Peri-urban environments: The ‘X Factor’ for plant pests

and diseases

David Williams, Jacky Edwards, Greg Lefoe, Ian Porter,

Brendan Rodoni & Alan Yen

What am I talking about?

• Definitions of per-urban

• Implications for biosecurity

• Some case studies

• Concluding remarks

Peri-urban areas

• Delineation difficult

• Victoria – Riverland

– Melbourne hinterland

– Most of eastern Victoria Aslin et al (2004) Bureau of Rural Resources, Canberra

What about Geelong, Bendigo, Ballarat, Wodonga, Shepparton,

Wangaratta, Horsham, etc?

• Urban and rural residential

• Commercial and “lifestyle” hobby farms

• Water catchments and storage

• Other rural industries, including intensive animal

production

• Nature reserves

• Recreation facilities

• Transport routes and hubs

Mosaic

Biosecurity

• Protection of people, farms, animals and plants

from entry and spread of unwanted exotic

animals, pests, diseases and weeds (Maller et al . 2007. Biosecurity and small landholders in peri-urban Australia. Bureau of Rural Resources, Canberra )

• Global peri-urban focus on animal diseases that

could impact on humans but virtually none on

plant pests & diseases

• Hobby farms and consumer demand – New animal and plant industries

– New invasive species

– New pathways to infest commercial farms and environment

• Neglected farms

Biosecurity 2

• Border protection

• Containment & eradication

• Pest infested zones

• Areas of low pest prevalence

• Pest free areas of production

• Pest exclusion zones

• Pest risk zones

Case study: Fireblight

• Bacterial

• Major threat to pome fruit, particularly major

Australian varieties of apple and pear

• Reported in RBG Melbourne 1997

• 1200 host plants removed

• Many high value plants

• Compensation

• Awareness program

Case study: Plum pox

• Virus of stone fruit

• Infects apricots, plums, peaches, nectarines,

ornamental prunus

• No cure except destruction of trees

• Eradicated in Pennsylvania 1999 • 300 sq.mile quarantine zone

• 1600 acres removed

• all prunus within 500m radius of infected tree

• Failure in Canada 2000 • high density of Prunus

• adopted threshold level of infection rather than removal of

trees around infected trees

Case study: grapevine leaf rust

• Private garden grapevine Darwin 2001

• Surveys within 15kms found 45 infected

plants

• Eradication program implemented

• Resistance from some residents • No commercial vineyards in region

• Greek culinary purposes

• Public awareness campaign

• Police escorts for survey teams

• Declared successful 2007

Case study: Myrtle rust

• Potted nursery plants NSW 2010

• Quickly spread to coastal NSW & Qld

• Expected to hit eastern Victoria forests

• 1st detection in Victoria at wholesale nursery in

Melbourne

• Delimitation survey

– Suburban parks and gardens

– Country towns

– Movement of infested nursery stocks

Case study: Oriental fruit moth (OFM)

• Endemic introduced pest

• Known to infest pome & stone fruit overseas

• Had been “restricted” to stone fruit in Australia

• Change of orchard pest management – pheromone-mediated mating disruption replaced pesticides

• Increased populations in pome fruit not treated

for OFM

• Mated females move back into nearby stone fruit

• Farmers & urban residents cooperated

Case study: Elm leaf beetle

Avenue of Honour, Bacchus Marsh, contains

an elm for each soldier from the local area .

(image from http://vegefarmer.blogspot.com.au/)

• Elms are important landscape

trees in urban centres

• Avenues of Honour in country

towns

• Dutch Elm Disease not in Australia

but vectors present

• Elm leaf beetle (ELB) defoliates

elms

• Causes tree stress

• Susceptibility to disease

• ELB hitch hikes on vehicles

• Spraying difficult, expensive, & has potential side effects

Case study: Elm leaf beetle cont.

• Integrated management

• Monitoring

• Biological control

• Safer pesticide application

• Complexity of tree ownership

• Friends of the Elms Inc.

Infested elms adjacent to a busy

urban traffic corridor

Aggregation of beetles sheltering in a log

Case study: Danger of exotic psyllids

• Sap sucking insects capable of transmitting plant viral and bacterial diseases.

• Asiatic citris psyllid (ACP) & Tomato potato psyllid (TPP) are high risk incursions

• Both species can infect commercial crops with bacterial disease

– ACP: Citrus species

– TPP: Solanaceous crops (potatoes, tomatoes, egg plants, capsicums)

Tomato potato psyllid Image: Uni. Nebraska Asiatic citrus psyllid

Case study: Danger of exotic psyllids

• Both species utilise non-commercial host plants

– ACP: Murraya paniculata (ornamental), native Citrus species?

– TPP: about 40 spp of Solanaceous plants (native & exotic)

• Potential entry pathways

– Natural wind dispersal (ACP from Papua New Guinea or Timor

Leste; TPP from New Zealand)

– People (ACP feeds on curry plants and live specimens have been

intercepted at the airports – likely that it could establish in an urban

or peri-urban backyard first)

Concluding remarks • Peri-urban zone

• incursion bridge between urban and rural

• complex nature of land uses

• Owners do not derive main income from property

• Non-commercial farmers not members of industry organisations so

difficult to trace

• Risk zone for establishment and spread before detection

• Informal networks increase risk

• Awareness and education critical

• Social media can help or hinder

• Municipal emergency planning should include biosecurity planning

• Biosecurity response success depends on what intelligence is

available