Risk of Eucalyptus tortoise beetle control Jon Sullivan Jon - PowerPoint PPT Presentation

Risk of Eucalyptus tortoise beetle control Jon Sullivan Jon Sullivan

Biology of the pest in NZ Egg parasitoids Enoggera nassaui and Neopolycystus insectifurax provide good  Adults and larvae strip all control of 2 nd generation eggs in NZ: flush, young leaves from Egg survival 4% hosts Egg survival 95%  Each female can lay ~ 2000 eggs  At least two generations per annum results in rapid population expansion  First generation needs biological control to optimise tree growth Refer Appendix Two

Biological control research in country of origin  Paropsis charybdis is one of many eucalyptus leaf beetles native to Australia  Field work collaboration with Dr Geoff Allen at the University of Tasmania  Earlier research evaluated all the parasitoids of P. charybdis  Eadya (initially named paropsidis ) most promising to be host specific  Molecular research confirmed host Results in Sharanowski range, and number of species. et al. 2018  Since 2000 reared thousands of leaf feeding caterpillars and 2700 Gonipterus larvae (weevils) reared – no Eadya

Eadya daenerys – larval parasitoid (Braconidae)  Parasitoid that attacks larvae in spring (first generation)  Lays one egg directly into the larva of any size  Eats it from the inside out, pushes out after 3 weeks Approx 10mm long  Spins cocoon in soil  Overwinters until emerges as an adult following Nov-Dec  Eadya only reared from 4 Paropsis and Paropsisterna beetles in Australia Described in Ridenbaugh et al 2018 Photo: Anthony Rice

Scion assessed the risk this parasitoid might pose to other non-target beetles in NZ  Pest paropsines are Chrysomelidae: Chrysomelinae beetles  New Zealand has no native paropsini beetles, only invaded pests  But NZ has other Chrysomelinae • Most risk if medium sized (>5mm), with leaf feeding larvae, active during early summer • Prioritise beneficial species in either subfamily Chrysomelinae or Galerucinae (weed agents) • Utilised both traditional and a model (PRONTI) to draw up the best host testing list

Phylogenetic Paropsis relationships charybdis Trachymela between target and Chrysomelini sloanei Exotic pests non-targets Dicranosterna semipunctata Allocharis tarsalis Chrysomelinae Largest Phyllocharitini endemic Chalcolampra chrysomelines speculifera Chrysolina abchasica Gonioctenini Gonioctena olivacea Beneficial Chrysomelidae weed Lochmaea Galerucini suturalis BioControl Galerucinae Agents Agasicles Alticini hygrophila Cassida Cassidinae Cassidini rubiginosa Neolema Criocerinae ogloblini

Undertook host testing (Appendix 5)  Eadya target is Paropsis charybdis the largest of the invasive pest paropsines in NZ Paropsis  Phylogenetically closest relatives exotic pests in NZ, subfamily Chrysomelinae: – tested 2 largest out of Paropsisterna spp. , Trachymela spp . (paropsines) , Dicranosterna, Peltoschema Dicranosterna Trachymela  Endemic species in subfamily Chrysomelinae - tested 1 we located – Allocharis. Also searched unsuccessfully for Chalcolampra , & Caccomolpus. Allocharis

…host testing continued  Beneficial weed biocontrol agents in subfamily Chrysomelinae – tested 2: Gonioctena olivacea on Scotch broom, and Chrysolina abchasica on Tutsan. Chrysolina Gonioctena  Beneficial weed biocontrol agents in sister subfamily Galerucinae – tested 2: Agasicles hygrophila on Alligator Weed, and Lochmaea suturalis on Heather Agasicles Lochmaea  Beneficial weed biocontrol agents in unrelated subfamilies – tested 2: Neolema ogloblini on Tradescantia (Criocerinae), Cassida rubiginosa on Californian thistles (Cassidinae). Neolema Cassida

Host testing methods in containment  No-choice physiological assays – 24 hours one female to 8 larvae on foliage, rearing and dissecting any dead larvae  Close-up behavioural observations in petri dishes

Results of No-choice physiological host range :  Viable parasitism – Paropsines only: Paropsines • Paropsis charybdis target pest 34+% (n=120) • Trachymela sloanei 12.5% (n = 5 reps)  Non-viable parasitism found only in Chrysomelines, after larval dissections Chrysomelines • Dicranosterna semipunctata 1.6% (n= 16) • Allocharis nr tarsalis 7.5% (n= 10) • Chrysolina abchasica 1.8% (n=14) • Gonioctena olivaceae 5.2 % (n=12)  All other species in Galerucinae, Cassidinae and Criocerinae, 0% parasitism (n=11 -16)

Conclusion from physiological tests  Non-target larval rearing survival in the laboratory ranged from 40% ( Chrysolina ) to 90% ( Allocharis ). Generally was good.  Target P. charybdis rearing survival dropped from 95% in the absence of parasitism, to 9% after stinging by Eadya.  Physiological host tests are considered worst case scenario, over- estimating likely field host range, as long as appropriate life stages are presented, and parasitoids remain active and viable through-out the tests.  Our tests ran for 24 hours, thereby allowing for nocturnal or diurnal activity by the parasitoid, and long enough for deprivation effects to become extreme.  Only paropsines tested, were complete physiological hosts

Body size comparisons among beetles  1/5 of the Eadya larvae emerging from T. sloanei became a minute but viable adult, confirming minimum host size of about 35 mg  Suggests the non-target beetles will be too small to be physiological hosts, therefore unable to form populations, even if had been hosts. Paropsines Hosts Chrysomelines Non- Hosts Predicted minimum host size

Behavioural observations  Often host testing of parasitoids only reports on results of physiological host range  But behavioural observations can assist with interpretation of any uncertain data  Therefore we report here the additional data on behaviour of individual female parasitoids in two-choice, and no-choice sequential petri dish assays  Non-parametric statistics (comparisons of medians)

Number of ovipositor-insertions per minute  Attack rate (number stings per minute) when given a CHOICE significantly less than against P. charybdis

 Attack rate (number stings per minute spent on the plant) when in a NO Choice test (n=12-16 reps^) ^Only in 8 reps with Trachymela sloanei was there no sig difference in attack

Conclusion on risk to non-targets  No non-target beetles feed on any NZ Myrtaceae  Eadya parasitoids show little interest in non-target except Trachymela and Paropsis that both feed on Eucalyptus leaves  All beetles on Eucalyptus leaves in NZ are pests  Some physiological effects (mortality) on sub-alpine native beetle Allocharis attack from no-choice 24 hour assay, but larvae ignored in two-choice petri dish tests  Cannot rule out that Eadya will reach sub-alpine areas, but without presence of Eucalyptus or paropsine hosts, believe they will move on, not stay and unlikely to search non-Myrtaceous plant species.

Minimal Risk to Non-targets

CLIMEX Composite Match Index for Eadya Tasmania cf. NZ -minimal overlap Larger native beetle species have been collected from alpine peaks such as: Mt Arthur, Gordons Knob, Mt Cook village, Mt Earnslaw, Ben Lomond, Mt Dick, Arthur’s Pass, Old Man Range ( )

Introducing Eadya will significantly increase P. charybdis larval mortality  This is what a sustainable eucalyptus forest industry needs > 90% survival ~ 9% survival

So benefits outweigh risks of introducing this parasitoid, Eadya daenerys  Biocontrol is environmentally sustainable method of pest control  Previous biocontrol agents have controlled the second generation of the pest Eucalyptus tortoise beetle  Eadya daenerys will reduce larval survival in first generation  It is specific in Australia to some Paropsis and Paropsisterna beetles (known as “ paropsines ”)  Eadya daenerys could prevent $7.2 million in yield losses per year from damage to susceptible Symphyomyrtus species  Sustainable control will reduce spraying, better for environment  Economic benefits outweigh any potential risks to air, soil, water, testing reveals a very low risk to any non-target beetles

Acknowledgements  Sustainable Farming Fund (MPI)  Scion SSIF (core funding)  NZ Farm Forestry Association: Dean Satchell  Speciality Wood Products Partnership  Southwood Exports Ltd: Graeme Manley  Oji Fibre Solutions: Adam Mills, David Fox, Richard Sherratt  Scion Forest Protection staff: incl. summer students, co-funded by University of Waikato  Uni of Tasmania: Geoff Allen, Bek Smart, Vin Patel, Steve Quarrell, Karina Potter  Helen Nahrung and Owen Seeman  TasForests, iFarm, PF Olsens for access to sites  Forest Owners Association  Landcare Research: Rich Leschen, Hugh Gourlay, Chris Winks, Paul Peterson  AgResearch: Mike Cripps

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