Flavescence dorée: a phytoplasma disease of grapevine

What it is

Flavescence dorée is caused by a phytoplasma — a wall-less bacterium living in the plant's phloem — of the 16SrV group. It infects grapevine (Vitis vinifera and related species) and belongs to the 'grapevine yellows' complex.

There is no cure for an infected plant: once affected it declines and itself becomes a source of inoculum for nearby vines.

Vector and contagion

Vine-to-vine infection is carried by an insect vector, the leafhopper Scaphoideus titanus, which lives and breeds exclusively on grapevine. After the insect acquires the phytoplasma there is a latency of a few weeks (about 10–45 days, depending on temperature) before it can transmit it; from then on it stays infectious for life.

The leafhopper has a single generation per year: it overwinters as an egg in the vine wood, hatches in spring and goes through five nymphal stages before becoming an adult in summer, the period of peak transmission.

The disease also spreads over long distances through infected propagation material (rootstocks and scions): using healthy, certified nursery material is therefore a key defence.

Distribution in Italy and Europe

In Italy flavescence dorée first appeared in 1973 in the Oltrepò Pavese (Lombardy); its vector Scaphoideus titanus, native to North America, had been recorded there a few years earlier.

It is now present across much of central-northern Italy — Piedmont, Lombardy, Veneto, Friuli-Venezia Giulia, Trentino-Alto Adige, Emilia-Romagna and Liguria — with recent outbreaks in Tuscany. Across Europe it affects numerous wine-growing countries, plus Switzerland and Serbia: its spread tracks that of the vector.

How to recognise it

Symptoms appear from summer and vary with the cultivar; they often affect only part of the plant:

• Leaves: sectorial yellowing (white cultivars) or reddening (red cultivars), with downward rolling and a brittle, papery texture.
• Shoots: failure to lignify, a 'weeping' habit, shortened internodes, sometimes blackening.
• Bunches: wilting and desiccation; flower and berry drop.

Symptoms overlap with bois noir (another yellows): a definite diagnosis requires laboratory analysis.

Why it is an emergency

Flavescence dorée is a quarantine pest (EPPO A2 list), regulated in the EU by Reg. (EU) 2019/2072, implementing the plant-health framework Reg. (EU) 2016/2031. In Italy it is subject to mandatory control.

There is no cure: an infected vine does not recover and must be removed, because it becomes a source of inoculum for neighbouring plants. The speed of contagion and the lack of any therapy make it one of the most serious threats to viticulture.

Across Europe, production losses linked to the disease — even under mandatory management — are estimated at around 0.5–1%; but local outbreaks left unchecked can compromise entire vineyards and force costly replanting.

Containment

With no cure available, management is integrated, compulsory in affected areas, and the more effective the earlier it acts:

• Vineyard monitoring and early diagnosis of symptoms (with laboratory confirmation).
• Rogueing and destruction of symptomatic/infected vines to remove sources of inoculum.
• Compulsory insecticide treatments against the vector Scaphoideus titanus.
• Control of feral vines and abandoned vineyards, which act as a reservoir of the phytoplasma.
• Use of healthy, certified propagation material.

In 2022 the National Phytosanitary Committee set up a dedicated technical working group on emergency measures against the disease, a sign of the growing attention to the problem.