Octocopters throw off parasitic wasps against corn borers

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. A so-called octocopter, a little helicopter with eight propellers, hovers almost silently over a maize field in Beckum-Roland, Germany. Following the tests in 2014, AGRAVIS Raiffeisen AG is testing for the second time how these drones can help in combating the corn borers by purely biological means.

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The octocopter flies across the maize fields in a certain grid pattern that has been worked out before and drops one of the balls every ten metres.Octocopters throw off parasitic wasps against corn borers
The octocopter flies across the maize fields in a certain grid pattern that has been worked out before and drops one of the balls every ten metres.

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.

However, the latest technology is not created without manual labour and understanding. Dr. Axel Weckschmied, owner of Hexapilots in Dresden, and Reinhold Wintergalen from the AGRAVIS crop cultivation consultancy crop cultivation consultancy have been on the road in respect of the corn borer for a number of days already – driving from Brakel in the Höxter district to the Warendorf district and even as far as St. Mauritz near Münster, to AGRAVIS' own test farm.

The procedure is always the same: Together the two man stand at the edge of a maize field and fill small white balls into a container, which is fixed beneath the octocopter. These balls are brimming with potential, in the truest sense of the word: around 2,200 eggs of the ichneumon fly (trichogramma brassicae) are resting in each of the paraffin and cellulose sleeves. "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. The drone flies across the maize fields in a certain grid pattern that has been worked out beforehand and drops one of the balls every ten metres. In this manner, roughly five hectares can be covered in the space of an hour.

AGRAVIS has dared to explore these new avenues for the first time in 2014 – successfully. This is why this year saw a repetition. "Success spoke for itself", Wintergalen justifies the rerun. The advantages of this method are obvious to him and his colleagues: The amount of work is reduced, the effectiveness increased and the pests are combated in a natural way. The costs for biological and chemical combatting of pest can also be kept under control in this way.

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 Reinhold Wintergalen. 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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