How one region copes with the spread of vine disease

Freitag, 1. Dezember 2017 - 12:30

Flavescence dorée/JosefKlement

Farmers are a tough breed; they face a litany of challenges. Mother Nature was especially cruel to winegrowers in Europe in 2017, doling out extremes of frost, hail and drought. Besides the vagaries of weather, the threat of debilitating vine diseases, such as esca, is on the rise. Above all, flavescence dorée — which has been compared to phylloxera in its gravity — has spread across Europe at an alarming rate.

Classified as one of the grapevine yellows, flavescence dorée is a phytoplasma disease. The pathogen, a microorganism similar to bacteria, accumulates in the plant’s phloem tissue and interrupts the flow of sugar from the leaves. Stricken vines usually die the same season but can survive for a few years and, in some cases, may even recover.

Its vector is the dreaded Scaphoideus titanus, the American grapevine leafhopper, that feeds first on an infected plant, then transmits the disease by feeding on another. The French National Institute for Agricultural Research (INRA) reports that the phytoplasma strain responsible for flavescence dorée is native to Europe, having existed in wild plants there. The leafhopper that transmits it to grape vines, however, is likely to have “hitchhiked” to Europe from North America on American rootstocks that were brought over to contend with phylloxera.

Infection zone
In Italy, flavescence dorée has cut a significant swath across the north. The Monferrato zone, which extends across Piedmont’s provinces of Asti and Alessandria offers a perfect storm of conditions for this disease. The area is renowned for its Barbera. In 2016, Barbera d’Asti DOCG alone accounted for 32.3% (153,685 hl) of Monferrato’s DOP production and Piemonte DOC Barbera made up 29.6% (140,746 hl). The bad news is that Barbera has an unfortunate genetic make-up that renders it particularly susceptible to flavescence dorée — as do Arneis and Dolcetto, as well as Chardonnay and Pinot Noir. Other important grapes in Piedmont, most significantly Nebbiolo, though not immune, are less prone. 

Gianni Bertolino, owner of Monferrato’s Tenuta Olim Bauda, first became aware of the problem in his family’s vineyards in 2000. He describes the symptoms as reddening of leaves, shoots that fail to lignify and become gummy to the touch, and bunches that remain small, refusing to ripen and eventually desiccate. The agronomist he consulted recognised the cause immediately. Despite replanting the afflicted vines, the problem persisted. “The replacement cuttings that were coming from the nursery were not controlled and became vehicles to diffuse the disease further,” explains Bertolino.

Today, nurseries have greater awareness and are scrupulous in the fight against flavescence dorée, according to Simone Lavezzaro, agronomist for the local consulting agency VitEn. “There is no regulation nor certification to guarantee disease-free cuttings but, from experience, the percentage of infected plants coming from a nursery is very low,” he claims. Instead, it is in the vineyard where the disease is contracted. 

Monferrato is a vast area. Unlike neighbouring Langhe — where the hills of Barolo and Barbaresco are densely planted almost exclusively with vines — it offers plenty of forests and uncultivated pockets. This is just the environment where the Scaphoideus titanus likes to hang out. Furthermore, poor returns on Barbera in the past led to the abandonment of many vineyards, leaving them to grow wild. “This means that there are many uncultivated vineyards that are not subject to the mandatory insecticide treatment, allowing Schaphiodeus titanus to live in an uncontrolled manner,” explains Lavezzaro. Due to the vector’s peripatetic nature, it transmits the disease to cultivated vineyards nearby.

Franca Miretti of Cantina del Pino in Barbaresco recently purchased 5 ha in the commune of Mombercelli, which has been hit hard. She believes the prevalence of “Sunday viticulture” exacerbates the problem. Whereas in the Langhe, viticulture is full-time profession, in Monferrato there is a greater number of small landowners who have other occupations, working in the vineyard on weekends or even less frequently. “This makes it more difficult to control a disease,” she points out. “When there is a risk, you have to act immediately. You can’t wait until Sunday to do a treatment.”

Containing the bug
No cure for flavescence dorée currently exists. Thus, controlling the vector population is crucial to curbing the disease’s proliferation. As in other regions of Europe, growers in Monferrato are required to treat vineyards with insecticide twice during the growing season, corresponding to the larval and adult stages of the life cycle. 

Chemical insecticides present an obvious philosophical issue for those who farm organically. The only option permitted in this case is a pyrethrum insecticide derived from pyrethrin extracts of daisies (Chrysanthemum cinerariaefolium). However, Lavezzaro emphasises “this is just active on the young form of Scaphoideus titanus and effective only for a brief period.” 
Luca Currado from Vietti, who has had vineyards in the area since 1995, admits that farming organically as he does poses a greater risk. “It is therefore of the utmost importance as a primary protection to grub up sick vine stock.” He calls it a continual battle and removes hundreds of diseased vines every year. 

Mariacristina Oddero, owner of the Oddero estate, says: “Whether using organic or conventional insecticides, eradicating diseased trunks is a fundamental and necessary practice to debilitate the disease.” Keeping the areas around the vineyard clean is equally important. Dr Andrea Schubert at the University of Turin’s research centre, has demonstrated that American rootstock or hybrids in abandoned vineyards are the major cause of the pathogen’s transmission, Oddero points out. Her vineyard, acquired by her father in 1989 in the commune of Vinchio, is close to a wild forest and an abandoned vineyard of partially destroyed old vines. “Over the years, we’ve had a high percentage of sick plants, regardless of applying insecticide treatments and replacing affected vine stock.”

In an effort to improve the situation, the Consorzio Barbera d’Asti e Vini del Monferrato has developed a protocol for the destruction of wild vines. The onus is on property-owners to follow it though. The Consorzio is also involved in the INTEFLAVI research project developed in collaboration with Department of Agriculture, Forest and Food Sciences (DISAFA) at the University of Turin. “This study is trying to find a form of coexistence between the vine and the disease, instead of destroying the carriers or the phytoplasma,” says the Consorzio’s president Filippo Mobrici.

While research continues, Lavezzaro believes the threat of flavescence dorée in Monferrato is getting worse. One of the reasons for this is the warmer autumns that allow the leafhopper to survive until late October. “The presence of the insect in the vineyard for a longer period has proportionally increased the possibility of infection,” he explains.

Moreover, Oddero notices that symptoms are aggravated in drought years such as 2017.
While flavescence dorée doesn’t affect quality for the simple reason that afflicted vines are rarely productive, it does have a serious impact on yields and the lifespan of a vineyard. The severity of the disease varies not just from one zone to another but also within a single estate. In extreme cases, Lavezzaro estimates that it affects 20% to 30% of the plants, with a death rate of 15% every year. “Fortunately, on average, the situation is better with 3% to 10% of plants showing symptoms and a yearly mortality of 2% to 5% in southern Piedmont,” he notes. Additionally, Currado notices that vulnerability depends on vine age, at least at Vietti’s property. The old vines in his La Crena vineyard planted in 1932 are less susceptible, but those planted since 1996 are easily affected. 

Despite the severity of the problem in Monferrato, investment in the area is on the rise. “This phenomenon is wide reaching, including buyers not just from estates in Monferrato but other territories as well foreign investors,” says Mobrici. Besides Vietti and Oddero, other Langhe-based producers include Marchesi di Barolo, Mauro Sebaste and most recently Poderi Gianni Gagliardo, who purchased the 15 ha Tenuta Garetto in July of this year. Also notable is the joint acquisition of Tenuta dei Vallarino di Gancia, which had been under Russian ownership, by Farinetti (of the Eataly empire) and Damilano. 

Mobrici believes that the viticultural territory of Monferrato is going through a renaissance and producers are focusing on quality over quantity. Recognition as a UNESCO World Heritage Site has also helped boost tourism and prominence of the area. This has led to an economic increase in the value of the vineyards, “from €30,000 ($35,164) to €35,000per ha four years ago, to a value of €50,000 to €120,000 per ha today,” he says.

Even with increasing land values, Monferrato remains affordable compared with the Langhe, where top crus in Barolo have been estimated upward of €2m per ha. Furthermore, Monferrato offers larger contiguous plots that are logistically easier to manage. “For us, the key is that the vineyard is a single piece,” says Miretti, noting that this also helps in managing flavescence dorée.

Above all, producers are drawn to the area by the desire to work with Barbera. In the Langhe, top vineyards are planted with Nebbiolo; in Monferrato, they are dedicated to Barbera. “The interest is concentrated not in all of Monferrato, which is a rather vast zone, but primarily in the 18 communes in the south of Asti that make up the Nizza denomination,” says Bertolino, who is also the president of the association of Nizza producers. Nizza is a newly created DOCG as of 2014. Originally designated as a subzone, it has been historically recognised as the best zone for Barbera.

In terms of flavescence dorée, Nizza is not impervious, especially where areas are more forested. Sustainability of viticulture remains a concern. “The preoccupation for us is to keep this vineyard alive and not have to replant it over the next six to 10 years,” says Miretti. However, according to Lavezzaro, the situation is slightly better in Nizza than the rest of Monferrato because it is more densely planted and there are fewer abandoned vineyards. Bertolino adds that most producers in the zone have learned to maintain proper phytosanitary conditions in and around the vineyard, recognise symptoms and take the necessary measures to contain the disease. “In Nizza there is a fantastic group of producers ready to accept the challenges of the future,” says Stefano Gagliardo, owner of Poderi Gianni Gagliardo.

Clearly, for those who have turned their attention to the Monferrato, the rewards outweigh the risks. 
Michaela Morris

This article first appeared in Issue 5, 2017 of Meininger's Wine Business International. There are plenty more where this came from - just sign up to our free weekly newsletter.