Weeds and Bushcare Issues
The Phytophthora Challenge
Phytophthora (pronounced Fy-toff-thora) is a microscopic organism that lives in soil and plant roots. The name Phytophthora is derived from the Greek meaning 'plant-destroyer'.
Phytophthora causes root rot in a broad range of plant species, including many native Australian and ornamental plants. Around 60 Phytophthora species have been identified, but P. cinnamomi is the species that is most destructive in native Australian vegetation communities.
Grass Trees (Xanthorrhoea species) are highly susceptible to P. cinnamomi which causes dieback as the picture shows.
The following downloadable PDF documents deal with the Phytophthora challenge:
- Facts about Phytophthora
a two-page brochure by the Plant Disease Diagnostic Unit, Royal Botanic Gardens, Sydney.
[ PDF file 237KB ]
- Best Practice Management Guidelines for Phytophthora cinnamomi within the Sydney Metropolitan Catchment Management Authority Area.
... a recent (June 2008) comprehensive document by the Botamic Gardens Trust, Sydney
[ PDF file 304KB ]
- Map of Phytophthora cinnamomi found in Hawkesbury Nepean Catchment bushland.
[ PDF file 1.6MB ]
- Survey of Phytophthora cinnamomi distribution in Hawkesbury Nepean Catchment bushland (June 2008).
[ PDF file 416KB ]
Phytophthora and Bushcare
In September, Dr Edward Liew of the Sydney Royal Botanic Gardens, ran a series of workshops for Council on the management of Phytophthora cinnamomi for staff, bushcare volunteers and other agencies.
Thirty-two bushcare volunteers attended the sessions and contributed to a lively discussion.
What is Phytophthora cinnamomi?
It is a microscopic organism that lives in soils and plant roots. It is a pathogen that infects the root tissue of plants and causes the root to rot.
Secondary symptoms include dieback of major branches, yellowing of leaves and stunted growth. Susceptible plants may die suddenly within weeks, whereas tolerant species may show some wilting of leaves then recover as conditions become less favourable for the pathogen.
How does Phytophthora cinnamomi spread?
Phytophthora cinnamomi thrives in areas with mild temperatures and rainfall above 600mm pa. Spores can spread a few metres a year through the soil or by root-to-root contact. Rapid spread is caused by the movement of infected soil or plant root material. This happens with earthworks, on vehicle tyres, by bike riding, horse riding, bushwalking, dumping of garden waste and also potentially on bush regeneratorsí tools.
What can we do about it?
There are no known methods to eradicate Phytophthora cinnamomi from a site once it is infested. However, we can help to stop its spread into uninfested bushland.
If you donít know whether bushland areas are infected, assume it is clean and take precautions to ensure you are not introducing the disease (adopt hygiene protocols).
If an area shows dieback symptoms notify your Bushcare Officer to arrange to have it tested. As there are other causes of dieback, it is necessary to ensure the cause isnít nutrient runoff, soil toxicity, drought stress or some other problem. Council is looking into developing a capacity to undertake soil testing. At this stage, it is undertaken by the Royal Botanic Gardens in Sydney.
If an infected site is identified, access to the area should be restricted and strict hygiene protocols adopted. There is a chemical which can be applied to protect susceptible species.
Bushcare Officers have started to adopt some basic hygiene regimes whilst seeking more information from the experts and ideas from volunteers.
Basic hygiene protocol for trial adoption:
- Keep vehicles to designated roads and parking areas
- Avoid working or walking in wet and muddy areas
- At the start and finish of a Bushcare session "dry brush" all footwear using a brush then spray with a mixture of methylated spirits (70%) and water (30%)
- At the end of a Bushcare session, tools and mats are to be either cleaned on site or packed in containers/bags to take to an offsite "wash down" area. Clean by dry brushing or washing off soil, then spray with the methylated spirit/water mix. Soil should also be removed from inside tool pouches.
- Gloves should be washed after each site, before re-use.
The detailed report on Best Practice Management Guidelines by the Botanic Gardens Trust was distributed at the workshop. Extra hard copies are available from the Bushcare Office or you can download it here as a PDF file.