Gamba Grass Management Guide
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DEPARTMENT OF LAND RESOURCE MANAGEMENT
Gamba Grass
Management Guide
This guide provides advice on how to manage
gamba grass on your property. The methods
described aim to make control as strategic,
cost effective and efficient as possible.
Description
Gamba grass (Andropogon gayanus) is a highly
invasive grass introduced from Africa. Key
identifying features include:
• tussocks up to 4m tall and 70cm in diameter;
• leaves up to 1m long and up to 3cm wide;
• leaves which stay green after native annual
grasses have died off;
• fine soft hairs on leaves and stems;
• distinctive white midrib on the leaves;
• a wide, shallow root system; and
• a ‘fluffy’ V-shaped seed head.
The problem
Gamba grass was introduced into the Northern
Territory as a pasture grass in the 1930’s.
Ensuing research and trials showed gamba grass
to be a highly productive and palatable fodder.
Subsequently, plantings occurred throughout
pastoral and agricultural areas of the Top End.
Since this time gamba grass has proved to be
highly invasive, establishing in savanna woodlands,
along creek lines, on floodplain fringes and in
disturbed vine thickets. A combination of impacts
on fire regimes, soil nutrient and soil water cycles
are dramatically changing these native plant
communities.
Fire
Gamba grass creates very high fuel loads. This
results in intense fires that destroy native plant
communities. Due to the intense heat and volumes
of smoke produced, gamba grass fires are harder
to control, require more resources and place fire
fighters, volunteers and the public at greater risk.
Gamba grass (Andropogon gayanus)
www.lrm.nt.gov.auJAN FEB MAR
Spray actively growing plants Cool early burns may kill seedlings, reduce seed production Slash/heav
before they seed and improve access for other control methods* plants befo
Step 1 Assess your situation
Draw a map of your property
Include the following:
• the density and distribution of gamba grass (other weeds should also be considered);
• the location of clean (weed free) areas;
• natural variations of the property, including slope, waterways and areas subject to flooding;
• any infrastructure, including fence lines, driveways, yards etc; and
• paddocks, where you intend to actively manage gamba grass pasture (B/C Zone only).
Your map will help to prioritise areas for control, determine a work program and develop a budget.
Step 2 Develop your plan
Determine
Which: management zone applies to your property (see maps on back)
Where: priority control areas are
What: are the most appropriate control method/s for each location
When: the works should be undertaken (refer to calendar on next page)
Who: will conduct the surveys, weed control and monitoring (self, family, contractor, staff)
Your plan should achieve the following management requirements:
Eradicate isolated plants and outbreaks (Class A/C and B/C Zones)
Design and implement a survey and eradication program for gamba grass.
Active containment of major infestations (Class B/C Zone only)
Major infestations, including grazing areas, must be contained through an integrated weed control prog
Boundaries should be mapped (using a GPS) to ensure no spread occurs.
Buffer zones
Buffer zones are required on all properties of more than 20ha in the B/C Management Zone. They mus
minimum width of 40m when adjoining a property in the A/C Eradication Zone. Seed set must be preve
within buffer zones by chemical, mechanical or physical means. Controlled burning or grazing (when in
combination with other control methods) may also be used.
Appropriate land management
Avoid creating conditions which promote gamba grass germination and spread by monitoring grazing
pressure, managing feral animals and controlling erosion and fire where applicable.
Implement early detection and management programs
Regularly monitor/survey land, including previously treated areas, to identify new or re-establishing gam
grass infestations at an early stage.
Prevent/minimise further seed production
Seed production can be suppressed using chemical control and slashing.Gamba grass annual growth and management cycle
R MAY JUN JUL
only) Flowering gamba grass
is sensitive to herbicide
Step 3 Implement your plan
Spread prevention
Spread prevention is the most successful and cost effective way of managing weeds. Always prioritise
eradication of isolated plants/infestations, working back towards major infestations.
Physical control
Individual plants can be removed by hand or by using a mattock. The entire root mat should be removed.
Physical removal is generally only feasible where plant numbers are limited. Slashing infestations prior to
chemical control of regrowth can reduce costs and increase effectiveness.
Chemical control
Chemical control of gamba grass will require at least 2 treatments within a growing season. The initial treatment
of existing plants should occur following rain, when there is active growth. A follow up treatment should be
undertaken in approximately 2 to 4 weeks time.
Fire management*
Gamba grass is extremely fire tolerant. Early controlled burns can reduce potentially dangerous high fuel loads
and can reduce seed production. Burning can also be used to get rid of ‘rank’ growth prior to applying herbicide
to regenerating tussocks. This integrated approach to management will reduce herbicide requirements and
provide better kill rates.
Grazing land management
Pastures should be managed so that seed production is minimised and spread is prevented. Stocking rates
should be maintained at a level which will keep the grass below a height of 60–90cm. Above these heights,
tussocks become woody and unpalatable, enabling the production of large quantities of seed.
Timing of control
Effective weed control relies on undertaking control works at appropriate times during growth and reproductive
cycles. Table 1 indicates when specific control methods should be employed. It should be noted that peak
growth and timing of reproductive events can differ due to seasonal variations, type of environment and as a
result of slashing and burning.
Table 1: Guide to the management of gamba grass
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Flowering
Seed fall
Germination
Slashing
Fire*
Spraying
Approximate times for reproductive events Control option less suitable
Months most suitable for control option specified Control option is not suitableAUG SEP OCT NOV DEC
Spray regenerating plants
and any new seedlings
The benefits of treating gamba grass at an early stage
3.5m
.5m It is very difficult to suf
sufficiently
wet the top part of the plant.
This may lead to potential
pote
0.4m herbicide
herbicide wastage and
he an off
Plants sprayed at this height can
targetet d
et damage.
amage.
be effectively treated in a single
pass with most herbicide hitting
the target.
1.75m
5m
Treatment at 0.4m in height can reduce herbicide
usage by as much as 85%. Effective
ective treatment of this
Effe
fe
part
p rt of the plant will require
pa r
Gamba grass is sensitive to herbicide when flowering. spraying from both si sides of
the plant.
Step 4 Monitor and review
Monitoring will help to determine the effectiveness of control methods, enabling improvements to future weed
management. Consider keeping a diary of control works and weed surveys as they are conducted.
Monitor for new outbreaks
Identify regrowth or new seedlings early, so follow up control can be undertaken quickly.
Regularly check areas:
• disturbed by fire, flood, heavy grazing or earth works;
• previously infested with gamba grass;
• near existing infestations (seed sources); and
• which are downstream from current infestations.
Document costs and resources used
Keep a record of which control methods were used and when. Also note whether or not they worked.
Implementing inappropriate management actions or the right actions at the wrong time can reduce success
and increase cost.
Establish photo points
Photos taken from the same point, at the same time each year will enable comparisons to be made. Photos
will show changes in weed infestations, as well as pasture quality and/or regeneration of native vegetation.
Review your plan
Assess whether your plan achieved your requirements. Make amendments or fine tune as necessary to
improve your weed control next year.
*Any management incorporating burning must be in accordance with the Bushfires Act and Fire and Emergency Act.
Please contact your local fire station for permits to burn if you live within a Northern Territory Fire and Rescue Service
Emergency Response Area (NTFRS ERA). If you live outside a NTFRS ERA, contact your local Volunteer Fire Brigade
Captain or local area Fire Warden through the Bushfires Council on 8922 0844 (Darwin) or 8976 0098 (Batchelor).Weed Management Plan for Gamba Grass (Andropogon gayanus)
Gamba grass is declared under the Weeds Management Act. The Weed Management Plan for Gamba
Grass (Andropogon gayanus) establishes the legislative requirements for land managers in relation to
weed control. The Plan describes required management actions as they relate to declaration zones.
Areas which have isolated and low density gamba grass populations have been classified as the Class
A/C (Eradication) Zone. Eradication in these areas is considered possible and highly desirable.
For example, the gamba grass populations which are developing in Arnhem Land are within Class A/C
and as such must be eradicated.
Widely distributed and dense gamba grass infestations, such as those in the Litchfield and Coomalie
Shires, are within the B/C (Management) Zone. In the Class B/C Zone eradication is not considered
technically or economically feasible at this time. Most large pastoral holdings which were legitimately
using gamba as pasture prior to its declaration are also within the B/C Zone. Management
recommendations for this zone focus on containing existing infestations and preventing any further
spread.
All declared weeds in the NT, including gamba grass, are considered to be Class C. This recognises the
need to prevent new introductions
Class A Eradication Zone - To be eradicated, in all areas of the NT, except where it is classified as Class B.
Class B Management Zone - Growth and spread to be controlled, in an area roughly bounded by the
NT coastline in the north, the western boundary of Kakadu National Park in the east, the town of
Katherine in the South, and the Daly River mouth in the west.
Class C Not to be introduced into the NT. All Class A and B areas are also classified as Class C.
www.lrm.nt.gov.auResources
Weed Management Plan for Andropogon gayanus (Gamba Grass)
Establishes the management requirements to be achieved by land managers in accordance with the
Weeds Management Act. The Plan contains detailed information on best management practice.
NT Weed Management Handbook
Contains ‘Weed control option tables’ for 37 weed species, detailing which herbicides are registered for
use in the NT. Information is provided on herbicide safety and integrated weed control techniques.
Weed Plan – A weed planning guide for properties
Provides information on how to develop a weed management map and a property weed plan.
Weed Monitoring Template
Details how to monitor, evaluate, report and improve on your existing property weed plan over time.
Weed Management Branch
Phone: (08) 8999 4567
Email: weedinfo.nretas@nt.gov.au
Web: www.nt.gov.au/weeds
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