Opinion on "Changes to the time/temperature combination in the hot water treatment of plant material"
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,
* Agrobacterium tumefaciens and Agrobacterium vitis,
* virus-vector nematodes,
* insects, particularly during the egg, larval and nymph stages of their development.
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