asia. We then performed approximate Bayesian computation (ABC) analyses on controlled simulated microsatellite data sets to evaluate (i) the risk of selecting incorrect introduction scenarios, including admixture between sources, when the populations of the native area are genetically structured and sampling is incomplete and (ii) the ability of ABC analysis to minimize such risks by explicitly including unsampled populations in the scenarios compared. Finally, we performed additional ABC analyses on real microsatellite data sets to retrace the origin of biocontrol and invasive populations of H. axyridis, taking into account the possibility that the structured native area may have been incompletely sampled. We found that the invasive population in eastern North America, which has served as the bridgehead for worldwide invasion by H. axyridis, was probably formed by an admixture between the eastern and western native clusters. This admixture may have facilitated adaptation of the bridgehead population.
Nieuwe ontwikkelingen in de biologische bestrijding van bladluis in paprika
Messelink, Gerben - \ 2011
augmentation - biological control agents - aphidoidea - sweet peppers - gliding - aphidoletes - aphidius - chrysoperla carnea - coccinellidae - reduviidae - research - station tests
Side effects of kaolin particle films on apple orchard bug, beetle and spider communities
Marko, V. ; Bogya, S. ; Kondorosy, E. ; Blommers, L.H.M. - \ 2010
International Journal of Pest Management 56 (2010)3. - ISSN 0967-0874 - p. 189 - 199.
pest-management systems - arthropod - aphid - coccinellidae - insecticide - assemblages - populations - pesticides - coleoptera - hungary
The effects of multiple applications of hydrophobic kaolin particle film on apple orchard bug (Heteroptera), beetle (Coleoptera) and spider (Araneae) assemblages were studied in the Netherlands. Insecticide-free orchard plots served as a control. The kaolin applications significantly reduced the abundance and species richness of the communities and also altered their composition and diversity. The treatments disrupted many non-target groups notably mycophagous, predacious and tourist beetles, zoophagous bugs and spiders. Among spiders, wanderer spiders (Thomisidae, Philodromidae) were most affected, whereas web building spiders (Dictynidae) were least affected. After ceasing the applications in July, the between-treatment differences in composition of all communities and diversity of heteropterans and spiders diminished while the differences in abundance and species richness remained for a long time, until the end of September. Many predator species with good colonisation ability recovered slowly after the treatments, mainly due to the scarcity of prey.
A comparative study on the functional response of Wolbachia-infected and uninfected forms of the parasitoid wasp Trichogramma brassicae
Farrokhi, S. ; Ashouri, A. ; Shirazi, J. ; Allahyari, H. ; Huigens, M.E. - \ 2010
Journal of Insect Science 10 (2010). - ISSN 1536-2442 - 11 p.
biological-control - ostrinia-nubilalis - quality assessment - host-plant - hymenoptera - eggs - parthenogenesis - coccinellidae - pentatomidae - heteroptera
Trichogramma species (Hymenoptera: Trichogrammatidae) are haplo-diploid egg parasitoids that are frequently used as biological control agents against lepidopteran pests. These wasps display two reproductive modes, including arrhenotoky (bisexuality) and thelytoky (unisexuality). Thelytokous forms are often associated with the presence of endosymbiotic Wolbachia bacteria. The use of thelytokous wasps has long been considered as a way to enhance the efficacy of biological control. The present study investigates the potential of a thelytokous Wolbachiainfected and an arrhenotokous uninfected Trichogramma brassicae Bezdenko strain as inundative biocontrol agents by evaluating their functional response towards different egg densities of the factitious host, the Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae). The results revealed a type II functional response for both strains in which parasitism efficiency decreases with host egg density because of an increasing host handling time. A model with an indicator variable was used to compare the parameters of Holling’s disc equation in different data sets. It was demonstrated that the two strains did not differ in host attack rate. However, the Wolbachia-infected strain did have an increased host handling time when compared to the bisexual strain. Some applied aspects of the findings are discussed
Foraging behaviour of predators in heterogeneous landscapes: the role of perceptual ability and diet width
Bianchi, F.J.J.A. ; Schellhorn, N.A. ; Werf, W. van der - \ 2009
Oikos 118 (2009)9. - ISSN 0030-1299 - p. 1363 - 1372.
spatial-patterns - prey density - lady beetle - aphid prey - responses - coleoptera - coccinellidae - time - strategies - dispersal
Oligophagous and polyphagous predators are confronted with spatially and temporally varying distributions of prey. Their species-specific foraging strategies should be able to cope with this variability. Using an individual based model, we explore how diet breath and the spatial scale at which predators respond to prey affects their capture efficiency in four heterogeneous prey landscapes, and combinations thereof. We interpret the spatial scale of the predator's response as perceptual range, and propose giving-up density as a proxy for diet breadth. Foraging behaviour is evaluated for a total of 121 perceptual range/giving-up density combinations, with four of them reflecting the strategies adopted by real ladybeetle species. Foraging rules of oligophagous ladybeetles were generally not very effective in terms of attained predation rate when foraging in a single prey landscape, but appear to be more effective when foraging in multiple prey landscapes. This finding is compatible with the notion that oligophagous predators do not adopt a foraging strategy that is especially adapted to a specific prey landscape, but to multiple prey landscapes. Simulations further indicated that there was not a `best' foraging rule that resulted in the highest predation rates for a range of spatial prey distributions and prey densities. The findings thus suggest that strategies of four ladybeetle species are effective in generating sufficient prey capture under a broad range of spatial distributions, rather than maximum capture under a narrower set of distributions
Harmonia axyridis: an environmental risk assessment for Northwest Europe
Lenteren, J.C. van; Loomans, A.J.M. ; Babendreier, D. ; Bigler, F. - \ 2008
BioControl 53 (2008). - ISSN 1386-6141 - p. 37 - 54.
biological-control agents - pallas coleoptera - united-states - arthropod pests - coccinellidae - trichogrammatidae - establishment - hymenoptera - biocontrol - phenology
In this paper, we summarize the international situation with respect to environmental risk assessment for biological control agents. Next, we apply a recently designed, comprehensive risk evaluation method consisting of a stepwise procedure to evaluate the environmental risks of Harmonia axyridis in Northwest Europe. This resulted in the very clear conclusion that H. axyridis is a potentially risky species for Northwest Europe, because it is able to establish, it has a very wide host range including species from other insect orders and even beyond the class of Insecta, it may feed on plant materials, it can cover large distances (>50 km per year), it does move into non-target areas, it may attack many non-target species including beneficial insects and insects of conservation concern, its activities have resulted in the reduction of populations of native predators in North America, it is known as a nuisance in North America and recently also in Northwest Europe, and it may develop as a pest of fruit in North America. Considering the H. axyridis case, current knowledge would lead to the conclusion that, although the predator is capable to effectively control several pest species, its risks are manifold and it should, thus, not have been released in Northwest Europe. At the time of the first releases in Nortwest Europe in 1995, the available scientific literature made clear that H. axyridis is a large sized polyphagous predator and has a great reproductive capacity in comparison with other ladybird beetles, and that there was a need to study non-target effects because of its polyphagous behaviour. In retrospect, this information should have been sufficient to reject import and release of this species, but it was apparently ignored by those who considered release of this predator in Northwest Europe. The case of Harmonia releases in Northwest Europe underlines that there is an urgent need for harmonized, world-wide regulation of biological control agents, including an information system on risky natural enemy species.
Insecten in het veranderende klimaat
Jong, P.W. de - \ 2008
In: Natuur als Bondgenoot / Osse, J.W.M, Schoonhoven, L.M., Dicke, M., Buiter, R., Leiden : Stichting BWM (Cahiers bio-wetenschappen en maatschappij 4) - ISBN 9789073196490 - p. 65 - 67.
klimaatverandering - insecten - coccinellidae - opwarming van de aarde - voedselwebben - climatic change - insects - global warming - food webs
Het succes van insecten is rechtstreeks afhankelijk van het klimaat. Daarom mag je verwachten dat klimaatsverandering een heel directe invloed heeft op insecten en andere koudbloedigen. Als je weet hoe belangrijk insecten zijn in ecosystemen dan kun je wel nagaan wat de impact zal zijn van klimaatsverandering op het leven op aarde
Predicting the potential geographical distribution of the harlequin ladybird, Harmonia axyridis, using the CLIMEX model - BioControl
Poutsma, J. ; Loomans, A. ; Aukema, B. ; Heijerman, Th. - \ 2008
BioControl 53 (2008)1. - ISSN 1386-6141 - p. 103 - 125.
pallas coleoptera - biological-control - united-states - 2 phenotypes - life table - coccinellidae - beetle - establishment - temperature - invasion
Harmonia axyridis (Pallas, 1773) (Coleoptera: Coccinellidae) is a ladybird beetle native to temperate and subtropical parts of Asia. Since 1916 populations of this species have been introduced throughout the world, either deliberately, or by accident through international transport. Harmonia axyridis was originally released as a classical biological control agent of aphid and coccid pests in orchards and forests, but since 1994 it is also available as a commercial product for augmentative control in field and greenhouse crops. It is a very voracious and effective natural enemy of aphids, psyllids and coccids in various agricultural and horticultural habitats and forests. During the past 20 years, however, it has successfully invaded non-target habitats in North America (since 1988), Europe (1999) and South America (2001) respectively in a short period of time, attacking a wide range of non-pest species in different insect orders. Becoming part of the agricultural commercial pathway, it is prone to being introduced into large areas across the world by accident. We use the CLIMEX programme (v2) to predict the potential geographical distribution of H. axyridis by means of matching the climate of its region of origin with other regions in the world and taking in account biological characteristics of the species. Establishment and spread seem likely in many regions across the world, including those areas which H. axyridis has already invaded (temperate Europe, North America). Based on the CLIMEX prediction a large part of Mediterranean Europe, South America, Africa, Australia and New Zealand seem highly suitable for long-term survival of H. axyridis as well. In addition we evaluate CLIMEX as a strategic tool for estimating establishment potential as part of an environmental risk assessment procedure for biological control agents we discuss biological and ecological aspects necessary to fine-tune its establishment and spread in areas after it has been introduced
Environmental risk assessment of exotic natural enemies used in inundative biological control
Lenteren, J.C. van; Babendreier, D. ; Bigler, F. ; Burgio, G. ; Hokkanen, H.M.T. ; Kuske, S. ; Loomans, A.J.M. ; Menzler-Hokkanen, I. ; Rijn, P.C.J. van; Thomas, M.B. ; Tommasini, M.G. ; Zeng, Q.Q. - \ 2003
BioControl 48 (2003)1. - ISSN 1386-6141 - p. 3 - 38.
lady beetles coleoptera - apparent competition - intraguild predation - host-range - coccinellidae - parasitoids - dynamics - hymenoptera - suppression - aleyrodidae
In the past 100 years many exotic naturalenemies have been imported, mass reared andreleased as biological control agents. Negativeenvironmental effects of these releases haverarely been reported. The current popularity ofinundative biological control may, however,result in problems, as an increasing number ofactivities will be executed by persons nottrained in identification, evaluation andrelease of biological control agents.Therefore, a methodology for risk assessmenthas been developed within the EU-financedproject `Evaluating Environmental Risks ofBiological Control Introductions into Europe[ERBIC]' as a basis for regulation of importand release of exotic natural enemies used ininundative forms of biological control (i.e.not in `classical biological control' thoughsome of the same principles and approachesapply). This paper proposes a general frameworkof a risk assessment methodology for biologicalcontrol agents, integrating information on thepotential of an agent to establish, itsabilities to disperse, its host range, and itsdirect and indirect effects on non-targets. Ofthese parameters, estimating indirect effectson non-targets will be most difficult, asmyriads of indirect effects may occur whengeneralist natural enemies are introduced. Theparameter `host range' forms a central elementin the whole risk evaluation process, becauselack of host specificity might lead tounacceptable risk if the agent establishes anddisperses widely, whereas, in contrast, amonophagous biological control agent is notexpected to create serious risk even when itestablishes and disperses well. Drawing onpublished information and expert opinion, theproposed risk assessment methodology is appliedto a number of biological control agentscurrently in use. These illustrative casehistories indicate that the risk assessmentmethodology can discriminate between agents,with some species attaining low `risk indices'and others scoring moderate or high. Riskindices should, however, not be seen asabsolute values, but as indicators to which ajudgement can be connected by biologicalcontrol experts for granting permission torelease or not.