Grape phylloxera (Daktulosphaira vitifoliae) is a devastating pest of grapevines worldwide, affecting both commercial and ornamental vines. Adult phylloxera feed on leaves and/or grapevine roots causing death of the European grapevine, Vitis vinifera (that we term ‘own-rooted’ vines).
In Australia, the roots of V. vinifera, are extremely susceptible to attack by the phylloxera present, but the leaves are resistant to these strains. Rootstocks used commercially in Australia are considered to vary in their resistance, or tolerance, to different phylloxera strains, and research continues in this area.
Phylloxera tolerant rootstocks are those on which phylloxera can feed, reproduce and cause root galling (nodosities), but limited economic damage. Phylloxera resistant grapevines are those on which phylloxera cannot develop to the adult stage so there is no egg production and no gall production.
With the lack of available chemical or biological controls for phylloxera, the only proven cultural method to manage phylloxera is to pull out infested own-rooted vines and replant with new vines that have been grafted onto phylloxera-resistant American rootstocks.
Grafted propagation material is traditionally used to manipulate vine performance. Drivers for rootstock use are wide ranging and include:
- Salt tolerance
- Water-use efficiency and drought tolerance
- Reduced vigour to counter the negative impacts of high vigour on berry composition
- Reduced potassium uptake to counter the impact of high berry potassium on pH
The fact that 74% of South Australian vineyards are on own roots underlines the susceptibility of South Australian vineyards to phylloxera. Vinehealth Australia is a keen supporter of research to better understand rootstock characteristics and their impact on vine attributes and wine quality and style.