The annual aerial survey for both East and West Kimberley rubber vine programs were completed in March and April. Nearly 93,000ha was surveyed taking a total of 13 days for a three man crew consisting of a pilot and two observers.
The surveys focuse on locating flowering plants as they can be easily seen in the tree top canopy from the air (see image below). Until the remote sensing program that uses cameras for the same task can be proven and rolled out from its trial area trained observers are still the best option.
Only 49 flowering plants were found in the East Kimberley infestation, which was about what was expected given its steadily diminishing work areas. The West Kimberley survey did however verify the location of a previously unknown satellite infestation approximately 8 kilometres away from the main site. The site had been reported by a mustering pilot through a local land manager just prior to the wet season in 2023. This new area covers about 60ha and has been in existence for perhaps up to 20 years. Fortunately access is fairly straight forward via an adjacent track so equipment can be bought in easily. With rubber vine’s relatively low seed viability of a year or two the site shouldn’t take too long to get under control. See image: The new infestation (brighter, darker green compared to the native vegetation) can be seen centre of the creek bed heading upstream a total of 4 kilometres.
Negotiations are currently being held with the lease owner as to the best methods to control such a large single infestation with hopefully a resolution coming soon.
These programs receive funding as part of the Western Australian Government's State Natural Resource Management Program.
This membership survey was the fourth undertaken by the KRBA since 2017. The role of the surveys is to provide the committee with an understanding of the current pest priorities at station and regional levels, how they align with current KRBA programs and feedback on the effectiveness of those programs. This survey was carried out over the 2023/24 wet season with a total of twenty-nine surveys completed. Below are a few points of interest that came from this and previous surveys.
Dogs: are consistently the highest priority pest in all four surveys constantly rating above 70/100. There’s daylight between them and the next highest priority parkinsonia rating around 44/100 as an average. This survey was the first where over half (59%) of those interviewed whilst marking them as a pest didn’t give them their highest score.
Interestingly two of the 29 interviewed considered them not to be a pest, one viewing them as a means to control other pests such as pigs and therefore of some benefit.
There is a trend in the increased usage of the aerial baiting program, it rated at 9.2/10 in this latest survey and for this coming year the annual budget for dogs is now set at $250,000.
Parkinsonia: Generally, just over half of everyone interviewed in every survey rated parkinsonia as a pest on their lease with its priority rating averaging around 38/100. Its most prevalent in both the Central and East Kimberley regions with over 60% of those surveyed in those regions marking with their highest score. There are no existing programs in the Kimberley to control parkinsonia but there is a weed subsidy available for those who wish to control it on their lease. The subsidy covers chemicals and licenced contractors and will cover up to $7,500 in expenses.
Horses and camels: were considered a pest on 39% and 29% of leases respectively with horses given a priority rating of 22/100 whilst camels were prioritised at 17/100. In the Central and East Kimberley regions those figures were marginally higher. Since 2015 over 4,500 horses and 1,100 camels have been culled mainly out of these regions through dedicated shoots. On top of those culls over 650 have been culled opportunistically on the donkey program, mainly in the North Kimberley sub-region.
Horses have an annual budget of $20,000 and camels $10,000. As all these shoots are management shoots where good numbers of animals are encountered in a relatively short period of time the comparatively small amounts of funds allocated to the budget are very effectively spent.
Noogoora burr: was considered to be only a minor pest in the 2017 survey when it was rated at 7/100. It’s now rated at 38/100, a fivefold increase in priority in seven years. Although the difference in distribution at a lease level hasn’t changed all that much 28% of leases in 2017 and 30% in 2024 its priority within those leases has been where the big increase has been made with now over half interviewed giving it the highest score possible. Its distribution and priority for control is highest in the East and Central Kimberley where there were a number of comments made in the interviews about the weed’s rapid spread in 2023 on the back of substantial flooding.
Neem: has been identified as another significant increaser weed, particularly along waterways. It was identified as a pest by 35% of managers surveyed and was prioritised at 22/100 in this latest survey but was considered to be only a minor pest in the 2017 survey where it was considered a pest by only 18% of those interviewed and rated at 7/100. Its distribution and priority for control is highest in the East Kimberley sub-region where its now considered to be widespread in some areas.
Donkeys: were considered a pest by 50% of those surveyed and were rated equal second with rubber bush behind dogs regarding distribution. However, they were rated tenth in terms of their density levels with only one manager rating them high on their lease.
In terms of their priority as a pest they rated an average of 22/100 across the region. Whilst they have always rated higher as a pest in the North Kimberley they only rated at 33/100 in this survey. In the initial two surveys of 2021 and 2019 donkeys rated at 75/100 and 76/100 in that sub-region, dropping to 43/100 in 2022.
Pigs: were considered to be a pest by 43% of managers and were given a priority rating of 21/100. Both these figures were well down on 2022 when 75% of managers rated them as a pest and they were given a regional priority rating of 39/100. In the initial 2017 survey they were considered to be a pest by only 45% of managers and their priority rating was 14/100. Reported density levels have also dropped by 25% between the 2022 survey and this one.
Macropods: were considered to be a pest by 29% of managers surveyed and given a regional priority rating of 14/100. This is a continuation of a drop from a high point in the 2019 survey where they rated as a pest by 76% of managers and given a regional priority rating of 71/100. Possibly seasonal fluctuations of numbers and densities account for these differences.
As part of its ongoing weed campaign the KRBA is building up a series of weed posters covering weeds of concern to the pastoral industry in the Kimberley.
It’s hoped that the posters will find their way into lunch and smoko rooms to increase land manager and staff knowledge of weeds they are likely to encounter in their job and how to properly tell them apart from the many look a-likes we have.
The posters are A2 in size to help with using them as an identification tool and laminated to keep them from deteriorating too quickly.Currently the posters are available for—
If anyone is interested in getting copies of any of the current crop of posters or have a request for some not already mentioned you can contact the EO on 0418 959 832 or dick@krbg.com.au.
The rubber vine program in the Kimberley the KRBA is partnering is looking at improving its surveillance methods for the weed. Up until now the West Kimberley site used the method of taking images from the air across the 18,000ha site and searching the images by means of computer looking for the white flowers of adult plants showing up against the green foliage background. On the East Kimberley site surveillance of the 30,000ha site was also carried out from the air but using human observers. Both had some advantages but also a number of weaknesses. In the case of the West Kimberley method only mature plants that were flowering on the day could be located. The East Kimberley had the disadvantage of the observers missing plants as they tired over the day.
The new option is an upgrade of the West Kimberley method using very high resolution cameras that will allow small leaf and stem structures of different plants to be accurately identified from an image, then teach a machine to pick up on those key identification points humans use and make a decision of yes or no on a plant. The critical issue is how much you can magnify the image before pixelation turns the image to mush.
In a field trial 11,000 images were collected by drone of which 2,000 were searched by eye to locate plants. This was based on a ground search of the site that located numerous plants to guide the image search. The information will all go to develop the algorithm to enable rubber vine plants as well as the flowers to be found and the remaining 9,000 images will then be searched using the algorithm and another on site from the ground to test the process. If both searches align it will indicate some form of initial success.
From there hopefully the new method will be used successfully to cover both sites.
The KRBA surveyed and controlled mesquite on just over 4,250 hectares of land just south of Derby in April this year. The work had been delayed from January due to the extreme flooding at that time.
In all very few plants were located, just 43 in total. The biocontrol that was found in the area in 2022 was still active, though nowhere near as active as it was in that July. It’s suspected that the moth that desiccates the flowers and leaves of the mesquite plant would have periods of high and low activity according to the climatic conditions with the wet season being a low point.
The interesting thing about this site currently is the lack of small seedlings. Mesquite does not compete well with thick grasses and the fact that a biocontrol is putting pressure on the plant’s seed production sites could be reducing that new recruitment.
Just about all plants were over two metres in height with some in the more heavily timbered area up to six metres high. The height of those plants does expose one weakness of aerial control in heavy timber, that being you have to wait until the target plant is big enough to have grown out from underneath a larger native tree that is sheltering it. Flying low and looking across as much as down does help but plants do remain invisible often for a number of years before being noticed. The other side of the coin is that you could never cover that amount of ground in just a couple of days on foot or vehicle. It would take weeks of labour gridding at distances as little as 20 metres to do the same job.
An interesting development coming from the flood was that it was noted that a number of sites that did have mesquite actively growing on them had disappeared. In all, just over 400 hectares of vegetated river flat had been washed away, along with it the mesquite growing on it. See the image below showing 2022 river banks and the red track line showing the current banks. Even the pilot observed that one of his fishing spots was no longer in existence, its remnants was now 500 metres off shore.
Where these mesquite trees ended up is anyone's guess but its thought that given the condition of the remaining plants, none or only a few would have had seed pods on them. as none were found on the plants controlled on this or the previous run.
Very little weed control was undertaken this wet season, the flooding of the Fitzroy River ruled out the planned mesquite program planned for mid January. However some mapping was undertaken from Camballin downstream to try and record the maximum flood height as it moved down the river.
This was done on two separate days and the map below was created. It was difficult to get a good handle on exact levels and their timing as gauging stations were been ripped out as the water moved downstream. Potentially this map can be compared with LiDAR mapping data as it becomes available.
What this will give us is a high point of where weed seed and material could have been swept to as the flood moved through and will help with directing further survey work over the next few years.
For the record the river in this survey at its narrowest point was six kilometres wide whilst its widest point down close to the mouth it was just under 30 kilometres wide. The total area under water at that point can be seen on the map calculator below as 1,546 square kilometres.
In the East Kimberley however the prickly acacia program had its first control run for the year with an additional 6,000ha surveyed and only 13 plants found. More importantly none were found outside the known infestation area.
Two programs in the Kimberley are supported by the KRBA, one in the East and the other in the West Kimberley. In the East Kimberley program a total of 718 plants were treated off 246ha of land this year, down significantly from of 2,949 recorded in 2021 and the 13,684 recorded in 2020. An aerial survey was undertaken in March covering 33,424 hectares and located 27 seeders with nil plants found outside the known search area.
The West Kimberley program conducted its annual survey over 18,470 hectares with 151 flowering plants located in March. These and an unknown number of associated plants were controlled in May/June 2022. However during the mesquite survey undertaken in July (see above) a number of significant infestations were found along the Fitzroy River from 5 to 30 kilometres below the parameters of the currently known site. The full extent of these new infestations is currently unknown and will be determined in early 2023 by an extensive survey extending down the river as far as Camballin and perhaps beyond at this point.
These programs received funds for the work undertaken in 2022 and have received funds in the past as part of the Western Australian’s State Natural Resource Management Program.
Prickly acacia was first found in WA in 2002 with a lone plant spotted along the Duncan Road in the East Kimberley and in the following year a single plant was found in the quarantine yards just outside Kununurra. In addition to the quarantine yards find in 2003 an infestation southwest of Wyndham was found by a DPIRD Biosecurity Officer carrying out donkey control. This outbreak was spread across over 10,000 hectares with densities varying from scattered plants to very dense stands and was the largest infestation found outside Queensland at that time.
Whilst stock can often be the major cause for the distribution of seed in this case flood events seem to have been the biggest influencer of movement.
The KRBA provided some funding to the eradication program very early in its inception and took over the role of managing the infestation in 2017. Detailed data has been kept since 2010, in that wet season 9,230 plants were controlled from 5,050 hectares. In the 2012 wet season 14,680 hectares were surveyed and controlled but by that time overall plant numbers had reduced down to 582 and has been reducing incrementally since then. In the 2021 wet 227 plants were found out of 7,847 hectares searched.
The biggest issue with prickly acacia is the longevity of the seed produced. As an example on one site visited in April 2022 four immature plants were located where the last seeder plant was found in November 2010. Previous to 2022 a small plant was found on that location in 2016, another in 2014 and two in 2013.
The application of Graslan is largely responsible for the low numbers of seedlings found subsequent to the control of the original seeder plants but it’s clear that the dormancy of the seed long outlives the residual nature of the chemical in its initial application. The longevity of the seed and its ability to enable a small number of plants to germinate each year as a survival strategy for the species is apparent in the graph above with 83% of seedlings found to date removed in the first couple of years of the program and the remainder spread relatively evenly over the next ten years.
Currently it’s believed that seed viability can be up to 15 years for the plant. This means that its likely a couple of hundred plants will be found each year for the next four to five years over the entire site.
Fortunately after the initial knockdown of plants early in the program very few plants seeded due to the frequency of control work done and the practice of all seed pods removed from trees and surrounding soil and destroyed. The last verified seeding plant was found in 2018.
With the above in mind it is expected that old seeder locations, particularly isolated ones will have Graslan re-spread as a means to ensure germinating plants will die as soon as their roots find the residual chemical.
Linear clearings are frequently used by dingos to increase their mobility and landscape access. They will however sometimes modify the animal’s predator–prey relationships.
Tenaya Duncan, Patricia Fleming and Dr Stuart Dawson from Murdoch University, Western Australia recently carried out a year-long study on the diet of dingoes in the West Kimberley to test the hypotheses that the clearing of seismic lines would change the diet of dingoes in that area.
A total of 199 scats were collected from inside and outside the footprint of a seismic survey at three collection time points (once before and twice after the disturbance). Overall, the diet of dingoes varied over seasons between control and treatment sites however there was no evidence of a shift in diet caused by clearing.
From the scat samples,
Compared with the national average diet of cattle being present in 13% of samples for the arid and tropical regions of Australia, the consumption of cattle (live cattle and carrion) in the West Kimberley is very high, with greater consumption in the control and treatment sites at the end of the dry season compared to the early dry season the researchers noted. The concern is that if dingo numbers are not managed adequately there is huge potential for increased calf predation at the end of the dry season.
Feral cat and feral pigs were only present in one scat sample each, along with birds and reptiles in low frequencies.
For more information you can find the full article at www.publish. csiro.au/AM/AM21016
A trial utilising encapsulated herbicides to control neem trees undertaken over a 12 month period has just been completed. Its scope was to –
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 blu@krbg.com.au
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.
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.
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.
