Predatory arthropods associated with potential native insectary plants for Australian vineyards

Dr. Mary Retallack

Viticulturist / Managing Director, Retallack Viticulture Pty Ltd

ASVO Member

Member, Global Alliance of Independent Agricultural Consultants, Certified Practising Agriculturist (CPAg)

RIRDC Rural Woman of the Year, 2012

Retallack, M. , Thomson, L. and Keller, M. (2019), Predatory arthropods associated with potential native insectary plants for Australian vineyards. Australian Journal of Grape and Wine Research, 25: 233-242. doi:10.1111/ajgw.12383

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What issue or problem does your research seek to solve?

Damage to grape skins caused by LBAM provides infection sites and may predispose bunches to bunch moulds. Annual losses from Botrytis and other bunch rots and LBAM were estimated at $52 million and $18 million respectively, with a combined national economic impact of $70 million p.a. So, if LBAM damage can be minimised, this will also potentially reduce the impact of Botrytis and other bunch rots. In addition, losses of $0.5 million per year can be attributed to garden weevils, grape phylloxera, mealybugs, scales and trunk boring insects. Other vineyard pests include the Australian grapevine moth, elephant weevils, and mites. The management of pests is required to minimise the economic damage caused by fruit quality and yield losses. This may be achieved through biological control of pest by predatory arthropods.

Over the last two decades there has been ongoing work on the role of native insectary plants and their contribution towards ‘conservation biological control’ (CBC). CBC involves the implementation of practices that protect and enhance the reproduction, survival, and efficacy of natural enemies of pests. Insectary plants provide food, shelter and alternative prey/hosts, which nourish and support the presence of predatory arthropods. Relatively little work has been done on the use of specific native plant species in the field of CBC within Australia. I chose to address this gap in knowledge.

I also sought to determine if candidate insectary plants:

  1. Have the capacity to support populations of predatory arthropods throughout the year, and
  2. If they may also provide habitat for economically damaging vineyards pests.

The data were analysed to answer these additional questions:

  1. What is the biological and functional diversity associated with each plant species?
  2. What are the features of an effective, functional native insectary plant assemblage for use in and around vineyards?
  3. What is the level of similarity and dissimilarity between the arthropod faunas of each plant species?

What was the most interesting thing you found in this research?

I investigated two key themes, firstly the role that native insectary plants can play in supporting populations of predatory arthropods or ‘natural enemies’. I evaluated three native plants in Adelaide Hills, Barossa Valley and Eden Valley to determine their capacity to provide insectary benefits to predatory arthropods in vineyards, and thereby to enhance biological control of insect pests. Locally-adapted native plants are preferred as supplementary flora, as they are naturally adapted to Australia’s climatic conditions.

The incorporation of native insectary plants Christmas bush, Bursaria spinosa, prickly tea-tree, Leptospermum continentale and wallaby grasses, Rytidosperma ssp. has the potential to enhance biodiversity, and conservation biological control efforts by providing a suitable habitat to support diverse and functional populations of predatory arthropods.

I found that predatory arthropods dominated the diversity of morphospecies present on each plant. The richness of predator morphospecies across all plant types was nearly double the number found in association with grapevines. By incorporating each of these native plant assemblages in and around vineyards it may be possible to increase the functional diversity offered by predatory arthropods by more than 3x when B. spinosa and L. continentale are incorporated versus grapevines only. Rytidosperma ssp. should provide complementarity through its association with dissimilar predatory arthropods. When Rytidosperma ssp. is included in a plant assemblage with of each woody plant species and grapevine, this could result in a further net increase in predator morphospecies richness in the order of 27%.

Secondly, I set out to clarify if LBAM is the main lepidopteran pest of grapevines in vineyards. Larvae of Tortricidae have no defining morphological features, so I used molecular methods to determine that LBAM is the key insect pest that causes economic damage in Australian vineyards. The study has revealed for the first time that larval Acropolitis rudisana, lucerne leafroller, Merophyas divulsana, and cotton tipworm, Crocidosema plebejana can be found on the grapevine canopy in South Australian vineyards at low densities. As they are closely related to LBAM it is anticipated they can be managed through existing integrated pest management (IPM) strategies. These lepidopteran species may provide a valuable source of alternative hosts for parasitoids and alternative prey for predators, if the larvae are predominantly located in vineyard mid-rows and don’t migrate to the grapevine canopy.

How will this help in the ‘real world’?

The opportunity to plant selected native insectary species could help wine grape growers save time and resources by producing fruit with lower pest incidence, while enhancing biodiversity of their vineyards. These studies support a truly integrated approach to pest management, which incorporates natural biological control and the use of native insectary plants to potentially provide long-term and sustainable solutions. The selected insectary plants are naturally adapted to all of the major wine growing regions within Australia and could be potentially planted virtually wherever wine grapes are grown. Enhanced biodiversity can lead to greater natural biological control, resilience within the system and improved ecosystem services.

The proposal to incorporate native insectary habitat provides an opportunity for wine grape growers to demonstrate their environmental credentials, and improve their individual biodiversity scores via national environmental stewardship programs. There is also a growing awareness by grape growers of ways to build competitive advantage along the value chain and in key export markets. Australian producers are well placed to demonstrate their environmental stewardship credentials and promote their ‘clean and green’ image. The incorporation of locally-adapted, native vegetation is a tangible way that vineyards and wineries can potentially convey their unique Australian offerings and stand out in a crowded international market place.

How soon will this be commercially available?

Vineyard managers are encouraged to explore the use of locally-adapted, native insectary plants in association with vineyards. Existing vegetation structures such as windbreaks, vegetation corridors, beetle banks, mid-row, under-vine and headland plantings can be enhanced to provide resources for predators that contribute to pest control throughout the year. Workshops and fact sheets will be progressively developed for growers in the near future.

Have you seen the outcomes being adopted yet?

Yes, in an effort to find ways to combine productive agriculture with on-farm natural resource management, my PhD research was utilised to help design a simple on-farm trial that could be easily replicated by growers in Victoria. The Port Phillip and Westernport Catchment Management Authority established series of trial sites, working with a wide range of growers commencing in 2016. The project has been an outstanding success. For more information see http://www.ppwcma.vic.gov.au/wp-content/uploads/2017/09/Insectariums-Case-study-AUGUST-2018.pdf.

I have also been working closely with the Wine Grape Council of South Australia (WGCSA) to raise awareness of the role of ecosystem services and the benefits of functional biodiversity enhancement. Each month an aspect of this work is showcased via the WGCSA email update https://www.wgcsa.com.au. There are lots of exciting initiatives planned. Watch this space!

There are a number of associated projects running in parallel with Natural Resources, Adelaide and Mount Lofty Ranges and local wine associations. Keep an eye out for the #Wildlife4wine hashtag.

Where can people hear more about your work?

In addition to my PhD thesis and two peer reviewed journal papers, I have written a series of seven articles which are published in The Australian and New Zealand Grapegrower and Winemaker journal. A final peer reviewed journal paper is also in preparation.

 

For more information contact Mary Retallack, Retallack Viticulture Pty Ltd www.viti.com.au