Two seasons with my drone: Cave des Vignerons Fully

About the author

Gaëtan Bender, winemaker and graduate oenology engineer from the Changins University of Applied Sciences, cultivates a 25-hectare family vineyard belonging to the Thétaz-Bender company in Fully, Switzerland. The entire production of the vineyard is destined for the Thétaz family, Cave de Vignerons in Fully. In 2022, Gaëtan decided to replace the traditional system of treatment with an attachment jet (Canon Cima type) with a spray drone, as he wanted to reduce spray drift, improve operator safety and comfort and reduce the noise nuisance caused by treatments. This decision was concretised by the introduction of the DJI Agras T30 drone, an innovative technology provided with training and support by DigitalRoots. After two seasons of use, Gaëtan shares in this article the benefits and challenges of this new approach, which is transforming his viticultural practices and offering a modern and powerful perspective on crop protection management.

Vineyard

Located between Saillon and Martigny, mostly on slopes that are difficult to access. Only 9 ha of plant protection, for the region in general and for the vineyard in particular, is represented by mildew.
The area considered favourable for drone application is 16 ha in total. It comprises two blocks, one of 9 ha in Saillon and one of 5 ha in Martigny, and plots ranging from 1 ha to 3000 m2. There are no residential buildings on the edge of this scattered area and only a few electricity and telephone masts or similar obstacles in the vicinity.

The machine and the authorisations

We use a DJI Agras T30 drone for the plant protection treatment of our vineyards. This drone, which can carry 30 litres of spray liquid, follows treatment lines created from 3D photos provided by DigitalRoots’ Agrivision software. Thanks to RTK-corrected GPS, it achieves an accuracy of 1.5 cm with fully automatic application. To use the drone, we obtained Swiss patents A1, A2 and A3 as well as a MANEX, which was created with the help of DigitalRoots, which also provides the training. In Switzerland, this drone is not considered an aerial treatment, as drift is controlled under appropriate conditions.

1st PI treatment: Reduction of synthetic plant protection products with a maximum of 1.5 kg of copper metal per hectare and year, spread over 6 to 7 rounds, as well as soil treatment for high-risk varieties.

Three different treatment plans are used in the vineyards:

2. biological treatment with Bordeaux mixture and sulphur, with 8 passes plus a soil treatment.

3. biological treatment “Vitistim”: 8 passes plus soil treatment.

The soil treatments are carried out with a sprayer or a turbo mounted on a small caterpillar. In terms of plant protection, variants 2 and 3 showed no significant differences and are summarised under the term “organic variant” in the remainder of the document. Grape varieties that were classified as low-risk, such as Chasselas, Pinot Noir, Gamaret, Cabernet Sauvignon, Merlot and Marsanne, were only treated with the drone, without soil treatment. Grape varieties with an increased risk of mildew, such as Johannisberg, Chardonnay, Humagne Rouge and Gamay, required additional treatments.

Parameters for the treatment

Filling

The drone is filled via a 400-litre mixing container, the so-called MixBox, which was specially developed for preparing the treatment broth. As the drone does not have an internal mixing system, it is crucial that the mixture is completely homogeneous before each filling. The drone’s battery is also replaced during each process, ensuring optimal operation. This filling system has the advantage that no product is lost on the floor, ensuring a clean and efficient application.

Litrage / hectare

The quantity of spray liquid applied per hectare is a key factor in ensuring the quality of the treatment. It increases gradually as the foliage grows and reaches 200 litres per hectare when the maximum foliage density is reached.

Flight altitude

Normally the flight height is set at 4 metres above the ground, except for the first pass where it is set at 5 metres to prevent young shoots from being damaged. The point cloud (or three-dimensional) photos used to set the flight lines are not always completely accurate. Therefore, we need to continuously monitor the altitude during the mission. Incidentally, this is the only flight parameter that we can adjust without interrupting the processing.

Airspeed

The flight speed varies depending on the distance between the flight lines, the amount of spray liquid per hectare and the delivery rate of the pumps. It is usually between 5 km/h (1.39 m/s) and 8 km/h (2.22 m/s).

Distance between the flight lines (treatment width)

As the machine has a wingspan of 3 metres, we have set the processing width to 3.5 metres. This means that the drone flies through every 3.5 metres and automatically changes the line.

Treatment rate/ha

The flight speed depends on the amount of spray liquid per hectare and, above all, on the configuration of the vineyard. In an optimised vineyard with large, combined areas and no topographical restrictions (such as trees, power or telephone lines), the time required for preparation (prepare the drone, receive GPS + RTK signal, fill tank) is around 10 minutes.

The following information refers to a range that has been optimised for the use of the drone. We refer to the entire cycle as “rotation”, which includes refuelling, battery replacement, take-off, reaching the mission start point, spraying and then the return flight and landing. It is important to note that the batteries are replaced during each rotation.

Limiting factors

Wind: Wind increases drift and reduces the quality of pesticide application. From 4.5 km/h (1.25 m/s) the treatment becomes suboptimal, and from 6 km/h (1.67 m/s) the drift forces us to stop. The ideal conditions in our area are between 4.30 and 10.30 in the morning, which limits treatment to around 7 hectares per day.

Temperature: Heat affects the charging of the batteries and can cause problems with the material mixer. The warmer the battery gets, the longer it takes to charge, which, as with any processing system, reduces the quality of the spreading material.

Accuracy: The extreme accuracy of the device (1.5 cm) can be a limiting factor. If a flight line misses some vines, they will not receive any product as the drift is very low. Experience shows that the area directly under the device (2 m radius) is better covered than the edges (75 cm on each side). In 2024, we will adjust the treatment departures by 1.5 m for each round.

Product and water quality: The miscibility of products and the water quality can lead to clogged filters and nozzles.

Cleaning

The residual volume of the spray liquid in the drone’s tank is approximately 3 dl (0.3 litres). The mixer is equipped with a bottom with complete drainage so that the FOAG recommendations for minimising the environmental impact of residues can be easily followed. We rinse the mixer with 40 litres of clear water, which is applied to the crops via the drone. The drone itself is rinsed twice with 15 litres (30 litres in total) of clear water, which is also applied to the crops. All equipment is then cleaned in a special washing system.

Danger from the use of the drone

The most serious risk would be contact with the propellers during the flight. Other risks are associated with the electricity, the batteries and the generator as well as the pesticides used. The aircraft are equipped with an independent circuit breaker that can be used to switch off the motors in the event of loss of steering.

Installation costs

• T30 drone, 4 batteries and charger: CHF 35,000
• Generator for rapid battery charging: CHF 5,000
• MixBox mixer for crop protection products: CHF 5,000
• Creation of the flight manex, subscription to the RTK network, point cloud photos, training and examination to become a pilot of a spray drone: approx. 7,000 CHF

The total investment for the area amounts to CHF 52,000, with amortised costs of CHF 0.32/m2⁽ incl.^products ).

Observable results in the vineyard

Observations after two years of use:

• With regard to downy mildew, no differences were found between the various treatment agents used by the company.
• In terms of the quality of the application, there is no significant difference compared to a ride-on cannon (Cima cannon type). However, the drone has an advantage in the hillier plots.
• Compared to a Fischer Turbo or atomiser type system, the application quality of the drone without soil penetration is significantly poorer for grape varieties susceptible to mildew.

Comparison of treatments:

• The following summarised tables compare the effectiveness of the different variants during the 2023 and 2022 vintages.
• The year 2023 was particularly favourable for mildew and the data was taken at the end of July. A harvest restriction was required in this vintage, indicating the percentage of grapes affected by mildew and the economic impact for each variant.
• The second table refers to the year 2022, a less favourable vintage for mildew.

Important notice:
This data was not collected according to a strict protocol for scientific studies. It was collected with the aim of managing future cuvées and assessing the general quality of use in this area.

The percentage of grapes affected is shown without taking into account the intensity of the infestation. The economic impact is shown in green if there is no loss, red if there is a significant economic loss and orange if harvest regulation has limited or avoided the loss.

Conclusion

Drone treatment has allowed us to effectively protect our hard-to-reach vineyards while improving the safety and comfort of our employees. Even if this technology is not perfect, it is still young and is developing rapidly. It secures production in vineyards where the costs or risks of treatment from the ground are high. In addition, the drone is better perceived by the public than other methods and offers an innovative, modern and powerful image of our profession.