Octocopters throw off parasitic wasps against corn borers

An octocopter, a little helicopter with eight propellers, hovers almost silently over the fields of the St. Mauritz experimental area east of Münster, Germany. AGRAVIS Raiffeisen AG carries out tests in its own fields, such as drones which can help in the purely biological combatting of the European corn borer.

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Have they finally landed, the aliens? And if so, why in the world is their flying machine dancing over a cornfield and shooting little white balls all over the place? This is somewhat akin to a scenario from a science fiction film, even though in reality it is cutting-edge agricultural technology.

An octocopter, a little helicopter with eight propellers, hovers almost silently over the fields of the St. Mauritz experimental area St. Mauritz experimental area east of Münster, Germany. AGRAVIS Raiffeisen AG is testing on its own areas how these drones can help in combating the corn borers by purely biological the corn borers by purely biological means. The corn borer is a pest that impairs the corn's steadfastness. Beyond this, it can also tap it to increase the probability that the plant is infested with fungal diseases. As much as 15 percent yield losses have been discovered in strip tests.

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However, the latest technology is not created without manual labour and understanding. Eduard Schönhalz, designer at Height-Tech GmbH in Bielefeld, is the pilot of the drone. He is supported by Reinhold Wintergalen from the crop cultivation consultancy of AGRAVIS and by Wilhelm Beitzen-Heineke, head of Biocare, Gesellschaft für biologische Schutzmittel mbH. Together they knee down at the edge of the maize field and fill small white balls into a container, which is fixed beneath the Octocopter. These balls have it in them, in the truest sense: around 2,000 eggs of the ichneumon fly (trichogramma brassicae) are resting in a sleeve of paraffin and cellulose. "The ichneumon fly is the natural enemy of the corn borer. Using it in fields with a pest infestation is an alternative to chemical plant protection," explains Reinhold Wintergalen. The tiny animals escape from the balls through two holes. As many as three generations of parasitic wasps start looking for the egg nests of the corn borers in the corn within two to three weeks.

They go from plant to plant in search of them. "Once they have found a clutch of eggs, they parasitize them so that ultimately the ichneumon fly rather than new pests emerge," the expert explains. Combating pests with trichogramma has proven itself over the years – although previously the balls or cards have been positioned by hand or distributed with converted special machinery. Both methods are clearly more work-intensive than using the octocopter. "We are daring to enter a completely new field," says Wintergalen. Previously, the unmanned mini-drones have mainly be used for aerial photography. The advantages of this new way are obvious to him and his colleagues: The amount of work is reduced, the effectiveness increased and the pests are combatted in a natural way. The costs for biological and chemical combatting of pest can also be kept under control in this way.

Farmer Benedikt Sprenker is already convinced and excited by the innovation. Since 2008 he has watched the corn borers infest his fields. "I have read about the possibility of distributing the ichneumon flies over the field using the octocopter," reports Sprenker. Almost simultaneously, AGRAVIS approached him with this idea. How his 29 hectares close to Beckum are test fields. To calculate the optimum pest combatting date, AGRAVIS ad the local agricultural cooperative societies carry out an extensive monitoring with pheromone traps and light traps. "The time window for us to react used to be very small," says Sprenker. The distribution of ichneumon flies has stretched this period from a few days to several weeks.

Some information on this topic:

In purely scientific terms, the corn borer is a small butterfly and is one of the economically most important pests. Originally at home in South and Central Europe, Africa and parts of Asia, it is now found in almost all parts of the world. In the wide spaces of moderate Europe, the corn borer continues its existence with a maximum of two generations a year, although in Southern Europe up to three generations are possible. The butterflies are active at night and lay several hundred eggs in small groups on the underside of leaves. Apart from maize, the main food plants of the caterpillars include other crops such as potatoes, hops. tomatoes and beets.

The corn borer weakens the plant's steadfastness with its feeding tunnels and inhibits its development. Another consequence of pest infestation may be diseases. The worst-case scenario is when the corn plant cannot be used as a plant for food or feed any longer. Then, it can only be used for energy a biogas.

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