Background
The property of Old Hidden Vale is located in Grandchester, Queensland and comprises 4,800 hectares of native bushland and farmland (Ecosure 2017), where the rehabilitation of the natural environment is the underlying organisational philosophy (Ecosure 2017). This restoration of native flora is currently being hindered by numerous invasive woody weeds such as Chinese Elm (Celtis sinensis), Tobacco Bush (Solanum mauritianum), Duranta (Duranta erecta), Lantana (Lantana camara) and Privet (Ligustrum lucidum). In particular, the restoration of Franklin Vale Creek and its neighbouring land (agricultural, pastoral and bushland) has been prioritised.
The clearing of this catchment for agricultural expansion has caused the degradation and erosion of the creek bank, as well as facilitated the spread of these invasive plant species (Ipswich City Council 2017). The current mechanisms of control include the cut, scrape, paint (CSP) technique, spot spraying and overspraying methods (Ecosure 2017). Whilst their efficacy is undisputed, these treatment methods often result in collateral damage to non-target species (Eucalyptus spp., Casuarina cunninghamiana) through herbicidal drift. This is accompanied by a reduction in the richness, abundance and diversity of sensitive plant species in the adjacent habitats. Therefore, the development of environmentally sensitive methods of weed control is paramount to the restoration of the sites natural assets.
This research project investigated the effectiveness of Bioherbicide Australia’s (BHA Pty Ltd) proprietary stem-injection system (“InJekta”) for controlling woody weed species in conserved or environmentally sensitive habitats.
Aims
- Evaluate the effectiveness of the stem-injection method for controlling woody weed species in conserved or environmentally sensitive habitats
- Determine the efficacy of selected encapsulated chemical herbicides in controlling infestations of Celtis sinensis and Solanum mauritianum
- Evaluate the relationship between the effectiveness of the stem-injection method, tree size and maturity in Celtis sinensis
- Examine the effect of a sublethal dose of glyphosate on the infectivity of the bioherbicide (Di-Bak ParkinsoniaTM , BioHerbicides Australia Pty Ltd) through pilot trials with Celtis sinensis and Solanum mauritianum
Methodology
A series of replicated trials were established among naturally occurring populations of Celtis sinensis and Solanum mauritianum at the lower region of the Franklin Vale Creek, Old Hidden Vale (27o44’50”S 152o27’13”E). The field trials involved the mapping, measurement and treatment of these invasive species with various encapsulated biological and chemical herbicides. The herbicide capsules were sourced from Bioherbicide Australia’s (BHA Pty Ltd) Di-Bak range of registered and developmental products.
These encapsulated chemical and biological herbicides were administered via the “InJekta” handheld device. This device is comprised of a handle, shaft and cartridge that is preloaded with thirty capsules and polypropylene plastic plugs. The shaft is attached to an 18V cordless drill that drills a hole (8mm diameter) into the plant stem. The swift withdrawal of the drill backwards is followed by the rotation of the cartridge thereby priming a single capsule and plug for delivery. The capsule and plug are then simultaneously inserted into the drilled hole through the forward movement of the drill.
The performance of these trials was assessed at approximate monthly intervals by recording the percentage of foliage loss, the colour composition (percentage green, yellow and brown) of the remaining canopy and the overall vigour of each individual tree.
Expected outcomes
It is hoped that the preliminary screening of these encapsulated herbicides will assist in the development of a protocol for the management of Celtis sinensis and Solanum mauritianum at at Franklin Vale Creek. Their successful eradication will facilitate the regeneration of native riparian vegetation thereby improving the habitat values for resident and migratory fauna (Ecosure 2017; Ipswich Regional Council 2017). The water quality of the catchment will also be improved following a reduction in creek bank erosion and instability (Ecosure 2017; Ipswich Regional Council 2017). This is expected to support an abundance of aquatic fauna, as well as better the health of the surrounding livestock that rely on this site as a water source (Ecosure 2017; Ipswich Regional Council 2017).
References
Ecosure 2017, Restoration Plan for Hiddenvale – April 2017, Brisbane.
Ipswich City Council 2017, Franklin Vale Creek Catchment Initiative, viewed 3 October 2019, https://www.ipswich.qld.gov.au/__data/assets/pdf_file/0009/125667/Franklin-Vale-Creek-Offset-Partnership-brochure.pdf
