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Retrospective risk assessment reveals likelihood of potential non-target attack and parasitism by Cotesia urabae (Hymenoptera: Braconidae): A comparison between laboratory and field-cage testing results

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... However, many historical releases of biological control agents were conducted in the absence of such testing (Van Driesche and . Carrying out retrospective host range studies following release can provide important information about the specificity of agents, fill lingering knowledge gaps about risks to non-target species, and may help to predict non-target risks posed by closely related agents currently being considered for release (Avila et al., 2016;Cameron et al., 2013;Haye et al., 2005;Hinz et al., 2014;Louda et al., 2003). ...
... No-choice oviposition tests provide unambiguous evidence of a biocontrol agent's physiological host range due to their simple design, and for this reason, are recommended as a first step in assessing host specificity (Babendreier et al., 2005;van Lenteren et al., 2006). Conducting retrospective no-choice tests is especially valuable in cases where host-specificity testing was never completed prior to release of the agent (Avila et al., 2016;Cumber, 1953). It is essential to understand whether or not a biological control agent can recognise non-target species as alternative hosts, and to understand the extent to which non-target species are suitable for the development of healthy progeny . ...
Article
Retrospective host range testing is essential for understanding the physiological host range of introduced biological control agents (BCAs) and updating forecasts of non-target risks. It is especially important to conduct this work if there was no host range testing prior to release of the agent. Trissolcus basalis Wollaston was released in New Zealand in 1949 against green vegetable bug (Nezara viridula [L.]), but host range testing was never undertaken, and subsequent work in the 1960s was only of a qualitative nature and remains incomplete. The host-parasitoid complex between New Zealand pentatomids, T. basalis, and the native pentatomid parasitoid Trissolcus oenone Dodd, is therefore poorly understood. We conducted no-choice oviposition tests between the two resident Trissolcus species and all available New Zealand pentatomid species to characterise the physiological (=fundamental) host ranges of these parasitoids. We present the results of the first retrospective host-specificity study on T. basalis in New Zealand. Our results show T. basalis attacks and develops in all nine pentatomid taxa we exposed it to (including the endemic alpine species Hypsithocus hudsonae Bergroth), while T. oenone attacks and develops in seven out of eight pentatomid species we tested it against (and its capacity to attack H. hudsonae remains unknown). Parasitism efficiencies for all treatments exceeded 60%, while development times were similar for both parasitoids regardless of host. We discuss the importance of physiological host range testing for understanding potential non-target effects. Trissolcus japonicus Ashmead (Hymenoptera: Scelionidae) was recently approved for release in New Zealand against brown marmorated stink bug Halyomorpha halys Stål (Hemiptera: Pentatomidae), subject to its potential establishment, and we examine our results in the context of potential competition between introduced parasitoids for non-target species.
... Even when nontarget species are exploited, differences in ecology such as phenology, semiochemical cues, habitat, and behavior are expected to further limit the realized host range in the field (i.e. ecological host range) (Avila et al. 2016). However, these ecological considerations are often not accounted for in evaluating biological control agents before they are released. ...
Conference Paper
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The Sixth International Symposium on Biological Control of Arthropods, held virtually from British Columbia, Canada, continues the series of International Symposia on Biological Control of Arthropods, organized every four years. The history of the meetings is: • First ISBCA, Hawaii, USA – January 2002 • Second ISBCA, Davos, Switzerland – September 2005 • Third ISBCA, Christchurch, New Zealand – February 2009 • Fourth ISBCA: Pucón, Chile – March 2013 • Fifth ISBCA: Langkawi, Malaysia – September 2017 The goal of these symposia is to create a forum where biological control researchers and practitioners can meet and exchange information, to promote discussions of up to date issues affecting biological control, particularly pertaining the use of parasitoids and predators as biological control agents. This includes all approaches to biological control: conservation, augmentation, and importation of natural enemy species for the control of arthropod targets, as well as other transversal issues related to its implementation. To this end, 12 sessions have been organized in order to address the most relevant and current topics in the field of biological control of arthropods, delivered by invited speakers, contributed talks and poster presentations. To kick off ISBCA 2022, Dr. Martin Hill, Global President of the International Organization for Biological Control, presents an opening keynote talk on the current state of biological control. Some of the topics covered in ISBCA 2022 have remained as important issues since the first meeting, like the importance of biological control for managing invasive species, sustainable pest regulation in agricultural landscapes, the continuing challenges for biological control of forest pests, and the role of native vegetation in conservation biological control. But also, as new challenges and environmental concerns arise, some fresh topics have emerged. Among them are climate change and the disruption of biological control, stakeholder knowledge and perceptions of biological control, the use of native and exotic natural enemies for augmentative biological control, and functional diversity supporting biological control. For the first time, a workshop on biological control of ticks will be held. To show that biological control is a continuum linked to other disciplines, there will be a session on the science underpinning the successful use of pathogens in biological control. An important goal of the International Symposium on Biological Control of Arthropods is to promote early career researchers, and the first session Proceedings of ISBCA 6 – D.C. Weber, T.D. Gariepy, and W.R. Morrison III, eds. (2022) iii is organized to showcase the work of select individuals. The International Organization for Biological Control (IOBC) has sponsored these presentations. Another important goal of these meetings has been to be truly international, and this is why every conference so far has been organized in a different continent. This year we are excited in having achieved this goal despite the many world crises, by having participants from over 30 countries and all continents except Antarctica. We are particularly happy for the many works and participants from South America, a region that in the past has been poorly represented in these symposia. As a result, this meeting represents an opportunity for creating and expanding networks between researchers worldwide. Thus we expect that, despite the virtual format, the 6th International Symposium on Biological Control of Arthropods would be an important milestone in keep moving forward the research and practice on biological control of arthropods, thereby helping to improve the sustainability of managed systems as well as aiding in the protection of biodiversity on the planet.
... Cotesia urabae Austin and Allen (Hymenoptera: Braconidae) is a solitary larval endoparasitoid of Uraba lugens Walker (Lepidoptera: Nolidae), the gum leaf skeletoniser, which is a lepidopteran pest endemic to Australia and a major defoliator of many Eucalyptus species (Avila et al., 2013). In 2011, Cotesia urabae was introduced into New Zealand as a biological control agent against Uraba lugens (Avila et al., 2013), and is now confirmed as established (Avila et al., 2016a). Prior to the release of C. urabae in New Zealand, laboratory host-specificity testing bioassays were carried out on several non-target species (Berndt et al., 2007(Berndt et al., , 2009(Berndt et al., , 2010 by conducting small arena no-choice and choice tests in containment, and following the overarching framework proposed by van Lenteren et al. (2006). ...
Chapter
This proceedings contains papers dealing with issues affecting biological control, particularly pertaining to the use of parasitoids and predators as biological control agents. This includes all approaches to biological control: conservation, augmentation, and importation of natural enemy species for the control of arthropod targets, as well as other transversal issues related to its implementation. It has 14 sessions addressing the most relevant and current topics in the field of biological control of arthropods: (i) Accidental introductions of biocontrol agens: positive and negative aspects; (ii) The importance of pre and post release genetics in biological control; (iii) How well do we understand non-target impacts in arthropod biological control; (iv) Regulation and access and benefit sharing policies relevant for classical biological control approaches; (v) The role of native and alien natural enemy diversity in biological control; (vi) Frontiers in forest insect control; (vii) Biocontrol marketplace I; (viii) Weed and arthropod biological control: mutual benefits and challenges; (ix) Maximizing opportunities for biological control in Asia's rapidly changing agro-environments; (x) Biological control based integrated pest management: does it work?; (xi) Exploring the compatibility of arthropod biological control and pesticides: models and data; (xii) Successes and uptake of arthropod biological control in developing countries; (xiii) Socio-economic impacts of biological control; (xiv) Biocontrol marketplace II.
... Cotesia urabae Austin and Allen (Hymenoptera: Braconidae) is a solitary larval endoparasitoid of Uraba lugens Walker (Lepidoptera: Nolidae), the gum leaf skeletoniser, which is a lepidopteran pest endemic to Australia and a major defoliator of many Eucalyptus species (Avila et al., 2013). In 2011, Cotesia urabae was introduced into New Zealand as a biological control agent against Uraba lugens (Avila et al., 2013), and is now confirmed as established (Avila et al., 2016a). Prior to the release of C. urabae in New Zealand, laboratory host-specificity testing bioassays were carried out on several non-target species (Berndt et al., 2007(Berndt et al., , 2009(Berndt et al., , 2010 by conducting small arena no-choice and choice tests in containment, and following the overarching framework proposed by van Lenteren et al. (2006). ...
Chapter
Full-text available
This proceedings contains papers dealing with issues affecting biological control, particularly pertaining to the use of parasitoids and predators as biological control agents. This includes all approaches to biological control: conservation, augmentation, and importation of natural enemy species for the control of arthropod targets, as well as other transversal issues related to its implementation. It has 14 sessions addressing the most relevant and current topics in the field of biological control of arthropods: (i) Accidental introductions of biocontrol agens: positive and negative aspects; (ii) The importance of pre and post release genetics in biological control; (iii) How well do we understand non-target impacts in arthropod biological control; (iv) Regulation and access and benefit sharing policies relevant for classical biological control approaches; (v) The role of native and alien natural enemy diversity in biological control; (vi) Frontiers in forest insect control; (vii) Biocontrol marketplace I; (viii) Weed and arthropod biological control: mutual benefits and challenges; (ix) Maximizing opportunities for biological control in Asia's rapidly changing agro-environments; (x) Biological control based integrated pest management: does it work?; (xi) Exploring the compatibility of arthropod biological control and pesticides: models and data; (xii) Successes and uptake of arthropod biological control in developing countries; (xiii) Socio-economic impacts of biological control; (xiv) Biocontrol marketplace II.
... Cotesia urabae was released in New Zealand in 2011 to control the eucalypt pest Uraba lugens Walker (Lepidoptera: Nolidae) (Berndt 2011;Avila et al. 2013). As predicted by quarantine host-range tests, post-release testing has shown that C. urabae is able to successfully parasitise a non-target New Zealand endemic species, Nyctemera annulata (Boisduval) (Lepidoptera: Erebidae) (Avila et al. 2016), and has been found to parasitise early instar larvae of this species at low rates in the field (G. Avila pers. ...
Article
Indirect effects of biological control agents (BCAs) are difficult to assess because they are mediated through the complex connections between species within the ecological community. Being able to visualise such complex connections by constructing qualitative food webs could greatly enhance our ability to predict indirect effects that could then be evaluated through empirical studies or modelling. Qualitative food webs were constructed for two case studies of entomophagous BCAs using the existing literature on invertebrate consumer relationships and status (e.g., as pest or rare species). We suggest that these webs can reduce uncertainty around the species that may be at risk, can predict species that perhaps should be monitored post-release, or identify knowledge gaps on species and their feeding relationships prior to the release of a BCA. Thus, these webs may be useful for those who need to consider the potential indirect risks of BCAs when making decisions about the release of a BCA into new regions.
... Cotesia urabae Austin and Allen (Hymenoptera: Braconidae) is a solitary larval endoparasitoid of Uraba lugens Walker (Lepidoptera: Nolidae), the gum leaf skeletoniser, which is a lepidopteran pest endemic to Australia and a major defoliator of many Eucalyptus species (Avila et al., 2013). In 2011, Cotesia urabae was introduced into New Zealand as a biological control agent against Uraba lugens (Avila et al., 2013), and is now confirmed as established (Avila et al., 2016a). Prior to the release of C. urabae in New Zealand, laboratory host-specificity testing bioassays were carried out on several non-target species (Berndt et al., 2007(Berndt et al., , 2009(Berndt et al., , 2010 by conducting small arena no-choice and choice tests in containment, and following the overarching framework proposed by van Lenteren et al. (2006). ...
... When N. annulata and T. jacobaeae were tested along with the target, U. lugens, C. urabae showed a significantly greater attraction towards the odour of U. lugens. The results of dissections of non-target larvae attacked in lab tests showed that C. urabae was able to parasitise both T. jacobaeae and N. annulata, but not P. suavis; and N. annulata was found to be a complete physiological host, with 14 cocoons recovered from attacked N. annulata larvae, and one viable adult male C. urabae produced (Avila et al. 2016c). These results suggest that the placement of T. jacobaeae and N. annulata at the top of the PRONTI list, and their inclusion on the original list, was appropriate. ...
Article
A computer-based tool called PRONTI (priority ranking of non-target invertebrates) has been developed to aid the selection of non-target species (NTS) for pre-release testing with entomophagous biological control agents. To test whether PRONTI can improve NTS selection, we used it to produce a prioritised list of NTS for the agent Cotesia urabae Austin & Allen (Hymenoptera: Braconidae), and compared it with the original list that was produced before this species was released in New Zealand in 2011. While the two lists were similar, with five NTS occurring in the top nine of both lists, the remaining four NTS in the top nine of each list were different, primarily because the selection criteria used by the two methods were weighted differently (e.g., PRONTI put more weight on the likelihood of a NTS being exposed to the agent). Post-release testing has demonstrated that C. urabae is able to oviposit in two NTS that were ranked highly on both lists, suggesting both methods are useful for species selection. The main advantages of PRONTI were considered to be its ability to rank hundreds of NTS simultaneously, and to provide a body of information that can be used to both understand each NTS’ ranking and to justify more objectively the selection of NTS for pre-release testing.
Chapter
This proceedings contains papers dealing with issues affecting biological control, particularly pertaining to the use of parasitoids and predators as biological control agents. This includes all approaches to biological control: conservation, augmentation, and importation of natural enemy species for the control of arthropod targets, as well as other transversal issues related to its implementation. It has 14 sessions addressing the most relevant and current topics in the field of biological control of arthropods: (i) Accidental introductions of biocontrol agens: positive and negative aspects; (ii) The importance of pre and post release genetics in biological control; (iii) How well do we understand non-target impacts in arthropod biological control; (iv) Regulation and access and benefit sharing policies relevant for classical biological control approaches; (v) The role of native and alien natural enemy diversity in biological control; (vi) Frontiers in forest insect control; (vii) Biocontrol marketplace I; (viii) Weed and arthropod biological control: mutual benefits and challenges; (ix) Maximizing opportunities for biological control in Asia's rapidly changing agro-environments; (x) Biological control based integrated pest management: does it work?; (xi) Exploring the compatibility of arthropod biological control and pesticides: models and data; (xii) Successes and uptake of arthropod biological control in developing countries; (xiii) Socio-economic impacts of biological control; (xiv) Biocontrol marketplace II.
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Phymastichus coffea LaSalle (Hymenoptera:Eulophidae) is an adult endoparasitoid of the coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera:Curculionidae:Scolytinae), which has been introduced in many coffee producing countries as a biological control agent. To determine the effectiveness of P. coffea against H. hampei and environmental safety for release in Hawaii, we investigated the host selection and parasitism response of adult females to 43 different species of Coleoptera, including 23 Scolytinae (six Hypothenemus species and 17 others), and four additional Curculionidae. Non-target testing included Hawaiian endemic, exotic and beneficial coleopteran species. Using a no-choice laboratory bioassay, we demonstrated that P. coffea was only able to parasitize the target host H. hampei and four other adventive species of Hypothenemus: H. obscurus, H. seriatus, H. birmanus and H. crudiae. Hypothenemus hampei had the highest parasitism rate and shortest parasitoid development time of the five parasitized Hypothenemus spp. Parasitism and parasitoid emergence decreased with decreasing phylogenetic relatedness of the Hypothenemus spp. to H. hampei, and the most distantly related species, H. eruditus, was not parasitized. These results suggest that the risk of harmful non-target impacts is low because there are no native species of Hypothenemus in Hawaii, and P. coffea could be safely introduced for classical biological control of H. hampei in Hawaii.
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The larval parasitoid Cotesia urabae Austin and Allen (Hymenoptera: Braconidae) is known to be attracted to odours of its target host Uraba lugens Walker (Lepidoptera: Nolidae), host plant (Eucalyptus species), and target plant-host complex. Cotesia urabae females were tested in both a Y-tube and four-arm olfactometer to further investigate these attractions as well as their attraction to three non-target Lepidoptera (two in the family Erebidae and one in the family Geometridae), and their corresponding host plants and plant-host complexes. In a Y-tube olfactometer, wasps were attracted to the odours of the non-target Erebidae larvae when tested on their own and when feeding on their host plants, but not to their non-target host plants alone, suggesting some rare circumstances in the field these non-targets could be attacked by C. urabae. The multiple-comparison bioassay conducted in a four-arm olfactometer indicates that target plant-host complex odours invariably produced the strongest attraction compared with any other of the non-target plant-host complex odours tested. Cotesia urabae females that were given prior exposure and the opportunity to oviposit within either non-target species were not subsequently more attracted to the Erebidae odours, suggesting that associative learning is unlikely to increase non-target attack. Such olfactometer assays could be a very useful addition to the host specificity testing methods able to be conducted within quarantine facilities, prior to the release of candidate biological control agents. We urge other biocontrol scientists to undertake similar assays to assist with non-target risk assessments.
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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 prejudge 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.
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Uraba lugens (gum leaf skeletoniser) is a serious pest of Eucalyptus spp. in Australia. It is now well established in the greater Auckland region, and is spreading. Two parasitoid species are under consideration as potential biological control agents of U. lugens. This paper describes host range testing methods developed using one of these species (Cotesia urabae) against two non-target species, Helicoverpa armígera and Spodoptera litura. Using sequential no-choice tests to test the response of mated C. urabae females, clear preferences were observed for U. lugens over both non-target test species. Some females did attempt to attack the non-target species, but no evidence of parasitism was observed when non-target hosts were reared or dissected. This method elucidated both behavioural responses and physiological development of C. urabae, and it is proposed to be a suitable host range testing method for full evaluation of this species.
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Classical biological control is being attempted for Uraba lugens (Lepidoptera: Noctuidae: Nolinae), an Australian eucalypt pest established in New Zealand. The Australian solitary larval endoparasitoid Cotesia urabae (Hymenoptera: Braconidae) is the most promising agent under investigation. A non-target species list was compiled for host range testing. The endemic species Celama parvitis is the sole New Zealand representative of the Nolinae and was highest priority. The next most closely related subfamily is the Arctiinae, of which New Zealand has four endemic species (Metacrias huttoni, M. erichrysa, M. strategica and Nyctemera annulata) and one introduced biological control agent (Tyriajacobaeae). The merits of including other, more distantly related, members of the Noctuidae, and unrelated Lepidoptera filling a similar niche are discussed.
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In July 2010, the Environmental Risk Management Authority New Zealand (now the Environmental Protection Authority) gave approval for release of the parasitoid Cotesia urabae Austin and Allen (Hymenoptera: Braconidae) as a biological control agent for the gum leaf skeletoniser Uraba lugens Walker Lepidoptera: Nolidae) in New Zealand. Between January and June 2011, five releases of adult C. urabae were made at two different sites in Auckland: three at the Auckland Domain (91 female: 102 male) and two at the Manukau Memorial Gardens (86 female: 54 male). Both release sites were closely monitored throughout 2011. The first cocoons were found one month after the first release, and thus far 132 cocoons have been found at the release sites suggesting initial establishment. The first confirmed progeny of field emerged parents was confirmed at the Auckland Domain in February 2012 with the finding of 18 cocoons at that site. Monitoring is continuing to determine if the population persists and further releases are planned at other sites to ensure establishment. Results of this study along with data gathered from ongoing monitoring will be useful to provide advice and guidelines to replicate a similar biocontrol program in other countries affected by U. lugens in the future
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Retrospective host specificity testing of the recently introduced biological control agent Cotesia urabae Austin & Allen, 1989 against Uraba lugens Walker, 1863 was conducted to assess the potential risk posed to the endemic nolid moth Celama parvitis Howes, 1917. The effect that different periods of host deprivation and prior host exposure (‘experience’) had on the parasitoid's readiness to attack a non-target species was examined in a sequence of consecutive no-choice tests. Even though C. urabae was observed to oviposit on C. parvitis in 91% of the no-choice tests, no parasitoids emerged from the 52% of larvae that survived to complete larval development. Host larvae that died during the laboratory rearing were dissected revealing that 63% contained a parasitoid larva, none of which had developed beyond the second instar within the larvae of C. parvitis. These results show a high level of developmental failure of C. urabae within C. parvitis, confirming that it is not a suitable physiological host. Therefore, potential negative impacts of C. urabae on C. parvitis in the wild are likely to be negligible. Significant differences were found in the attack times between parasitoids with different levels of host deprivation, with younger parasitoids taking longer to initiate attack behaviour. Also, it was observed that the lag until first attack decreased significantly after previous experience with the same host in a succession of no-choice tests. These results suggest that host deprivation and experience may play an important role in increasing the responsiveness to non-target species by C. urabae.
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Responses of individual females of the parasitoidCotesia marginiventris to the odors of four different complexes of host larvae feeding on leaves were observed in a four-arm olfactometer. The plant-host complexes were composed of fall armyworm (FAW) larvae or cabbage looper (CL) larvae feeding on either corn or cotton seedlings. Prior to testing, each female was given a brief foraging experience on a plant-host complex and was then exposed to the odors of the same complex in the olfactometer. The experienced females responded to familiar odors in a dose-related manner, and these responses were virtually identical to all four complexes. Preferences for the odors of one of two plant-host complexes were tested in dual choice situations. Generally, FAW odors were preferred over CL odors and corn odors over cotton odors. A short foraging experience significantly affected the females' odor preferences in favor of the odors released by the experienced complex. Additional experiments revealed that neither longer bouts of experience nor bouts that included ovipositions resulted in a stronger change in preference. Experience affected preference in combinations where only the host species was varied as well as in combinations where only the plant species was varied. The results, therefore, strongly indicate that both the plants and the hosts somehow are involved in the production and/or release of the semiochemicals that attractC. marginiventris.
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The population dynamics of Cotesia urabae (Austin and Allen) (Braconidae: Microgastrinae), a biological control agent from Tasmania, and its eucalypt feeding host, Uraba lugens (Walker) (Lepidoptera: Nolidae) was investigated prior to its introduction to New Zealand in 2011. Previous host range testing on potential New Zealand non-targets determined C. urabae had some potential to attack an endemic species, Nyctemera annulata (Boisduval) (Lepidoptera: Arctiidae). A closely related species in Tasmania, Nyctemera amica, was thus investigated as a potential host along with the native host U. lugens, to better understand the host range of C. urabae and the synchrony with its host in Tasmania. Adult C. urabae emerged from pupal cocoons in the field during January which confirmed a five month window in which its host, the larvae of U. lugens, was absent in the field. Experiments using sentinel N. amica and U. lugens larvae, field collections of N. amica and of larvae of other Lepidopteran species during this five month time window detected no parasitism by C. urabae. In the laboratory, host specificity testing showed reduced attack rates and no resultant C. urabae eggs or developing larvae or any successful pupation of C. urabae larvae from attacked N. amica larvae. It was concluded that N. amica is most unlikely to be a host for C. urabae in Tasmania and no evidence of any other alternative host was found.
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The life cycle and seasonal phenology of the endemic geometrid Pseudocoremia suavis (Butler) is described, as well as a method for rearing the species continuously in the laboratory on cut foliage of radiata pine (Pinus radiata D.Don). Both males and females demonstrated developmental polymorphism, having either five (Type I) or six (Type II) larval instars. These two larval types did not differ significantly in the total development time (from egg hatch to adult) of around 60 days in either case.The development time and head capsule widths of the penultimate and ultimate instars of each type suggest that these two instars are equivalent in both Type I and Type II larvae. In the field, most instars were present throughout the sampling period from mid-November to mid-March, and no clear peaks in activity were observed for adult males caught on female-baited sticky traps. These results support the findings of others that this species does not have clearly synchronised generations. Catch data from femalebaited traps revealed that calling peaked in one-day old females, with a mean of c. 27% of catches, and declined steadily with age. About 99% of cumulative catches occurred by the time females were 12 days old.
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Estimation of the host range of entomophagous biological control agents (parasitoids and predators) is complex. It is not always possible to inoculate all test organisms with eggs or neonates to determine "physiological suitability". We argue that, for the host range testing of parasitoids, it is important to initially employ test procedures that will maximize the prob- ability that the test species will be accepted for oviposition. This is vital to ensure that our testing methods do not generate data with a false impression of host specificity. No-choice tests are generally thought to maximize the expression of host range. The main reason for this may be increases in readiness to oviposit induced by host deprivation per se and/or associated changes in egg load, which has the potential to counteract any effects of prior experience. Sequential no-choice tests should only be used with caution as they have the potential to produce false negative results if the period of access to the lower ranked host is insufficient to allow time dependent changes in responsiveness of the parasitoid to become apparent, or if insufficient controls are utilized. Choice tests including the target host have the potential to mask the acceptability of lower ranked hosts, thereby producing false negative results. Ex- amples where wider host ranges have been expressed in no-choice tests than in choice tests, and vice versa are presented. Sufficient variation exists that we recommend that researchers routinely use both assay methods for host range testing of parasitoids and predators.
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When testing non-target effects of biological control agents, it is essential that conclusions can be drawn with high precision and confidence. However, testing non-target effects confronts the experimenter with a number of difficulties. First of all, biologically positive cases of not finding any non-target effect are more difficult to substantiate, since in stan-dard statistical hypothesis testing, we can only associate a precise probability to err with rejecting the null hypothesis that assumes no effect, but not with accepting it. The main problem here is the effect size, i.e., the difference from the null hypothesis that is consid-ered biologically meaningful. Secondly, there will usually be a trade-off between the costs associated with increased sample sizes and the confidence of the results of non-target effects testing. Often, sample size will be a limiting factor due to a shortage of animals, space for testing arenas, research funding, etc. Thus, it becomes especially important to optimize the experimental design and to use the most powerful statistical tools to obtain maximum confidence in the test results. Here, we will briefly (i) introduce the reader to common pitfalls of experimental design, (ii) explain the nature of errors in statistical test-ing, (iii) point towards methods that determine the power of statistical tests, (iv) explain the distribution of the most commonly encountered types of data, and (v) provide an introduction to powerful statistical tests for such data.
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It is generally accepted that knowledge of the natural and novel host range of proposed biological control agents can help to inform predictions of potential host range in new areas of introduction. To test this hypothesis, this paper describes a retrospective study conducted to contrast and compare the natural host range of Microctonus aethiopoides Loan (Hymenoptera: Braconidae) with its novel host range found in Australia and New Zealand, where it has been introduced to control the adult stage of the weevil Sitona discoideus Gyllenhal (Coleoptera: Curculionidae), a pest of lucerne. Surveys carried out in and near lucerne crops in Morocco and Australia each resulted in collections of over 3,000 weevils, of which respectively 84 % and 93 % were S. discoideus. The host ranges determined from these surveys for each M. aethiopoides population were then compared with information already available for field host range in New Zealand. In Morocco, species in the genera Sitona and Charagmus (Curculionidae: Entiminae: Sitonini) and Hypera (Curculionidae: Hyperinae: Hyperini) were found to be parasitised by M. aethiopoides. In Australia, an earlier record of non-target parasitism of ‘Prosayleus’ sp. 2 (Curculionidae: Entiminae: Leptopiini) is still the only known instance of non-target parasitism by M. aethiopoides. The known non-target field host range in New Zealand is much greater, comprising 19 native and introduced weevil species mainly in the subfamily Entiminae (tribe Leptopiini) but also in Curculioninae, Cyclominae and Lixinae. This is discussed in the context of predictions that could have been made at the time of introduction 30 years ago had the Moroccan and Australian data, modern molecular technologies and current understanding of weevil classification been available. The absence of Leptopiini in Morocco and the record of a native Australian leptopiine host could have indicated that native weevils in this tribe in New Zealand might be at risk of attack by M. aethiopoides.
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Biological control is an important component of pest management systems. It was generally considered safe and sustainable until the reality of this was challenged by researchers who pointed out that there was a lack of study, and hence evidence for this, and provided examples of non-target impacts. Biosafety of biological control subsequently received considerable attention from both biocontrol practitioners and regulators. Many countries now have legislation in place which is focussed on risk assessment for biological control and protecting native and valued biota and the environment from potential adverse impacts. This review summarises the biosafety debate, and characterises the direct and indirect risks of biological control mainly for weeds and insect pests. During a biological control programme, there are several stages during which aspects of biosafety can be considered and addressed: exploration in the native range of the target species; from literature and knowledge of the biological control agent and host; experience from use of the biological control agent elsewhere; and host range tests. The value of post-release monitoring and retrospective studies for validation of pre-release predictions is discussed. Poorly studied is analysis of the population impacts of non-target attack by biological control agents. The literature from the last 20-30 years can help define some useful principles by which a risk assessment can be conducted to minimise adverse environmental effects. It has become clear over this period that comprehensive assembly of information and robust quarantine testing to provide a well structured risk assessment, can reduce uncertainty in decision-making in this area.
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Laboratory host specificity of 2 biological control agents, already introduced in New Zealand, was compared with actual field parasitism. The parasitoids were Microctonus aethiopoides Loan and Microctonus hyperodae Loan, braconids imported to control the curculionid forage pests Sitona discoideus Gyllenhal and Listronotus bonariensis (Kuschel), respectively. The nontarget weevil species tested included native, introduced, and beneficial species. M. aethiopoides oviposited in 11 of the 12 species to which it was exposed and successfully parasitized 9 species. M. hyperodae oviposited in 5 of the 11 species to which it was exposed and developed successfully in 4 species. Higher percentage parasitism was recorded with M. aethiopoides than with M. hyperodae. Field collections of weevils from Otago, Canterbury, and Waikato indicated that 10 New Zealand native species and 3 other nontarget species, including the weed biological control agent Rhinocyllus conicus (Froehlich), were parasitized by M. aethiopoides. M. hyperodae has been found parasitizing 1 native species, as well as Sitona lepidus Gyllenhal, which was accidentally introduced to New Zealand recently. In nontarget species, parasitism levels in the field of >70% have been recorded for M. aethiopoides and <5% for M. hyperodae. The results of this study suggest that laboratory host range testing is indicative of nontarget parasitism in the field.
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Abstract  The hyperparasitoids reared from three species of primary parasitoids of the gum leaf skeletoniser, Uraba lugens Walker (Lepidoptera: Nolidae) collected in South Australia and Tasmania are recorded and discussed. Seven hyperparasitoids were reared. Diatora sp. and ?Paraphylax sp. (Ichneumonidae: Cryptinae); Tetrastichus sp. (Chalcidoidea: Eulophidae); Megadicylus dubius (Girault) (Chalcidoidea: Pteromalidae) and Elasmus sp. (Chalcidoidea: Eulophidae) were reared from Cotesia urabae Austin and Allen (Braconidae: Microgastrinae). Megadicylus dubius, Elasmus sp. and Anastatus sp. (Chalcidoidea: Eupelmidae) were reared from Dolichogenidea eucalypti Austin and Allen (Braconidae: Microgastrinae). Pediobius bruchicida (Rondani) (Chalcidoidea: Eulophidae) was reared from Euplectrus sp. (Chalcidoidea: Eulophidae). This appears to be the first record of the cryptine ichneumonid genus Diatora Förster from Australia. Of the seven hyperparasitoid species reared, only one (P. bruchicida) is known to be present in New Zealand. Implications for the selection of a biological control agent for U. lugens in New Zealand are discussed. Some prior misidentifications of associated hyperparasitoids are noted.
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This greatly expanded second edition of Survival Analysis- A Self-learning Text provides a highly readable description of state-of-the-art methods of analysis of survival/event-history data. This text is suitable for researchers and statisticians working in the medical and other life sciences as well as statisticians in academia who teach introductory and second-level courses on survival analysis. The second edition continues to use the unique "lecture-book" format of the first (1996) edition with the addition of three new chapters on advanced topics: Chapter 7: Parametric Models Chapter 8: Recurrent events Chapter 9: Competing Risks. Also, the Computer Appendix has been revised to provide step-by-step instructions for using the computer packages STATA (Version 7.0), SAS (Version 8.2), and SPSS (version 11.5) to carry out the procedures presented in the main text. The original six chapters have been modified slightly to expand and clarify aspects of survival analysis in response to suggestions by students, colleagues and reviewers, and to add theoretical background, particularly regarding the formulation of the (partial) likelihood functions for proportional hazards, stratified, and extended Cox regression models David Kleinbaum is Professor of Epidemiology at the Rollins School of Public Health at Emory University, Atlanta, Georgia. Dr. Kleinbaum is internationally known for innovative textbooks and teaching on epidemiological methods, multiple linear regression, logistic regression, and survival analysis. He has provided extensive worldwide short-course training in over 150 short courses on statistical and epidemiological methods. He is also the author of ActivEpi (2002), an interactive computer-based instructional text on fundamentals of epidemiology, which has been used in a variety of educational environments including distance learning. Mitchel Klein is Research Assistant Professor with a joint appointment in the Department of Environmental and Occupational Health (EOH) and the Department of Epidemiology, also at the Rollins School of Public Health at Emory University. Dr. Klein is also co-author with Dr. Kleinbaum of the second edition of Logistic Regression- A Self-Learning Text (2002). He has regularly taught epidemiologic methods courses at Emory to graduate students in public health and in clinical medicine. He is responsible for the epidemiologic methods training of physicians enrolled in Emory’s Master of Science in Clinical Research Program, and has collaborated with Dr. Kleinbaum both nationally and internationally in teaching several short courses on various topics in epidemiologic methods.
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Biological control is one of several strategies used to control pests to avoid economic damage on crop plants, in husbandry, or on recreation areas. It is also used against nuisance pests. In this chapter, I use the terms ‘pest’ and ‘pests’ for insect, mites and vertebrate pests, plant diseases, and weeds.
Book
This book provides an invaluable review of the current methodologies used for assessing the environmental impacts of invertebrate biological agents used to control pests in agriculture and forestry. It explores methods to evaluate post-release effects and the environmental impact of dispersal, displacement and establishment of invertebrate biological control agents. It covers methodology on screening for contaminants, the use of molecular methods for species identification and the determination of interbreeding. The book also discusses the use and application of information on zoogeographical zones, statistical methods and risk-benefit analysis. It gives practical advice on how to perform science-based risk assessments and on how to use new technology and information.
Chapter
The defense reactions of insect hosts towards parasitoids and the means by which parasitoids sometimes evade the host’s defense have been the subject of numerous reviews (Salt, 1963a, 1968, 1970; Nappi, 1975a; Whitcomb et al., 1974; Jackson et al., 1969; Lafferty and Crichton, 1973). There is, however, very little consensus of opinion concerning the mechanism of the host’s defense reaction or the means by which a parasitoid escapes it. As has been pointed out (Nappi, 1975; Whitcomb et al., 1974; Salt, 1970), the major factors responsible for the immune response of vertebrates, notably the antigen-antibody complementary system and antigenic memory, appear to be lacking in insects.
Article
Townes described an early fossil ichneumonid, Tanychora petiolata, from early Cretaceous amber of Russia, which is still the earliest known probable member of the Ichneumonidae dating to 121–125 Mya. This chapter talks about the phylogeny and systematics of the Ichneumonidae. Tanychora shows several plesiomorphic features and has been important in interpreting various characters in modern taxa. The Brachycyrtiformes was an almost completely unsuspected clade until molecular data became available. It includes four small subfamilies, the cosmopolitan Brachycyrtinae, together with two small groups occurring in Chile (Clasinae and Pedunculinae) and Australia (Pedunculinae), and was named the brachycyrtiformes by Quicke et al. A close relationship between many of the subfamilies of the Ophioniformes was suspected back in the 19th century, based largely on the laterally compressed metasomas with the spiracle of the first metasomal tergite being placed well behind the middle as in Ophioninae, Anomaloninae, Campopleginae, Cremastinae and Tersilochinae.
Book
1. Introduction 2. Estimation 3. Hypothesis testing 4. Graphical exploration of data 5. Correlation and regression 6. Multiple regression and correlation 7. Design and power analysis 8. Comparing groups or treatments - analysis of variance 9. Multifactor analysis of variance 10. Randomized blocks and simple repeated measures: unreplicated two-factor designs 11. Split plot and repeated measures designs: partly nested anovas 12. Analysis of covariance 13. Generalized linear models and logistic regression 14. Analyzing frequencies 15. Introduction to multivariate analyses 16. Multivariate analysis of variance and discriminant analysis 17. Principal components and correspondence analysis 18. Multidimensional scaling and cluster analysis 19. Presentation of results.
Article
Cotesia urabae (Hymenoptera: Braconidae) was released in New Zealand in 2011 for the biological control of the Eucalyptus pest Uraba lugens (Lepidoptera: Nolidae) (gum leaf skeletoniser). Methods for rearing C. urabae and its host under containment conditions are described. An intensive method was developed to allow tracking of individual female parasitoids and their progeny for use in host specificity testing experiments and to maximise the production of female offspring for culture maintenance. Of females paired using this method, 26.3% (35/133) were observed mating, and subsequently produced offspring that were 57.0%±5.9SE (n=21) female on average. To maximise the use of parasitoids that were often in short supply, females that failed to mate with the intensive method were caged with multiple males and females. Of a sample of these females, 19.4% (6/31) produced female offspring (indicating mating had occurred). Refinement of a technique for maximising courtship and mating probability was critical to the success of this laboratory culture.
Article
Retrospective host specificity testing of the recently introduced biological control agent Cotesia urabae Austin & Allen, 1989 against Uraba lugens Walker, 1863 was conducted to assess the potential risk posed to the endemic nolid moth Celama parvitis Howes, 1917. The effect that different periods of host deprivation and prior host exposure (‘experience’) had on the parasitoid’s readiness to attack a non-target species was examined in a sequence of consecutive no-choice tests. Even though C. urabae was observed to oviposit on C. parvitis in 91% of the no-choice tests, no parasitoids emerged from the 52% of larvae that survived to complete larval development. Host larvae that died during the laboratory rearing were dissected revealing that 63% contained a parasitoid larva, none of which had developed beyond the second instar within the larvae of C. parvitis. These results show a high level of developmental failure of C. urabae within C. parvitis, confirming that it is not a suitable physiological host. Therefore, potential negative impacts of C. urabae on C. parvitis in the wild are likely to be negligible. Significant differences were found in the attack times between parasitoids with different levels of host deprivation, with younger parasitoids taking longer to initiate attack behaviour. Also, it was observed that the lag until first attack decreased significantly after previous experience with the same host in a succession of no-choice tests. These results suggest that host deprivation and experience may play an important role in increasing the responsiveness to non-target species by C. urabae.
Article
Rearing the parasitoidM. croceipes on hosts fed cowpea-seedling leaves instead of artificial diet increased the percentage of oriented flights to odors of a cowpea seedling-H. zea complex in a flight tunnel. However, the increase in response was much stronger after adult females had searched a fresh plant-host complex just prior to a test. The host plant appears to be of major importance in the parasitoid-host relationship: host-plant species, growth phase, and part of the host plant influence the parasitoid's response in the flight tunnel. The percentage of inexperienced females responding to infested leaves was higher for 4- to 5-day-old females than for 0- to 1-day-old females, while the response to uninfested flowers was equally high for both age groups. Olfactory experience with odors of an attractive plant-host complex increased the response to an unattractive plant-host complex. Possible implications of the results are discussed.
Article
Nyctemera annulata Boisduval was reared in the laboratory at 26±1°C and 50 ±5% RH on a host plant, ragwort (Senecio jacoboea L.), and on an artificial diet. On ragwort the average life cycle of 34 days embraced a larval period of 24 days, with up to 6 larval instars, and a pupal period of 9–11 days, depending on whether pupation occurred at the 5th or 6th instar. On the artificial diet the larval period of 56 days, involving up to 10 instars, was followed by a pupal period of 9 days, for an average life cycle of 65 days.
Article
The braconid wasp genus Diolcogaster Ashmead is revised for the Australasian region, and is recorded from New Zealand and New Caledonia for the first time. A key to species is presented, the relationships within the Microgastrinae and among species-groups of the genus, the size of the world fauna, the biology and host relationships, and the distribution of Australasian species are discussed. The connexus-group sensu Nixon is expanded and redefined to include two monotypic, non-Australasian groups (D. ippis Nixon and D. reales Nixon), while the spretus-group sensu Nixon is expanded to include the monotypic group for D. coenonymphae (Watanabe) from Japan. Twenty-six species are recognised from Australasia:D. adiastola, sp. nov., D. alkingara, sp. nov., D. ashmeadi, sp. nov., D. dichromus, sp. nov., D. eclectes (Nixon), D. euterpus (Nixon), D. hadrommatus, sp. nov., D. harrisi, sp. nov., D. iqbali, sp. nov., D. lucindae, sp. nov., D. masoni, sp. nov., D. merata, sp. nov., D. muzaffari, sp. nov., D. naumanni, sp. nov., D. newguineaensis, sp. nov., D. nixoni, sp. nov., D. notopecktos, sp. nov., D. perniciosus(Wilkinson), D. rixosus (Wilkinson), D. robertsi, sp. nov., D. sons (Wilkinson), D. tearae (Wilkinson), D. tropicalus, sp. nov., D. vulpinus (Wilkinson), D. walkerae, sp. nov. and D. yousufi, sp. nov.
Article
A system of environmental ethics recently developed by Lawrence Johnson may be used to analyze the moral implications of biological control. According to this system, entities are morally relevant when they possess well-being interests (i.e., functions or processes that can be better or worse in so far as the entity is concerned). In this formulation of ethical analysis, species and ecosystems are morally relevant because they are not simply aggregates of individuals, so their processes, properties, and well-being interests are not reducible to the sum of their individual members. Following Johnson's thesis, species and ecosystems have morally relevant interests in surviving and maintaining themselves as integrated wholes with particular self-identities. This theoretical structure gives rise to a number of ethical criteria that are particularly relevant to biological control, which apply to the ecosystem (the extent to which it is large, native, unique, and integrated) and to the action being considered (the extent to which it is novel, omnipresent, monitored, reversible, and necessary). In these terms, it is evident that not all biological control efforts are ethically defensible. In general terms, natural biological control is most desirable, followed by augmentative strategies, classical approaches, and finally neoclassical biological control. Two specific cases (neoclassical biological control of rangeland grasshoppers and classical biological control of prickly pear cactus) illustrate the ethical concerns. Finally, it can be shown that formalized restrictions of biological control are necessary, given the unique properties of this technology
Article
The need to improve methods and interpretation of host specificity tests for arthropod natural enemies has been clearly identified, yet there remains a paucity of empirical evidence upon which to base recommendations. Factors influencing test outcomes and the mechanisms underlying them must be understood so they can be controlled, and test results can be interpreted correctly. In this study, an established exotic host/parasitoid system was used to assess the outcomes and predictive accuracy of no-choice compared to paired choice tests within small laboratory arenas. Host acceptance by two egg parasitoids, Enoggera nassaui and Neopolycystus insectifurax (Pteromalidae), was interpreted in light of percent parasitism, offspring sex ratios and observed parasitoid behavior. No-choice tests showed that the four host species, Paropsis charybdis, Dicranosternasemipunctata, Trachymelacatenata and Trachymela sloanei (Coleoptera: Chrysomelidae) were within the physiological host ranges of both parasitoids. The results of paired choice tests with the first three species supported this interpretation, with two exceptions. Trachymela catenata eggs were not accepted by E. nassaui and were accepted significantly less often by N. insectifurax when compared to no-choice tests. Both test designs predicted that D. semipunctata is within the ecological host range of the two parasitoid species, whereas field evidence suggests this is a false positive result. Percent parasitism of all hosts was higher in no-choice compared to choice tests and was predictive of rank order of host preference in choice tests. Presence of the most preferred host did not increase attack on lower ranked hosts. Offspring sex ratios of E. nassaui were independent of host preference. In contrast, N. insectifurax allocated more females to P. charybdis and mostly males to D. semipunctata and T. catenata. The results support our assertion that both no-choice and choice tests along with detailed behavioral studies should be conducted for correct interpretation of pre-release host specificity tests. This will enable more accurate predictions of parasitoid host ranges and risks parasitoids may pose to non-target organisms in the field.
Article
The number of concerns regarding potential non-target effects of invertebrate biological control agents of arthropods has risen over the last decade and an increasing number of studies have since dealt with this topic. Despite some recent international initiatives aimed at providing guidance for risk assessment of biological control agents, detailed methods on how tests should be designed and conducted to assess for potential non-target effects still need to be provided. It is believed that this review comes at an ideal time, giving an overview of methods currently applied in the study of non-target effects in biological control of arthropod pests. It provides the first step towards the ultimate goal of devising guidelines for the appropriate methods that should be universally applied for the assessment and minimisation of potential non-target effects. The main topics that are reviewed here include host specificity (including field surveys, selection of non-target test species and testing protocols), post-release studies, competition, overwintering and dispersal. Finally, a number of conclusions that have emerged from this comprehensive compilation of studies are drawn, addressing potential non-target effects in arthropod biological control.
Article
The higher classification of the families of the Noctuoidea with a quadrifid forewing (Nolidae, Strepsimanidae, Arctiidae, Lymantriidae, Erebidae, and Noctuidae) is reviewed from the perspective of recent classifications and the distribution of derived character states. On the basis of recent morphological and molecular studies, we propose a more inclusive definition of the family Noctuidae that adds the subfamilies Nolinae, Strepsimaninae, Arctiinae, Lymantriinae, and Erebinae to the subfamilies more traditionally included in the Noctuidae. Consequently, the superfamily Noctuoidea comprises the families Oenosandridae, Doidae, Notodontidae, Micronoctuidae, and Noctuidae. The tribe Cosmiini, currently in the subfamily Xyleninae, is downgraded to the status of subtribe Cosmiina and placed in the tribe Xylenini. The tribe Balsini, currently in the subfamily Xyleninae, is elevated to the status of subfamily Balsinae. The tribe Phosphilini is transferred from the subfamily Psaphidinae to the Xyleninae.
Article
Insects have evolved many mechanisms that reduce their potential for serving as hosts for entomophagous species. Some of these mechanisms involve escape, mimicry, and repellancy, which are effective defense mechanisms against both predators and parasitoids. But, insects have a second line of defense against parasitoids and parasites. These may include repellancy and a cuticular barrier to invasion but they include several internal defenses that are collectively referred to as immune mechanisms. The current understanding of insect immunity is reviewed as background to examining the ways in which insect parasitoids have evolved to successfully handle the immune system of the host. The various means that parasitoids utilize to handle the insect immune systems have been divided into five approaches. These five approaches are described and current knowledge of the mechanisms used by parasitoids to deal with the immune system of their host is explored.
Article
Host specificities of 3 species of Pseudacteon decapitating flies (P. litoralis Borgmeier, P. tricuspis Borgmeier, P. wasmanni Schmitz) were tested in quarantine facilities in Gainesville, FL. Female flies from Brazil were placed into test trays containing either red imported fire ants, Solenopsis invicta Buren; tropical fire ants, Solenopsis geminata Forel; or native ants from 6 other genera (Crematogaster, Pheidole, Aphaenogaster, Neivamyrmex, Forelius, Camponotus). Tests lasted 60-90 min. The 3 species of flies tested were all at least 15 times more likely to attack their natural host, S. invicta, than they were to attack the native fire ant, S. geminata. More than 200 larvae resulted from numerous attacks on S. invicta workers. No larvae resulted from the few possible attacks on S. geminata or the other species of ants that were tested. We induced several P. tricuspis to attack a few S. geminata workers by mixing these workers in with freeze-killed S. invicta workers. One adult fly emerged from these attacks, demonstrating that P. tricuspis can develop in S. geminata workers. This indicates that the field release of P. tricuspis poses some risk to native fire ants; however, the extremely low rates of attack on S. geminata in the laboratory and in the field indicate that this risk would be minimal. The argument is made that this small risk is acceptable because, among other things, native fire ants are under much more risk from expanding populations of imported fire ants than they would be from imported Pseudacteon flies.
Article
Chapter 1. The basic ideas are considered: like event, survival time, censoring, survival function, hazard function. Data layouts and some descriptive measures are discussed. The principles of confounding and interaction are discussed. In a multivariable example the similarities and differences between linear, logistic regression and survival regression and the concept of a hazard ratio are discussed.This chapter was overall clear. In this book the hazard is introduced as the instantaneous potential per unit time for the event to occur. The derivation of the relationship between the hazard function and the survival function is not given (the author finds it not important, since a computer can do the calculations), while the calculations are easy to perform. We also missed a warning that censoring should be independent of the occurrence of an event. Competing risks and left censoring are mentioned but not treated in detail.Chapter 2. This chapter is about Kaplan-Meier curves, the log-rank test and the Peto test. The proof of the Kaplan-Meier formula is difficult to follow, just because the author is so hard trying to make it easy to understand. The log-rank test and Peto test are clearly explained.Chapter 3. Here the Cox Proportional Hazards model is discussed. The chapter starts with the computer output of a rather complex example with a treatment effect, a confounder plus an interaction term. Hereafter the general model is discussed. The partial likelihood is discussed but the formula is not given. The interpretation of the coefficients is discussed using the data example. Somewhere in the midst of several examples, the general rule is given, which is confusing.Chapter 4. Four different ways of checking the assumptions of the Cox model are discussed: log-log plots, comparing observed with model survival curves, Schonfeld's goodness of fit test and time dependent covariate methods. Suggestions are given about how to proceed in practice. Overall this is a good chapter, although the part about log-log plots is too elaborate.Chapter 5 is about stratification in the Cox model. There is a discussion of when to use stratification (if the PH assumption does not hold), and the possibility of interaction between the stratification variables and the other predictors is considered, with statistical tests.In Chapter 6 time dependent covariates are discussed. A distinction is made between two different situations. The first situation is a variable that changes in time (like employment status, smoking status). The second situation is a variable that is constant in time, but its effect on the hazard changes in time, so that the proportional hazards assumption does not hold. By multiplying the variable by some function of time, the model can be improved.
Article
Twenty-two species were found in the parasitoid complex attacking Uraba lugens Walker: 11 primary parasitoids, 10 hyperparasitoids and 1 facultative hyperparasitoid. All immature stages of U. lugens were parasitised, with larval parasitoids killing hosts from the third instar onwards. The majority of parasitoids were found in both the summer and the winter generations of U. lugens, and at least 4 of the primary parasitoids produced more than 1 generation per generation of the host. Parasitoids were collected from hosts on several species of Eucalyptus. The longevity of adult female parasitoids in the complex varied between 8 and 254 days. Of the hyperparasitoids, many were gregarious and polyphagous, and all but 1 species parasitised the pupae of primary parasitoids.High mortality occurred among early instar larvae of U. lugens, but older instars were much less affected by mortality factors. The survival of larvae between trees and even between different groups on the 1 tree was variable. Caging of larvae greatly increased overall survival and decreased the fluctuations in mortality between larvae on different trees. Although parasitism was very high in some individual groups, it accounted for only a small proportion of mortality of U. lugens. Hyperparasitism and the presence of many polyphagous primary parasitoids in the complex may be a contributing factor to the low levels of parasitism observed on U. lugens.
Article
Gumleaf skeletoniser, Uraba lugens (Lepidoptera: Nolidae), is a native Australian defoliator of many Eucalyptus and related species, and has recently established in New Zealand. Outbreaks of this species have caused significant damage to natural and commercially managed forests in Australia, and threaten plantations and amenity trees in New Zealand. With the arrival of this pest in New Zealand, research interest in U. lugens has increased. This stimulated this review and update, with previously unpublished data presented, on its taxonomy, biology, distribution, pest status and management. Host species and natural enemies are also listed, including previously unpublished records.
Article
Three parasitoids of citrus leafminer, Phyllocnistis citrella, Ageniaspis citricola (Logvinovskaya), Citrostichus phyllocnistoides (Narayanan) and Cirrospilus quadristriatus Subba Roa and Ramamani were introduced from southern China and Thailand to eastern Australia in 1990-91. After quarantine testing against 17 other insect hosts with leafmining and gall forming habits, they appeared to be restricted to citrus leafminer and releases were made in Queensland, New South Wales, South Australia and Victoria. A. citricola established throughout Queensland and C. quadristriatus in all four states. Some recoveries were made of C. phyllocnistoides but establishment has not yet been confirmed.
Article
1. Natural enemies may reduce the effectiveness of weed biocontrol agents and can also cause environmental damage, for example to a shared native insect host through apparent competition. Indeed, successful biocontrol may rely on enemy-free space and avoidance of apparent competition in the area where the biocontrol agent is introduced. 2. We surveyed parasitism in 28 insects released for weed biocontrol in New Zealand (NZ). We reviewed the global literature and databases to complement this survey, and to collate records of these insects being parasitized in their area of origin. We also collated records of native insects that feed on weeds targeted for biocontrol in NZ to test Lawton’s (1985) hypothesis that, to find enemy-free space, selected agents should ‘feed in a way that is different’ and ‘be taxonomically distinct’ from native herbivores in the introduced range. 3. We found that 19, mostly native, parasitoid species attack 10 weed biocontrol agents in NZ, of which 15 were confined to five agents that possessed ‘ecological analogues’, defined as a native NZ insect that belongs to the same superfamily as the agent and occupies a similar niche on the target weed. Parasitoid species richness in NZ was positively correlated to richness in the area of origin. However, only agents with ecological analogues contributed significantly to this pattern. 4. A review of NZ weed biocontrol programmes indicated that parasitism is significantly associated with the failure of agents to suppress weed populations. 5. Synthesis and applications. Although our conclusions are based on an unavoidably limited data set, we conclude that biocontrol agents that escape attack from parasitoids are more likely to suppress weed populations and should be less likely to have significant indirect non-target effects in food webs. Biocontrol practitioners can reduce the chance of weed biocontrol agents attracting species-rich parasitoid faunas after introduction by (i) selecting agents that have species-poor parasitoid faunas in their area of origin, and/or (ii) avoiding agents that have ‘ecological analogues’ awaiting them in the introduced range.