8 Weeds Management
8 Weeds Management
8 Weeds Management
CONTENTS
8.1 WHAT IS A WEED?..........................................................................................8.2
8.2 THE IMPACT OF WEEDS IN COASTAL ENVIRONS...........................................8.2
8.3 HOW DID THE WEEDS GET THERE? ...............................................................8.2
8.4 RATING OF WEEDS.........................................................................................8.3
8.5 TYPES OF WEEDS ...........................................................................................8.3
8.6 WEED REMOVAL TECHNIQUES.......................................................................8.4
8.6.1 Physical/manual control .....................................................................8.5
8.6.2 Biological – introduction of natural predators or disease ....................8.7
8.6.3 Ceasing irrigation...............................................................................8.7
8.6.4 Chemical control – the use of herbicides ...........................................8.7
8.7 DISPOSAL OF WEEDS .....................................................................................8.9
8.8 SAFETY ..........................................................................................................8.9
8.9 WEED MANAGEMENT STRATEGY .................................................................8.10
8.10 COASTAL WEED SPECIES ..............................................................................8.10
8.11 DESCRIPTIONS OF THE “TOP TEN” WEEDS FROM EACH
OF THE COASTAL REGIONS .........................................................................8.11
FIGURES
Figure 8-1 Examples of Tetragona decumbens providing a functional role ...........8.2
Figure 8-2 Hand pulling......................................................................................8.5
Figure 8-3 Ringbarking .......................................................................................8.5
Figure 8-4 Slashing .............................................................................................8.6
Figure 8-5 Topping .............................................................................................8.6
Figure 8-6 Solarisation ........................................................................................8.6
Figure 8-7 Suppression .......................................................................................8.6
Figure 8-8 Foliar spraying ...................................................................................8.8
Figure 8-9 Drilling (or chip/cut) and injection.....................................................8.8
Figure 8 10 Wiping...............................................................................................8.8
Figure 8-11 Cutting and painting .........................................................................8.8
Figure 8-12 Top ten environmental weeds for each coastal region .....................8.11
TABLES
Table 8-1 Rating of weeds .................................................................................8.3
Table 8-2 Summary of weed control techniques................................................8.9
“A weed is defined as a plant which has, or has the potential to have, a detrimental effect on economic, social or
conservation values.” (Definition adopted in WA.)
Coastal weeds fall into the category of environmental weeds. They occupy a unique niche in a harsh
environment with a limited number of competitors. They have developed survival mechanisms to allow them
to cope with the extreme coastal elements such as wind, low nutrients, salt, lack of protection and water. Some
coastal weeds stabilise mobile dunes, thus preventing the damaging effects of natural processes, such as sand
movement, from engulfing infrastructure. The function of a weed in an ecosystem needs to be considered when
deciding on a course of management and
control of weeds in the coastal zone.
• Past coastal rehabilitation efforts have introduced, for example, Marram grass, Pyp grass, Victorian Tea
Tree and Spinifex sericeus.
• An altered environment, for example increased nutrients and water, may encourage the germination and
growth of weeds that otherwise wouldn’t be have been able to grow in the coastal environment.
• Where there is access for people, vehicles and animals, there is access for weeds.
1 High – invasive weed with a wide distribution and Prioritise control, seek funding to
environmental impacts ensure control
4 Low – a weed that is neither invasive, does not Low level of monitoring
have a wide distribution nor impacts
the environment.
The Environmental Weed Strategy for Western Australia (EWSWA) uses three key criteria to rate weeds:
invasiveness, distribution and environmental impacts. The three key criteria can be applied to any weed
species found on the coast to provide an indication of management response required and which ones to
tackle first (Table 8-1).
The control of invasive weeds can vary from site to site depending on the conditions present at the site and
the seriousness of the particular weed species that is being tackled. Guidelines for weed control are based on
generalisations about the occurrence of the weed species and its growth habit. Many weed species will fall
into more than one of the following categories depending on the stage of growth the plant is at.
Woody trees
The removal of the adult tree may only be half of the issue dealt with when removing woody weeds. Many
woody weeds, for example the Victorian Tea Tree (Leptospermum laevigatum), produce thousands of viable
seeds. Removing the adult only provides space for ‘kids’ to take over from where the parents left off. Being
able to identify the seedlings and remove them before they flower is paramount for successful eradication.
Herbaceous plants
Herbaceous plants make up the vast majority of coastal weeds. They are not woody and can be broad leafed,
succulents or fleshy plants.
Grasses
Grasses are narrow leafed plants that have a variety of growth forms, they can form distinct clumps, for
example veldt grass, or they may be more spreading, such as couch, or pyp grass. Small clumps of grasses
can be manually removed; distinct patches of spreading grasses can be successfully killed by solarisation (see
section 8.6.1). It is important to note that some grasses found along the coast such as Marram grass and pyp
grass have been planted to stabilise dune blowouts and any removal strategy should have an immediate
erosion control strategy in place.
Cultivating
Cultivating is the turning over of the soil to bury and kill
1. Dig down weeds. However, in some cases, it may have the
3. Pull upwards
tap root intact
opposite effect of chopping up and spreading
propagules. It is important to know what you are
dealing with before this method is used.
Hand pulling
Hand pulling is the most environmentally friendly and
2. Loosen soil labour intensive method of weed control. It requires the
use of many hands. The key to hand pulling is to remove
the entire plant, ensuring propagules are not left behind
to prosper.
Hand pulling
Figure 8-2
Hand pulling.
Ringbarking
Ringbarking involves cutting away a complete ring of bark from
a tree trunk, which prevents movement of nutrients from the
roots to the leaves.
Figure 8-3
Ringbarking.
Slashing
Slashing involves mowing down, or Figure 8-4
brushcutting, aboveground biomass. It is
very useful for the removal of flowers and
seed heads but is rarely useful on its own.
Topping
Topping is cutting the top off a plant. For
woody weeds this maybe done with a
chainsaw or handsaw, and for smaller Slashing.
herbaceous weeds it can be done with
secateurs.
Solarisation
Solarisation is smothering with plastic
sheeting until seeds or plants have been
cooked. Solarisation to kill weeds and sterilise
soil can be achieved by laying good quality,
Figure 8-5
UV resistant black plastic sheeting over areas
of low weeds or newly turned soil and leaving
Topping.
undisturbed for 2-3 weeks. For best results
the black plastic should be in direct sunlight
and the soil should be damp. This
encourages the weed seeds to germinate,
after which they die due to the high
temperatures under the plastic. The best
success is achieved during summer and early
autumn.
Figure 8-6
Residual
These herbicides remain active in the soil and are absorbed into the plant by the roots. They are not
recommended for areas to be planted or direct seeded. An example is Ronstar®.
Contact
These herbicides only kill the plant material they come into contact with. Not effective for plants with
underground propagules such as bulbs, rhizomes or stems. An example is steam, Basta®.
Translocated
The most commonly used herbicide, this chemical is translocated into the roots of the plant killing the above
and below ground parts. An example is Roundup ® or glyphosate)
Selective
Examples of selective herbicides are Verdict® and Fusilade®. They are very useful especially for targeting
grasses in native vegetation. Low concentrations of some of the hormone-based herbicides containing
2,4-D amide, for example Ally® and Brushoff® can also be safely sprayed amongst native vegetation without
killing it. The key coastal weeds these herbicides target are Bridal Creeper and Pelargonium.
As a precaution native vegetation, especially seedlings, should be guarded from direct spray.
Herbicides should always be used as per specifications on the Material Safety Data Sheets (MSDS)
supplied with all herbicides. Off label licenses for the use of some herbicides can be issued. Further
information can be obtained from Department of Agriculture.
A herbicide training course detailing the use of herbicides should be taken before using any herbicides.
These training courses may be available through your local Landcare Centre or TAFE college.
The use of some herbicides is restricted and may require a licensed operator to use them.
Herbicides can be applied in a number of different ways. These are demonstrated by the diagrams below:
Figure 8-8
Foliar spraying.
Figure 8-9
Figure 8-10
Wiping.
Figure 8-11
Pull all year all year all year all year all year all year
NB Seasonal timing for the southern temperate zone. Check growth and flowering times of individual species to
ensure weeds are targeted at the optimum time.
Large volumes of material such as tree branches that have to be carried through the bush for disposal should
be placed onto a tarp and wrapped up while being carried to the disposal site ensuring no litter is dropped
en route.
8.8 SAFETY
Protective clothing, sturdy shoes and gloves should always be worn when undertaking bushland work. Wear
glasses/goggles when removing spiny plants. Wear the appropriate protective clothing, such as chaps,
goggles and gaiters, when using motorised equipment or handling chemicals. Protect yourself from the sun
by wearing sunscreen, glasses and hat. Always have plenty of water nearby, and a first aid kit on hand.
A checklist of key considerations for developing a weed management strategy for an area is provided below:
1. Identify weeds at the site
A herbarium (pressed plants) or photographic records can be helpful. Being able to identify weed
seedlings will also be extremely helpful.
2. Map weed infestations
See the Environmental Weeds Awareness Network (EWAN) web site for techniques.
3. Determine the weed species that represent the most serious threat
Weeds that are the most serious threat can be determined from the following criteria:
• Invasiveness – based on how it reproduces
• Distribution – how widely is it distributed?
• Impact – is it displacing native vegetation?
4. Work from light infestations to heavy infestations
Once the distribution of the weeds has been identified, it will be possible to identify a starting point for
weed control using the principle of working from light infestations to heavy.
5. Draw up a calendar for the timing of weeding events
This should include:
• the best timing to undertake control for the individual species to be targeted (i.e. spraying prior to
seed set, or hand pulling of seedlings after spraying). This will identify a suite of weeds that can be
targeted at a particular time.
• how weeding activities fit in with other activities at the site, such as plantings, or stabilisation work
• a scheduled follow-up program
• identifying the weeds that require chemical spray, such as Pelargonium and scheduling these activities
before hand weeding of seedlings should be considered.
Weed control is an ongoing task and will always require follow-up to ensure success. This should be recorded
on the calendar.
Figure 8-12 Top ten environmental weeds for each coastal region
Shark Bay
Cape Naturaliste
Images of the individual weed species used in this section of the manual were generously provided by
the Plant Protection Society of WA (Inc.) from the book Western Weeds –a guide to the weeds of Western
Australia which was compiled with the assistance of the Gordon Reid Foundation for Conservation.
The Western Australian herbarium’s FloraBase, was used to check current species names and status as an
exotic species.
Comments
No specific information available on control for this species. Suggest hand
pulling for small plants. Wear gloves as sap may cause skin irritation. Fleshy
herbs tend to respond best to low concentrations (20mL in 10L of water plus
0.25% wetting agent) of hormone based herbicides such as 2,4-D amine.
Comments
No specific information available on the control of this species. Suggest
solarisation, hand pulling for small plants, slash to remove flowering heads
prior to seed set or foliar spray Glyphosate (50mL in 10L) when actively
growing prior to flowering.
Comments
Marram Grass has historically been planted to stabilise dune blowouts and aid
in sand accumulation. Care should be taken to ensure the removal of the
Marram Grass does not cause further degradation of the dunes. Methods for
controlling this species include foliar spraying with either Glyphosate or one of
the selective grass herbicides or solarisation. Once killed the below ground
biomass should be left in place (as it will continue to provide dune
stabilisation) while new vegetation cover is established.
Low growing herb usually found in wastelands and cultivated areas. 0.03 to 0.3m.
Distribution Cen, SWC, SC
Form Herb
Lifecycle Perennial
Flowering Flowers yellow with black centres, Aug. to Nov.
Comments
Cape weed readily invades bare and overgrazed areas. Control methods
include solarisation, hand pulling, repeated slashing to remove flowering
heads prior to seed set, and foliar spray using Lontrel® or Glyphosate (100mL
in 15L of water). The related plant Arctotheca populifolia (Beach Daisy) can
be treated using the same techniques.
Blue green spiny thistle with poppy flowers and yellow sap.
Distribution Gas, Cen, SWC,
Form Herb
Lifecycle Annual
Flowering Yellow, orange or white flower, Nov. to Feb.
Comments
Noxious weed in WA. Control of young plants can be achieved by solarisation,
hand pulling and repeated slashing prior to seed set. Chemical controls
include; hormone-based herbicides (2,4-D amide) for young plants in
bushland and Glyphosate in non-selective areas.
Comments
Biological controls have been developed for this species, which interfere with
the growth, thus weakening the plant and making it more susceptible to
chemical treatments. This species can be successfully eradicated by foliar
spraying with a hormone-based herbicide. Ally ® or Brushoff ® (0.1gm in 10L
water plus 25% wetting agent) prior to flowering. Experimental applications
of a mixture of glyphosate and brushoff have been used to successfully
eradicate bridal creeper from bushland areas in Perth (Kings Park and Bold
Park).
Comments
Selective grass herbicides can be used on Bromes. Foliar spray before flowering
using Fusilade® or similar (at a rate of 2L per ha). Small populations can be
controlled using solarisation or hand pulling. The seeds have sharp bristles
that can pierce the skin.
Lobed wavy leafed, succulent, low spreading herb. Found on beaches and seashores.
Distribution Gas, Cen, SWC, SC
Form Herb
Lifecycle Annual
Flowering Four petalled white, pink and purple flowers, Jan. to Dec.
Comments
This species is considered beneficial in some situations as the roots bind sand
dunes. The control of this species is usually dependent upon the immediate
replacement with local species. Control by hand pulling or with selective
herbicide such as Metosulam ®. No application rates suggested. This species
is similar to Cakile edentula (American Sea Rocket), which can be treated in
the same manner.
Comments
Buffel grass is considered a valuable feed for cattle in the north. However, it
produces allelopathic substances that prevent the germination and growth of
native plants in coastal and bushland environments. It may be difficult to
control using manual techniques due to the vigorous growth once it is
established in an area. Foliar spray with Fusilade ® or Glyphosate (20mL/10L)
when actively growing. Related grasses that can be treated in a similar
manner include Cenchrus setiger (Birdwood Grass), C. echinatus (Mossman
Grass).
Tufted grasslike herb with low growing stems that root at the nodes.
Distribution K-P, Gas, Cen
Form Grass
Lifecycle Annual and perennial (rarely)
Flowering Green with purple flowers, Jan. to Aug.
Comments
Noxious weed in WA and NT. It is an aggressive pioneer plant that readily
establishes in denuded areas. The spines can cause foot injury in recreation
areas and can cause eye, mouth and foot injuries in dogs and horses. It may
be difficult to control manually due to sharp spines. Foliar spray with Fusilade
® or Glyphosate (20mL/10L) when actively growing prior to seed set. It is
important to eliminate all plants in the area as the masses of seed produced
by a single plant are readily spread by the wind. Related grasses that can be
treated in a similar manner include Cenchrus setiger (Birdwood Grass), C
ciliaris (Mossman Grass). See Queensland DNR fact sheet for more
information on Mossman Grass.
Comments
This species is similar to the other Cenchrus species. May be difficult to control
manually. Foliar spray with Fusilade ® or Glyphosate (20mL/10L) when
actively growing.
Comments
Listed as a weed of national significance. Boneseed was planted in the Eastern
States during the 1950s and 1960s to stabilise sandy areas. It produces toxins
from the leaf litter and fruit that inhibit germination and the vigour of
neighbouring plants. Two biological controls have been developed for this
species: Bitou tip moth and a rust fungus. Hand pull seedlings; larger shrubs
can be cut and painted with glyphosate. Cut material should be burnt on site
to prevent seeds being spread.
A leafy hairy erect plant usually less than a metre tall, with fluffy seed
heads.
Distribution K-P, Gas, Cen, SWC, SC
Form Herb
Lifecycle Annual or biennial
Flowering White to yellowish flowers, Sept. to May
Comments
Hand pull and bag prior to seeding. Gloves should be worn as the sap causes
skin irritation. Foliar spray with Glyphosate (10mL in 10L). This species may
naturally decline with heavy plantings of native species.
Comments
Pyp grass was introduced and planted for erosion control on beaches.
It can spread between 4 and 9m per year. Hand pulling should be avoided as
the pulling up of the vigorous rhizomes will severely disturb the site and
possibly lead to erosion. Solarisation can effectively kill Pyp Grass. Foliar
spraying with Glyphosate (20ml per L with 25ml of wetting agent).
Comments
Hand pull small infestations. Foliar spray using either a selective herbicide
Fusilade® (2L per ha) or Glyphosate (20ml per 10L).
Erect bushy herb 0.2 to 0.6m grows in white beach sands and dunes.
Distribution Cen, SWC, SC
Form Herb
Lifecycle Annual
Flowering Yellow to green flowers Oct. to Jun.
Comments
Care should be taken when handling any of the Euphorbias as the milky sap
irritates the skin and may cause temporary blindness if it gets into the eyes.
Foliar spraying using hormone herbicide such as 2,4-D amine (0.05g in 10L
with 10ml of wetting agent). Mechanical slashing is not recommended due to
increased possibility of contact with the toxic sap.
Comments
Care should be taken when handling any of the Euphorbias as the milky sap
irritates the skin and may cause temporary blindness if it gets into the eyes.
Foliar spraying using hormone herbicide such as 2,4-D amine (0.05g in 10L
with 10ml of wetting agent). This small Euphorbia can be effectively controlled
using solarisation.
Comments
Geraldton Carnation Weed is a noxious weed of WA and SA. Care should be
taken when handling any of the Euphorbias as the milky sap causes skin
irritation and may cause temporary blindness if sap gets into the eyes. Manual
removal should ensure the entire root system is removed. Slashing is only
effective after seeding. Seeds can not germinate if buried deeper than 5cm in
the soil. Foliar spraying using hormone herbicide such as 2,4-D amine (0.05g
in 10L with 10ml of wetting agent).
Comments
Bellyache bush is shallow rooted and can be effectively removed by hand
pulling. Care should be taken as the sap may cause skin irritations. Foliar spray
using 2,4-d amine (Brushoff® 10g/100L plus wetting agent).
Comments
Slash or fell thickets, then burn when dry. Alternatively remove all brush from
the site immediately as the seeds are released from the capsules upon drying.
Foliar spray regrowth with Garzon® (100mL in 10L water plus 25mL wetting
agent). Herbicide mixed with diesel sprayed onto the lower trunk is reported
to kill trees. Landcare groups in Esperance have used a Glyphosate soaked
sponge attached to the tree using a wire clip to successfully kill trees.
Comments
Boxthorn was introduced as a hedge plant. It readily regenerates from pruning
fragments. Manual removal is difficult because its thorny seedlings tend to
break off and regrow from the root. Cutting and painting with 1L of Garlon ®
in 30L of diesel has achieved effective control. Successful eradication has also
been recorded for thickets that have been removed using a bulldozer followed
by spraying of regrowth with Glyphosate for up to three years.
A number of alternative chemicals are registered for the control of Boxthorn
(some information is contained in a Queensland DNR Fact sheet).
Erect herb 1 to 3m
Distribution Cen, SWC, SC
Form Herb
Lifecycle Biennial
Flowering Blue-Purple flowers, Aug. to Dec.
Comments
There are a number of Malvas that are weeds of the coastal zone and islands
of WA. Manual removal must ensure the removal of the taproot. Malvas can
be difficult to control using herbicides. Chemical control using Glyphosate
(20mL per 10L water) should be applied as soon after the second leaf stage
as possible. Larger plants can be cut and painted.
Low growing herb covered with large glistening wart on the leaves and stems 0.05 to 0.15m
Distribution Cen, Esp
Form Herb (succulent)
Lifecycle Annual/Perennial
Flowering White flowers with many thin petals, Sept. to Dec.
Comments
Ice plant is difficult to control. As this species holds its seeds until the onset of
rain, manual removal strategies should be undertaken in summer before the
seed is released. However, the fractious nature of the vegetative structure of
the plant makes it difficult to remove manually. Solarisation may be successful.
There are no specific recommendations for herbicide control of this species;
most succulent species can be controlled using a hormone-based herbicide
(e.g. 2,4-D amine). Herbicide control should be undertaken well before seed
set. This species may be the only soil stabiliser in erosion-prone sites; ensure
site is suitably stabilised immediately following treatment.
Spiny shrub or tree with zigzagged drooping branches up to 8m; can form dense thickets.
Distribution K-P
Form Tree
Lifecycle Perennial
Flowering Flowers yellow and orange, Mar. to Dec.
Comments
Manual removal is effective. Larger trees can be cut and painted using a
hormone based herbicide. Smaller trees and seedlings can be hand pulled.
Removal may encourage seed germination so a follow-up visit to remove the
seedlings will be necessary. Herbicide control using foliar spray (using 2,4-D
amine) or cut and paint immediately (within 15 seconds) using Tordon®.
Three species of insects have been introduced as biological control agents.
Contact CSIRO for further information.
Comments
Cut or scrape and paint with glyphosate; small seedlings may be hand pulled
or spot sprayed.
Comments
Large infestations can be sprayed initially with 2,4-D amine (10mL in
10L water plus 25% wetting agent) followed up with hand removal of new
seedlings. Manual removal of larger plants is rarely successful as stems and
underground parts readily regenerate.
Comment
Mesquite was deliberately introduced as a shade tree around homesteads. The
seed is long-lived and may remain dormant for years. Cut and paint
(immediately within 15 seconds) larger trees; small seedlings may be hand
pulled or spot sprayed. Plants bearing pods should not be sprayed. See
Queensland DNR Fact Sheet.
Comments
Small plants and infestations can be controlled by hand pulling. Foliar spray
using glyphosate (10ml in 1L of water).
Tree to 10m.
Distribution Gas, Cen
Form Tree
Lifecycle Perennial
Flowering Pink and white flowers, Feb. to May
Comments
Mechanical removal using a dozer can be very effective. Suckering from the
roots usually only occurs where the roots have been exposed and worn down
such as on paths and roads. The most effective method for chemically
controlling Tamarisk is to make incisions around the entire trunk of the tree
using a small hatchet and filling the incision with Tordon (50% solution).
Comments
Solarisation, hand pull, foliar spray using glyphosate. This species may
naturally decline with the planting of native vegetation.
Comments
Solarisation, hand pull, foliar spray using glyhposate.
Comments
Foliar spray with Brushoff®. This will require several applications.
Try to spray before flowering to stop seed set. In wetland areas only use
Biactive Roundup®. Manual removal has proven to be ineffective.