PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT POTECTION 1 – Pests, Diseases and Weeds
Management (IDM)
1.Planning. Soilborne diseases generally are
widespread and like other diseases, their control
requires appropriate planning and management.
Most states and territories have management
plans for Phytophthora to reduce its impact
and prevent further spread. Select a program for
managing Phytophthora for your situation, eg
Biodiversity conservation in forests, bush
areas, etc (Management of Phytophthora
cinnamomi for Biodiversity Conservation in
Australia) www.cpsm.murdoch.edu.au/
Nursery Industry Accreditation Scheme
Australia (NIASA) is a national scheme for
production nursery (growers) and growing-media
(potting mix) supplier businesses.
Australian Garden Centre Accreditation
Scheme.
Cutflowers (Phytophthora diseases of cutflower
crops).
Key Avocado Management Issues.
Most states provide information on Phytophthora
management in their region or on certain crops.
Management plans are available for many other
soilborne diseases, eg Total Crop Management -
Clubroot (of Brassicas), Management of Soilborne
Diseases in Vegetable crops (Biological Crop
Protection www.biolcrop.com.au/ ).
Horseriders, bushwalkers, landcare groups.
2.Crop, region. The wide host range of Pc in many
regions means that you must know your crop history
and susceptibility, and your local climatic variations
favouring Pc.
3.Identification by laboratory analysis is essential
to ensure effective control and prevent spread (page
xiv). Pre-plant soil tests can now be carried out
months prior to planting. Any water supplies in
contact with the ground must be suspect, eg dams,
streams, soaks must be tested.
4.Monitor symptoms and, hygiene procedures and
chain of production. Also monitor for the presence of
Phytophthora in water, soil, roots and other plant
material. Record all results. Remember know when,
where, what and how to monitor.
Symptoms. First look at plants closely for evidence
of wilting. Examine indicator plants in bush
areas, eg grass trees (Xanthorrheae sp.). Assess
root health of potted plants, eg closely examine
the collar region and cut into the internal tissue with a
knife to detect evidence of infection, also wash potting
mix/soil from roots and examine them under a
dissecting microscope against a white background,
comparing them with a known specimen of healthy
root material.
If diseased, seek expert testing, as there is
increased detection of new Phytophthora spp.
5.Threshold. This will be determined by relevant
regulations. Beyond that you will have to decide your
own economic, aesthetic or environmental threshold.
6.Action. Take appropriate action when any threshold
is reached. In practice, this usually includes cultural
methods, sanitation (hygiene), quarantine, use of
tolerant rootstock, Pc-free planting material and
media and the application of fungicides.
7.Evaluation. Review the program, compare methods
and results with previous years. Make improvements if
needed, eg ensure planting material is disease-tested,
varieties have some resistance, improve culture and
sanitation, preplant soil treatments, eg solarization, bio
fumigants, water treatments, etc.
Control methods
Control of root diseases is difficult both in the
field and in intensive crop production systems - there is
often a combination of ‘causes’ and therefore a
combination of control methods are required.
Methods used depends on the situation, eg forest,
bushland, cutflowers, nurseries, hydroponic systems,
containers, soil/media, water sources, etc. The aim
being not only to control disease on current crops but
also prevent further spread. It is difficult to eradicate
Phytophthora and other soil diseases from an infested
site especially when perennial crops are grown.
LEGISLATION, REGULATIONS.
The Commonwealth‘s Environment Protection and
Biodiversity Conservation Act 1999 seeks to promote
the recovery of species and ecological communities
that are endangered or vulnerable and to prevent other
species and ecological communities from becoming
endangered. An off shoot of this law is:
A Threat Abatement Plan enables a national
management approach for Dieback caused by the
root-rot fungus (Pc).
Lists of threatened species and ecological
communities have been prepared. Some states have
developed priorities and coordinate management
to limit spread of Pc into area which is Pc-free.
Certification schemes for the production of
Pc –tested planting material and media.
Cultural methods.
Large scale remediation can protect rare taxa and
communities of high conservation value threatened by
nearby Pc infestations. It may involve long term in situ
seed conservation and prioritization of certain species.
Select sites unfavourable to Pc and avoid conditions
favouring disease (page 365). Prepare soil appropriately.
Grow plants in soilless media or hydroponics.
Suppressive compost and mulches are suitable
only for small areas. Marri, karri and other hardwood
bark can be highly suppressive of Phytophthora after
composting. It suppresses weeds and aids soil moisture
retention during summer. Take care not to import
contamination. Add organic manures.
Maintain crop vigour. Plant when temperatures are
favourable for crop growth, not Pc. Seek advice
regarding nutrient requirements for your crop.
Irrigation and drainage
– Design, maintain and monitor irrigation systems
to avoid overwatering throughout the year and
minimize the time soil is saturated. In infected
blocks of trees, adjust irrigation to suit smaller trees.
In greenhouses reduce excess water lying in bays.
– Sub-irrigation may result in spread of motile
zoospores from infected to healthy plant.
– Most serious problem associated with zero runoff
involves Pc. Regulations require zero run-off
for some nursery growers resulting in rapid change
to closed systems of production.
– Use free-draining potting mixes and avoid overwatering.
Improve surface and sub-soil drainage in
poorly drained sites by various means including
planting into raised beds.
– Avoid exposure of susceptible trunks to infection,
eg avoid irrigation spray directly contacting trunks.
– Maintain plantings under sod rather then bare soil;
keep areas at base of trees free from weeds.
Surface water management and drying of sites.
– Avoid ‘balling roots’ in old potting mix during
repotting (page 367).
– Compacted soil could be ripped, mounded beds.
Crop rotation and fallowing.
– Avoid continuous cropping with susceptible hosts.
– Where different species are being planted undertake
risk assessment.
– When replanting understand ‘sick soil syndrome’.
– Consider including a bio-fumigation crop in a rotation
(page 267). Green manure cropping reduces soil
crusting, improves filtration, increases soil organic
matter and reduces subsoil compaction. Brassica
green manure crops produce high concentrations of
bio-fumigants and may improve soilborne disease
management. The native legume (Acacia pulchella)
protects Banksia grandis from infection, suppressing
the fungus in the soil.
Reduced tillage.
– Can encourage some soilborne diseases, eg Fusarium
graminearum, F. culmorum, F. avenaceum of wheat
and Cephalosporium gramineum, Pythium and
Rhizoctonia. Crop residues can maintain the
inoculum of these fungi while fields are left fallow or
sown with a non-host break crop.
– However, long periods (10 years or more growing
seasons) of stubble retention can induce disease
suppression of pathogens such as Rhizoctonia. The
induced disease suppression is thought to be due to
the proliferation of indigenous micro-organisms in the
soil, some of which are antibiotic and antifungal that
prevent the outbreak of pathogenic fungi.
368 Fungal diseases - Examples of fungal diseases