Drone spraying maize

When maize is too tall for a tractor

A tractor sprayer passes safely through maize up to 1 to 1.5 m tall. Once the rows close, though, the wheels break plants, and the average loss in the wheel tracks is 5 to 6% of the crop. Our agronomist sees this in the field regularly. The drone flies about 3 m above the tops of the plants and follows the terrain automatically, so it sprays 2.5 m maize as well as 1 m maize.

After rain, only the access road needs to dry out. If there is tarmac to the field, we spray the same day the rain stops. A tractor has to wait 2 to 5 days before it can go into the mud.

Drone spraying maize takes only 15 to 20 litres of water per hectare, against 150 to 400 litres with a tractor. On 40 ha that means 600 to 800 litres of water instead of 6,000 to 16,000 litres. Our DJI Agras T70P carries up to 70 litres of liquid per flight and treats about 20 ha an hour on grouped fields. For the full comparison, see drone or tractor.

European corn borer: when to spray by drone

Corn borer has to be treated as the larvae hatch, before they bore into the stalk or the cob, because after that the insecticide no longer reaches them. The first generation flies in June and the second in late July and August, exactly when maize is at its tallest and a tractor can only go in by trampling a lot of the crop. That is why the second generation is usually sprayed by drone.

The treatment date is set by the moth flight, which depends on temperature, not by the calendar. Our agronomist Nikola therefore follows the PIS warnings: the Vojvodina Plant Protection Forecasting and Warning Service records the flight in the field and announces when it is time to spray. Egg masses are whitish and overlap like fish scales on the underside of the leaf. When black dots (the larvae's heads) appear on the eggs, hatching begins, and that is the moment to fly.

For grain maize the treatment threshold is usually 10% of plants with egg masses. For seed maize the tolerance is much lower (3 to 5%), and for sweetcorn lower still (Agrosava, Savacoop).

Your agronomist chooses the insecticide and the rate. Nikola mixes the product at the field, programs the flight map and sprays at the agreed time. Before every insecticide treatment we notify local beekeepers so they can close their hives.

More on monitoring and timing: European corn borer: when and how to spray.

Pre-emergence spraying of maize

For soil-applied herbicides straight after sowing and before the crop emerges, we recommend a conventional tractor sprayer. With no plants up yet there is nothing to trample, and the herbicide needs a larger volume of water placed as close as possible to the soil and the weed seeds.

We apply these herbicides by drone only when we have to, when long spells of rain keep the tractor off the field, and only if the neighbouring fields are sown with the same crop, so that any drift does no damage.

More on this: spraying maize before emergence.

Post-emergence herbicides, up to 8 and 10 leaves

Basic weed control in maize is usually finished by the 4 to 5 leaf stage at the latest, and treatments from 3 to 8 leaves are used as a correction (Syngenta). Label wording such as "up to 8 leaves" or "up to 10 leaves" sets the latest growth stage at which maize can safely take the herbicide.

We carry out late herbicide corrections by drone only when mud or crop height keeps the tractor out, and only if the surrounding fields are under the same crop. Your agronomist must confirm the product and the application stage.

Read more: maize herbicides up to the 10th leaf.

Foliar feeding of maize

The drone applies foliar feed at any maize height. The strong downdraught from the rotors pushes the fine droplets down to the lower leaves, so the whole canopy is covered evenly, not just the top of the plant.

We never do this treatment in the hottest part of the day, because uptake stops. Foliar feeding is done early in the morning or in the evening, at 15 to 25 °C (AgriNova). The choice of fertiliser and rate is left to your agronomist.

Prices and how we work: foliar feeding of maize by drone. Timing by growth stage: foliar feeding of maize.

Maize treatment calendar

We do the summer treatments, when maize is tall, by drone and leave spring herbicides to the tractor. The exact day is set by the crop stage, the forecast and your agronomist.

How much drone spraying maize costs

Drone spraying maize costs €25/ha up to 20 ha, €22/ha from 20 to 100 ha and €20/ha over 100 ha. The same price applies to foliar feeding. Travel within 50 km of Opovo is free; beyond that it is €1 per kilometre over 50 km, one way, per visit. You supply the product and the water.

For comparison, tractor spraying costs about RSD 2,000 per cadastral jutro (around €30 per hectare), and that price does not include the yield lost to trampling.

Worked example: 40 ha near Kovačica (22 km from Opovo)

If we agree a package of three treatments on the same field (for example two for corn borer and one fungicide), you get 5% off; for five or more visits the discount is 10%. For those 40 ha, three treatments with the discount cost €2,487.10 in total, an average of €829.03 per treatment. You pay after each treatment.

Note: we take fields smaller than 10 ha only within 20 km of Opovo.