Large swathes of Europe are devoted to vineyards. Indeed the International Organisation of Vine and Wine estimates that in 2008 the 27 European Union member states accounted for more than half the world’s vineyards, with around 3.8 million hectares of land dedicated to growing grapes.
And growing grapes and making wine have long been part of European culture. As early as the 5th century BC Greek historian Thucydides wrote: “The people of the Mediterranean began to emerge from barbarism when they learnt to cultivate the olive and the vine.”
Unfortunately, though, long experience of growing grapes does not mean that producers are exempt from the hazards facing any agricultural product, including poor weather conditions and a wide range of pests and diseases. And while ENDURE cannot do anything about the weather, it is aiming to provide better options for dealing with the pests and diseases through its grapevine case study, which is placing special emphasis on the societal aspects affecting vine growers (ecological, economical and qualitative concerns).
The recently launched grapevine case study has a truly multinational team, including representatives from the University of Talca in Chile in addition to ENDURE partners from France, Switzerland, Italy, Germany, Hungary and the Netherlands, and contributions from the International Biocontrol Manufacturers Association. To find out more, we spoke to the grapevine case study leader Christian Gary (pictured left), from INRA (the French National Institute for Agricultural Research).
QUESTION: The grapevine case study is in its early stages, what are the first steps?
CHRISTIAN GARY: The first activity for the group is to gather information about the existing strategies of grapevine protection in the participating countries. It is quite important to be able to analyse the actual practices among grape growers, to see their variations and changes, and quantify the rate of adoption of low input techniques. Unfortunately, this type of information is still scarce and uneven among countries. It will be helpful to identify the possible sources of data, and suggest surveys to be carried out.
QUESTION: What are the longer term ambitions?
CHRISTIAN GARY: The next objective is to analyse the bottlenecks for the reduction of pesticide use in viticulture. Some innovations such as biological control or decision support systems have been validated in our research labs but are still poorly disseminated. What would be the technical, economic or organisational conditions for a wider adoption? The group has identified a set of existing or promising innovations that will be analysed. This will enable us to suggest research to promote in this field.
QUESTION: Are grapes particularly vulnerable to pests and diseases? If so, which are the major ones and what problems do they cause?
CHRISTIAN GARY: Unfortunately, the most widely used grape cultivars are very sensitive to fungi such as downy mildew, powdery mildew and Botrytis . These diseases cause damage, through different mechanisms, to leaves and grapes. Other fungi attack woody tissues, insects such as Lobesia botrana and Eupoecilia ambiguella attack fruit berries, not to mention the numerous foliar, wood or root diseases, some of which are well known (phylloxera, mildews, Flavescence dorée, yellow dwarf disease etc) [Read more about these pests below.]
QUESTION: Do alternative growing systems less reliant on pesticide use exist? Are there some obvious alternatives to pesticides?
CHRISTIAN GARY: Alternatives to the intensive use of pesticides do exist, yet are not always ‘obvious’. For example, spiders are effectively controlled by taking care of the ecological balance with their natural enemies (the choice of pesticides harmless to these predators). Herbicides can be totally replaced by soil tillage and/or cover cropping, but these alternatives need specific equipment and are both labour and energy intensive. Other techniques such as sexual confusion or biological controls are effective, yet costly and require specific technical skills. Other techniques such as the use of stimulators of natural defences exhibit only partial effects. Push-pull strategies and strategies based on behaviour modification of arthropod pests may also be successfully assayed. There are already a few cultivars resistant to major fungi, but not enough to satisfy wine makers and consumers. Finally, decision support systems have a high potential for reducing the number and dosage of pesticide applications. Alternative cropping systems generally combine several of these techniques. Recent surveys reveal that in most regions, some grape growers have already prototyped low input cropping systems, in both conventional and organic vineyards. This is quite encouraging.
QUESTION: We note there is a partner from Chile involved. This must be an interesting development for European researchers. What will this contribute? Is grapevine production very different in the southern hemisphere?
CHRISTIAN GARY: Our colleagues from Chile are providing inputs similar to those of the European partners in the case study. However, their contribution is specific and useful in two respects. First, they grow the same cultivars in climatic conditions and biological environments (pests and diseases) that differ from the ones experienced in Europe. Does this justify different strategies for grapevine protection? Second, the grape and wine production is more concentrated than in Europe: some farms can be several thousands hectares wide. In this context, the availability of labour and equipment and the management process are quite specific. Does this facilitate or hinder the adoption of alternatives to the intensive use of pesticides? Widening the range of natural and economic conditions studied by the case study should help us in analysing the conditions and bottlenecks for reducing pesticide use.
More about the pests
Of the best known diseases affecting grapevines, wine lovers may be most familiar with ‘noble rot’ which is welcome in certain vineyards as it helps produce sweet dessert wines such as Sauternes (the fungus removes water from the grapes, leaving a higher percentage of solids such as sugars and is said to produce wine with a more intense taste). Unfortunately, ‘noble rot’ is really Botrytis cinerea (also known as grey mould) and this fungus does not limit itself to helping produce sweet wines. It can also trigger bunch rot, which causes substantial losses for grape producers, and can appear early in the season as shoot blight. The University of California (UC) notes that flowers can become infected during bloom and, after laying dormant, fungus can infect the entire berry before spreading through the bunch. Alternatives to fungicide use do exist, including canopy management and leaf removal in particular, as the disease is more frequent under conditions of high canopy development.
Unfortunately for wine makers, some of the most popular varieties of grape such as Chardonnay, Cabernet Sauvignon and Riesling are particularly susceptible to powdery mildew, also known as oidium and caused by the fungus Uncinula necator . Of the 70 million tonnes of fungicides used in Europe on vines annually, 53.3m tonnes (76%) is used to control powdery mildew at a cost of €164m per year. Many wine makers have very low tolerance levels for powdery mildew even if it is proved that its effect on wine is very mild. However, early powdery mildew infections can reduce berry size and antocyanin levels, and losses due to uncontrolled powdery mildew represent 2% of the total European yield (€300m per year). Then, powdery mildew is often systematically treated whereas in most situations it could be efficiently controlled with much fewer treatments. Alongside fungicides, good cultural practices such as pruning and training vines in a system could be an important tactic to modify the vine’s susceptibility to the disease. A European project, BCA-grape, is dedicated to the improvement of biological control against the disease.
Most European varieties are also susceptible to downy mildew, caused by the fungus Plasmopara viticola . Humid, rainy conditions with cool to moderate temperatures are likely to provoke an attack and researchers from the IPM (Integrated Pest Management) programme in Illinois, USA, report that crop losses of up to 75% have been reported on untreated susceptible varieties in these conditions. Affected clusters become stunted and distorted and will quickly whither and die after severe infection. Affected leaves often drop prematurely exposing grapes to potential damage from excessive sunshine and can have an impact on the sugar stored in canes.
Lobesia botrana (also known as the European grapevine moth) and Eupoecilia ambiguella (Hubner) (also known as the grapeberry moth or vine moth) attack grape berries; the larvae damage or destroy berries at almost all grape phenology and favour the growth of various moulds such as Botrytis cinerea (grey mould) or Aspergillus carbonarius or niger , responsible for ochratoxin production in Mediterranean vineyards. INRA reports that damage can be considerable and the presence of larvae and rotten fruit lowers the quality of the crop, with moulds making wine making difficult. Besides insecticide control currently based on growth regulators, mating disruption has been successfully developed against these two pests. Natural biological agents (parasitoids and predators) ensure a natural control of these pest in several vineyards (see INRA publications or Thiery 2008 'Les ravageurs de la vigne' eds Féret for more information). Releases of Trichogramma species (Hymenopterous egg parasitoids) have been assayed in different European countries with variable efficiencies. Trichogramma are tiny wasps and the females inject their eggs into the eggs of pests, the larvae consuming the embryo and other contents. They are also used successfully to target a range of pests, including codling moths and the European corn borer.