Thermotherapy applied to vineyards

On-site treatment with direct radiation for the elimination of Flavescence dorée phytoplasma.

A rather ambitious project was started in 2012 in Asti (Piedmont, Italy) at the Istituto Agrario Giovanni Penna by a group of students with the help of their teachers and the school staff. AgriFreeCO2 is the name of the project and the workgroup. The project offers technicians and winegrowers the possibility to take advantage of the experience acquired regarding  solving the problem of Flavescence dorée (grapevine yellows) with thermoterapy. This technique has been implemented for some time by several Piedmont grapevine nurseries on plants in the propagation stage (submerged in hot water), resulting in greater health and improved traceability of grapevines placed on the market.

The new technology, based on direct heating affecting the phytoplasma of Flavescence dorée (very sensitive and heat-labile), does not jeopardize individual plants and can be implemented by conventional, organic, and biodynamic farms. In fact, this method does involve the use of natural or artificial pesticides or waves and radiation that may be harmful to human beings or the environment.

Electric cell and heating sleeves

The winning idea that initiated direct thermotherapy tests in vineyards was the brainchild of several students of the Penna Institute, passionate fans of motorcycling events, who decided to exploit the techniques used for warming up the rubber of racing tyres. Thus electric heating sleeves were created, also called heating socks, using carbon-fibre heated flexible panels, insulated with adequate natural fibres, providing for even temperature and limited dissipation of thermal energy. These sleeves are applied on-site onto the aerial parts of individual  grapevine plants. For the power supply, the experiment team developed a mobile electric unit equipped with photovoltaic modules which produce electricity that is then stored in buffer batteries. This 100% environmentally-friendly photovoltaic cell supplies enough continuous power to run dozens of heating panels at the same time in perfect silence. For road transport, it can be placed on a simple trailer, and hooked to any kind of agricultural vehicle; battery recharge occurs by simply connecting the battery to the mains, thus accounting for a work autonomy corresponding to a full day of treatment.

Stepping in: where and how

Treatment should be applied only to plants showing the first symptoms on leaves and  shoots, thus preventing the phytoplasma from migrating below the graftings and affecting part of the roots. Two phenological stages can be identified.  In  the summer, when the plants show the first symptoms during the growing season with fruit enlargement, the fruit-bearing cane which is often totally or partially compromised, is removed. In doing this, the only necessary precaution is an extreme pruning of the plant.  In a second stage, during the period of vegetative rest, the plants near the damaged ones are treated, which often show similar symptoms the following year or at the end of the same season. In this case, thanks to the pruning, the aerial parts of the grapevines can be slipped into the heating sleeves and the effectiveness of the treatment is guaranteed. “Beginning with this first year of trials – explains Daniele Piotti, professor at the Istituto Penna and project leader – in vineyards with many plants showing symptoms, we treated even healthy plants growing near afflicted grapevines, in order to monitor or reduce the presence of diseased plants the next year. This procedure will continue during the winter when we’ll treat entire portions of rows, so that in the summer 2014 we’ll be able to observe whether there are significant differences compared to rows that were not completely treated”.

On-line mapping and monitoring

Some of the tests performed with this technique can be followed on-line at the website www.agrifreeco2.it, where all the sponsors and involved wine-growing companies are listed. Along with the treatment tests, the vineyards have been mapped according to topographical map and visibility coordinates using Google Maps technology. Thanks to this, everybody will be able to follow future tests even from home, using a PC with an Internet connection. “Our aim is  – claims Piotti – to offer effective technical support and shared experience through the IT platform on our website, to which all users  have free access. The last open-day events we organized for a demonstration of our method were on October 25, 2013, at the Castello del Poggio vineyards (Asti, Piedmont) of the Zonin family, and October 26, at the Bersano spa vineyard La Generala near Agliano Terme (Piedmont). Given the results obtained with the first tests, the companies that supplied all the necessary equipment are now assessing production and marketing possibilities. It is most likely that heating sleeves will be available also individually, whereas the electric cell – which can be sold separately –  will undergo to further changes and extensions, making it suitable for implementation in vineyards where it can provide, even in the absence of light, enough power (kW) to supply dozens of heating sleeves at the same time, as is required for the treatment”.

Test results

Regione Lombardia is among the institutions that performed several tests on the implementation of thermotherapy in grapevine nurseries, pointing out the best temperature and time conditions necessary to produce healthy propagating material free of phytoplasma causing grape yellows (Flavescence dorée and Bois noir) on monitored varieties (Barbera, Chardonnay, Croatina, Pinot Noir, Italian Riesling, Rhine Riesling and Uva Rara): 52°C for 30 minutes, with the only risk of damaging up to 19% of the buds due to the high temperature.
We performed our tests – explains Piotti – in the middle of summer, at even higher temperatures, and we ascertained that, thanks to transpiration and  photosynthetic processes occurring during the day, grapevines (Barbera, Grignolino, Dolcetto and Albarossa) can withstand, without damage, treatment temperatures up to 70°C, whereby the results within the cultivar are similar to those of the tests performed by the experts of Regione Lombardia. For the moment, due to the low budget and the great number of treated plants, we can not perform serological tests to ascertain the real elimination of the disease on the treated plants. However, our intention is to continue with the tests in the winter, and to directly monitor the plants during the upcoming spring, at the beginning of the shoot growth, assessing the condition of plant health and performing sample serological tests  with the assistance of research centres”.

 

All farms participating in the on-going tests, as individually mentioned in the website www.agrifreeco2.it, have made their vineyards available to calibrate the equipment in the first phase. From now on, with a small funding, they will support the prosecution of the tests, as well as the verification of the compliance of the involved varieties.

 

In the next months  ‒ explains Daniele Piotti ‒ we’ll continue with the tests in the vineyards, by virtue of the fact that we have more technologically improved heating sleeves, and also thanks to insulation materials  and simple use. We hope more winegrowers will ask to extend our tests to their vineyards and might be willing to pay a small contribution to cover at least our processing costs. From a simple assessment taking into account the time required for the treatment and the confirmation of the elimination of the disease, and comparing the alternative of rooting out all diseased plants and waiting for three years before reaching the same production, the profitability of this method will  be quite obvious to all farmers”.

(Article by Laura Turrini)

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