Grape phylloxera (Daktulosphaira vitifoliae) is a plant pest of grapevines in parts of New South Wales and Victoria.
A plant pest is a disease causing organism or an invertebrate which threatens agricultural production, forestry or native and amenity plants.
This insect is a serious threat to Australia's grape and wine industry.
Grape phylloxera (Daktulosphaira vitifoliae) is a small (less than 1 mm) aphid-like insect that lives and feeds on the roots of grapevines (Figure 1). Root damage caused by phylloxera results in grapevine decline and eventually death of the plant.
In spring and summer, phylloxera emerge at the soil surface before crawling up into the grapevine canopy where they move around on leaves and grape bunches but do not feed or cause damage.
There is no control for phylloxera and once established in a vineyard the only way to manage it is to remove all susceptible grapevines.
In North America there is a winged form of phylloxera however it has rarely been seen in Australia and appears to be sterile.
The first signs of a phylloxera infestation in a vineyard are yellowing and stunted growth of individual grapevines (Figure 2).
Another sign is an increase in weed growth under an infested grapevine. These symptoms usually appear 1-3 years after the initial infestation.
Phylloxera feeds on grapevine roots by puncturing the root surface. The grapevine responds by forming galls on the root hairs and swellings on older roots.
Galls on the root hairs have a characteristic hook shaped form and hinder the growth of feeder roots. On larger roots there can be swelling of the root tissue and subsequent decay through secondary fungal or bacterial infections.
Root damage and the loss of feeder roots causes the grapevine to decline and eventually die (Figure 3).
Once phylloxera is established in a vineyard the only way to remove phylloxera is to remove all susceptible grapevines and replant with tolerant rootstocks.
Phylloxera adults are 1 mm in length. They are yellow in colour in the summer, tending to brown in the winter.
Immature phylloxera are called crawlers or nymphs and resemble the adult in shape.
Eggs are yellow and less than 0.3 mm long.
Phylloxera is able to reproduce asexually. An adult female is capable of laying up to 200 eggs per year without mating.
Phylloxera crawlers hatch from eggs laid on the grapevine roots during spring and summer. Crawlers may remain in the root system or climb up the vine into the leaf canopy where they undergo four development stages.
Peak population numbers in Australia occur in January and February. Phylloxera survives the winter in the form of eggs or crawlers on the nodules or galls on the grapevine roots.
Host plants of phylloxera are grapevines in the genus Vitis. Vitis species differ in tolerance or resistance to phylloxera.
Roots of European grapevine (Vitis vinifera) are susceptible to attack by the root feeding form of phylloxera, but the leaves are resistant.
The American grapevine (Vitis riparia) withstands extensive galling of the leaves but is resistant to root attack by phylloxera.
Phylloxera has spread worldwide with the movement of infested plant material.
The natural spread of phylloxera within an infested vineyard is approximately 100 m a year.
Once established in a vineyard phylloxera can be spread by:
Phylloxera can survive for up to eight days without feeding on grapevines.
Phylloxera is native to North America and has spread to most of the world's wine regions including in Australia.
Phylloxera was first discovered in Australia in 1877 at Geelong, Victoria. The first detection in New South Wales occurred in 1884 at Camden.
Currently, most of Australia's main vineyard regions are free of phylloxera. In order to protect these areas phylloxera zones have been declared in New South Wales and Victoria.
Quarantine boundaries have been established in Australia to prevent spread of phylloxera from known Phylloxera Infested Zones (PIZ) to phylloxera free areas known as Phylloxera Exclusion Zones (PEZ). Areas of unknown status are referred to as Phylloxera Risk Zones (PRZ).
In New South Wales, two PIZ's have been declared, one around Albury/Corowa and another in the Greater Sydney Region.
The rest of New South Wales is a declared PEZ because rigorous phylloxera surveillance in 2002-05 found no further infested areas.
In Victoria, declared PIZ's are Nagambie, Mooroopna, Whitebridge, Upton, North East Victoria and Maroondah.
The whole of South Australia and some parts of Victoria and Queensland are declared PEZ's and large areas of Queensland and Victoria have PRZ status.
The common form of surveillance for phylloxera is called ground surveying. Ground surveys are best conducted in vineyards between December and April when phylloxera is most active.
Surveillance should be done at the margins of deteriorating vine patches. Close inspection for phylloxera colonies and damage on fibrous roots should be carried out near the base of vines. Infested vines will have fleshy yellow galls on fibrous roots with pinhead sized yellow insects on the gall surfaces and swellings on older roots.
Vines in the centre of deteriorating patches have badly damaged root systems with no fibrous roots.
As well as ground surveys, aerial surveys using near infrared photography of the grapevine canopy can be used to identify vines showing decline or premature yellowing. If phylloxera is the suspected cause of these symptoms, always follow up with a root inspection to confirm phylloxera presence or absence.
Another method currently under development for detection of phylloxera is an emergence trap. This method of trapping can be used in spring and summer months as crawlers move from the vine roots onto the soil surface.
The trap involves a bucket or similar container which is moistened on the inside surface and then placed upside down at the base of a grapevine (Figure 4). The container is pegged to the ground to create an airtight seal and encourage a build up of humidity within.
As phylloxera crawlers move from roots to canopy, some will emerge within the inverted container and move up the inside walls. Condensation on the inside surface of the container catches the phylloxera crawlers.
When traps are retrieved after 3 to 4 weeks the accumulated condensation can be collected in ethanol or methylated spirits and inspected for phylloxera using a microscope. Suspected phylloxera should be verified by an expert.
Spread of phylloxera to new locations is generally a result of unintentional movement of the insect by people. Phylloxera can be transferred on grape and grapevine material, through equipment that has been used in infested vineyards and by people on their clothing or footwear moving from infested to non-infested vineyards.
Signage discouraging entry into phylloxera-free vineyards should be observed at all times.
Planting material should always be purchased from certified nurseries in phylloxera-free areas, and should be hot-water treated in accordance with state regulations.
At present there is no effective and economic long-term solution for controlling phylloxera. The use of tolerant rootstock is the only effective way to prevent damage and reduce pest populations in phylloxera infested vineyards.
All vineyards in actual or potential danger from phylloxera should be planted with vines grafted onto tolerant rootstocks.
No insecticides are known to provide effective control of phylloxera. There are no chemicals registered for the control of phylloxera in Australia.
Phylloxera crawlers can be present on the leaves and fruit of infested grapevines. Any grapes, must, unfiltered or unfermented juice, harvesting machines, picking buckets, grape bins or other equipment in contact with fruit or foliage may be contaminated with phylloxera crawlers and should be treated accordingly.
For vineyards in a PIZ it is illegal to move vineyard soil, vine cuttings, rootlings, potted vines, unprocessed wine grapes or non-packaged table grapes out of the infested zone.
No viticultural equipment, including mechanical harvesters, can be moved from a PIZ without washing, steam cleaning or heat treatment and certification from quarantine authorities.
Put in place biosecurity best practice actions to prevent entry, establishment and spread of pests and diseases:
There are movement restrictions in place to protect phylloxera exclusion zones from the threat of phylloxera. Conditions of movement relating to phylloxera are available on the Biosecurity Act 2015 web page.
If you suspect grape phylloxera inside a Phylloxera Exclusion Zone: