Grapevine golden flacescence

GENERAL INFORMATION. Flavescence dorée is an EU-relevant quarantine pest characterised by its considerable ability to spread and cause severe damage. In view of the importance of the problem for provincial wine production, and the considerable production and economic losses caused by the progression and spread of the disease, compulsory control measures are in force to contain its expansion, and reinforced monitoring and phytosanitary surveillance activities are carried out by the Provincial Phytosanitary Service and the Edmund Mach Foundation. It is difficult to think of completely eradicating the disease, but it is important to contain it to minimal levels. This is why it is essential that all wine growers, no matter whether they are small, medium or large, work responsibly and in a coordinated manner: the behaviour of the individual producer in fact conditions the result at territorial level as well. Only with the cooperation of each professional, but also of each individual citizen, is it possible to effectively protect the territory and contain the expansion of the disease.

SYMPTOMATOLOGY. The symptoms of the disease can affect the entire plant or, much more commonly, only a part of it (even a single shoot or a few shoots). Several organs can be affected: leaves, shoots and bunches. In midsummer, the simultaneous presence of symptoms on at least two different organs (e.g. leaves and bunches) is necessary to define a plant as 'infected' with certainty. Symptoms affecting only one organ are in fact often attributable to other causes (lack of elements, other diseases, etc.).The first symptoms of the disease appear in recent years earlier and earlier (the first manifestations are found as early as the end of May) and as the season progresses they become more typical and more easily recognisable.In addition, the appearance of diseased plants in the field occurs in stages, and it is therefore essential to implement constant self-control activities in one's own vineyards in order to ensure a rapid reduction of the inoculum present in the field thanks to their early identification.Due to the long latency period, symptomatic manifestations are generally the result of an infection that occurred in the previous season.FD symptoms are the same as those caused by another phytoplasmosis that affects vines: Blackwood. Unlike the latter, however, due to the different behaviour of the vector insect, FD spreads epidemically in vineyards, making it more dangerous.

Symptoms on leaves

1. folding of the leaf margins downwards which, as the season progresses, determines the characteristic triangular shape of the leaves
2. sectorial or total discolouration of the leaf blade: yellowing in white berry varieties and reddening in red berry varieties also affecting the veins;
3. papyraceous-papery texture.

Symptoms on the shoot

1. no or poor lignification of the shoots (the shoot remains fully or partly green even in late season);
2. rubbery consistency;
3. folding of shoots downwards (bushy vine appearance);
4. presence of small blackish pustules.

Symptoms on the bunch

1. desiccation of the inflorescences (early symptoms)
2. partial or total wilting of the berries;
3. bunch desiccation.

ROUTES OF SPREAD. Transmission of the disease can take place via: vector insect, infected nursery material, grafting.Phytoplasma is not transmitted via pruning shears or through wounds and lives exclusively in the phloem vessels of infected vines or inside the body of the insect. Thanks to its sucking stinging mouthparts, the insect is able to acquire phytoplasma during the feeding act and, after a latency period of approximately one month, is able to transmit it to a healthy plant. For this reason, the presence of the insect and diseased plants is decisive and represents a possible source of infection for the other plants in the vineyard.

COMPULSORY CONTROL. Flavescence dorée is a quarantine disease for which compulsory control measures are in force at European, national and provincial level. Every year the Provincial Phytosanitary Service issues a Determination in which the specific phytosanitary prescriptions that vineyard owners and conductors must comply with are indicated.

OBLIGATIONS AND PROHIBITIONS

1. timely grubbing up of symptomatic plants;
2. grubbing-up of areas with a presence of symptomatic plants of more than 20%;
3. grubbing-up of wild vines and abandoned vineyards;
4. control of the vector insect by means of insecticide treatment (carried out with appropriate timing and methods);
5. use of healthy plant material (rooted cuttings);
6. prohibition of grafting with non-certified buds.Containment is effective if both vector control and uprooting of symptomatic plants are applied.

Since the appearance of symptoms in the vineyard is scalar, checks must be carried out throughout the growing season in order to ensure that symptomatic plants are identified and eradicated in good time. The grubbing-up must be carried out correctly by uprooting the entire plant including its root system and not just by topping, which in any case should only be temporary.Neglecting the first signs of the disease in the vineyard may compromise the containment of the disease and cause serious economic damage, also to surrounding vineyards.

SIGNS. Since Flavescence dorée is considered a serious danger to provincial viticulture, the presence of abandoned vineyards or vineyards with a high incidence of symptomatic plants must be reported immediately to the competent phytosanitary authority, communicating by pec the cadastral details to allow the identification of the property. For reports and information contact the Provincial Plant Protection Service (tel. 0461-495660; e-mail serv.agricoltura@provincia.tn.it; pec serv.agricoltura@pec.provincia.tn.it)

REFERENCE LEGISLATION. Reg. (EU) 2016/ 2031; Implementing Reg. (EU) 2019/2072; Commission Implementing Regulation (EU) 2022/1630 of 21 September 2022 laying down measures for the containment of Grapevine flavescence dorée phytoplasma within certain demarcated areas; Order no. 4 of 22 June 2023 'Emergency phytosanitary measures for the control of Grapevine flavescence dorée phytoplasma aimed at preventing its spread within the territory of the Italian Republic'; Legislative Decree No. 19/2021.