TECNICA 78 TECNICA considerando anche il rischio di danni al prodotto in caso di regolazioni scorrette, ne hanno ridotto la diffusione a pochi ambiti sperimentali o a vigneti particolarmente difficili da trattare con sistemi meccanici. Le defogliatrici meccaniche sono oggi le più diffuse, grawere measured in the skin of the berries with defoliation. In any case, the effectiveness of this practice depends on several factors, such as the timing of the intervention, the training system, the vegetative state, and environmental conditions. The definitive success of defoliation, however, was determined by the appearance on the market of defoliating machines that, using different techniques, can carry out controlled, selective removal of part of the canopy, even for different purposes at various stages of the growing season. Thermal defoliators were the first to appear on the market. An LPG or propane burner heats air to 70-100°C; the heat generated is directed onto the leaves, causing a thermal shock that leads to protein coagulation and interruption of lymphatic circulation, resulting in the leaves wilting within a few hours and falling off after about two weeks. The main advantage of this solution is its gentle action on the bunch, because the heat acts selectively on the leaf blades and has no effect on the berries (thanks to their high liquid content), but above all because no mechanical stress is produced, thus preventing any damage. However, thermal defoliators are highly complex to use and incur significant operating costs due to fuel consumption and low operating capacity. In fact, this equipment operates at low speeds of about 2-3 km/h. These limitations, together with the risk of damage to the product in the event of incorrect adjustments, have reduced their use to a few experimental areas or vineyards that are particularly difficult to treat with mechanical systems. Mechanical defoliatorsare now the most widely used, thanks to their good balance between effectiveness, operational capacity, and cost. They remove leaves using cutting or tearing mechanisms (rotating blades, mowing bars, milking rollers), assisted by a powerful suction air flow that intercepts and captures the leaves and conveys them to the removal devices. In models with rotating blades, leaf cutting is facilitated by a rear fan driven by a hydraulic motor, which sucks the leaves in and channels them through a protective grid, preventing the entry of shoots. The versions with milking rollers, now considered more advanced, use two counter-rotating rollers that grab the leaf and tear it from the stem. These machines guarantee excellent quality of work, with good uniformity and a minimal risk of damage to the bunches. Their main limitation is their sensitivity to the structure of the canopy: in very vigorous vineyards or those with irregular vegetation, the action can be uneven and require multiple passes. In addition, the cutting mechanisms require periodic maintenance and, above all, continuous and accurate adjustment of the distance from the bunch area. Pneumatic leaf removers differ from the previous ones in that they do not operate by suction: their operating principle is based on powerful jets of compressed air, which tear the leaves by striking the leaf blades directly. The damaged parts dry out and fall naturally after a few days. The system is highUna panoramica dei diversi tipi di defogliatrice An overview of the different types of leaf removers
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