Gold Coast City Council IVM trials

The objective of these trials was to investigate alternative strategies that might help to overcome some specific operational difficulties with relation to vegetation management activities in Gold Coast City Council. The effectiveness of these alternative strategies was compared to current practices in order to determine the potential benefits of the implementation of such Integrated Vegetation Management strategies into typical GCCC operations.

Vegetation management issues currently absorbing a disproportionate amount of the funds in GCCC include:

•objects that are difficult to mow around in parks and other public open spaces (e.g. trees, bollards, telegraph poles, fence lines, etc.),

•weeds growing on hardstand areas along roadsides (e.g. under armcos, in gaps in concrete and paved areas), and

•weeds growing in amenity gardens along roadsides and landscaped areas in parks.

Objects in parks are currently mown around using a hand mower, or sprayed around with Glyphosate. However, hand mowing has to be done often and spraying with Glyphosate encourages the growth of dicot weeds.

Weeds growing in hardstand areas and amenity gardens are currently controlled with Glyphosate. While this gives excellent short-term control, its effect is relatively short-lived and it needs to be repeated often.

In the first two experiments, plant growth regulators were evaluated for their potential to reduce the growth of vegetation surrounding furniture in open space environments (i.e. along fence lines and bollards). It was found that these plant growth regulators could significantly reduce grass growth and delay the requirement for hand mowing activities. The results also suggest that application of a selective herbicide in combination with the plant growth regulator would be advantageous in some circumstances.

In the final three experiments, pre-emergent herbicides were evaluated for their potential to provide longer-term control of weeds in hardstand areas (i.e. under armcos and in paved areas) and amenity gardens. When pre-emergent herbicides were applied in combination with Glyphosate they provided longer-term control of weeds, and the time period between interventions was likely to have been significantly increased.

These studies have demonstrated that IVM strategies have the potential to save money for GCCC vegetation managers and improve the quality of the managed areas. Some of these strategies will be further investigated in a series of pilot programs during the coming year, and if successful, they may be implemented into regular GCCC management activities in the future.

Powerlink IVM trials

Experiments were undertaken in collaboration with Powerlink to determine the potential benefits of the implementation of an Integrated Vegetation Management (IVM) program into Powerlink operations.

Following on from the IVMP project, where certain plant growth regulators were found to effectively suppress Bahia grass seed-heads for 11 weeks, a commercial demonstration was conducted within the boundaries of the Mudgeeraba Substation during autumn 2010. In this demonstration, one of the treatments provided a 70% reduction in grass seed-head production during the entire observation period (i.e. 15 weeks). The period of suppression was probably extended by the cooler weather towards the end of the trial and an associated slowing of grass growth and seed-head production at this time.

This demonstration confirmed the results of the IVMP project and showed that some benefit can also be gained during autumn, though the benefit is not as great as during the height of summer. It showed that an IVM program has the potential to reduce the cost of managing grassed areas in Powerlink facilities by reducing the mowing frequency. More importantly, an IVM program has the potential to reduce the number of interventions required in the management of the vegetation at Powerlink sites.

Other areas within Powerlink facilities are required to be kept maintained without any vegetation whatsoever. These "no vegetation zones" surround vital equipment and are usually covered with concrete or coarse gravel. They are currently sprayed with Glyphosate to control weed species in an effort to maintain them free from vegetation.

This practice provides excellent control of the weeds present, but does not provide substantial long-term control. For safety reasons, such facilities have to be shut down every time that these vegetation management activities are undertaken, thereby interfering with their normal function.

Hence, an experiment was undertaken to evaluate the effectiveness of two pre-emergent herbicides for the longer-term control of weeds growing within areas of Powerlink infrastructure where no vegetation growth is an essential requirement. These herbicides were compared to the current standard practice of spraying with Glyphosate.

This experiment demonstrated quite clearly that the addition of pre-emergent herbicides to a regular Glyphosate application can provide much longer-term control. Seedlings were already quite abundant in the Glyphosate treated areas at 6 weeks after application. However, in the areas treated with Glyphosate and a pre-emergent herbicide, seedling growth was greatly inhibited (i.e. significant numbers of seedlings were not present until 15-25 weeks).

The results indicate that the use of pre-emergent herbicides in combination with Glyphosate will greatly increase the time period between interventions in "no vegetation zones". This may be of great benefit to Powerlink operations, as it will require facilities to be shut down less often for vegetation management activities to be undertaken.