News and Updates

Look out for Siam weed

January 2025

This warning first appeared in one of our 2023 Newslettter. Siam weed is currently not known to be present in WA but is not too far away, only 10 hours by vehicle and just a couple by chopper. If anyone sees what they believe to be this weed they should immediately report it to Biosecurity Officers at either the Broome or Kununurra DPIRD offices.

In 2019 it was first detected in the Northern Territory based on a report of a plant that seemed to be out of place. Subsequent surveys revealed it had spread across multiple pastoral, private and Aboriginal land trust properties in the western top end of the Territory. By 2024 surveys had shown that infestations have been found within an area of approximately 950,000ha.

It was first detected in Australia in 1994 in North Queensland. A program to eradicate it was ultimately unsuccessful and as of 2024 infestations in Queensland range from Mossman to Rockhampton with especially large concentrations around the Townsville and Innisfail regions.

The weed is native to the central and south Americas, it is a perennial shrub, forming dense impenetrable thickets up to 2–3 metres tall. It can scramble up surrounding vegetation up to 20 metres high and readily invades sheltered areas such as creek banks, hillsides, rocky outcrops and vine thickets. It will outcompete pastures and native vegetation and has led to the abandonment of prime farming areas in some countries. It has now become a major land management issue across tropical Asia and Africa and has led to cattle deaths and aborted calves. It can cause skin complaints and asthma in allergy prone people.

Flowering time is mid dry season, this is the easiest time to detect Siam weed given the distinct flower it produces. Seeding occurs in August – September, the plant can look quite dry and brown and leaves can all drop off, leaving bare stems making it hard to detect amongst other vegetation. By the build-up most seeds have become airborne and dispersed. Wet season sees seedlings germinate and grow throughout the wet season until flowering again.

Rubber vine control 2024 summary

January 2025

It was a harder than usual year for rubber vine control in 2024, largely as a response to the impact of the recently discovered new infested areas found on the West Kimberley site. The partnership’s costs came close to $370,000, a 40% cost increase compared to the five-year average. That outlay was shared between the KRBA, the State NRM Management Program and both Government agencies DBCA and DPIRD.

The increases were felt in both the East and West Kimberley sites. The East Kimberley increases came on the back of good seasonal rains two years in a row. This gives the existing plants an extra growth boost and as a result plants become easier to spot as they get bigger and flower quicker. It takes anywhere from three to seven years for rubber vine to become a mature plant capable of flowering and seed production. Having that occur in a smaller time period allows the control program to get on top of the infestation quicker provided the field resources can keep up with the accelerated growth. As it appears that the site has already had 300mm of rain in November, expectations at this point are that there will be more than the average number of plants found again in 2025.

As previously mentioned, the West Kimberley was where much of the resources were aimed in 2024, taking up just over 60% of the budget. Total area controlled was 472ha compared with the East’s 279ha with 38,000 plants controlled compared to 11,500. Since rubber vine was discovered in 2022 outside the pre-existing control area much of the focus has been on re-establishing a reliable boundary around the site. More areas were located in early 2023 and one particularly large area was found by station personnel and a Pearl Coast chopper pilot later in that year. As a result, the 2024 survey increased from 18,000ha to 56,000ha in a ‘one of’ survey attempting to determine the actual boundaries. No more areas were located in that survey providing some relief to the partnership. .

The partnership is looking at the possibility of holding a forum in the near future to increase the engagement of stakeholders in the program. Even though the actual work areas (751ha in 2024) are small compared to the 5,000ha work area the KRBA works in control in prickly acacia the threats to industry and environment are similar. However, working in heavily forested river frontages and eroded gullies compared to open grasslands is exponentiationly more difficult and manpower hungry.

These rubber vine programs receive funding as part of the Western Australian Government's State Natural Resource Management Program that is essential to their success.

Cull programs back on track

January 2025

The last donkey cull for 2024 was recently carried out. It was the first using local shooters, finally reauthorised to shoot after two years of indecision and confusion. Minister Jarvis in recent correspondence to the KRBA acknowledged that there had been disruptions to the program and was aware of the implications. The Minister also indicated that DPIRD was working to minimise the risk of future disruptions and the planned tracking programs into 2025 would go ahead.

As a result the cull commenced on 12th November and concluded after six days of targeting last known judas donkey locations and reports from locals in the region. Priority was to find collars not located in previous runs and deploy fresh collars in existing judas locations with old or non-transmitting collars and then cover any gaps. Conditions were variable during the operation, with localised storms present creating very hot and humid conditions and large thunderstorms having to be avoided on most days. Details from the run include—

  • 119 donkeys and 17 pigs were culled.
  • 19 Judas collars were tracked and found.
  • 21 Judas collars were tracked and not found (these collars are likely to be out of date and no longer transmitting).
  • 66 Donkeys were culled opportunistically (off collars).
  • 5 New Judas collars were deployed.
  • Shooting hours - 48.
  • Having avgas available to purchase from bulk tanks at some of the more isolated areas within the cull area made refuelling more efficient and was much appreciated.
  • The collars deployed from a set of yards in the central Kimberley in 2023 yielded well, with three of the original four collars still alive, all holding donkeys.
  • 30 donkeys were controlled entering WA from the NT border.

New rubber vine find in the West Kimberley

June 2024

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.

2024 membership survey summary

June 2024

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.

Long term priorities

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.

New priorities

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.

Comments, issues and suggestions

Following are the most popular comments fed back to the KRBA out of just over 100 individual comments—
    • The baiting run is organised and communicated well. If we need to change the schedule they work around it, can’t fault the service (eleven other similar comments were received).
    • Was not aware of the weed subsidy please send information (six other similar comments were received).
    • Some posters (or books) placed in the kitchen etc. of what weeds are on stations for staff to look out for would be good. (four other similar comments were received).
    • Feel with baiting twice per year dogs were are at a good level of control but it does mean a few more Kangaroos(three other similar comments were received).

Other pests

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.

Weed posters now available

June 2024

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—

  • Bellyache bush
  • Mesquite - species glandulosa and pallida
  • Neem
  • Noogoora burr
  • Parkinsonia
  • Prickly acacia
  • Rubber bush
  • Rubber vine

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.

Building the algorithm for rubber vine

September 2023

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.

 

Mesquite work south of Derby

September 2023

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.              

 

 

Weed update

September 2023

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.          

 

Rubber vine Update

December 2022

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 update

November 2022

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.

Diet of dingoes in the West Kimberley

November 2022

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,

  • cattle were detected in 65.3% of samples,
  • agile wallaby were detected in 24.6%,
  • antilopine wallaroo in 5.5%
  • and most scats (67%) contained only one prey type.

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

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 blu@krbg.com.au