Phytophthora

Phytophthora cinnamomi is a water-borne soil pathogen that infects the roots and stems of certain susceptible native plants and also introduced plants including ornamentals (lilies, camellias, hibiscuses and rhododendrons), vines (grapes), fruit (avocados pears, apples, citrus, raspberries, cherries, apricots, peaches, olives), nuts (macadamias, chestnuts and walnuts) and vegetables (potatoes)1. It reduces their ability to transport water and nutrients, ultimately leading to plant death. Phytophthora is native to South East Asia and was probably introduced into Australia shortly after European settlement. It is now present in all states of Australia2, but mainly across southern Australia where rainfall zones are within the 400 - 600mm annually.

The pathogen has the potential to significantly impact upon plant communities by modifying floristics and community structure, often leading to local extinctions of populations of susceptible species. There is currently no cure for Phytophthora, so areas that become infested, remain infested. Dieback caused by the root-rot fungus is listed as a key threatening process under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.

P. cinnamomi is known to be a threat to many plant species listed under the EPBC Act, and other species listed as threatened under state or territory legislation are also at risk. See Appendix in Phytophthora Management Guidelines for specific native plant species susceptible to P. cinnamomi in South Australia.

Common signs to look for:

  • Death or deterioration of health of susceptible plant species (eg. Eucalyptus obliqua (Messmate Stringybark), Eucalyptus baxteri (Brown Stringybark), Xanthorrhoea sp. (Yacca), Banksia sp. (Banksia), Isopogon ceratophyllus (Conebush), Leptospermum sp. (Tea Tree), Acacia myrtifolia (Myrtle Wattle), Pultenaea involucrata (Mount Lofty Bush-pea), Acrotriche fasciculiflora (Pink Ground-berry) and species from Fabaceaea (Pea family)
  • Diseased plants with general discolouration of foliage, usually red or yellow foliage
  • Phytophthora resistant species remain unaffected
  • Progression of deaths over time, particularly down slope and an obvious boundary may be apparent between diseased and healthy areas6.

Minimising the spread:

  • Avoid areas of known Phytophthora infestations
  • Stay on designated roads and tracks
  • Obey road signs indicating restricted areas associated with Phytophthora infestation
  • After entering or working in areas of infestation, clean soils from footwear (and/or horses hooves) with a stiff brush and spray with undiluted methylated spirits (see Hygiene procedures table below)
  • Using hygiene stations on tracks/trails where provided
  • Clean machinery and equipment and other tools appropriately before using in other areas
  • Undertake works in Phytophthora infested areas when conditions are driest (avoid winter months)
  • If infestation areas are known, use machinery in areas that are un-infested first, moving to infested areas last, following up with appropriate hygiene measures
  • Avoid excavating in infested areas.

Summary of Hygiene procedures (source: Phytophthora Technical Group (2006) Phytophthora Management Guidelines2):

Items for Management

Hygiene procedure

Disinfectant / rate

Comments

Vehicles, machinery, large equipment

Dry brushing

Disinfection

Phytoclean – 1 part to 50 parts water

OR

Sodium Hypochlorite (pool chlorine) 1 part to 1500 parts water

Pay particular attention to wheels, mudflaps, undercarriage and other areas difficult to access

Remember to disinfect brush or tool used in dry brushing

Small equipment, hand tools, footwear

Dry brushing

Disinfection with spray bottle

1 part household bleach to 4 parts water

OR

Methylated spirits (undiluted)

All soil should be removed before disinfecting

Avoid recontaminating Footwear

Remember to disinfect brush or tool used in dry brushing

Footwear

Dry brushing

Disinfection with footbath

Phytoclean – 1 part to 10 parts water

OR

1 part household bleach to 4 parts water

All soil should be removed before disinfection

Useful for large groups of people

 

The Department of Environment, Water & Natural Resources can provide further information on Phytophthora and how to control it. Download a brochure on Phytophthora here.

1Department for Environment and Heritage (2009) Phytophthora is killing our plants! Fact sheet.

2Phytophthora Technical Group (2006) Phytophthora Management Guidelines - Second Ed. Unpublished report prepared for the Government of South Australia.