ENGINEERING SERVICES

ATTACHMENT A

ES - WEED CONTROL - CABOMBA

ORDINARY MEETING

25 FEBRUARY 2014

Cabomba Controlfor the protection of the

Ramsar listed Myall Lakes

Case Study2011 - 2013

Cabomba caroliniana

Weed of National Significance

Cabomba Control Case Study2011 - 2013

Contents

About this report.

1. Background of cabomba

2. History in the Great Lakes

3. The project concept

4. The nuts and bolts of the project

5. Site details and results of the treatment program

6. Capacity building and stakeholder engagement

7. Contributing to national best practice management

20.

18

10.

7.

4.

3.

2.

AcknowledgementsDocument Design, Layout, Preparation & ReviewTerry Inkson - Great Lakes CouncilAndrew Petroeschevsky - National Aquatic Weeds Management GroupDavid Officer - NSW Department of Primary IndustriesTerry Schmitzer - Mid North Coast Weeds Co-ordinating Committee

Project Steering CommitteeAndrew Petroeschevsky - National Aquatic Weeds Management Group Terry Schmitzer - Mid North Coast Weeds Co-ordinating CommitteeDavid Officer - NSW Department of Primary Industries Terry Inkson - Great Lakes CouncilGeoff Keech - Macspred Australia

Cabomba Management TeamTerry Inkson - Great Lakes CouncilDavid Officer - NSW Department of Primary IndustriesTerry Schmitzer - Mid North Coast Weeds Co-ordinating CommitteeBrad Pitt - Great Lakes CouncilAnthony Thornhill - Skilled EmploymentAlwyn Simon - Skilled Employment (Indigenous)Wendy Bushell - Greater Taree City CouncilRod Spicer - Greater Taree City CouncilWayne Deer - Wayne Deer ServicesDean Drury - Pro SprayMiles Dixon - Active Bush Works

Other ContributorsFMC Agricultural Products - Shark HerbicideMacspred Australia

PhotographyTerry Inkson - Great Lakes CouncilDavid Officer - NSW Department of Primary IndustriesAndrew Staniland - Great Lakes Council

Land HoldersGolden Ponds Retirement ResortStingray DevelopmentsGreat Lakes CouncilJenny BromageMartin BawdenKeith GrahamDon TullochJohn YatesTed Tatum

About this report

This report details the results of the cabomba control project “Cabomba WoNS control, for the protection of the Ramsar listed Myall Lakes”, which was a joint initiative between the Mid North Coast Weeds Co-ordinating Committee (MNCWCC), Great Lakes Council (GLC), NSW Department of Primary Industries (NSW DPI) and the National Aquatic Weeds Management Group (NAWMG).

This project initiated the first broad scale use of the recently registered Shark™ herbicide against cabomba in Australia. Information from the report is drawn from Caring for our Country annual reports, monitoring results and interviews with key stakeholders. The report demonstrates that the project made significant gains towards achieving the following key project goals:

• eradicating cabomba to protect the Myall Lakes• increasing landholder and indigenous capacity to manage cabomba• contributing to national best practice initiatives for controlling cabomba with herbicides.

However, despite these significant inroads into reducing the extent of cabomba infestations, the report also shows that further efforts are still required.

Andrew Petroeschevsky David Officer Terry Schmitzer Terry Inkson

2

Cabomba (Cabomba caroliniana) is an aquatic plant native to South America. It is fully submerged except for the occasional floating leaves and emergent flowers. It is identified by its characteristic fan shaped leaves that are arranged opposite on the stem, white flowers that emerge from the water and a seasonally purple stem.

Cabomba was introduced to Australia through the aquarium industry as an ornamental and oxygenating plant for aquariums. It was first found naturalised in Australia in 1967 and has since spread to over 100 sites across eastern Australia. Its sale is now banned in New South Wales, Northern Territory, Queensland and Victoria.

Cabomba has the potential to cause significant impacts to water bodies. It can form dense underwater monocultures that affect the biodiversity and function of wetland and riparian ecosystems, water quality, water storage and distribution, infrastructure, and impact on recreation and amenity values.

Cabomba is a Weed of National Significance (WoNS) because of its invasiveness, impacts, and potential for further spread. It is also a very difficult plant to control due to its submerged habit and rapid growth rates.

Background of cabomba

3

“The Ramsar listed Myall Lakes contains a mosaic of wetlands from fresh to brackish and estuarine, within

a near pristinecoastal lake system

unique in NSW.”

Cabomba was first discovered growing in the Great Lakes Council Local Government Area (LGA) circa 1995 in a wetland at a retirement home in Forster. Between c.1995 and 2011 an additional nine infestations totalling approximately 16 hectares were found in the Great Lakes Council LGA and the southern reaches of the Greater Taree City Council LGA, as a result of local council property inspections or self reporting by the land owners.

It is uncertain as to how cabomba invaded and spread through the Great Lakes Council LGA. Experts believe that some infestations were the result of deliberate plantings by aquatic plant traders for commercial harvest. Other infestations may have been the result of either movement of contaminated eel traps or backyard trading of exotic water lilies.

A do nothing approach with cabomba management in the region, would potentially result in the further spread to key waterways, including the freshwater sections of the Ramsar listed Myall Lakes National Park.

These wetlands are the largest fresh – brackish water system on the NSW coast covering approximately 10,000

hectares. They are in a near natural condition and support a rich biodiversity of plants and animals, including threatened flora & fauna and 22 migratory bird species.

Cabomba, along with salvinia (Salvinia molesta) and sagittaria (Sagittaria platyphylla), are recognised by the National Parks and Wildlife Service (NPWS), Hunter Region Pest Management Strategy as a threat to the biodiversity values of the Ramsar wetlands of the Myall Lakes National Park.

History in the Great Lakes

4

This project fulfilled the strategic values of various weed management plans and programs including:

• Australian Weed Strategy• National Cabomba Strategic Plan (2012 - 2017)• NSW Invasive Species Plan (2010 - 2015)• NPWS - Hunter area - Regional Pest Management Strategy (2012 - 2015)• MNCWCC Regional Weed Management System (suite of plans and strategies)• Great Lakes Council Noxious Weeds Policy• NSW Weed Action Program

The project concept

Control issuesThe cabomba infestations in the Great Lakes Council area are a high priority for control, both nationally and regionally, due to their outlying nature, and their potential threat to the Ramsar listed Myall Lakes Wetlands.

However, up until 2011 a control program was not able to be instigated due to the lack of suitable control strategies for infestations in this region. Drawdown (draining of water bodies) was considered unsuitable due to the high rainfall climate of the Great Lakes region, and mechanical removal was unlikely to provide a long term option.

In 2011 the herbicide Shark™ (240g/L carfentrazone-ethyl) was registered for use on cabomba, which provided weeds managers with a much needed tool to control this weed.

Prior to the registration of Shark™ there had been no herbicides registered for use against cabomba following the suspension of the registration of Rubbervine Spray™ in 2004. Shark™ is a contact herbicide with no systemic properties. It works by attacking the fats and proteins of the plant cell membranes. It does not translocate through the plant and requires a good level of contact with the plant to achieve control.

The herbicide is applied to the water body either through surface or sub surface spraying/injection, with effective control reached when the concentration of carfentrazone-ethyl within the water column reaches 2ppm.

FundingWith the impending availability of this new herbicide the Mid North Coast Weeds Coordinating Committee in 2011 successfully applied for $191,760 from the Australian Government’s “Caring for our Country” program to implement a two year project to:

• control cabomba and prevent its spread to the Myall Lakes Ramsar site• build landholder and indigenous capacity to manage cabomba, and;• refine herbicide management techniques for cabomba.

A project team consisting of representatives from the Mid North Coast Weeds Co-ordinating Committee, Great Lakes Council, Macspred, NSW Department of Primary Industries and National Aquatic Weeds Management Group was established to oversee the implementation of the project and the rollout of the Shark™ herbicide.

This project commenced in late 2011 and concluded in June 2013. The results of the project are discussed further on in this document. 5

6

The nuts and bolts of the project

The project aimed to target the ten cabomba sites that were located within a 50km radius of Myall Lakes National Park.

These infestations could potentially spread to the parks wetlands and other water bodies in the region through floodwaters, as a contaminant on eel traps, or via the backyard trading of ornamental aquatic plantscollected from infested sites.

On ground control programs aimed to reduce the biomass of cabomba infestations to less than 1% of their original size within the two year time frame witha longer term goal of eradication.

Initial control of cabomba would in turn lead to:

• a reduced risk of floodwaters or other vectors (e.g. eel traps) further spreading cabomba to nearby water bodies, including the Myall Lakes and other water bodies, and;• infestations being reduced to a level where eradication could be achieved through follow up efforts after the two year project period.

7

Herbicide control was selected as the primary treatment method for cabomba by the project Steering Committee, as it was the most cost effective. Given the climatic conditions of the region, the use of Shark™ provided a greater likelihood of eradicating infestations than anyof the other control methods.

One landholder, however, had concerns over the use of herbicides killing exotic water lilies on their dam, and subsequently withdrew from the offer of assistance within the scope of the project.

The project team in conjunction with NPWS will be pursuing adequate control of cabomba in this water body over the coming years through negotiations with the landholder and, if necessary utilising the functions of the Noxious Weeds Act 1993.

Prior to the commencement of the control program, baseline data on the size and density of the infestations was collected.

Baseline data on cabomba density (percentage cover) was collected through visual estimates and samples. Sampling entailed the use of two separate devices (as pictured right) for gathering cabomba from strategic locations on the floor of individual water bodies.

These samples were washed, dried and weighed so later comparisons could be made to measurethe effectiveness of subsequent treatments.

In addition to sampling, photo points were established at each site to provide visual records of the changes to cabomba density pre and post treatment.

Accurate measurement of water body volumes was essential to ensure that compliance with chemical label requirements was met, and to maximise the effects of the herbicide.

Water body volumes were accurately gauged

by mapping dam depths, and combining these profiles with the surface areas of each dam.(see photo, top of page 8)

Both the cabomba, and non-cabomba infested sections of each dam were mapped concurrently.

All gathered data was used to calculate the amount of chemical needed.

Site name Size (Ha)Cabomba % cover

(Pre treatment) Description

Charlotte Bay 0.3 66% Dam on private propertyGolden Ponds (Forster) 2 80% Four separate water bodies at retirement villageMayers Flat 5 66% Dam on private propertyNabiac 1 (East) 2 50% Dam on private propertyNabiac 2 (West) 3.8 80% Dam on private propertyTea Gardens 1 0.5 100% Storm water retention pondTea Gardens 2 0.5 100% Constructed wetland on private propertyTopi Topi 0.5 33% Dam on private propertyWootton 1 0.5 50% Dam on private propertyWootton 2 1.5 50% Dam on private property

Table 1: percentage of cabomba cover within Infestations of the project area

Larger water bodies were broken up into management units to assist with the precise delivery of herbicide mixtures to the respectively mapped areas. See map below.

Some ponds required pre-treatment of other vegetation (e.g. reeds, exotic water lilies, water primrose, etc) with aquatic registered glyphosate formulations of up to 1.3% concentration.

This was done either to provide improved access to the cabomba infested sections of the dam, or to increase efficacy by minimising the wastage of Shark™ herbicide on nontarget vegetation.

Shark™ herbicide was applied only where cabomba was present, at a rate of 2ppm (active ingredient) to a maximum of 50% of each water body, as per label directions.

Due of the broad geographic and micro-climatic variations between the individual areas, each site posed its own unique challenges for the management team.

Consequently, every treatment was a learning experience as site specific delivery techniques had to be

developed, often on the fly, to overcome each sites unique challenges. 8

Picture right correlates

to map.

9

A range of plant and equipment was utilised to apply the herbicide, including:

Treatments were originally scheduled to be undertaken at all sites in 2011 - 2012 with re-treatments in the following year where necessary.

However, high rainfall during the optimum time frame of spring and summer 2011 - 2012 prevented some sites from being treated until the 2012 - 2013 season.

Following the herbicide treatments, each site was monitored by the landholders for any adverse effects.

All sites were inspected post treatment by members of the project team at strategic intervals.

A comprehensive assessment of each pond was conducted at the completion of the project during September and October 2013 and again in January 2014. The results of the findings are revealed later in this report.

• A flat bottomed punt (3.6m)• Argo® amphibious vehicle• Minn-Kota i-pilot electric

outboard motor• 4WD Polaris quad bike• Perception Flow kayaks• 400L Quikspray unit with

100m long hoses

• 100L low volume electric spray unit

• GPS units• Cameras• 100m long ropes• Waders, life jackets and

standard job specific P.P.E.

Site details and results of the treatment programAll sites were originally scheduled to be treated in Summer 2011/12. However adverse weather conditions postponed treatment of smaller ponds until late March 2012. The larger water bodies were further postponed until January 2013, in an attempt to mitigate wastage of the very expensive chemical.

The herbicide control program has resulted in effective control of cabomba at all nine targeted sites, with each reduced to less than 1% of their original density by January 2014.

Note: Although there were originally 10 sites, one of the landholders withdrew from

the project. Of the 9 remaining sites, one contained multiple

water bodies infested with cabomba. Seven

of the twelve water bodies treated overall,

exhibited zero or only trace quantities of cabomba by January 2014.

All sites with cabomba present

in October 2013 have since been retreated.

Every site will continue to be monitored in future years and retreated as necessary.

A summary of each infestation is displayed in table 2 and further discussed over the following eight pages.

At three sites cabomba has yet to reemerge since initial treatments in March 2012, however it is too early to determine if cabomba has been eradicated from these sites.

Site 1: Charlotte BaySize: 0.3 ha.Location: Great Lakes Council LGATreatment dates: 21 March 2012. Results: Reduced from 66% cabomba coverage pre-treatment, to no observable cabomba in January 2013. Monitoring of the site has found no trace of cabomba as of January 2014.Comments: This pond received only 1 treatment, outside of the optimum treatment time frame.The decline in cabomba was initially slow however the final results exceeded expectations of the

management team.

10

Site name March2012January

2013October

2013Oct - Dec

2013January

2014Charlotte Bay 100% 0% 0% Not Treated 0%*

Golden Ponds 2 100% 67.3% 8% Treated 0%*

Golden Ponds 3 100% 100% 35.5% Treated 0%*

Golden Ponds 4 100% 100% 0% Not Treated 0%*

Nabiac 1 (East) 100% 100% 0% Not Treated 0%*

Nabiac 2 (West) 100% 100% 0% Not Treated 0%*

Tea Gardens 1 100% 0% 0% Not Treated 0%*

Tea Gardens 2 100% 14.7% 24.3% Treated 0%*

Topi Topi 100% 0% 0% Not Treated 0%*

Wootton 1 100% 100% 16.2% Treated 0%*

Wootton 2 100% 100% 18% Treated 0%*

Total % remaining 100% 62% 9.3% - 0%*

Total % Decline (treated) 0% 38% 90.7% - 100%*

Table 2: Percentage % of cabomba biomass remaining at key monitoring intervals.

*determined by visual observations. Formal sampling needed for precise results.

113

4

21

Site 2: Golden PondsSize (total): 2 ha./ 4 water bodiesSub Site: G.P. 1Size: 0.1 ha.Location: Great Lakes Council LGATreatment dates: 15 March 2012 & 21 January 2013.Results: This pond only ever contained trace amounts of cabomba due to competition from yellow water lily (Nymphaea mexicana).It was therefore unable to be successfully sampled for density and has been excluded from the treatment monitoring table.Monitoring of the pond has found no trace of cabomba as of January 2014.Comments: This pond received 2 treatments, one of which was outside of the optimum treatment time frame.An abundance of water lily rendered this area difficult to treat without wasting the very expensive shark™ herbicide and formed the basis for pretreatment of other species with glyphosate.A second treatment was necessary to ensure total control was achieved.

Sub Site: G.P. 2Size: 0.3 ha.Location: Great Lakes Council LGATreatment dates: 15 March 2012, 21 January 2013 & 2 December 2013.Results: Reduced from 100% cabomba coverage pre-treatment, to 67.3% in January 2013 and further to 8% by October 2013. Re-treatment occurred in December 2013 and further monitoring of the site has found no trace of cabomba as of January 2014.Comments: This pond received 3 treatments, one of which was outside of the optimum treatment time frame.High rainfall and localised flooding five days after the second treatment may have reduced herbicide

efficacy and a third treatment was deemed necessary to achieve maximum results.High turbidity levels in the water also plagued this pond further reducing herbicide efficacy.

Sub Site: G.P. 3 (photos below)Size: 0.4 ha.Location: Great Lakes Council LGATreatment dates: 22 January 2013 &2 December 2013.Results: Reduced from 90% cabomba coverage pre-treatment, to 32% in October 2013.Re-treatment occurred in December 2013 and further monitoring of the pond has found no trace of cabomba as of January 2014.Comments: This pond received 2 treatments. High rainfall and localised flooding four days after the first treatment reduced the efficacy of the herbicide and a second treatment was deemed necessary to achieve maximum results.

Sub Site: G.P. 4 (photos right)Size: 1.2 ha.Location: Great Lakes Council LGATreatment dates: 22 January 2013.Results: Reduced from 50% cabomba coverage pre-treatment, to no observable cabomba in October 2013.Further monitoring of the site has found no trace of cabomba as of January 2014.Comments: This pond received only 1 treatment.The high rainfall and localised flooding event occurring four days after treatment that hampered the other 2 ponds, posed no detrimental effect to this pond.The cabomba management team believe it may have actually assisted the herbicide reach parts of the water body that were unnavigable on treatment day.

12

Site 3: Nabiac 1 (East)Size: 2 ha.Location: Greater Taree City Council LGATreatment dates: 23 January 2013.Results: Reduced from 50% cabomba coverage pretreatment to no cabomba able to be sampled by October 2013. Further monitoring of the area has found no trace of cabomba as of January 2014.Comments: This pond received only 1 treatment. A high rainfall and localised flooding event occurred three days after treatment, having no detrimental effect to this pond.Due to low water levels at the time of application, the following rainfall merely filled the dam to capacity.The cabomba management team believes the rainfall may have improved efficacy of the

herbicide by assisting it to mix thoroughly through the water column.Note: The pond pictured below outlined in yellow, (also seen in the background of the above photo) was a trial treatment site from a previous project undertaken to gauge the efficacy of Shark™ before seeking label registration, and implementing a full scale control project.It received 2 treatments of the herbicide, each conducted in January and February respectively of

the 2009/10 summer season.Further monitoring of this dam has found no

trace of cabomba as of January 2014.The success of these

treatments confirmed that cabomba could be

adequately

controlled with Shark™ herbicide. This made the protection of the Myall Lakes from cabomba a reality and formed the catalyst to seek funding for this project.

13

Site 4: Nabiac 2 (West)Size: 3.8 ha.Location: Greater Taree City Council LGATreatment dates: 24 - 25 January 2013Results: Reduced from 80% coverage pretreatment to no cabomba able to be sampled by October 2013.Further monitoring of the area has found no trace of cabomba as of January 2014.Comments: This pond received only 1 treatment. A high rainfall and localised flooding event occurred two days after treatment, but had no detrimental effect to herbicide efficacy.Due to low water levels at the time of treatment, high rainfall merely filled the dam to capacity.The cabomba management team believe the rainfall may have assisted the chemical mix thoroughly through the water column.This water body took a team of eight people two days to treat utilising a vast array of plant and equipment.Chemical costs alone were in excess of $17,000 (105 Litres) to effectively treat this dam.The landholder implemented mechanical controls as part of his in kind contribution to remediate the dams aesthetics, by removing a build up of sediment that had occurred over the years

and floating water lily rafts created by decomposition of treated exotic water lilies.

14

“The weed was so thick I couldn’t take the dogs for a swim or paddle a canoe.

It was very aesthetically unpleasing and I felt like selling the property”

“Now that the cabomba has been cleaned up the swans and pelicans are back”

“You guys have done a fantastic job and I feel happy to pay my rates now”

Don Tulloch - 11 July 2013.

Site 5: Tea Gardens 1 (photos top right & bottom left) Size: 0.5 ha.Location: Great Lakes Council LGATreatment dates: 16 March 2012Results: Reduced from 100% cabomba coverage pretreatment to no cabomba able to be sampled by January 2013.Further monitoring of the area has found no trace of cabomba as of January 2014.Comments: This pond received only 1 treatment.

Site 6: Tea Gardens 2 (photos bottom right) Size: 0.5 ha.Location: Great Lakes Council LGATreatment dates: 16 March 2012, 16 January 2013 & 13 October 2013.Results: Reduced from 100% cabomba coverage pretreatment, to 14.7% in January 2013. An increase in cabomba density to 24.3% had occurred by October 2013.

Retreatment took place in October 2013 and further monitoring has found no trace of cabomba as of January 2014.Comments: This pond received 3 treatments.Extremely low water levels hampered the January 2013 treatment, and a subsequent refilling of the pond some months later, assisted regrowth in cabomba density.

15

Site 7: Topi Topi (photos left & above)Size: 0.5 ha.Location: Great Lakes Council LGATreatment dates: 27 March 2012Results: Reduced from 33% coverage pretreatment to no cabomba able to be sampled by January 2013.Further monitoring of the area has found no trace of cabomba as of January 2014.Comments: This dam received only 1 treatment, and was the first in this project to receive deliberate stirring from an electric motor.

Site 8: Wootton 1 (Photos below)Size: 0.5 ha.Location: Great Lakes Council LGATreatment dates: 25 January 2013 & 3 December 2013.Results: Reduced from 50% coverage pre-treatment, to 8.1% in October 2013. Re-treatment occurred in December 2013 and further monitoring has found no trace of cabomba as of January 2014.Comments: This pond received 2 treatments. High rainfall and localised flooding one day after the first treatment reduced the efficacy of the herbicide and a second treatment was deemed necessary to achieve maximum results.

16

Site 9: Wootton 2Size: 1.5 ha.Location: Great Lakes Council LGATreatment dates: 18 - 19 February 2013 & 2 - 3 December 2013.Results: Reduced from 50% coverage pretreatment to 9% cover by October 2013.Further monitoring of the area has found no trace of cabomba as of January 2014.Comments: This pond received 2 treatments to achieve maximum results. A host of contributing factors including some shallow areas, submerged tree stumps, old fence posts, fallen tree branches and palm fronds, combined with limited access due to heavy forestation and some moderate to heavily shaded areas made this dam an extremely challenging work site.

17

Capacity building and stakeholder engagement

Stakeholder capacity building and engagement activities specific to this project included one Cabomba information session, two field days, several media releases, erection of interpretive signage, training of indigenous workers and the involvement of landholders in on ground works and monitoring.

The first information session was held at Great Lakes Council Chambers 14 December 2011, with the purpose of educating attendees on the potential impacts of cabomba in local ecosystems, and rallying support from all identified stakeholders.

A field day was held 4 October 2012 to showcase the importance of waterway vehicle hygiene incorporating an aquatic plant I.D. It was attended by 15 representatives from Roads and Maritime Services, Midcoast Water, Hunter Central Rivers Catchment Management Authority, Taree Indigenous Development Employment, National Parks and Wildlife Service, Local Councils and NSW Department of Primary Industries.

The second field day was held in June 2013 to both promote the projects achievements and to showcase the innovative control techniques used during the project. It was attended by 28 people, including landholders, community members, staff from Local Government agencies, National Parks and Wildlife Service, herbicide companys, Crown Lands and Department of Primary Industries.

18

One indigenous person was employed by the project on a part time basis to assist with herbicide applications, and several have been given skills in aquatic weed identification due to this project.

The project had a strong emphasis on working with landholders, who provided the project team with in-kind support where requested.

These contributions included the provision of on ground assistance during treatments, visual monitoring of waterways post herbicide treatment, before and after photography, and storage and maintenance of plant and equipment.

One landholder has undertaken site remediation post herbicide treatment.

A landholder survey was conducted in June 2013. Results show that landholders have a high degree of satisfaction with the project and that the project team undertook satisfactory consultation with them.

All respondents agreed that the project has helped them to develop an improved understanding of the impacts of cabomba and how to control the weed.

19

Contributing to National Best Practice ManagementThis section discusses some of the challenges encountered by the management team and offers potential solutions:

• thermal stratification of water• physical obstacles to control• the treatment window• water quality and daylight hours• adverse weather conditions• conclusion.

This project was the first opportunity for broad scale use of the herbicide Shark™ following

its registration in late 2011.

As such the project pioneered some innovative herbicide application techniques and learned some key lessons about this herbicides effectiveness against cabomba.

Thermal stratification of water.The project team identified that a ‘water penetration’ and ‘mechanical mixing technique’ provided a far more effective means of treating cabomba than herbicide broadcasting.

This technique helps improve the deep distribution of the herbicide throughout the water column, which is important for cabomba control.

Large and deep water bodies can contain different temperature layers within the water which is known as stratification. These stratified layers can impede the movement of the herbicide through the water column and prevent it from reaching the cabomba.

Some past treatment efforts have shown that broadcasting of chemical onto the surface of thewater can result in a poor kill, with the cabomba

merely getting a haircut and having rapid re-growth.

Injecting the herbicide into the water at high pressure (15-20 bar with a 3mm nozzle) helped the herbicide break through the surface tension of the water being treated.

Different means were used to ensure the chemical mixed rapidly within the water column. Applying the herbicide close to the motors propellor, enabled it to mix through the water column more efficiently. Traversing the boat through the treatment area immediately after application also assisted with mixing.

Physical obstacles to control.The presence of trees around some dams created accessibility issues when treating the cabomba, and also for monitoring the sites pre and post treatment.

Treatment sites were often plagued with old tree stumps, branches and palm fronds, many of which were not visible from the surface. Fallen branches sometimes impeded the use of motors for propulsion, which caused problems for fluent navigation.

Branches in the water often meant the need to use ropes to move the spray platform around and also made sampling a challenge.

20

The use of propellors through cabomba leads to fragments in the water. These fragments can foul the intakes on water cooled motors leading to overheating problems. This was overcome by the use of an electric motor, which enabled the spray crew to get access to even the densest infestations.

Where the electric motor was not suitable to propel the flat bottomed punt due to obstacles, the punt was moved with the assistance of two people pulling long ropes attached to either end. Then the prop of the motor was used only to stir the chemical throughout the water column or direct it into hard to access nooks and crannies, while the punt was held in position until the chemical had reached its target.

Non target plants were pretreated with aquatic registered glyphosate mixes 4-6 weeks prior to the cabomba treatments. This was done to:

• provide better access for watercraft• help prevent low dissolved oxygen issues, and• treat other vegetation that would otherwise absorb the Shark™ herbicide, ensuring that more Shark™ was available for uptake by cabomba.

The spray crew used a high volume QuikSpray™ unit with a 100m retractable hose for most of this project. One person was tasked with management of the spray hose allowing the spray operator the freedom to concentrate on herbicide distribution. Even with a dedicated hose manager some

areas proved to be very challenging, with the hose getting snagged on fallen branches or weighed down with very dense collections of cabomba.

The treatment window.It was common practice during this project to use tank mixes of around seven to eight litres of Shark™ in 100L of water to treat a surface area of approximately 800m2. If physical challenges were present in a particular area, the water volume was increased to 150 or 200L to ensure adequate coverage of the chemical throughout the section of the dam being treated.

The Shark™ label only allows for treatment of up to 50% of the total water volume of a dam, when 50% or more contains cabomba. This means that for dams with 100% cover of cabomba, the maximum concentration of Shark™ that can legally be applied to a water body in a single application is 1ppm over the whole dam or 2ppm over ½ the dam, meaning that a second treatment would be required to complete a treatment in the same growing period.

In this scenario the label was not prescriptive, so an application pattern tailored to cabomba density of each water body was used. This allowed for as much cabomba as possible to come in contact with the chemical soon after application.

Note - that as soon as Shark™ is mixed with water it will start to break down and lose efficacy, so unlike other herbicides, tank mixes of Shark™ cannot be stored for any period of time.

The label also has the restriction of a minimum of three months before re-treatments can be made to the same water body. For effective control, the cabomba needs to be actively growing. This means treating in late spring and summer is the optimum treatment window.

It was our experience in most cases that Shark™ treated cabomba was still declining three months after treatment (late summer or autumn). Because the cabomba was not showing signs of recovery we found only one treatment per year was possible in our environment.

At one dam, “Charlotte Bay”, the cabomba took six to nine months to deteriorate. We can offer no explanation as to why this decline took so long.

21

As Shark™ is light dependant, ideally at treatment time the water will have low turbidity. This means there are low levels of inorganic or organic solids suspended in the water column allowing maximum penetration of light.

The higher the turbidity the less effect the chemical may have on its target. As a rough

guide, if possible avoid treating cabomba when you cannot see the tips of your fingers at a depth of around 45cm.

It is also important not to begin treatment too late into the day. The more daylight hours available immediately after application of the chemical, the better the results will be.

Sections of a water body which are moderately to heavily shaded

throughout the day should be treated early in the morning or a least prior to

treating areas that receive full sun.

Adverse weather conditions.Although weather forecasting has improved significantly over the past decade, accuracy when predicting rainfall is particularly challenging.

Rescheduling programmed treatments when rainfall events have been predicted is a difficult call, especially when taking into account inaccuracy of both long and short range weather forecasts, and the potential of missing windows of opportunity in regards to optimum treatment times within a growing season.

Optimum treatment times for cabomba control on the mid north coast of NSW, often coincides with a period of high rainfall.

Organising a group of people to carry out control works, from various organisations, covering a large geographic area requires sound planning. These challenges also adds to the difficulties in rescheduling works at short notice.

Delaying treatments in a growing season could lead to missed opportunities for up to a twelve month period. On the other hand, careless applications could lead to unnecessary treatments adding further cost to a significantly expensive program.

Where there is potential for significant rainfall to flush the herbicide from water bodies, then careful consideration needs to be given to delaying control, especially when treating large areas where a lot of chemical is required to achieve the desired 2ppm concentration.

Water quality & daylight hours.

22

Conclusion.Sound planning prior to commencement of a cabomba treatment project is very important.

Just as it is necessary to assess each site for potential hazards prior to commencing control works, it is also necessary to approach each water body knowing that the control program may need to be tailored to address some unique or site specific challenges.

The project team also found that in most instances the herbicide has provided far better efficacy than what was expected prior to the commencement of the project. The project had initially planned to undertake multiple treatments at each site over the two year project period but in many instances

the cabomba had not returned 12 months after treatment. At three sites (Charlotte Bay, Tea Gardens 1 and the trial treatment site at Nabiac 1 east) the cabomba has not returned for two years or more, following one treatment.

The monitoring program discovered that cabomba can still be present in water bodies for three to six months after treatment, and in some cases can take up to nine months to fully die off. The reasons why cabomba dies off in this manner could be diverse and is not yet fully understood.

In response the project management team recommends that it can take up to nine months after treatment before the efficacy of herbicide treatments can be effectively measured.

The project team also learned that treatment of exotic water lilies (Nymphaea mexicana) can result in large rafts of dying root matter floating to the surface, which can result in aesthetic impacts at the site. It is recommended that allowances be made in projects to remove these rafts.

These key lessons learned were presented at the national cabomba best practice workshop at Benalla in Victoria, which was held in March 2013.

A cabomba herbicides best practice guideline is currently in production and when completed will serve as a supplement to the national cabomba control manual. This guideline is expected to be finalised in mid 2014. 23

“We continue to learn”