PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Management (IDM)
Are you a commercial grower or home gardener?
1. Access/prepare a plan that fits your situation. If
large or protected trees are involved, check
environmental legislation, tree preservation orders,
health and safety regulations, etc. Obtain advice from a
qualified arborist as trees may fall over and there may be
public and personal safety issues.
2. Crop, region. Recognize variations.
3. Identification of wood rot and its extent must be
confirmed. In the absence of obvious fruiting bodies,
consult an arborist or diagnostic service (page xiv).
4. Monitor or have a qualified arborist monitor all
suspect trees regularly trees for fruiting bodies,
evidence of canker diseases, insect borers, termite
damage, pruning wounds, especially after stormy
weather or prolonged drought. Keep accurate records of
soft dry wood in fallen branches, etc.
5. Threshold. For large trees where there is a risk that
they may fall, there is a nil threshold. What is you
threshold, eg economic, aesthetic, environmental?
6. Action. Follow recommended safety regulations
for trees at risk. For other trees perform
recommended cultural and sanitation measures. All
trees should receive regular maintenance.
7. Evaluation. Review your program to see how well
it worked. Compare records from year to year; make
improvements or seeking advice when necessary.
Control methods
Control in living trees can be difficult. Seek advice
for your particular tree. Wood rot takes a large annual
toll of trees, much of which could be prevented.
Legislation
Safety. If the tree is large and the trunk decayed to
the extent that the tree may possibly blow over and
damage personnel or property, or fruiting bodies are
present on the trunk, it should be removed.
If there is any doubt. about a tree’s safety,
seek advice from a professional arborist.
If the tree is small (less than 3 metres tall) and the
trunk has extensive decay, eg Prunus spp., fruit
trees, wattles, it is often not possible to save them and
they can be removed.
Control of wood rot is often impractical except if
identified at an early stage, badly infected trees are
best removed before it infects others.
Cultural methods. The best treatment for all
tree problems is to ensure that the trees are as healthy
as possible (Alan Mann, Canopy Tree Experts, ACT).
Maintain/improve tree vigour to reduce stress
by mulching, fertilizing and watering. Avoid stress
and ensure trees are established properly.
– After tree surgery fertilizing and watering will
assist new bark to quickly cover the wound.
– Aerate compacted soil around trees by digging lightly
with a fork. protect root zone from compaction.
Avoid parking underneath trees, dripping oil, etc
– Avoid injury to trunks and roots and mulching
around trunk bases.
– Correctly space of groups of trees in amenity
plantings. In forestry stocking density is used to
manipulate branch size; minimize wounding during
forestry operations. Forestry operations can be timed
to coincide with low levels of inoculum.
Minimize sunburn injury to trunks/branches by:
Avoiding reflective mulches.
Pruning appropriately to shade limbs and trunk.
– Controlling diseases and pests (if applicable) to
prevent leaf fall in summer.
– Applying flat white plastic paint reflects the sun.
Have a plan to replace ageing trees because like
us they do not live forever.
Sanitation
Remove old tree stumps and roots before
replanting a site or orchards in bushland.
Avoid wounding bark with lawn mowers and
whipper-snippers.
Decayed trees near houses should be pruned or
cut down. Remove sick or dying trees and dead
stumps to reduce food sources.
Pruning.
– Prune when weather is to be dry for more than 24
hours, avoiding periods of rapid vegetative growth.
For silver leaf prune in late summer or early autumn
as trees are less susceptible at this time.
– Avoid leaving long pruning stubs without buds.
– Prune deciduous plants while dormant.
– Prune storm-damaged trees to remove badly
damaged branches. Branch pruning removes stress
on the root system of trees and shrubs on poor sites
and favours rehabilitation.
– Cut off and burn all dead wood and rotted limbs to
prevent wood rot fungi growing on dead wood.
– Trim all wounds including pruning wounds
carefully using a clean sharp implement. Cut wound
cleanly at an angle to encourage bud development
and favour healing.
– Prune trees carefully at collars and shape young
trees carefully to avoid large pruning cuts.
Limbs. Cut off affected branches well below the
decay, preferably just beyond the ridges or shoulder
of bark where the branch meets the trunk or another
large branch, leaving as small a scar as possible, so
that callus tissue will grow quickly over the
exposed wood.
Trunk. Attempts to save severely affected trees
can be made by careful tree surgery, eg
– Chisel back to healthy wood and bark and burn
excavated material. Clean wounds by cutting off
torn bark so there is a neat smooth surface for
callusing. Avoid large pruning cuts if possible.
– Drain hollows in stems which hold water.
Biological control
Overseas, Rotstop (Phlebia gigantea) targets
Heterobasidion annosum in trees and BINAB T
(Trichoderma harzianum and T. polysporum) targets
wood decay fungi (Agrios 2005).
Resistant varieties.
Species vary in susceptibility. Match species to site.
Avoid using susceptible trees as windbreaks.
Plant quarantine.
Many wood rot fungi occur overseas, eg inocutis stem
rot (Inocutis spp.) which attacks many species
including grapevines, eucalypts and wattles.
Physical & mechanical methods.
Use only properly composted potting mixes from
reputable sources for potted plants. The fruiting bodies
in potting mixes will disappear when all food sources
in the mix has been used by the fungus.
Fungicides
Disinfect tools when moving from plant to plant.
Wound treatments. Tar-based pruning paints are
available but not commonly used as water may
collect underneath the painted surface. However,
where wood rot is prevalent on susceptible trees in
commercial orchards, cuts larger than a 50c piece,
prescribed wound treatments within hours of
pruning, may reduce incidence in some species, eg
– Garrison Pruning Wound Dressing Fungicide
(cyproconazole + iodocarb) for the prevention of
silverleaf fungus (Chondrostereum purpureum) on
pruning wounds and wind damaged limbs of apples,
apricots, peaches, plums and ornamentals.
– Seek advice regarding wound treatments for your
situation.
Fungal diseases - Examples of fungal diseases 363