Confined spraying is an opportunity for winegrowers because it combines efficiency and respect for the environment. The average product recovery rate over an entire season is estimated at 40%. Explanation.

Introduction
Techniques for spraying vines using collector panels have been around for a long time. They were frequently used to carry out winter treatments to prevent grapevine trunk diseases, for example. For several years now, many manufacturers have been marketing sprayers of this type for preventive treatments, but so far they are not in widespread use. In fact, the commonest sprayers in service in vineyards with wide spacing (inter-row spacing over 1.5m) are pneumatic arch and aeroconvector models. The higher purchase price of collector panel sprayers and their reputation of being complex to operate are probably the two main reasons why they are so rarely chosen. However, in the current context in which farmers are being asked to restrict the use of phytosanitary inputs (EcoPhyto II plan), confined spraying techniques offer many advantages, especially if a number of tips to optimize their use are taken into account.

Confined spraying: one of the highest-quality spraying techniques.
The measurements carried out by the IFV and INRAE teams on the EvaSprayViti artificial vine show that, compared to the most common spraying techniques, the collector panel sprayers, like all other “face by face” sprayers, make it possible to improve both the quantity and homogeneity of product deposited on the leaves. The sanitary protection of the vine is therefore more reliable when carried out with this type of machine, which targets each side of the vine row directly and regularly. By using these spraying techniques and following the instructions of an advisor, lower dosages can be used throughout the spraying season (follow the OptiDose® method, for example).

Confined spraying reduces loss of sprayed product to non-target areas.
Collector panel sprayers not only provide good spray quality but also significantly reduce the loss of sprayed product to non-target environmental compartments (soil and air). This is because a large proportion of the spray that crosses the vine row (less vigorous zone, gap in the vegetation, etc…), instead of being “lost”, hits the collection panel facing it and is recovered. The solution that runs off the bottom of the panels is then fed back into the main tank of the sprayer via a return pump and filter system.
The recovery rate of the spray solution varies during the season: it is high during the first treatments (about 70%) due to the high porosity of the vegetation and decreases with vine growth. The recovery rate obtained on average over the entire season can be estimated at about 40%. If the solution is recovered, confined spraying reduces the quantity of plant protection product used by around 40%, which is beneficial for the environment and significantly reduces operating costs in relation to this input.
When equipped with air induction nozzles (known as anti-drift), collection panels can significantly reduce the risk of spray drift. Drift is the amount of spray that exceeds the plot boundaries due to natural air currents at the time of treatment. Preliminary measurements show that collector panels can reduce the amount of drift emitted by 15 to 30 times compared to conventional spraying techniques. As a result, several such types of equipment have been officially recognized by the Ministry of Agriculture as “drift-reducing means”, entitling the width of untreated areas around water points to be reduced.

What is the net financial impact of using collector panels, taking into account the financial savings on plant protection products, the additional cost of purchase and the work rate?
It is not easy to calculate the net financial impact as this depends on the characteristics of each farm. In certain situations, if the equipment is used over large areas and if disease pressure requires a sufficient number of treatments, the 40% saving in plant protection product generated solely by collecting it will offset the extra cost of purchasing the equipment and the longer working time. In other cases, the extra cost of using this technique will not be offset by the lower amount of product used, but the environmental benefit will remain. Precise assessments of work times will be carried out during the next wine year in order to refine this assessment.

The lower work rate could possibly be offset by increasing speed of travel.
Sprayers with collector panels used in widely spaced vines (inter-row equipment) treat a maximum of two rows of vines per pass, unlike other spraying techniques which allow a higher throughput by treating four rows per pass (but protection quality is lower). However, several test results show that on even terrain, towed collector panels provide good spraying quality even at very high speeds of travel (up to 9 km/h). Some of the increase in work time associated with these techniques can thus be offset by this increase in speed.

Conclusion
In the context of the EcoPhyto II plan, which aims to limit the quantities of plant protection inputs used and their impact, the use of sprayers with collector panels in viticulture seems to offer a pragmatic means of rapidly achieving the objective in hand. However, their use entails significant disadvantages, such as additional costs and increased work times, which can be partially or fully offset by the savings in plant protection product and an increase in speed of travel.
During the next viticultural year, trials will be carried out with a view to identifying ways of optimizing the use of these machines. Dose-reduction schemes (in addition to collector panels) will be tested, with work times precisely measured and compared with those inherent to the most common spraying techniques, in order to accurately assess the consequences of using this equipment.
Demonstrations involving 10 manufacturers of collector panel sprayers were organised for the first time by the Chambers of Agriculture, IRSTEA, IFV and CUMAs (farm machinery cooperatives) in the Gard, Hérault, Aude and Pyrénées Orientales départements respectively on 4, 5, 6 and 7 October 2016. The equipment was demonstrated in the vineyards and yielded a large amount of information.

Article written by Adrien Vergès of IFV Rhône-Méditerranée, on behalf of the Languedoc-Roussillon Machinery Group (CA 30, 34, 11, 66, FD CUMA, INRAE and IFV). Updated May 2020.