Ground beetles for sustainable food – University of Innsbruck
A research group headed by Corinna Wallinger has examined the food choices of ground beetles in native grain fields. It was shown that these insects can play an important role in weed regulation, as they eat significantly more plant seeds than previously thought. This knowledge should help to make agriculture more sustainable.
Ground beetles are a lesser-known group of beneficial insects. They form the beetle family with the most species, with over 6,000 species in Europe alone. “Ground beetles are misunderstood as beneficial insects compared to ladybirds, for example,” says the ecologist Corinna Wallinger. She therefore carried out a project run by the Austrian Science Fund FWF, in which the regulation of weeds by ground beetles in the cereal field ecosystem was investigated. Wallinger’s team found that their role in agriculture had previously been underestimated.
DNA from beetle food
To study the insects, the research team set up traps, which in the sign were cups buried flush in the ground, as project leader Wallinger explains: “The beetles fall in and the traps are emptied daily.” So that the animals can hide in them from each other , wood chips were placed in the cups. The stomach contents of the animals were then examined in the laboratory without having to fight them. “Ground beetles have a natural defense mechanism. When they’re stressed, they regurgitate their food,” Wallinger said. “We take advantage of this: We put the beetles head first in small reaction vessels, which were briefly heated at the tip, which was enough to stimulate the beetles to regurgitate the contents of their stomachs.” The animals were then able to go outside again be cleared wild. In this form, samples were collected from 6,500 ground beetles in grain fields between France and Austria.
The stomach contents were then examined using molecular methods similar to the PCR tests for Covid-19, except that instead of viral RNA, the DNA of certain species in the diet was looked for. It was found that plant seeds are a popular food for ground beetles, and to a much greater extent than previously thought. The previous knowledge about the food choice of ground beetles is largely based on observations and correlative analyses. However, what these extremely mobile, small creatures actually do in the field, could for the first time through them studies be empirically proven.
Beetles as a “vaccination” against pests
Wallinger’s colleague and project collaborator Oskar Rennstam Rubbmark emphasizes the importance of ground beetles in agriculture. he explains that, unlike other beneficial insects such as aphid-eating ladybirds, they are “generalists” who are not specialized in a specific type of pest. In addition to weed seeds, they also eat various pests such as aphids and slugs, whose eggs are also on their menu. Rennstam Rubbmark tried to make a medical comparison: “Carabids are ecological in the agricultural system what vaccinations are in medicine. At best, they prevent pests from spreading explosively, since they are already there when they arrive in the field. Only if that goes wrong can the specialized beneficial insects limit the damage.” In this picture, the latter are the medication that is only used once the disease has already broken out.
Sustainable Agriculture
For the implementation of the new findings in practice, the two researchers do not primarily have the area of organic agriculture in mind, the value of which they unanimously emphasize. “Organic is great,” says Rennstam Rubbmark, “but it only works in certain landscapes where the framework conditions are optimal and only to a certain extent.” itself leaves and dies are automatically regulated, cannot be implemented in the agricultural sector. In order to ensure that the world’s population is fed, we need optimal yields and therefore sustainable cultivation of agricultural land. This requires a functioning, self-regulating system.” The previous strategy in conventional agriculture included intensive fertilization and tillage as well as the use of toxins to regulate pests and weeds. But this access has an expiry date; in a delayed 40 to 50 years this will be over. We must also consider alternatives at an early stage.
Enhancement by Green Stripes
And what could crop protection using ground beetles look like in concrete terms? Wallinger rejects the image of releasing bred swarms of beneficial insects: “It only works under certain conditions, such as in glass houses or vegetable tunnels.” One effective measure is narrow green strips between the fields that remain uncultivated, so-called beetle banks. “Experience has shown that there are a particularly large number of ground beetles there. From there, the animals can migrate into the fields and withdraw again if necessary,” explains the ecologist. A reduction in the use of chemicals is also a prerequisite. Rennstam Rubbmark recalls the species richness of beetles, which all have a comparable range of food. The occurrence of the species is subject to seasonal fluctuations and disturbances can also lead to the loss of individual species. In a functioning system there would always be a species that can take over the regulation. Biodiversity is once again an important factor, also in pest and weed regulation by ground beetles.
What do the farmers think?
In a follow-up project that was recently started and is also being carried out by the FWF, the team from the Institute of Zoology now wants to see at EU level how the knowledge gained can be put into practice in agriculture. It is about a socio-economic approach in which farmers and other stakeholders are contacted to find out their perspectives. It is crucial to know what agriculture needs, what causes and difficulties there are. It was already apparent in advance that farmers: are fundamentally open to alternative methods such as promoting beetle populations. Nor is it in their interests to poison themselves or their fields or to deplete the soil. “They are particularly interested in preserving healthy farmland for future generations,” says Wallinger. In the many years of cooperation, only one rejection has been received so far, all other companies contacted were open to cooperation and very interested in the research results.
To the people
Corinna Wallinger is an ecologist with a focus on the interaction of plants and insects. She conducts research at the Institute of Zoology at the University of Innsbruck and, together with partners, has founded a company that focuses on services in the field of DNA analysis.
Oskar Ragnar Rennstam Rubbmark also conducts research at the Institute of Zoology at the University of Innsbruck and is interested, among other things, in the functioning of the ecosystem with a special focus on insects and their role as natural regulators of pests in agriculture.
The project “Ecosystem services of ground beetles” had a duration of five years and was completed in 2021. The funding from the Austrian Science Fund FWF was 348,000 euros. The follow-up project “Sustainable restoration of semi-natural habitats (FRESH)” has been running for three years as part of the European partner program BiodivERsA since March 2022 and is co-financed by the FWF with 256,000 euros.