Functional biodiversity solutions for Australian vineyards: Harnessing groundcovers, vineyard surrounds and native plants to deliver key ecosystem services
Abstract
This project identified the benefits of vineyard groundcovers and vegetation in the landscape. Laboratory, field trial and survey studies encompassed 32 vineyards in the 2021-2022 and 2022-2023 seasons. Several plant species produced nectar that promoted beneficial wasps but denied benefit to lightbrown apple moth. Field trials showed that groundcovers were challenging to establish but can replace taller weeds and reduce levels of pest damage and associated bunch rot. Surveys showed that beneficial insect densities in vineyards were promoted by linear riparian and roadside vegetation, especially when this extended to the wider landscape. A suite of grower-facing communications has been produced.
Summary
This project aimed to determine the extent of pest, plant disease and weed suppression and changes in frost risk that arise from the planting of the selected groundcovers. A blend of laboratory, field trial and field survey methods were used, encompassing 32 vineyards in the 2021-2022 and 2022-2023 seasons.
A suite of plant species, including several Australian natives, were able to promote the lifespan of two species of parasitoid wasp. These beneficial wasps attack the major Australian vineyard pest lightbrown apple moth (LBAM). Trichogramma carverae and T. pretiosum, had improved fecundity under laboratory conditions when feeding on nectar of selected species. Several of these plant species did not provide an equivalent benefit to LBAM so can be considered ‘selective food plants’ that could be used in vineyards to promote the parasitoids without inadvertently promoting the pest. This laboratory screening also identified several groundcover species that do benefit LBAM so should be avoided in future plantings.
Field trials in two NSW vineyards showed that undervine and midrow groundcovers can reduce levels of LBAM damage and the associated bunch rot. Most of the tested groundcover species were shorter growing than the spontaneous weedy vegetation they replaced. This offers several advantages including the promotion of air flow in the vineyard conferring lower risk of frost damage and fungal disease. Generally, however, the addition of groundcover vegetation to established vineyards was logistically challenging, especially under organic production conditions where herbicide control of existing vegetation was constrained. Groundcover establishment prior to or in the early stages of vineyard establishment is likely to be easier.
More broadly than the results obtained for the particular plant species used in the laboratory and field trial studies, it is possible to infer the major traits of plants that are indicative of benefit in a vineyard context. These are: white flowers, capable of blooming early in the season and for a prolonged period, prostrate or short-growing growth habit, vigorous early vegetative growth, dense and competitive habit, and low susceptibility to frost. Ease of availability of inexpensive planting material (seeds or young plants) is a further consideration. None of the plants tested in the present study are considered to present a significant weed risk because all are native or widely grown exotics that have not already become weeds. Growers exploring wider species choice options should consider potential weed risk including toxicity or injury to livestock that may be used in the vineyard. Whilst there is growing interest in the Australian vineyard sector in the use of native plants in and around vineyards for wildlife conservation and aesthetic reasons, it is not possible to make a general recommendation to use Australian native plants to provide pest management related benefits. Some native plants, such as Acacia, did not promote beneficials when used as groundcovers whilst others, such as Myoporum, did.
Field surveys revealed that the density of beneficial arthropods (insects and spiders) within a given vineyards is far from uniform and is influenced by the nature of adjacent land use. Densities of beneficials on vines were promoted by linear riparian and roadside vegetation in adjacent areas. This is likely to reflect the facts that these forms of vegetation are lightly managed and have low levels of disturbances such as spraying, grazing and cultivation. Reflecting this, these areas are characterised by structural complexity (e.g. banks and ridges, tussocky and woody vegetation of different heights and ages, standing and fallen timber) and taxonomic diversity in plants that would tend to make resources such as nectar and pollen available for extended periods compared with less diverse vegetation. In addition to those attributes, the fact that riparian and roadside vegetation is – by definition – linear in form. This allows such land uses to provide habitat linkage between vineyards and more remote habitat patches that may serve as refuges for beneficial arthropods.
At spatial scales wider than the vineyard-adjacent land use, there were strong effects of vegetation patterns on densities of beneficial in vineyards. At the scale of 5 km from a given vineyard, an abundance of non-perennial crops and pastures tended to be associated with higher abundance of beneficial arthropods as a whole, and parasitoids as one of the numerically dominant types of beneficial, on vines. This effect could result from those crops harbouring pest species that allowed beneficial insects and spiders to build up in density and ‘spill-over’ into nearby vineyards. Such an effect would be promoted by the disturbance regimes of those systems in which harvesting or grazing might propose emigration of beneficials. Densities of beneficials on sampled vines were also favoured by landscapes in which there was native woodland present in configurations that led to relatively high edge density (e.g., small patches and strips rather than low numbers of larger patches).
Consistent with this finding, beneficials were also favoured by linear strips of vegetation of the type that were also favourable when located immediately adjacent to vineyard.
Results have been communicated to industry at the Australian Wine Industry Technical Conference (AWITC) where Geoff Gurr gave an invited presentation. He also co-convened a workshop at the AWITC with Mary Retallack entitled ‘Managing non-vine vegetation in and around the vineyard to deliver production benefits’. Both Prof Gurr and co-investigator Dr Jian Liu presented talks on aspects of the project. Additionally, findings have been presented in Grapegrower and Winemaker and at six regional workshops in the NSW Department of Primary Industries Spring Vine Heath Field Days.
This work was financially supported by Wine Australia and Charles Sturt University. The authors gratefully acknowledge See Saw Wines and Angullong Vineyard for hosting field trials and the dozens of vineyard owners and managers who allowed data and samples to be collected. We thank Mark Bourne, NSW Wine Industry Association; Nicole Samodol, Rowlee Wines; Brendan Jarrett, See Saw Wines; Stephen McKenzie, Angullong Vineyard for their service on the project’s Industry advisory Panel and Anne Johnson (PhD student) for invaluable assistance.