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B.I.P. Barratt, C.M. Ferguson, S.L. Goldson, C.B. Phillips M.R. McNeill AgResearch, New Zealand

Potential for impact of Microctonus spp. (Hymenoptera: Braconidae) outside the target host environment. B.I.P. Barratt, C.M. Ferguson, S.L. Goldson, C.B. Phillips M.R. McNeill AgResearch, New Zealand. Introduction.

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B.I.P. Barratt, C.M. Ferguson, S.L. Goldson, C.B. Phillips M.R. McNeill AgResearch, New Zealand

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  1. Potential for impact of Microctonus spp. (Hymenoptera: Braconidae) outside the target host environment B.I.P. Barratt, C.M. Ferguson, S.L. Goldson, C.B. Phillips M.R. McNeill AgResearch, New Zealand

  2. Introduction • two braconid species introduced into NZ for biocontrol of forage pest weevils • used as ‘case studies’ to: • conduct laboratory testing to predict host range • testing predictions in field • evaluating post-release environmental impacts • assist regulators with decision support for future biological control releases

  3. Microctonus aethiopoides introduced 1982 Sitona discoideus control in lucerne minimal host range testing Microctonus hyperodae introduced 1991 Listronotus bonariensis control in pasture extensive host range testing Case studiesHymenoptera: Braconidae: Euphorinae (solitary - endoparasitic - koinobionts - adult hosts)

  4. M. aethiopoides with Sitona discoideus

  5. M. hyperodae with ASW

  6. Programme approach examine taxonomic and ecological affinities between target and native species investigate extent to which native and target species occur in mixed populations ID ‘at risk’non-targetspecies laboratory host range tests field survey for non-target parasitism compare predicted with realised host range investigate environmental impact

  7. Results from lab testing

  8. Results from field sampling

  9. Comparison lab vs. realised field host range • M. hyperodae: • demonstrated high level of host specificity as predicted • non-target parasitism only in target host environment • M. aethiopoides: • relatively broad host range as predicted • non-target parasitism in and outside target host environment

  10. Environmental impact (M. aethiopoides) • Approach: • non-target host phenology and parasitism in developed grassland • assess parasitism of non-target spp. along altitude sequence away from target host environment ‘native’ grassland • release M. aethiopoides at replicated sites: • native grassland • M. aethiopoides not present • historical data on weevil populations

  11. Environmental impact (M. aethiopoides) • Approach: • non-target host phenology and parasitism in developed grassland • assess parasitism of non-target spp. along altitude sequence away from target host environment ‘native’ grassland • release M. aethiopoides at replicated sites: • native grassland • M. aethiopoides not present • historical data on weevil populations

  12. Developed pasture • survey of 87 developed pasture sites: • 56 weevil spp. in total • 44 in sub-family Brachycerinae • sampled native spp. from 6 pasture sites for 3 years • measured density of: • adults (tenerals) • fecund females • parasitised weevils

  13. Seasonality of non- target parasitism % parasitism incidence mean % parasitism

  14. Environmental impact (M. aethiopoides) • Approach: • non-target host phenology and parasitism in developed grassland • assess parasitism of non-target spp. along altitude sequence away from target host environment ‘native’ grassland • release M. aethiopoides at replicated sites: • native grassland • M. aethiopoides not present • historical data on weevil populations

  15. Altitude sequence

  16. Parasitism non- target spp.

  17. Environmental impact (M. aethiopoides) • Approach: • non-target host phenology and parasitism in developed grassland • assess parasitism of non-target spp. along altitude sequence away from target host environment ‘native’ grassland • release M. aethiopoides at replicated sites: • native grassland • M. aethiopoides not present • historical data on weevil populations

  18. M. aethiopoides release • Area: • 850-900m • 3 sites for release (2 km apart) • paired with 3 botanically similar control sites - similar weevil population densities • Release: • 500 parasitoids/site (parasitised S. discoideus) • spring • Sampling: • turf samples spring and summer (30x0.1m2) • weevil density and parasitism levels

  19. Conclusion • In general: • comparison of predicted vs. realised field host range useful • assist in validating future containment testing • more case studies required • Environmental impact: • what does it all mean? • threat to species or biodiversity?

  20. Conclusion • M. aethiopoides parasitism of native spp. • occurs widely outside target host environment • lower altitudes: • parasitism may be significant for some species • mostly occurs after spring oviposition period • higher altitudes: • parasitism probably less significant • oviposition period may be later • no evidence that survival of native weevil populations are under threat • long term studies required

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