design to an unbalanced randomised complete block.
As for the Cape Riche experiment, treatments with herbicides, fungicides and fumigants added macronutrients to the soil in organic form. Estimates of elemental additions from chemical applications, not including those in wetting agents and carriers, were: C, 91 g/m2; N, 38 g/m2; P, 1.3 g/m2; and S, 168 g/m2. Like the Cape Riche site, chemical treatments are likely to have increased soil fertility.
Experimental set-up: operational matters
Logistics
A better study site could not have been chosen. Located within the National Park and within 1.5 km from the ranger station, access to the site is controlled and security is excellent. We have been able to access workshop facilities, tools and other equipment, storage space, space for laboratory work and accommodation at short notice within the park. Materials and services for setting up the experiment have been sourced locally at Latrobe and Devonport, within a 30 - 45 min drive from the site. Laboratory supplies and equipment have been sourced through the Launceston campus of the University of Tasmania.
Hygiene
Operations to set up the experiment were undertaken during a period of prolonged drought in autumn with conditions providing the least risk of spreading Phytophthora. While the riskiest operations have been completed, further fumigation treatments may require vehicular access across infested vegetation when conditions will make the risk of spread much higher. In addition, the access track intersects and adjoins Phytophthora infestations and should therefore be treated as infested. Before future operations at the site, a simple wash down point should be established at the beginning of the access track.
Site preparation
The experimental site had not been burnt for approximately 30 years. In the preparation of plots that were to receive complete treatments, significant amounts of live and dead plant material, some of it probably infested with P. cinnamomi, were removed. If larger infestations are to be treated then safe disposal of potentially contaminated material within the infested site will pose an additional problem.
Barrier installation
At Narawntapu NP, a ‘Dingo Digger’ (Dingo Mini Diggers, Dalby, Qld) was used in trenching, whereas a Bobcat machine (Ingersol-Rand) was used at Cape Riche. However, directional control in trenching was poor with the Dingo Digger (16.9 kW/650 kg), it had difficulty in dealing with trenching in plots with gravel and cobbles in the B horizon, and it was less stable on uneven ground. The Dingo Digger has characteristics that may be advantageous for carrying out similar operations elsewhere:
x smaller size (width 1.05 m, compared with 1.8 m for the Bobcat) allowing it to be used in more restricted spaces (forest),
x causes less damage to vegetation and is much easier to clean down; and
In the process of installing barriers most of the time and physical effort was used in cleaning out trenches and filling them back in. In future operations, the amount of effort in these tasks could be reduced significantly by using a narrower cutter (available in 10 and 15 cm widths). This would reduce the amount of excavated spoil, and trenching to a depth greater than the depth of the barrier material, with the aim of eliminating the need to undertake the laborious task of cleaning out trenches. The Rootwall barrier used in this experiment is strong and durable enough to stop practically any root and last for decades in the soil. However, it is quite heavy (20 m roll = ~20 kg) and difficult to roll out and install, even under the favourable conditions at Narawntapu NP. For operations in areas more difficult to access, by terrain or vegetation, a lighter weight material would have to be sourced and used.
Fumigation
Fumigation of plots generally proceeded well with the equipment used. The injection points bent to some extent, but did not become unusable. Welding in the probe failed and it had to be re-welded onsite. In soft soil the injection probe system failed, and must be rebuilt to a much more robust design. The three probe design of the injection system proved useful in that the application time for the fumigant was reduced to 1.2 - 1.8 min/m2, faster than expected.
In conclusion, similar results were achieved in this experiment as those at Cape Riche. A combination of vegetation removal, herbicide use to ensure P. cinnamomi has no living host material to invade, fungicide and fumigant treatments were effective in eradicating the pathogen from the Narawntapu NP treatment plots for the duration of the study. The fungicide treatments alone were ineffective, and additional treatments with other fungicides in addition to Metalaxyl-M, and at higher application rates, need to be applied to the site and their efficacy assessed. The installation of the heavy-duty root barriers will further facilitate keeping these sites disease-free in the future, by preventing reinfestation of the site from adjacent diseased vegetation. These results are extremely promising in terms of protecting key plant species and plant communities from P. cinnamomi. However, it is critical that the Narawntapu NP plots are reassessed at least twice more (e.g. after a further 12 and 24 months) to confirm that the pathogen has been completely eradicated.
Tender Number: 19/2005DEH Sub Projects 19.3.a(i and ii) 30 May 2008