Risk of Eucalyptus tortoise beetle control

Jon Sullivan Jon Sullivan

Biology of the pest in NZ

Adults and larvae strip all

flush, young leaves from

hosts

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

Egg parasitoids Enoggera

nassaui and Neopolycystus

insectifurax provide good

control of 2nd generation

eggs in NZ:

Egg survival 4%

Egg survival 95%

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

range, and number of species.

Since 2000 reared thousands of leaf

feeding caterpillars and 2700 Gonipterus

larvae (weevils) reared – no Eadya

Results in Sharanowski

et al. 2018

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

Spins cocoon in soil

Overwinters until emerges as an

adult following Nov-Dec

Eadya only reared from 4

Paropsis and Paropsisterna

beetles in Australia

Approx 10mm long

Photo: Anthony RiceDescribed in Ridenbaugh et al 2018

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

relationships

between target and

non-targets

Chrysomelidae

Chrysomelinae

Chrysomelini

Paropsis charybdis

Trachymela sloanei

Dicranosterna semipunctata

Phyllocharitini

Allocharis tarsalis

Chalcolampraspeculifera

Gonioctenini

Chrysolina abchasica

Gonioctena olivacea

Galerucinae

GaleruciniLochmaea suturalis

AlticiniAgasicles hygrophila

Cassidinae CassidiniCassida

rubiginosa

CriocerinaeNeolema ogloblini

Exotic pests

Largest

endemic

chrysomelines

Beneficial

weed

BioControl

Agents

Eadya target is Paropsis charybdis the

largest of the invasive pest paropsines in

NZ

Phylogenetically closest relatives exotic

pests in NZ, subfamily Chrysomelinae: –

tested 2 largest out of Paropsisterna

spp., Trachymela spp. (paropsines),

Dicranosterna, Peltoschema

Endemic species in subfamily

Chrysomelinae - tested 1 we located –

Allocharis. Also searched unsuccessfully

for Chalcolampra, & Caccomolpus.

Undertook host testing (Appendix 5)

Dicranosterna Trachymela

Allocharis

Paropsis

Beneficial weed biocontrol agents in

subfamily Chrysomelinae – tested 2:

Gonioctena olivacea on Scotch broom,

and Chrysolina abchasica on Tutsan.

Beneficial weed biocontrol agents in

sister subfamily Galerucinae – tested 2:

Agasicles hygrophila on Alligator Weed,

and Lochmaea suturalis on Heather

Beneficial weed biocontrol agents in

unrelated subfamilies – tested 2:

Neolema ogloblini on Tradescantia

(Criocerinae), Cassida rubiginosa on

Californian thistles (Cassidinae).

…host testing continued

Chrysolina Gonioctena

Neolema Cassida

Agasicles Lochmaea

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:

• Paropsis charybdis target pest 34+% (n=120)

• Trachymela sloanei 12.5% (n = 5 reps)

Non-viable parasitism found only in

Chrysomelines, after larval dissections

• 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)

Paro

psin

es

Chry

som

elin

es

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

Predicted

minimum

host size

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.

Ho

sts

Non-

Hosts

Paro

psin

es

Chry

so

me

line

s

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)

Attack rate (number stings per minute)

when given a CHOICE significantly less

than against P. charybdis

Number of ovipositor-insertions per minute

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

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 ( )

CLIMEX Composite Match Index for Eadya Tasmania

cf. NZ

-minimal overlap

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

www.scionresearch.com

Scion is the trading name of the New Zealand Forest Research Institute Limited

Prosperity from trees Mai i te ngahere oranga