What is Phylloxera

Phylloxera (pronounced 'fil-ox-era') is a small, yellow-coloured aphid (insect). It looks much like a rose aphid, only smaller. An adult insect is about 1mm long, and therefore is just visible to the naked eye. It is native to North America, where it lives in comparative harmony on vines of American origin without causing them any obvious harm. ie these American vines are resistant (or tolerant) to phylloxera. It feeds on the roots and leaves of these vines, and what is characteristic of phylloxera is that it causes the vine to react by forming a gall around the insect (either on the roots or on the leaf), which continues to live, feed and lay eggs safely inside these galls. The life-cycle of phylloxera is complicated - it can reproduce both asexually (adult females lay eggs which hatch without fertilisation) and sexually. The asexual cycle can occur both below ground and on the leaves, while the sexual cycle only occurs on the leaves.

Grapevines used in growing grapes for winemaking are a different species from the North American vines. They all come from the vitis vinifera species, which originated around the Black Sea and was transported to Europe by early explorers. When grapevines are exposed to phylloxera, they do not show the same reaction as the American vines. Firstly, they do not form leaf galls - so the phylloxera are confined to living on the roots of the plant (which do form galls similar to those on American vines). Secondly, and more importantly, the vitis vinifera vines do not have any resistance to the insect parasite, which gradually destroys the vine's root system - leaving it without any means of taking up water or nutrients.

What damage does phylloxera do?

Phylloxera is without doubt the greatest threat to any vineyards planted on own roots. Inadvertently imported to England and France on nursery stock between 1854 and 1860, the insect quickly invaded nonresistant Vitis vinifera wine grape blocks throughout Europe. By the end of the 19th century, grape phylloxera had destroyed two-thirds of the vineyards on the continent. When it was first discovered, it was called Phylloxera vastatrix - "the devastating louse". The losses suffered in France as a result of the phylloxera invasion in the 1860s have been calculated as being greater than the total cost to the French of the Franco-Prussian war. Over 2000 hectares of vineyard were wiped out in France, before the reconstruction on phylloxera-resistant rootstocks began.

Since that time, this pest has invaded most of the grape growing areas of the world. Grape phylloxera was introduced into California in the 1850s, where it currently infests an estimated 20% of the vineyards. The British Columbia Department of Agriculture found grape phylloxera in the Penticton area in 1961; growers discovered the insect in Oregon in the early 1970s.

In Australia, phylloxera was first discovered in Victoria in 1875. The Victorian government attempted to eradicate the pest by destroying vines and sterilising the soil. This was very expensive, and proved to be unsuccessful. It spread to Rutherglen in 1899, which at the time was the principal vine-growing district in the country. It has never recovered this status since the setbacks it suffered as a result of the phylloxera infestation (although it is still a premium winegrape-producing region). Once the government realised that it was futile to continue eradication efforts, money was redirected to helping the growers replant their vineyards with grafted vines

In New Zealand it has been present in the North Island since the the end of the 1800's. Romeo Bragato found it on his travels in 1895 and lamented its presence. It remained North Island bound until the 1990's when it found its way to Malborough devastating the vineyards there and forcing the replanting of most the region on resistant roostocks. So far it is not known in Canterbury or Otago where a large proportion of vineyards have vines planted on their own roots and would be immediately susceptible to the disease should it find its way to these regions. It would be devastating for these vineyards to have Phylloxera introduced.

How does it kill ?

The effect of phylloxera on grapevines is totally devastating. They attack the fibrous roots, destroying them, and leaving the vine without an effective root system. Inevitably, this means that the vine weakens and loses vigour. The rate at which this occurs will depend on several factors - including the type of soil, the age of the vine (and extensiveness of its root system), how much it is stressed, etc. This is much like the effect of a cold virus on humans - how badly you are affected depends on your general health status, stress levels etc. Good growing conditions can compensate for the damaging effects of phylloxera, especially in sandy soils (which are difficult for phylloxera to move through).

The first above-ground symptoms show up somewhere between one and five years after the vines are first infested. The symptoms include premature yellowing of leaves, reduced yield, and progressive weakening of the vine. Typically, the symptoms appear initially in an "oil spot" pattern within the vineyard, which expands as the phylloxera population increases and spreads.

Satellite spots develop begin to develop following the initial infestation. These spots appear to occur at random in the infested vineyard; however, the spread of phylloxera tends to be more rapid in the direction of the prevailing winds

Is there any cure?

No effective chemical or biological control methods exist. It is virtually impossible to eradicate and the only treatment is replanting on resistant rootstocks. Eradication has been tried by pulling up all vines within approximately 100m of the boundaries of the infestation, fumigating the soil, and not replanting for at least five years. While this worked in Geelong in the 1870s, the area has never since been developed with vineyards, and recent attempts at eradication in the King Valley - despite seeming to be very thorough and prompt - have been unsuccessful.

By the time infestation is detected, it is likely to have spread so far that eradication can not be considered. All the major winegrape growing countries in the world, with the notable exception of Australia, have been infested with phylloxera. France, Italy, South Africa, California and New Zealand (not in Otago or Canterbury) all manage to grow grapes profitably despite the aphid's presence throughout their vineyards. This is through the use of resistant rootstocks. Most growers are familiar with the concept of grafting vines onto rootstocks - whether it is for protection from phylloxera, or for other reasons - such as resistance to nematodes, salt or drought tolerance, or vigour control.

Resistant Root Stocks or Buried Toads?

The idea of using rootstocks developed entirely in response to the problem of phylloxera. In the 1870s, the French government offered a handsome reward to anyone who could develop a cure for phylloxera. While some of the ideas were pretty unusual, not to mention ineffective (such as burying a live toad under each vine, or watering the vineyards with white wine or sea water!), the solution of using the naturally tolerant American species of vines as a rootstock was soon developed (although it took a bit longer to be accepted). All rootstocks used commercially are derived from breeding programs around the turn of the century, crossing different American species with each other to try and find stocks that would be easy to graft and grow in different conditions. A spectacular example of the failure of this approach to phylloxera management was the widespread planting of AXR or ARG-1 in California in the 1960s. ARG-1 is a cross between one of the American species (vitis rupestris) and the grapevine variety, vitis vinifera. While it seemed to be tolerant initially, its resistance collapsed when a new and more aggressive strain of phylloxera emerged in the vineyards. It seems that only the pure American rootstocks have sufficient resistance to be used for phylloxera management.

How does it spread?

• Grapevine material (cuttings and rootlings)
• Soil
• Machinery and vehicles
• People
• Grape products (must and juice)

Phylloxera can spread naturally - by crawling or flying (particularly with the help of a prevailing wind). However, by far the most likely way for phylloxera to spread is through the activities of people. The main ways in which phylloxera can be transferred is on grapevine material (cuttings and rootlings), grape products (grapes, juice or must) or in soil or vine fragments (including leaves, stems or particularly roots) carried on machinery, vehicles or people (clothes and footwear). Although phylloxera insects are fragile, they can live for up to three days out of the soil, provided that the conditions are right. Generally, they are less likely to survive in high temperatures or low humidities. As they only live on grapevines, a phylloxera insect accidentally caught in a pot plant, or a truck's mudguard will not cause an infestation unless it can come into contact with another grapevine before it dies of starvation, heat or lack of moisture. Therefore, the biggest risks come from machinery (particularly harvesters) or people (eg tourists, contractors, vineyard consultants, pickers, sales reps etc.) moving from one vineyard to another - or from grapevine planting material - which can harbour dormant eggs or adults under the bark or on the roots.

I am planning to visit Otago what should I do or not do ?

Don't bring any grape material into Otago from other regions or even fro elsewhere in Otago (Phylloxera might be here unknown and we don't want to spread it around if it is). Make sure if you are touring the wine regions and going on to vineyards on your visits that your shoes and anything else that could potentially carry soil or grape vine material are thoroughly cleaned and preferably disinfected prior to moving on to the next region/vineyard. When here please respect any requests for clothing or footwear to be cleaned and any restrictions to entry of vineyards. Remember cars can bring dirt with them and potentially transfer the disease so if driving on to a vineyard make sure it is cleaned before visiting the next region/vineyard. Don't pick fruit, leaves, or any grape vine material to take with you on your travels to the next region. Do remember to have a good time though and enjoy the Phylloxera free wines of Otago !