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Building on cultural and biological management of apple and pear pests and diseases

Pest and Disease Management

As the fourth phase of the Productivity, Irrigation, Pests and Soils program commences, we look at how the integrated work of the recently completed PIPS3 project, Strengthening cultural and biological management of pests and diseases in apple & pear orchards (AP19002), will be catapulted over the next five years in the PIPS 4 Profit – Pest and disease management (AP22001) project. 

One of the greatest challenges when managing pests and diseases is how to reduce inputs, including repeated use of broad-spectrum pesticide sprays, while also having confidence that alternative managements are effective, environmentally sound and profitable. The integrated pest and disease management (IPDM) focused project of the PIPS3 program aimed to provide growers and industry advisors with increased confidence in IDPM decision-making. In particular, it demonstrated ways to optimise the efficacy of biological control methods and addressed gaps in knowledge hindering uptake of managements that support biodiversity and soil health, both of which are essential for low-input pest and disease management. The next phase of work in the PIPS 4 Profit program will focus on demonstrating regionally based, profitable IPDM solutions and will arm growers with the local information and resources they need to support their IPDM decisions. In order to achieve this, Agriculture Victoria will lead the national project, with the Tasmanian Institute of Agriculture (TIA-UTAS), Pomewest and the NSW Department of Primary Industries (NSW DPI) delivering research and extension activities in Tasmania, Western Australia and New South Wales.

 

Greg Lefoe and Neil Penfold of Agriculture Victoria set up monitoring traps in the Experimental Pear Orchard of the Tatura SmartFarm in October 2023.

Promoting biological control

Tiny parasitic wasps, commonly known as Trichogramma, have been successfully utilised worldwide as biocontrol agents that parasitise the eggs of a range of pest insects, including codling moth and light brown apple moth. In research specifically focused on the contribution of different species of Trichogramma, the PIPS3 project team at Agriculture Victoria confirmed that codling moth is a suitable host for Trichogramma carverae under laboratory conditions. Furthermore, results indicated that T. carverae has considerable potential for control of codling moth in orchard situations and that further ecological studies are warranted. The team also discovered previously unrecorded diversity among the beneficial Trichogramma taxa occupying an experimental pear orchard. These findings highlight the importance of understanding the role of existing parasitoids in apple and pear orchards and how habitat manipulation and IPDM can support their populations. 

DNA barcoding revealed that Australian populations of the specialised codling moth parasitoid Mastrus ridens were impacted by low genetic diversity, probably due to undergoing genetic bottlenecks over the extended period it was maintained in laboratory culture. This low genetic diversity may have limited the parasitoid’s ability to establish permanent populations in Australian orchards. A major achievement of the PIPS3 project was the importation of a new, genetically diverse strain of M. ridens that is predicted to establish more readily in Australia. Six releases of this new strain were conducted in orchards in four states in 2022–23. While it was too soon to conduct impact assessments for these new releases in PIPS3, follow-up monitoring and additional orchard releases are planned as part of the PIPS 4 Profit project.

 

The more robust Mastrus ridens population was imported, quarantined, mass reared and released as part of the PIPS3 program. The next phase in PIPS 4 Profit will see more releases undertaken across regions, and monitoring of the spread and effectiveness upon codling moth control.

Demonstrating economic benefits of IPDM

The codling moth example was used as a case study to investigate the potential economic benefits of biological control. Based on preliminary scenario analyses using a prototype discounted cash flow model, it was found that biological control of codling moth with M. ridens is a worthwhile investment, especially if parasitoid populations prove to be sustainable without ongoing releases (benefit to cost ratio of 5.5:1). The model is a valuable tool for planning future codling moth management priorities. It is recommended that the model and scenario analyses be further developed. 

Orchards as habitat for beneficials

Beneficial natural enemies, such Mastrus ridens and Trichogramma parasitoids, need resources such as shelter, nectar, alternative prey or hosts and pollen (often termed ‘SNAP’) to maximise their numbers and pest control potential. These SNAP resources can be provided by maintaining or introducing appropriate plants or substrates in or around the orchard. Biological control experiments conducted in apple and pear orchards in Victoria and Tasmania highlighted the potential for habitat manipulation. The research demonstrated that manipulating ground cover within orchards can alter arthropod abundance and diversity. For example, certain vegetative groundcover treatments within the tree line encouraged predators such as earwigs and spiders. These gains have the potential to promote nutrient cycling and suppress ground-dwelling and canopy-borne pests during the production season.  

The research also highlighted practical barriers to adoption, particularly of native vegetation within orchard blocks. Principal among these barriers was the difficulty and cost of establishing native groundcover forbs and grasses within highly modified, conventionally managed apple and pear orchards. Findings such as these demonstrate the importance of assessing both the economic feasibility and environmental benefits of changing orchard management practices. Further research in the PIPS 4 Profit program will develop tailored inter-row and tree line cover crop recommendations that promote resident natural enemies and specialised biological control agents.

 

Jess Fearnley, NSW DPI, releasing Mastrus ridens at an orchard in Nashdale, NSW.

Spreading the word

Communication and engagement activities are an ongoing priority in the PIPS program. The PIPS3 Strengthening cultural and biological management of pests and diseases in apple & pear orchards project produced YouTube videos, held field days and workshops, and published dozens of IPDM articles on the ExtensionAus Australian Apple and Pear IPDM website and in the industry publications AFG and Industry Juice. An immediate outcome of this work is expected to be improved access to high-quality information on IPDM practices and technologies for all sectors of the apple and pear industry. The project also hosted an IPDM Community of Practice for growers and advisors, featuring regular online meetings and seminars. The Community of Practice is highly valued by the advisors who participate as it provides a platform for exchange with those in similar roles across the country. This work continues in the PIPS 4 Profit program, with an even greater focus on identifying and addressing regional issues.  

Next steps

The PIPS 4 Profit Pest and disease management (AP22001) project is an example of industry supporting momentum and prioritising whole-of-system research, development and demonstration of sustainable and profitable practices. Without this approach, it is highly unlikely that the potential for IPDM, including development and introduction of new biological control agents, could be realised as PIPS has done, and will continue to do, for the apple and pear industry.   

To access the valuable resources generated on the topic of IPDM in PIPS3, head to the PIPS 3 Program resources webpage on the APAL website: https://apal.org.au/programs/more-industry-programs/pips3program/pips3resources/.  

Acknowledgements  

The PIPS 4 Profit Program’s Pest and disease management  (AP22001) project has been funded by Hort Innovation, using the apple and pear research and development levy, contributions from the Australian Government and co-investment from Agriculture Victoria. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.  

About the author: 

Greg Lefoe, Senior Research Scientist 

Agriculture Victoria Research 

This article was first published in the Summer 2023/4 edition of AFG.

 

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