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New application technology for beneficial insects in strawberries

Koppert Biological Systems not only continues to seek new beneficial insects to add to the current range of more than 30, but new ways to apply them. The latest is a tractor-mounted system, but before going into detail, some background to this story.

It is not always possible to walk through strawberry crops in greenhouses or polytunnels to release beneficial insects, and a decade ago Koppert Biological Systems launched the Airobug, a portable device that slides along the heating pipes or a roof rail, with two fans blowing insects out each side of the device to cover the crop.

The Airbug, a simple handheld device for structures lacking heating pipes and roof rails, followed, and more recently, so did a boom-mounted prototype. Again, conceived in-house in the Netherlands, the Rotabug-W is also known as the Bugbike. Made from aluminium, with elevated rotating axles on both sides, the axle on each side of the device is fitted with 5-litre dosing drums. The distance between the drums, as well as the size of the dispersal opening, can be adjusted. Pushed through strawberry crops by a single person, the wheel at the front of the Rotabug-W is connected to the rotating axles, making it easy to keep track of how much material is being dispersed.

Tractor-mounted system

Koppert UK saw potential for the concept, but with a higher capacity system that sees manual input replaced by mechanical power. The company linked with Protechnic (Chichester) Ltd, and in 2014 a prototype was developed for mounting on the back or front of a tractor. Called the Rotabug-R and designed for use in polytunnels, on soil-beds or tabletops, it comprises a 5-litre dosing drum with an aluminium-covered motor fitted to a horizontal boom. The opening size determines the dosing, together with the forward speed of the unit, which is normally around 3km/h.The Rotabug-R units can be switched on and off individually from the tractor cab.

The first five tractor-mounted prototypes were all tested by growers, and, using their feedback, several modifications were made, and another five machines manufactured. Two more followed, and today all 12 machines, the latest of which features a central axle that rotates the drums from which the predatory mites are delivered evenly onto the crop for the control of thrips and spider mites, work in soft-fruit crops grown in polytunnels. The machine is suitable for applying Spidex, Thripex, and Swirski-Mite, and David Foster of Koppert UK claims that the machine provides some significant labour savings. “Savings can be as high as 80% and it is far more efficient way of applying beneficial insects,” he said. Thripex is the most widely used product and the current machines can easily dose the typical rates of 50 predators/plant. Further increases up to 85 predators/plant are also possible, all at 3 km/hr.

The concept is still in development, so the company does not sell the machines, but offers a rental agreement. The company has done the calculations and reckons that a minimum of 10ha are needed to justify the costs. Various boom-widths can be made, and grower requests to apply heavier doses of predatory mites for the control of western flower thrips has led Koppert to develop a motorised double-drum option. The widest Rotabug-R currently in use is an 8m version fitted with eight applicators. However, an improved model with an air-assisted system is coming soon.

Also, while the standard 6m-wide dispersal system provides protected strawberry crops with a fast and efficient tool to apply beneficial insects, growers of outdoor crops have also expressed an interest in the concept, but with greater working widths, so an 18m wide tractor-mounted Rotabug is in development.

This will not be easy and will require a hydraulically-folding system to get the width down to 3m for road travel. Also, in the case of the predatory mite Spidex (Phytoseiulus persimilis), for example, each litre contains 10,000 mites, and Koppert is looking to develop a high capacity system that will allow the 18m version to cover a much large area more efficiently.

Drones

Application services product manager Tom Vroegop joined Koppert two years ago. As well as working with existing application techniques, he is researching new smart technologies, one of which could soon see beneficial insects applied only to infested areas of a field rather than a blanket treatment. The first stage of this is already underway at a strawberry farm in the USA where a drone is used to apply predatory insects – a process that is normally done by hand.

The trials began earlier this year, and initial results show that it makes no difference whether the beneficial insects are applied using the drone or by hand. “However, the main advantage is that the drone allows us to apply insects much more quickly,” said Mr Vroegop. The drone uses an advanced version of the intelligent pest-management software currently used in glasshouses to register pests. The information is converted into a field map, but at present still applies a blanket treatment. “However, five years from now we expect to be able to apply beneficial insects using GPS,” he said. The current work requires someone to walk through the crop to monitor pests and then to input the location into the system. But sensor technology is developing rapidly and in 10-15 years it is expected that this manual work will be replaced by insect-monitoring sensors.

The drone used is a commercially-available one, fitted with a Koppert-developed insect application device. The company continues to develop and patent the technology, but one potential issue with drones is battery life. “It does not last long, and we need more powerful batteries,” added Mr Vroegop. Ultimately, he reckons that tractors and drones offer the potential to apply beneficial insects to large outdoor areas. The current thinking is that drones offer a method to apply beneficial insects in a line in crop rows, whereas the tractor-mounted system could be more suited to blanket treatments. However, with GPS and field maps, there would appear to be no reason why tractor-mounted systems could not be used to apply variable rates of beneficial insects.