The plant health regulations relative to the Grapevine Flavescence Dorée (FD) leafhopper state that the hot water treatment (HWT) of grapevine plant material must be carried out with a time/temperature combination of 45 minutes at 50°C (Annex IV, Part B. Art 32 of Directive 2000/29/EC).
However, according to some professionals, performing this hot water treatment hampers renewed growth of the plant material and delays bud break, which is harmful to the wine-growing sector.
In view of this, FranceAgriMer and the French Federation of Vine Nurseries (FFPV) have co-financed a study programme by the French Wine and Vine Institute (IFV). This study shows that a time/temperature combination of 35 minutes at 50°C sanitises grapevine plant material concerning FD without the harmful effects on renewed growth or delayed bud break.

In view of all these factors, this expert appraisal was expected to determine:
1- the effectiveness of hot water treatment on Flavescence Dorée (FD) and Xylella fastidiosa (X.f.) with a time/temperature combination of 35 minutes at 50°C,
2- the effectiveness of hot water treatment on Flavescence Dorée (FD) with time/temperature combinations of 35 minutes at 50°C and 45 minutes at 50°C on:
 * the organisms responsible for yellows diseases in general,
 * Xylophilus ampelinus,
 * phylloxera,
 * Agrobacterium tumefaciens and Agrobacterium vitis,
 * virus-vector nematodes,
 * insects, particularly during the egg, larval and nymph stages of their development.