Why are earthworms helpful to farmers

Genetic engineering information service

A new study raises further questions about the herbicidal active ingredient glyphosate, which the WHO Cancer Research Agency classifies as "probably carcinogenic". Austrian researchers found that the weed killer mixture "Roundup" - manufacturer is Monsanto - significantly reduces the activity of earthworms. The fertility of beneficial animals also suffers.

For the study, the scientists from the State University of Natural Resources and Life Sciences in Vienna planted beds with various plants in the greenhouse - similar to those in agricultural fields or in gardens. They added two types of earthworms - the dewworm (Lumbricus terrestris) and the small meadow worm (Aporrectodea and Allolobophora caliginosa, respectively). After eight weeks, part of the areas was sprayed with "Roundup" for the first time - with a significantly lower dose than Monsanto recommended.

While the meadow worm continued to dig its tunnels into the earth, the activity of the rope worm initially increased. Probably, the researchers explain in the journal Scientific Reports, because the spraying of the weed killer made more dead plant material available for earthworms to feed on. But after a week the activity decreased "dramatically", after three weeks there was almost no activity. In the untreated beds, however, everything remained normal.

The scientists assume a “direct effect of the herbicide”. Because they had offered the earthworms additional sources of food in the form of dry hay, which usually increases the activity of the animals. But nothing happened in the beds sprayed with "Roundup" and in which there were dewworms.

Fertility also seemed disturbed. The Viennese researchers recorded “significantly” lower rates of reproduction for both earthworm species. In the meadow worm, if no "roundup" was used, 71 percent of the cocoons hatched offspring. When using herbicides, it was only 32 percent.

It is the first time that the effects of glyphosate-containing agents on earthworms have been shown under almost realistic conditions, the researchers believe. Earlier investigations had taken place in the laboratory and were often carried out on the compost worm (Eisenia fetida), which, however, does not play a role in agro-ecosystems. Quite the opposite of dewworm and small meadow worm: these earthworm species are extremely important for the diversity in the soil. They fertilize the soil with their excrement, their tubes help with the oxygen supply and water absorption and offer smaller animals and microorganisms valuable living space. Beetles and birds also feed on them. "Earthworms are key organisms in the soil," says the Institute for Agroecology at the Bavarian State Research Center for Agriculture.

The authors of the new study also point out that, because of its mode of action, glyphosate should only damage plants and some microorganisms. In theory, animals should not be directly affected. But the evidence that amphibians, beneficial fungi and earthworms are also affected, the scientists said. [dh]