Researchers at the University of Neuchâtel have discovered two effective natural methods for fighting one of the most destructive pests ravaging corn in North America and spreading across Europe. This could unlock opportunities to reduce pesticide dependence.

In a studyexternal link published in Scientific Reports this week, researchers led by the Laboratory for Basic and Applied Research in Chemical Ecology (FARCE) at the University of Neuchâtel found that a small worm living underground (Nematodes) and a bacterium (Pseudomonas) can reduce the impact of the western corn rootworm by 20% to 50% based on field tests.

This specific rootworm, Diabrotica virgifera in Latin, is the most destructive pest of corn in North America and has recently spread across central Europe. In North America, the cost of the damage from the pest is between $1-2 billion each year. It is also responsible for crop losses in Central and Eastern Europe of approximately €500 million per year.

Switzerland is also affected by the pest. It appeared in the Italian-speaking region of Ticino twenty years ago and was found in canton Vaud in 2017 and in the Jura last year.

The subterranean larval stages of the pest are hard to reach with pesticides. For a number of years, crop rotation was seen as the most effective management option but soil and seed insecticides have also been used. The study indicated that the western corn rootworm has developed resistance to most insecticides classes over the years.

The application of beneficial soil organisms is being considered as a sustainable and environmental friendly alternative to pesticides, says the study.

Impacts and implications

The researchers carried out field trials for three years in the US state of Missouri where there are massive infestations of the pest. On Swiss public television RTSexternal link, Geoffrey Jaffuel, a biology researcher involved in the study, explained that "we used organisms that are already in the soil and bacteria that are beneficial to plants and applied them in the fields to fight against this pest without pesticides or GMOs”.

In two out of the three trials, plots treated with nematodes or bacteria or both, showed less damage to the corn’s roots than those from untreated plots. In one year, the rootworm survival was significantly lower in plots treated with the bacteria than in control plots.

"The effects of the treatments varied considerable among the three years, but they were always positive for the plants," explains the study.

The study authors write that “we think studies such as this one can be the basis for the development of effective soil treatments that can replace the use of pesticides, and provide a more sustainable control of western rootworm and other soil pests.”

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