Phylloxera is famous as the pest that destroyed vast areas of European vineyards in the 19th century and nearly destroyed some of the most prestigious wine regions.
We’ve reported earlier this month that it is becoming a concern in Washington, Walla Walla. What exactly is phylloxera ? And what can we do?
Grape phylloxera is a tiny, Aphid-like insect that is pale yellow, is part of the Phylloxeridae which is an order of insects in the Hempitera family. It was first identified as Phylloxera farratix (devastator vines) in the 1860s French crisis. Then it was discovered as being identical to Daktulosphaera vitifoliae and Phylloxera vifoliae that were previously mentioned.
The insect is a sap suckers feeding on the roots and leaves of grapevines. It is able to traverse up to 18 stages in its complicated life cycle. It can be broken down into four major types: sexual leaf root, winged and root.
One insect is enough to cause sexual form of infestation. The Nymph first lays eggs that are female or male on the leaf’s underside. The eggs hatch into male and female forms (without the mouth part) that mate and then die. But first the female first laid an egg during winter within the bark of the vine’s trunk. This develops into the leaf shape.
The leaf-form nymph – also known as the stem mother or fundatrix climbs onto the leaf of suckers that is growing from the rootstock at the bottom of the vine. She produces galls with saliva. In these, she lays eggs parthenogenically (without fertilization). There aren’t any clear indications of phylloxera attack on the upper canopy of the vine at this time. An adult could lay up to 200 eggs in a cycle.
Root form In turn, the new nymphs could move to other leaves, or to the roots, which is where they start new infections in their root. They pierce the roots to find nourishment, secreting a poison to keep wounds open. Swellings form on older roots and the characteristic hook-shaped galls develop on the hairs of the root. The latter hinder the development of feeder roots and ultimately kill the vine. The root form produces eggs for seven or more generations. They is also able to reproduce parthenogenically every summer. Crawlers move to other roots on the same vine, or other vines through cracks in the soil across the surface or through the canopy. Though unwinged, root form crawlers can be carried only a short distance in wind.
Winged form nymphs hatch in autumn and hibernate in the roots until spring when they feed on the rising sap. The eggs lay new eggs under the leaf to restart the cycle. Nymphs may change into winged shapes in areas of high humidity and fly to unaffected vines where they are able to start new cycles.
Individual vine plants may be affected in the beginning. In the absence of flying insects present, the problem tends to spread across rows more quickly than when it jumps across the inter-row spacing.
It is believed that plants affected when they are planted tend to show signs of decline after a few seasons. It could take up to 10 years for the signs to be evident in an established vineyard. The only way to escape is to rip the vines.
The soil type and the climate are two of the factors that influence the phylloxera population. The bug prefers humid conditions above and below ground.
Warmer, sandy soils and vineyards in areas with schist rich soils were more resilient to the 19th Century worldwide epidemic. This holds true for a variety of regions that have battled phylloxera well through the 20th century. Examples are Colares in Portugal and Santorini in Greece.
Islands can be protected when the human movement of the insect is controlled. Similar to that, Chile has been protected by the Andes on one side and the Pacific on the other and the Atacama desert to the north.
Assyrtiko is located on Santorini as well as Juan Garcia, which are both planted on terraces made by humans at the Arribes River Canyon in Spain is possibly the only Vitis vinifera varieties with the natural ability to resist phylloxera. Both cases have very specific growing conditions.
There is a major warning with soils that are extremely dry. If the insect is able to survive, the lack of moisture could increase the severity of its effects. This could exacerbate the recent outbreak in the Walla Walla region.
The phylloxera cycle of reproduction is believed to be affected by harsh winters. Climate change appears to be a factor in the development of new outbreaks as several regions have milder winters. Walla Walla is again one of those regions.
The most crucial thing for owners of vineyards, American vine species have evolved alongside the insect, and thus have developed (varying) levels of resistance. The sticky sap they produce can block their mouths. They can also form the protective layer of tissue around a wound to prevent fungal and bacterial infection when they open it.
The phylloxera blight that occurred in the late 19th Century.
Phylloxera didn’t suddenly appear in Europe out of the ether. Paradoxically, it is understood that the insect was initially introduced to Europe on specimens of American vines collected by British and European botanists.
The fascination with American vines had been prompted by the outbreaks of powdery mildew that were ravaging European vineyards during the 1850s. It was hoped the American vines would exhibit more disease resistance. The vines survived, and alarm bells didn’t sound.
The outbreak was brought on by technological advances. The Ward Case is a sealed glass container that permits plants to get exposed to sunlight but also protected from the elements of spray and wind. In general, the invention of the steamship also contributed.
At first vineyards in Britain were destroyed. The issue later began to spread to France as well as other regions of Europe. The first Rhone vineyards started to vanish in 1863. In France the total production of wine was just 28 percent in 1889 , compared to 1875.
Identifying phylloxera as the culprit
Knowledge spread slowly. Many owners of vineyards lost their vines without ever knowing why. In France certain growers decided to put alive toads beneath each vine in order to remove the poison.
The complex life-cycle of phylloxera can make initial detection tricky. Furthermore, growers rarely dug out healthier-looking vines. They moved on once the dead ones had been removed and inspected. Jules-Emile Planchon, along with colleagues, found phylloxera growing on vines in the lower Rhone in 1866. It was believed to be due to their error in pulling up an active vine.
Unfortunately, this discovery was not a catalyst for an organized response. Certain experts, particularly in Paris and Bordeaux, rejected the findings of country bumpkins in the south who were not professional entomologists , or plant scientists.
In addition, many believed the symptoms of the disease were symptomatic rather than a cause. This was due to the 19th-Century obsession with the physiological model of disease. The focus is on internal causes of the plant, not external factors. Therefore, they continued to look for other solutions.
Although it would take five more years for the opposition to completely dissipate by then the year 1869, phylloxera began to be more popular as the reason. An infested, dying vineyard in the southern Rhone was devastated by the floods that swept through the region in the year. The vines flourished after the pests were gone.
It was observed that sandy soils appeared to provide some form of protection. The vineyards were established in the dunes of the Rhone delta, and in areas that would not otherwise be considered to be suitable. These plots were a success, and also support the theory of phylloxera.
People like Planchon believed that the vines that carried the insect might also trigger a response. These theories were backed by prominent American people like CV Riley the Missouri’s state insectologist. He was strongly influenced by Darwinian views and also emphasized the resistance to phylloxera within American species.
Hybrids vs grafted vines
Transatlantic cooperation under the leadership of Riley and Planchon, resulted in that 700,000.00 vine cuttings were brought into France from St Louis in 1872-73. However, there was not much information available about American vines in France and the US. It was a gamble on whether direct-producing vines or rootstocks were more effective The initial focus was, at great cost, on the least effective American species.
Planchon recommended earlier hybrid varieties like Concord and Clinton to Planchon on his return to the USA in 1873.
The vines are a good source of amount of Vitis labrusca, an indigenous plant from the cooler northern forests of the US. The vines struggled with the French heat and, when utilized as rootstock materials or grown in whole plants were less resistant to phylloxera under the new conditions.
And, even more importantly, the wines were unpleasant tasting, displaying the smoky, sweet odor of labrusca. A lot of the growers who placed their faith in these imports from the beginning eventually ended up in bankruptcy.
It was difficult to transplant vines. A rootstock that is effective must be simple to graft, have a long-term affinity with the French wine variety, and also be resistant to the phylloxera.
The American vines needed to be properly classified, as research led to new species being discovered, most importantly Vitis riparia as well as Vitis rupestris. Different species possess distinct traits and preferences, based on the conditions in which they evolved. Not all wild vines from each species perform exactly the same.
The University of Montepellier’s 1870s collection of cuttings was selected to permit the propagation and distribution of around 12 rootstocks. Riparia Gloire de Montpellier and Rupestris du Lot were among the most effective. The work continued in the 1890s to create a new generation hybrid rootstocks that were better suited to French conditions.
The University of Bordeaux led efforts to develop new hybrid varieties that did not require transplants (direct producers) to compete with the Montpellier program. The idea of genetic inheritance was the basis of the project. It suggested that traits from rootstocks of American varieties could be combined to produce fruit systems that are derived from French grapevine parents.
This duality existed until 1900, and it was not as prominent across the globe until the beginning of the century. The hybrids didn’t have the flavour of their vinifera parents, however, they proved to be more robust in colder climate and to resist other diseases. Although generally prohibited for high-quality wine within the EU however, a number of these varieties remain the pillars of the North American wine industry outside California, Oregon and Washington.
Other efforts to combat phylloxera
The concept of using American vine species to fight back was a cause of great conflicts in France. They were viewed by many as villains in the tale. In addition there were many people in the French wine industry did not wish to for the integrity of French vineyards, wine and grape varieties through the introduction of foreign plants. These groups created a phase of non-biological countermeasures called La Defense, which was based on water and sand.
Flooding methods require a amount of infrastructure, and the government was not quick to design the necessary canals. (War between France and Prussia ended 1871. The war and its aftermath hampered the effectiveness of the French government throughout this period.) But there were 400.000 acres (100,000. acres) were still inundated.
The total area of sand plantations was around 20,000ha (50,000 acres). Even today there are still vineyards dotted around the dunes in Aigues-Mortes within the Carmargue Gardoise. But, in sand, nearly all nutrients to the vine is provided by fertilizers. The pest was reintroduced when silt from rivers was attempted to be pumped onto the plots. The sand was often carried away by the wind that blew across these sandy areas. The wines had a distinct taste from those made earlier into the interior, but still acceptable to drink.
Insecticide trials in the 1870s were promoted by the government and the Academie Francaise. They were often laughable, and all were ineffective and only resulted in a shift away from rootstock-based strategies.
Treatments with carbon disulfide, which was invented by Baron Paul Thenard, proved the most effective. The oily liquid is absorbed by soil and kills bugs that are asphyxiating. It was especially effective against phylloxera , but not all. It was necessary to treat the vine annually, which slowly weakened the vine. Additionally the need for skilled workers was a necessity to do the work. It was only successful in the most aerated and fertile soils, and costs more than most growers could afford.
The pest was not as bad in the Champagne region. It was there that the pest was at its most widespread in the 1890s. Even as late as 1890, the trade journal of the region was recommending the planting of alfalfa, lupins and sainfoin in the vineyards to help keep phylloxera away.
All the blind alleys eventually ended. La Reconstitution was a greater emphasis on replanting hybrid rootstocks. France was able to exert some control over the pest by 1900.
The spread of phylloxera across the globe
Phylloxera was introduced to different European countries either via American or French cuttings, or by both. In the 1870s, we witnessed the demise of Spain’s wine industry as well as Portugal Germany and Switzerland. Phylloxera was first discovered in California in 1874, near the city of Sonoma. In California, 12,000ha (30,000 acre) was destroyed in the year 1900.
The Balkans and Greece was affected from the mid-century. At the same time, Victoria and New South Wales in Australia were also affected. Other regions were protected with strict quarantines as well as restrictions on the transportation of plant material, including South Australia.
French companies were heavily involved in the planting of Croatian and Slovenian grapes. These vineyards were devastated between 1902 and 1905 and prompted emigration that would energise the wine industry across North America and Australasia.
The world’s industry was able to learn the majority of the conclusions drawn from France’s debate lasting 30 years in the early 20th century. Use of carefully selected vine scions that were grafted on rootstocks (and to a lesser extent resistant hybrid varieties) appeared to stabilize the situation for most of the 20th century.
Rootstocks vs. phylloxera during the 20th Century
Different rootstocks may not be equally resilient. The resistance that a rootstock can offer diminishes as time passes. One reason could be that Phylloxera alters when it comes into contact with vines resistant to it. There are hundreds of phytolloxera genetic strains which have been found worldwide.
Many vines that were grafted onto AXr1 (Aramon Rupestris Ganzin no. 1.) in California in the 1990s were discovered be infested. Aramon Vinifera, a varietal of vinifera was believed to be the reason for this problem. However, other hybrids such as 41B have proven to be more productive.
Investigative work found that phylloxera has changed into Biotype B that is able to overcome rootstock resistance. About two-thirds (or more) of Napa’s vineyards were required to be planted. It was the expense of replacing phylloxera-ravaged vineyards that obliged the Mondavi family to move their company into public ownership.
Importantly, only certain rootstocks have enough resistance to stop the insect from egg-laying. Although phylloxera is less common in vineyards that have been grafted than elsewhere however, it is still able to be reproduced and survive in many of them. The disease can then spread to non-grafted grapevines, which was the case with transatlantic cuttings in the late 19th century.
Sandy soils, however are not guaranteed. They are not infallible either. Nacido Vineyard, located in Santa Maria Valley AVA, is comprised of vines with roots that have been phylloxera-free so far. Casa Castillo’s Pie Franco (French Foot) red wine, which is originates from Jumilla, Spain is made by utilizing roots that are grown by the owner Monastrell vines that were planted in 1942 on soils that had sandy. The pest did take control after several years; each year, a few vines die and volumes of the wine diminish. In Champagne in 2004 Bollinger was unable to salvage one of the ungrafted parcels which were used in the Vieilles Vignes cuvee. In 2006, Phylloxera was discovered.
In fact, many growing regions have given insufficient attention (with the benefit of hindsight) to the choice of rootstock. This isn’t necessarily due to a lack of trust in soil types or other mitigating aspects. These regions were first developed in the 1960s, and are now more focused on expanding. Grafted vines are three times more than ungrafted vines, sometimes more.
Since the 1910s, phylloxera has existed throughout Washington in various forms. The first time it was reported was this year in the Walla Walla area. The region is particularly at risk because the majority of growers choose to plant their own-rooted vines.
The reason for this was that phylloxera’s reproduction was slow due to the severe winters. Grated vines seem to recuperate more slowly from frost. There is also many sandy soils. But climate change means that luck has run out, as hard freezes are getting more scarce.
In 2002 in 2002, the Central Otago wine area in New Zealand’s South Island was hit by phylloxera. The rapid growth of the region meant that it was estimated at the time that only 55 percent the vines were resistant rootstock. This number was less than that of other parts of the country. Winters that were harsh and cold were not a sufficient security measure in this region.
The Phylloxera plant: the present and the future
There is no “cure” for vines that have been attacked by the phylloxera. There is no chemical or biological methods to prevent the phylloxera from becoming established. The idea of flooding the vineyards is not an option at all. The best method to save a vineyard is to remove it and then plant it on better rootstocks. There is a silver lining: the owner of the vineyard can select an improved clone or change the grape selection. But the financial consequences can be severe.
It’s not easy to determine the best rootstock (commercially available). Apart from the local soil and macroclimate, viticulturalists also have to be aware of which strain(s) of phylloxera they are up against. Vinehealth Australia (formerly the Phylloxera and Grape Industry Board of South Australia) test rootstocks against at least seven strains.
Protocols are being developed across the world to control the movement of individuals and machines between vineyards. Steam cleaning is a method to wash the equipment. The staff may also wear shoes that are specific for every visit.
This may be a reason why the use of mechanized or manual passes through the vineyard should be avoided. This would seem to make sense in an affected vineyard However, otherwise, cultivators (especially biodynamicists) are likely to want or require to have a high degree of vigilance. The measures are not mandatory.
Researchers are working to create new rootstocks that are more resistant to phylloxera. This is to counter its ability to develop biotypes that can defeat the defenses of particular rootstocks. Smith et and., BMC Plant Biology (2018) discovered one gene (RDV2) which confers this characteristic in a study that analyzed the genetic factors that confer phylloxera resistance.
Vinehealth Australia also reported in 2018 that it had tested successfully DNA profiling techniques for phylloxera detection in cores of soil in the vineyard. Though sample taking is easy but the storage and transportation conditions are vital (as is laboratory availability). It could take time for this become routine. But together with use drones for cost effective aerial imagery, at least Australian wine producers will soon be able to implement a reliable early warning system toolskit.
Phylloxera is famous as the pest that destroyed vast areas of European vineyards in the 19th century and nearly destroyed some of the most prestigious wine regions.