PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
Brush and woody weeds
Types
Trees and shrubs, introduced and native species have
increased to undesirable densities in some areas of
Australia. They may be agricultural, noxious weeds or
environmental weeds, garden escapes, Weeds of
National Significance (WONS) or other types of weed.
Impact
In central Australia brush and woody weeds can
impact on biodiversity, cause mustering difficulties,
harbour vermin, added expense either maintaining or
relocating fences, roads and waterways, industrial
sites, suppress pasture growth and lower nutritional
levels, hence carrying capacity and production.
Management (IWM)
Are you a commercial grower or home gardener? If
wood weeds are > 3 metres tall, seek advice.
1. Prepare a plan that fits your situation. Weed
Management Systems are available for some woody
weeds, eg bitou bush, and for some situations, eg
plantation forestry (Sindel 2000). Special Taskforces
deal with some woody weeds, eg Aleppo Pine
Management Group in SA, Lantana Taskforce in NSW.
2. Crop, region. Recognize variations.
3. Identification of weed(s) must be confirmed.
Consult a diagnostic service if unsure (page xiv).
4. Monitor weed(s) and impact and record results (page
429).
5. Threshold. How much infestation is acceptable?
Have any thresholds been established? If so, what are
they, economic, aesthetic, environmental?
6. Action. Take appropriate action when any threshold
is reached.
7. Evaluation. Review IWM program to see how well
it worked. Recommend improvements if needed.
Control methods
Legislation. Some woody weeds are declared
noxious weeds, control may be compulsory and the
method of control prescribed by legislation.
Biological control. For some, biological
control agents have been released, eg the blackberry
rust fungus (Phragmidium violaceum). It is hoped
that it will provide some economic control of
blackberry infestations, avoiding the need for
herbicide applications.
Plant quarantine. All plant introductions
should be assessed for their potential to be become
weeds (Weed Risk Assessment) (page 436).
Physical & mechanical methods.
Small infestations of brush or woody weeds can
be dug out diligently over time. Many such weeds
may have large seed banks in the soil.
Fire may be economical and provide effective
control of some seeds, seedling trees and shrubs,
but can only be used occasionally when seasonal
conditions have resulted in buildup of sufficient
fuel. Local Fire Services must be consulted.
Chaining or blade ploughing may increase
production but does not justify cost and may not
be sound environmentally.
Grazing management, eg by goats.
Herbicides.
Local Shires/Administrations have leaflets and
bulletins with recommendations for control. The
following should be regarded as a guide only.
Not all herbicides work against all woody
weeds. Confirm that the herbicide selected is
registered and effective against the problem weed
in your situation.
Depending on the weed species and herbicide
being used, sprays may be applied using knapsacks
or handguns to foliage of young woody weeds evenly
wetting all foliage. Sprays are also applied as basal
bark or soil treatments using spot guns (page 468).
Hack and squirt and stem injection techniques are
also used.
Timing of application is critical, follow label
Directions For Use. Some deciduous woody vines
and rhizomatous perennial weeds are controlled by
late summer or early fall applications – spring
applications may only burn the top of the plants.
Fig. 84. Brush and woody weeds – Some herbicides.
What to use?
HERBICIDES
Group M, eg Roundup (glyphosate)
Soil residuals – for use in certain situations only,
check label Directions For Use:
Group B, eg Brush-Off (metsulfuron-methyl)
Group C, eg Velpar (hexazinone)
Groups I/I, eg Garlon (triclopyr), Grazon (triclopyr +
picloram), Tordon Herbicide Gel, Vigilant
Herbicide Gel (picloram)
When and how to apply?
Apply when plants are growing actively, moist soil.
Use a white or other herbicide marker dye.
Many are soil residuals and should not be applied
near desired plants or in areas where their roots
might extend, or where chemical may be washed
to their roots. Do not use if rain is likely to fall with
12 hours of application. Follow label Directions For Use.
For stem injection to be successful, the herbicide must be
injected into the sapwood (see diagram) immediately after
the cut is made.
Penetrants may aid uptake by woody weeds.
Weeds - Examples of weed situations 467