Biology 11–12 · Year 12

Response of Australian native plants to Phytophthora dieback: a no-contact field survey

Module 7: Infectious Disease (Responses to Pathogens)

PracticalMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

The idea

A soil-borne water mould kills the roots of susceptible native plants, and the pattern of dieback across a site, mapped without touching or moving soil, shows how the pathogen spreads and which plants respond by dying back.

Safety card

Medium riskA teacher supervises

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

Uneven ground, snakes and ticks in bushland
Sun and heat
Spreading the pathogen on footwear

Controls

Stay on tracks in closed shoes and long trousers; carry a first aid kit
Hats, sunscreen, water
Boot hygiene on arrival and departure; no soil or plant material collected

Note

Excursion risk assessment under the school's outdoor procedures; pathogen hygiene per the Dieback Working Group advice. No cultures or plant material are handled.

What you need

Access to a bushland reserve, botanic garden or school bush regeneration site where Phytophthora dieback is signposted or known to land managers (arranged in advance with the manager)
Site map or a mapping app; clipboards; a plant identification guide for local Banksia, Xanthorrhoea (grass tree) and other species the Dieback Working Group names as susceptible
Camera; tape measure; soil-free footwear hygiene: boot brush and disinfectant station as the site requires
Secondary sources on the pathogen and on the host's response

How to do it

Before the visit, read the site manager's information and the Dieback Working Group hygiene rules: stay on tracks, keep out of quarantined areas, do not move soil or mud.
From the track, identify individual plants of a susceptible species and score each on a four-point scale (healthy, partial dieback, severe dieback, dead); record its position and distance from drainage lines or track edges.
Photograph representative plants at each score; do not collect any material or leave the track.
Note the distribution of scores across the site and relate it to water flow, since the pathogen spreads in water and soil.
Using secondary sources, describe how the pathogen infects roots and how the host responds (root death, reduced water uptake, crown dieback), and compare susceptible with resistant species on the site.
Clean footwear at the hygiene station on leaving.

What you should see

Where the pathogen is active, dieback scores are expected to be uneven: severely affected and dead plants cluster downslope, along drainage lines and near track edges, because the pathogen spreads in water and soil, while plants of the same species upslope score healthier; species the source names as susceptible (banksias, grass trees) show more dieback than co-occurring resistant species. The learner knows it worked when every plant of the chosen species along the route has a score and a mapped position, all recorded from the track.

What changes

What you change: position relative to drainage lines and tracks (and plant species)
What you measure: dieback score per plant
What you keep the same: scoring criteria
observer
season
species compared

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Dieback is caused by drought; the water mould kills roots so the plant cannot take up water even when it is available.
Only sick-looking plants carry the pathogen; infected soil spreads it before symptoms appear.
All native plants are equally susceptible; species differ, which is why the site shows survivors beside dead plants.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Biology Stage 6 Syllabus (2017), current: Year 11 taught to the end of 2026 and Year 12 to Term 3 2027BIO12-14 BIO11/12-1 BIO11/12-3 BIO11/12-4
Biology 11–12 Syllabus (2025), Year 12 focus area Biodiversity; new syllabus not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027BI-12-03
Biology 11–12 Syllabus (2025), Year 12 Working scientifically; new syllabus not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027BI-12WS-01 BI-12WS-03 BI-12WS-04
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

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