Regenerative Viticulture Insights: Discovering the power of native insectary plants with Mary Retallack

Regenerative Viticulture Insights: Discovering the power of native insectary plants with Mary Retallack 1079 721 Sectormentor

Regenerative Viticulture Insights: Discovering the power of native insectary plants with Mary Retallack

We recently shared three amazing discussions from our second edition of the Regenerative Viticulture Series.

To celebrate our learnings, we’re releasing a roundup of each of the sessions and some of our favourite insights from them. In our previous instalments we pulled together some highlights from our conversations with Mimi Casteel and Sergio Nicolau.

Our last conversation was with the brilliant Mary Retallack, third generation viticulturist and agro-ecologist based in the Adelaide Hills, South Australia, with a particular interest in native insectary plants and their potential in biocontrol.

After studying ecology at school Mary returned to viticulture, managing her first vineyard in 2003 where she combined her knowledge in ecology and wine growing, using native insectary plants to manage pest and disease within the vineyard. At the time this idea was perceived as quite radical, and not promoted in conventional viticulture. 

To prove the benefits of these species and encourage their use within the industry Mary decided to embark on a PHD in viticulture and plant protection. After finishing her PHD in 2019 Mary worked to share this knowledge with other viticulturalists, using funding to develop the EcoVineyards programme in conjunction with the Wine Grape Council of South Australia. This programme has since gone national, funded by Wine Australia

Today, Mary runs her own small vineyard & consultancy Retallack Viticulture Pty Ltd, spending most of her time on the road providing advice to wine growers, alongside running events and writing educational materials for the EcoVineyards programme.

               Mary discussing soil health at the Great Aussie EcoVineyards Earthworm Count event

Mary explains what a native insectary plant is, how to encourage their growth within vineyards

A native insectary plant is a plant that is native to a certain region or historical plant community that provides Shelter, Nectar (food), Alternative prey and Pollen to local wildlife (encapsulated in the acronym SNAP!). These plants assist in biocontrol as they provide habitat and food for predators including arthropods, micro bats and insectivorous birds. 

Mary explains that the aim is to plant a range of species that provide habitat to a diversity of insects throughout the year. When looking at flowering insectary plants we want to grow species with a diversity of flower shapes, which have overlapping flowering periods at key times in the growing season. This is especially important during the grape flowering period to keep the inflorescences clean of pests, preventing an outbreak which could affect yields later on in the season.

In vineyards we are specifically looking at the use of ground cover and shrubs as these will work best within the wider ecosystem. Choosing species that are able to outcompete weeds, while possessing low potential to become a weed, have low establishment and maintenance costs, and low potential to host pest species.

When deciding what species to grow it is useful to look at the quality of the resources that the plants provide, in terms of nectar or pollen. Nectar is essential to provide food & energy, whereas, pollen is needed as it’s this which determines how many eggs these insects can produce, and how healthy they are. 

Mary states that diversity is key here and encourages a move away from monoculture, which she describes as a “fragile” and “poorly buffered” system in which “problem weeds and pests often dominate”, towards a polyculture system that promotes functional biodiversity, soil health, has better resilience, and is able to self regulate producing – a crop without continual intervention.

Stand of native grasses and forbs (including wallaby grass) and insectary shrubs at EcoGrower Clare Valley Vineyard

Mary goes on to explain some amazing findings from her own research

During her studies, Mary found that the capacity for biocontrol of insect pests increased more than 3x when native evergreen shrubs are planted in the vicinity of grapevines. In her experiments, Mary found that when planted concurrently shrubs like sweet bursaria (blackthorn), and prickly tea tree provide habitat for at least 65 species of predatory arthropods, including parasitic wasps, which provide biocontrol of grapevine scale and mealybugs, like light brown apple moth. 

She also studied a species called kneed wallaby grass, which is a native perennial that can be planted in the mid row or under vine and provides habitat and breeding sites for brown lacewing larvae, wolf spiders, and a range of predatory ground beetles. 

In a field trial Mary found a net increase of predator richness of around 27% when wallaby grasses were planted in combination with grapevines, including at least 37 different species of arthropods, and 100 other unidentified insect species – demonstrating the amazing richness of wildlife diversity we can get at ground level through the use of these plants!

We then moved on to discuss how Mary combined her thirty years of practical experience and scientific knowledge to create the amazing EcoVineyards programme

EcoVineyards is a national programme which aims to increase the land area dedicated to functional biodiversity in and around Australian vineyards. The programme combines academic peer-reviewed research, and evidence-based learning, working with over 45 vineyards across Australia, that act as demonstration sites to trial and showcase new management practices. These sites focus on three main areas of management: soil health, ground covers, and functional biodiversity

Mary and the team at EcoVineyards share new knowledge learnt on these sites through the EcoVineyards website, a knowledge hub which provides resources on how to implement these practices, including: a native plant species list for different regions; soil health indicators for Australian vineyards, and a wide range of EcoGrower case studies.

They also host events and are working on creating best practice management guides for all three focus areas, providing complimentary support to EcoGrowers from regional on ground coordinators. 

“We embrace all growers however they are currently growing and provide an ecological focus – we want to remove any barriers to uptake and accelerate practice change, working closely with growers to empower them to find these answers for themselves.”

            Ladybirds on western new holland daisies from native seedbank at Watervale Vineyard

Delving into the three pillars: soil health, ground cover and functional biodiversity

The EcoVineyards programme promotes the use of ground covers instead of cover crops, encouraging a move away from the idea of annual intervention and soil disturbance towards more perennial cropping. Once this is established they move on to encouraging more diversity through cropping multispecies mixes, then working to encourage the growth of species that are naturally adapted to the site.

“What we’re always looking for is to cover bare soil meaning 100% functional groundcover and active roots 100% of the time where possible. We know that the plants that we select to plant above ground will have an impact on microbes below ground, it’s all interconnected – the lovely thing about nature and ecology is every species has a place and they’re all really important!”

Mary states that the more diversity you have, the more benefits you will get in association; going on to outline some examples from the exciting research looking at the best species to plant in the under vine area, and how this affects soil health. One of these studies found that wallaby grasses and leguminous mixes with annual grasses grow well alongside grapevines, and were able to more than double the amount of soil microbial activity and sequester more carbon than systems using traditional herbicide practices. 

“Nature will always work to fill a void, so we would like to fill it with something functional that will work well for us.”

It is really exciting to see new knowledge being developed around these native species and that EcoVineyards is helping to establish and share this knowledge!

To learn more about under vine planting in action visit the case studies page on the EcoVineyards website and hear from a wide range of EcoGrowers.

Twiggy daisy bush (left) and New Holland daisy planted in under vine area (middle) in Morella Vineyard – see case study here. Hydroseeding seed and liquid mulch in under vine area (right) at Grindstone vineyard – see case study here.

A small note on sulphur use…

Mary believes there’re a lot of misconceptions in conventional viticulture including the unintended consequences of using sulphur as a fungicide. The overuse of sulphur can knock out predators like parasitic wasps and predatory mites that could provide biocontrol, while also reducing mycorrhizal fungi and earthworm populations in the soil. Mary instead suggests that during signs of a disease outbreak growers should first look towards biocontrol as a solution and use chemicals as a last resort. 

She suggests that we should be looking to instead increase the health of our vines naturally to decrease their susceptibility to pest and disease outbreaks (referred to as the trophobiosis theory). Mary explains that when our vines have a brix of 12% or more, it means that they are healthy and will more able to overcome pest pressures as “a pest starves on a healthy plant”. If growers are using sulphur Mary advises keeping applications below 400g per 100L to reduce its negative effects on wildlife populations, and the soil.

Many of these practices really challenge conventional beliefs in viticulture so we asked Mary how she works to change practitioners’ mindsets

“We can’t use the same thinking to fix some of the mistakes we’ve made in the past – we need a new way of thinking. Some practices just aren’t working for us anymore – we need to embrace ecologists in production landscapes.”

“I say to growers that are worried about changing practices and are already producing really good quality fruit – imagen how much better it could be! It’s not necessarily going to be a negative, maybe we can take it to a whole new level.”

Mary believes that the economic benefits that native insectary plants and wider biodiversity provide can also help to convince practitioners and create wider industry change. We know that establishing inter-row vegetation and minimising bare earth will support mycorrhizal fungi which can in turn “provide up to 90% of plants nitrogen and phosphorus requirements”, reducing the need for artificial inputs. 

“Setting ourselves up for these longer term benefits, means we are not intervening as often, saving both time and resources.”

Ecovineyard’s also publish all of the financial costings of each project in the EcoGrowers case studies so that readers can see first hand how these practices can improve profitability. See the case study on Dan Falkenburg who was able to reduce his input costs and weed burden, and improve soil health and biodiversity, while saving 615$ a year by switching over from an annual cover crop to a  four species blend of self-regenerating wallaby grass.

“I think we are at the most exciting time to grow wine grapes certainly in my career. We’re challenging some of those established practices and looking for new solutions and I find that really exciting.”

We loved connecting with Mary and learning how she is applying an ecological approach to viticulture! Whether or not you are farming in an Australian environment, Mary’s philosophy and research can help us understand the experiments that are going on, so that we can learn from them and apply them in our own locations.

All the images in this blog were taken from the EcoVineyards website & Instagram account and Mary’s social media – follow them @ecovineyards & @retallackviti to learn more!