News and Updates

Neem control trial summary

February 2022

A trial utilising encapsulated herbicides to control neem trees undertaken over a 12 month period has just been completed. Its scope was to –

  • Assess the effectiveness of encapsulated chemicals, including mortality rates and cost per unit of each treatment.
  • Assess the efficiency of use of the applicator tool.
  • Determine if control is possible at a reduced capsule rate.

The encapsulated chemicals used at full rate proved they could kill trees, though effectiveness in some instances ranged between 80 and 98%. The applicator used proved to be bulky and difficult to use in thickets of trees (note later versions are less bulky).

The trial identified that some of the encapsulated chemical rates could be halved and still be effective. Both Di Bak M and P provided similar effectiveness at a 50% application rate. Although the trial identified basal bark spraying as the quickest and most effective control option, encapsulated chemical injections do have a place in the weed control “toolbox”. For isolated weed control requiring a hike in on foot or transported by helicopter, it is easier to carry, and safer to transport encapsulated chemicals than sprayers for basal bark spraying.

A full summary of the trial can be obtained by emailing

State NRM funded weed programs

February 2022

The KRBA is a partner organisation in three weed programs trying to eradicate rubber vine and gamba grass infestations in a number of locations across the Kimberley. In 2021 these programs produced some mixed results but overall quite satisfactory progress has been made. Covid restrictions meant the usual contractor from the NT couldn’t be used on a couple of these programs and a coordinating contractor for one became unavailable at the last minute.

The East Kimberley rubber vine program ended up controlling 3,191 plants over 352 hectares with 137 considered to be breeders. This was down from the previous year’s total of nearly 14,000 plants from 685 hectares indicating the infestation is rapidly shrinking in terms of area covered and plants found.

The West Kimberley rubber vine program hit a speed bump with over 15,000 plants controlled of which 152 were breeders. This total was up considerably from the previous year of 961 plants. Most likely the increase came about from the 2020 survey having to be abandoned due to a lack of flowers because of the dry conditions at the time. In this survey program cameras detect flowering plants and the information is downloaded allowing the control team to find those plants.

In the East Kimberley gamba grass program only 13 plants were found, down from 23 plants found the previous year and 277 the year prior. It’s expected that within a couple more years the total should get down to zero plants found.

Ongoing funding for all these looks to be reasonably secure in the short term with both rubber vine programs gaining State NRM funding for 2022. The gamba grass program should have enough funds available for a couple of years and they may well see the control component through to completion. All programs receive and have received funds in the past as part of the Western Australian State Natural Resource Management Program.

Large feral herbivore program summary

July 2021

2020 was a reasonably successful year for our large feral herbivore cull program despite the initial delay due to COVID.  Numbers were down by 30% on the previous year due to the reduction in camel numbers reported. 

In total the numbers were 1,292 animals culled made up of donkeys, camels, some horses and pigs.  A total of 292 horses were removed from the Great Northern Highway between Kununurra and Halls Creek highway.  Previous to the work being undertaken there were a number of road accidents reported between horses and vehicles, particularly trucks along that stretch of road.  Ten new collars were deployed on donkeys including another three GPS collars that are assisting in determining the extent of the animal’s home range.  Additionally more genetic samples were collected as part of a project to see if there is any connectivity between separate donkey populations within the region. 

Rubber vine survey in West Kimberley breaks new ground

July 2021

The survey component of the rubber vine control program in the West Kimberly has been trialling cameras as a means to find adult flowering plants so they can be controlled before they seed.  During the proving process human observers were also used as a back up to the cameras.  This meant that the chopper had to be flown at speeds where those observers could see the plants without missing them.   In the recent survey the speed of the chopper was increased to up to 150kph.  At no more than 20 metres above ground level spotting flowers at this speed can be extremely hard.  However the cameras did an excellent job and easily met the standard hoped for with just over 80 plants found. Once the images are processed they are run through a software program designed to pick up the colour of the flower.  Those images are then passed on to volunteers who examine the image to determine if it is a flower or some other trigger such as a leaf reflecting light.  It should be noted that this project has received funding as part of the Western Australian Government’s State Natural Resource Management Program.

Weed control activities

July 2020

The annual prickly acacia wet season program in the East Kimberley was completed in February just prior to a week of good rains that will help with the uptake of the applied chemical.  Of the two control runs done over the wet a total of 95 plants were removed including just one seeding plant.  This is the second consecutive year the numbers of plants found has been under 100 and only a fraction of the 9,000 plus initially removed in 2010. 

All the seeds off the one plant were collected and destroyed on site. The East Kimberley rubber vine program started in early May with an initial aerial survey that covered approximately 30,0000 hectares, very few seeders were found in the existing control area however a new infestation covering approximately 13 hectares was found 11 kilometres away from another existing outlier infestation and 26 kilometres from the core infestation.  Estimates put the initial control at this location to take up to three weeks with follow up work for at least three to five years.

The West Kimberley rubber vine control program will start in July, the survey work due for earlier this year was suspended due to a lack of flowering.  The survey uses camera technology to identify rubber vine flowers by their distinctive colour so without flowers the survey cannot be run successfully.  In a normal year this method of detection has been demonstrated to have about a 30% higher success rate of finding plants compared to human observers.  

Vale Mick Everett

July 2020

Earlier this year long-time Kimberley shooter for DPIRD ‘Mick Everett’ sadly passed away in Perth.  Mick was a very popular figure in the region, particularly within the pastoral industry having been involved in aerial shooting programs since the early 1980’s.  He was the DPIRD coordinator for our ‘Judas’ donkey program in the Kimberley and at times would assist in a similar program in the Pilbara.   

A few years back he also got involved in rubber vine survey work in the West Kimberley with John Symanski’s Aquila program.  The annual survey uses cameras mounted on a chopper to find plants along the Fitzroy River but in the development of the techniques both human observers and the cameras were used in unison to properly test and refine those techniques. 

Mick’s last job for us was a five day cull in December last year of wild horses and camels south of Halls Creek under trying conditions.  

His knowledge of the local landscape and the people who operated within the region was huge and he was widely acknowledged as one of the good guys.  He will be greatly missed at both a professional and personal level right across the Kimberley. 

Kimberley Pig Research Project 2016 -2019

July 2020

In 2017 the KRBA provided funding through the Royalty for Regions program to the Australian Wildlife Conservatory (AWC) to expand an existing study looking at automatic feeder traps as a method of control for feral pigs.  That project came to an end in December 2019.  Following is a summary of the program and some of its results.    

There were five components to the research that were investigated over the duration of the project: 
  1. Investigate the best method for attracting feral pigs to bait stations and traps. 
  2. Develop and test an automated bait station that can be transported by helicopter, used in remote areas and left for long periods unattended. 
  3. Develop and test trap set-ups suitable for helicopter slinging for use in remote areas. 
  4. Gather data of pig damage throughout the year at specific swamps, before and after pig control efforts. 
  5. Gather and analyse location and habitat data using GPS collars, to determine -  
  • How far pigs travel and how this varies with seasonality. 
  • Home range size and overlap for male and female pigs. 
  • Habitat requirements and how behaviour changes throughout the day and night. 
  • What are the drivers for pig presence in the Kimberley.   

Automated feeders were constructed and erected in areas, across a range of pig densities.  All feeders had two cameras facing the feeder to identify if a subset of pigs would come in to the feeder but not feed from it.  In addition, a feeding experiment was conducted at a station’s bone pit, where cameras were deployed on both the automated feeder and pit to examine which food source was preferred.     A total of 20 feral pigs were fitted with GPS collars in three areas to encompass a latitudinal spread across the rainfall gradient and to enable research on differing land uses (pastoral and properties managed for conservation).  All collars ran for more than 2 years after deployment. 

 A trial was undertaken using the placebo version of the commercially produced “Pig-out” bait.  While the baits seemed palatable their use was ruled out as they are prone to drying out when exposed to the air and are relatively expensive.  A previous study in the Kimberley trialled the use of 1080 laced grain, which was found to be very successful.  At the time of the project lacing grain with 1080 to target pigs was not permitted however this was changed in 2019 and is now permitted under the code of practice for the safe use of 1080, PAPP & strychnine. This means approved pastoralists can now access 1080 concentrate for the purposes of lacing grain to target pigs.  

 Two experiments were undertaken to look at different ways of introducing poison to pigs.   First was a trial using grain, offered in piles adjacent to the feeder to see how much grain would have been consumed by pigs.    This would help calculate how much laced grain will be required when undertaking trials using poison.  The largest group of pigs observed in a single event did not exceed 15 animals.  It is estimated that to kill a group of this size at least 10 kg of laced grain should be deployed.  Also trialled was the use of gel capsules dispersed through heaped grain. The idea being that the capsules were small enough to be consumed along with the grain.  Initial results were promising as pigs consumed the capsules but it’s unlikely that this method could be used in the short term as it will need more evidence to be potentially registered as an approved method.   

 In brief, the research has achieved the following –

  • Successful development of an automated baiting system that can be deployed for control of feral pigs in remote parts of the Kimberley, and optimised the delivery of baits using that system. 
  • Identification of movement patterns of pigs in the central and western Kimberley, including differences in habitat use across the rainfall gradient from north to south.  

Modelling conducted by AWC shows that suitable habitat for feral pigs is much larger than the area currently occupied and pigs are still expanding throughout the Fitzroy Basin and in the North Kimberley, there is a significant potential for the spread of feral pigs due to the high rainfall and the many small rivers that dissect the region.  

 Feral pig management in the north will be complex as pigs are likely to be dispersed throughout the area due to the abundant water.  In the south, however, pigs are largely constrained to the larger watercourses, particularly in the drier parts of the year. 

Weed work summary

December 2019

Prickly acacia seedsWork continues on the prickly acacia infestation that is scattered over 10,000 hectares to the west of Wyndham.  Less than 100 plants were found and controlled on the site in October of this year.   Recent fires made the work difficult with many plants burnt or just half burnt meaning some plants may not take up the chemical applied.  Only two seeding plants were found this year, the seed pods from those plants were removed and deep buried on site to ensure that the wild cattle in the area would not eat the seed and cause its spread.  

Rubber vine plant numbers controlled in both the East and West Kimberley continues to decline.  In the east 3,471 plants were located, just over half the plants found in the previous year.  In the west just 728 plants were found of which only 16 vines were mature.  

The KRBA’s Field Officer “Blu’ carried out a survey of grader grass in the North Kimberley.  In many locations the density and extent of the plant had increased significantly since the North Kimberley LCDC survey in 2011.  In some spots the movement along roads was measured at more than 20 kilometres in the eight years between surveys.   The KRBA will be carrying out field trials in conjunction with some land managers across the Kimberley this wet season to gauge the effectiveness of new chemicals and methods of application on grader grass.  Additionally we will be keeping an eye on similar work being done in the NT looking at other means of control.

New Board Member

December 2019
The committee is pleased to announce it has a new member joining its ranks as of the AGM in October.  New Board Member Linda Evans from Napier Downs adds a ‘West Kimberly’ dimension to the group and will be a valuable asset. Meanwhile both Rick Ford and Lynette (Jim) Craig put up their hand to serve another three year term.  Lynette has been a member of the committee since the KRBA formed out of the old ZCA’s in 2010 whilst Rick has been a member since 2013. Mike Shaw was once again elected Chairperson with Lynette Craig taking up the Vice Chair’s role.

Cost Benefit Analyses - Donkey Program

November 2019

In 2019 two benefit cost analyses were undertaken to provide an estimation of the cost-effectiveness of various options for the Kimberley Rangelands Biosecurity Association’s feral donkey control program in the Kimberley region.  Only the economic benefits and costs of feral donkey control were considered, it is emphasised that other benefits include the opportunistic removal of other large herbivores and pigs, reduced environmental impact, reduced biosecurity risk, more timely identification of significant weed infestations, and reduced nuisance value for the cattle industry. 

The first analysis looked forward over a 30 year time period with four different options considered - 

  • Current control: This option represents the current level of donkey control resulting in a 3% increase in donkey numbers through time.  This option gave a Benefit Cost Ratio of 2.1 with a net present value gain to the pastoral industry of $2,623,000 over the 30 years.
  • Maintain numbers: This represents a small increase in control effort compared to current effort, such that current donkey numbers in the region are maintained over the 30 year time horizon.  This option gave a Benefit Cost Ratio of 2.6 with a net present value gain to the pastoral industry of $3,831,000 over the 30 years. 
  • Eradication: This option reflects halving donkey numbers in the region each year until donkey numbers are kept low, only increasing through migration.  This option gave a Benefit Cost Ratio of 2.0 with a net present value gain to the pastoral industry of $3,934,000 over the 30 years.
  • Stop control for 10 years then start again: This option represents a break from control activities for 10 years, then starting again in year 11 through to 30 with control effort resulting in a similar number of donkeys in the region after 30 years as is expected from option 2.  This option gave a Benefit Cost Ratio of 2.1 with a net present value to the pastoral industry of $2,468,000 over the 30 years.

The second analysis provided an estimation of the cost-effectiveness of the program over the last 40 years.  The results suggest that the program has provided excellent value for money. The Association has spent approximately $8.4million over the 40 years life of the program. Adjusting this value for inflation and compounding it to account for the opportunity cost of investing this money elsewhere, this has an estimated present value of $78million.  The benefit derived from this effort is estimated to be $268million (in present values and accounting for inflation). The Net Present Value (the difference between the benefits and costs) is estimated to be $220million and the Benefit Cost Ratio (the ratio of the benefits to costs) is estimated to be 3.8 (for every dollar spent, the ‘bang for the buck’ is $3.80).

Grader Grass – a new weed to the Kimberley

July 2019
Grader Grass (Themeda Quadrivalvis)

Grader grass is thought to have entered the Kimberley region relatively recently. Although it is not yet widespread across all the region it is common in parts of the North Kimberley. In particular along sections of the Gibb River, Kalumburu and Mornington Roads. Infestations range from a scattering of plants on the road verge to large swathes moving away from the road down table drains. Grader grass seeds are not adapted for dispersal by wind or water so its spread is primarily been associated with earth moving equipment and collecting seed in the radiator or under carriage. It can rapidly grow up to two metres tall, sometimes reaching full height within 6-8 weeks. Seed heads can appear within 5-6 weeks of germination but much earlier on late germinations. It generally germinates at the onset of the wet season and typically starts to seed from February through to April.

It is an undesirable species in grazing and conservation areas of Australia. It can invade both native and improved pastures and, due to its low palatability, greatly reduce animal productivity if it becomes the dominant species. It is an opportunistic invader which when established competes strongly with existing and establishing perennial grass tussocks, particularly in overgrazed and degraded pastures and disturbed areas. Because it is generally ungrazed grader grass can generate large fuel loads increasing the risk of wildfires. These impacts on ecosystems are often long-term or irreversible.

Currently the RBG is mapping as many of the known infestations as possible. This work will be ongoing over the dry season along with documenting different control strategies both in the Kimberley and the Northern Territory. The information once gathered will be made available to land managers and other stakeholder groups and could potentially influence direction of the organisation’s own weed programs. This is a weed that could potentially become common across the Kimberley and if so would become a significant problem for land managers.

If you think you may have seen grader grass please contact our Field Officer Blu Gaff on 0429 171 016. Grader Grass is currently not a declared weed in the Kimberley but that may change in the future.