Report: Forest Pest Management (FPM) Research Consortium April Field Trip

TAS FIELD TRIP: Forest pest, weed and disease management in Tasmania

Devonport, TAS | 24 April 2024

By Sam Van Holsbeeck

On Wednesday 24 April 2024, the Forest Pest Management (FPM) Research Consortium hosted its third annual field day in collaboration with local Tasmanian forestry partners, including Forico, Reliance Forest Fibre, Timberlands Pacific, SFM and Sustainable Timber Tasmania. The FPM Research Consortium is funded through Forest & Wood Products Australia and strives to maintain the health and the productive capacity of forests by finding and taking appropriate measures to reduce the negative impact of weeds, pests and diseases. The core research activities of the consortium include developing customised screening and operational trials in partnership with forest growers and control agent providers and delivering capacity-building opportunities for the industry to improve national pest, weed and disease management strategies.

This year’s field trip took us to northwest Tasmania, where the group visited locally established research trials. Present on the day was a group of 34 very enthusiastic attendees and presenters who came from as far as Western Australia. The field day began early in Devonport where the group gathered. Following site inductions and acknowledgement of Country, the group received a brief introduction to the FPM Research Consortium and its activities provided by the project manager, Sam Van Holsbeeck (UniSC).

At the first stop in Beulah, Southern Environmental provided a brief introduction and demonstration on the use of drones (Remotely Piloted Aerial Systems) for pesticide application in forestry. In this case, a DJI T40 drone was used, and the advantages of drone-based pesticide application were discussed. The FPM Research Consortium has done a lot of work in forestry on spray technology for improved pesticide application and reduced exposure of humans and the environment to drift. The

group had the opportunity to have a closer look at the vehicle and saw the drone in action during a water-only spray demonstration.

At the same location, the group visited a post-plant weed control trial in a Eucalyptus nitens plantation. This trial aims to identify new weed control solutions that can be applied over the top of trees and provide sufficient weed suppression while maintaining or improving tree health and growth. The trial consists of 8 treatments and 4 replicates including controls. All treatments are a variation of the operation standard where one of the active ingredients is replaced by an alternative solution of interest. Tree height, health, survival and weed control are assessed several times within the first year of tree growth. While early to be conclusive, the trial shows that most treatments provide good weed control and that several new active ingredients can potentially be used to diversify weed control solutions available to forestry.

During stop 2 in South Nietta, the group visited another E. nitens plantation where two trials were discussed. The first trial explores environmental- and animal-friendly control measures for mammal browsing during seedling establishment. Several biodegradable nets are applied around tree seedlings and their durability and effectiveness are being evaluated as the trial progresses. The trial contains 1024 trees in 4 replicate blocks and initial results show promising results for custom-designed biodegradable nets. As a result of this trial, it is quite likely forestry will be able to eliminate the use of plastic tree nets applied as a protection against browsing mammals and shift to biodegradable equally effective solutions.

The second trial was an operational clothianidin uptake trial, established to assess the effect of clothianidin against damaging insects. Damage caused by leaf beetles seems to occur more consistently on higher-elevation Tertiary Basalt soils, however, it is quite difficult to spot the insects as they are generally nighttime feeders and are often not reported during systematic monitoring. Clothianidin is a systemic insecticide that is safe for pollinators. Because it can be applied as a granule or via liquid soil injection, the exposure to the applicator is minimised compared to spray application for example. There is a clear visible distinction between areas treated vs areas untreated, where treated areas show much better tree health and the damage caused by leaf-eating insects is reduced.

After lunch at the Leven Canyon Picnic Area, the group visited a E. nitens plantation in Hampshire that was badly impacted by unfavourable climatic factors (cold air ponding and exposure) combined with inappropriate genotypes (cold tolerance), insect and disease pressure, and weed competition. As a result, tree growth has stalled, and the health of the plantation is in decline. Most trees show signs of leaf damage caused by leaf-eating insects such as Paropsisterna agricola (Chrysomelid), with clear signs of Teratosphaeria Leaf Disease (Kirramyces) infection. The group discussed different management strategies that could have been applied here to minimise the effect of present health-declining factors. Management strategies included regular monitoring to detect the presence of damaging insects and pathogens early in the rotation, better control of weeds to reduce competition with trees and allow for better airflow to reduce disease pressure, species and genotype selection and reducing exposure to climatic conditions by providing protection from more mature neighbouring stands.

The final stop of the field day was at a Tewkesbury demonstration trial for biomass recovery. On this site, biomass/woody residue was mechanically removed after log harvest as a strategy to reduce site-preparation costs and improve plantation establishment. The biomass removed from the site could be used as a feedstock for biofuel generation. While it is still early to explore any benefits on tree growth, nutrition or effects on the weed spectrum, alternative weed control strategies like this are supported by the FPM Research consortium in an attempt to reduce the use of pesticides in forestry.

The FPM Research Consortium would like to thank Forico, Reliance Forest Fibre, Timberlands Pacific, SFM and Sustainable Timber Tasmania for their help and organisation of the field trip, and most importantly all attendees for making the day a big success and being enormously engaged throughout the day. We look forward to hosting the next event and welcoming you once again.