Council Wide Herbicide Review
Council has undertaken an independent review of all herbicide usage with a 6-month trial of alternative herbicides and other weed management methods within Bellingen Shire. The drivers for this project are Council’s commitment to the community and ecologically sustainable development, together with our invasive weed management role.
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Summary
Bellingen Shire Council (BSC) has an integrated approach to weed management, using herbicides alongside other methods including mechanical and manual removal techniques, biological controls and other bush regeneration activities. Following increasing community concern regarding impacts on human health and the residual environmental impacts of herbicides used for weed management, BSC has resolved to review its use of herbicides. Advisian were engaged by Bellingen Shire Council (BSC) in late 2021 to undertake a review of herbicide use in the BSC Local Government Area (LGA) as well as design and assess the results of an alternatives herbicide trial for the LGA.
The Scope of works included:
1. A literature review on international and Australian considerations of herbicides in use and trials of alternative herbicide products and methods.
2. Assessment of BSC’s current herbicide use including type of product, quantity used, cost, labour time and areas of application.
3. Stakeholder engagement to identify areas in the LGA of greatest concern regarding herbicide use.
4. A 6-month trial period of herbicide alternative/s at sites identified through stakeholder engagement.
5. A comparison between BSC’s current herbicide practices ((i) above) and the adoption of herbicide alternative practices ((iv) above); and
6. A review of the BSC Pesticide Use Notification Plan (2014) in accordance with findings of (i)-(v) above.
A review was undertaken of herbicide usage within the three main weed management areas of urban, roadsides and bush regeneration within a 12-month period (generally between July 2020- August 2020). Herbicides used by BSC during this period included glyphosate, metsulfuron methyl, triclopyr, picloram and aminopyralid. Methods of application were targeted using cut and paint (metsulfuron methyl) or multipurpose targeted sprays using a backpack, hand spray or powered units. Within urban areas, most weed management was undertaken using mechanical methods with very low volumes of glyphosate applied with a targeted spot spraying application. Similarly, within bush regeneration sites there were minimal herbicides used and only when required. Roadside maintenance had the highest volume of herbicide usage, given the challenges of applying integrated methods over large and often steep roadside areas.
There are also currently few viable alternative methods or products available for woody weeds. A review of herbicide alternatives or alternative methods was undertaken based on case studies undertaken in Australia. Alternative methods that have been previously trialled include organic (acid or oil based) herbicides, alternative synthetic herbicides, other mechanical methods, sodium chloride, flame weeding, steam weeding or alternative application methods (such as wick wiping). A considerable amount of work has already been undertaken to trial and investigate these alternative methods within BSC. While many methods have been integrated into the BSC toolbox approach, there are no alternative herbicide products which have met the four criteria of cost (labour and product), effectiveness, environmental and human health risks. Alternative approaches have also tended to be more suitable for urban type areas and multipurpose treatment of more fragile (non-woody) species.
Stakeholder consultation was undertaken through a survey and workshop to gather feedback on all areas of weed management and also to inform the design of the herbicide alternative trial. The outcome of the consultation was an overview of community concerns which ranged from inappropriate use of herbicides, human health impacts, environment impacts, difficulties in logistics of using alternative methods, risks of glyphosate, lack of effective weed management and applying the lessons learnt from previous trials. The consultation also guided the methods for the herbicide alternative trial.
The herbicide alternative trial was undertaken during Summer of 2021/22 over 12 weeks at Bellingen Waste Depot, Dorrigo Sewage Treatment Plant and Mylestom Tennis Courts, to represent the variety of climate conditions within BSC LGA. The effectiveness of weed treatments (including glyphosate, imazapyr, acetic acid and steam weeding) were assessed on fixed transects and fixed photoquadrats (n=5 per location) with measurements of weed species and percentage cover (%Cover) taken at 0, 3, 6, 9 and 12 weeks. A total of 300 photoquadrats were measured in the trial (three locations x four treatments x five photoquadrats). The photoquadrats were used in SamplePoint© software to calculate the %Cover of the main weed categories of grasses, herbs, bulbs, woody and sedges. Multivariate analysis was then used to determine if there was significant effectiveness of the treatments at each location and how long this lasted.
The results of the herbicide alternative trial found the following:
▪ Imazapyr had similar effectiveness to glyphosate in treating grass weeds at Dorrigo and Mylestom but was not very effective on herbaceous weeds. This herbicide has similar short term toxicity as glyphosate but much lower long-term toxicity (based on review of available studies in mammals). This product is a viable alternative for grasses but more expensive (at least five times that of glyphosate based on chemical costs).
▪ Local Safe® (acetic acid) was more effective than glyphosate at reducing herbaceous weed cover at all locations but was not very effective on grass weeds. This product requires more product to be effective and more frequent applications. The costs of using this product (including labour) are at least 10 times that of glyphosate. This product is considered to be viable for herbaceous weeds but more expensive (at least ten times that of glyphosate based on chemical and labour costs).
▪ Steam weeding only provided effective reduction to 3 weeks at Bellingen and Mylestom but had no reduction in weed cover following a second application. The poor results are likely to be related to the higher soil moisture across all locations. Based on this trial, this method would be very labour intensive and may not be as suitable for the region (compared to other Australian locations) given the high rainfall within the Bellingen LGA.
▪ None of the trialed alternative products are considered suitable as a replacement of glyphosate usage in terms of meeting the criteria that are required for a long-term replacement. However, imazapyr and Local Safe® are recommended for inclusion as part of the toolbox approach, particularly in urban areas.
Based on the outcomes of this review, including stakeholder consultation and the alternative trial, the following recommendations are made to BSC:
1. Herbicide alternatives should continue to be considered where practical, especially in areas of high public use. There are currently no suitable alternatives to synthetic herbicides for large operational areas (such as roadsides) or for woody weeds.
2. Glyphosate should be continued to be used where required (where there are no suitable and practical alternatives).
3. Herbicide ‘no spray’ 20 m exclusion zones are recommended around urban sensitive areas.
4. Provision of education and training for all pesticide applicators including volunteers.
5. Maintain weed profile to assist with management.
6. Consistent pesticide application record keeping and training on how to fill out.
7. Continued review of pesticide usage and weed management options.
8. Revision of Pesticide Use Notification Plan (2014).