How their behaviour changes after exposure to plant protection products is now the focus of a cross-habitat study by scientists from the Helmholtz Centre for Environmental Research (UFZ). The behavioural changes found in the animal models were significant and are an indication of the effect of plant protection products on non-target organisms in the wild. The work indicates that more complex and relevant behavioural tests should be included in the risk assessment of plant protection products in the future. The study was published in the journal Environment International.
The application of plant protection products in agriculture is subject to strict regulations. Nevertheless, organisms that are not the primary target of their use, so-called non-target organisms, inevitably come into contact with these substances and can potentially be harmed by them. "Wild bees and other pollinators can come into contact with quite high concentrations shortly after spraying. But animals in aquatic habitats are also at risk," says UFZ biologist Prof. Martin von Bergen, one of the two joint principal investigators. "Rainfall gradually washes plant protection products into the surrounding waters. They don't simply remain and only affect the area where they are applied."
The UFZ team selected a research approach in which pollinators and fish were analysed, which are model systems for effects of chemicals in the terrestrial and the aquatic habitats. The honeybee (Apis mellifera) was selected as a model organism for pollinators and the zebrafish (Danio rerio) for aquatic animals. The researchers focused on behavioural changes as a result of exposure to plant protection products. "Of course, plant protection products do not always have a lethal effect on non-target organisms. However, depending on the type of product, even low concentrations can damage their health or impair their behaviour in such a way that this can have a negative impact on the individual, the population and ultimately even on the biodiversity of the ecosystem," says Cassandra Uthoff, UFZ doctoral student and lead author of the study. "Although animal behaviour tests following exposure to low concentrations of chemicals are already included in the risk assessment of chemicals in some cases, these tests are not complex enough and are typically not mandatory."
The UFZ researchers, an interdisciplinary team from the fields of animal behaviour research, ecotoxicology, and biochemistry, focused on precisely these complex behavioural patterns. "We wanted to find out whether and to what extent these behavioural patterns change when exposed to insecticides, herbicides and fungicides. To do this, we exposed the model organisms to concentrations of plant protection products that actually occur in their respective habitats in the environment and analysed their behaviour," explains Cassandra Uthoff. In the honeybees, the researchers observed reduced foraging activity and altered nectar processing behaviour following treatment with the insecticide. Fungicides and herbicides, on the other hand, led to less intensive brood care behaviour. "Such behavioural changes, triggered by environmentally relevant concentrations of plant protection products, can impair the performance and maintenance of the colonies and ultimately also their pollination services," says Uthoff.
To test the effects of plant protection products on aquatic organisms, the researchers used a behaviour-based screening method in the zebrafish embryo model. This enables rapid testing of chemicals for neuroactivity effects, including altered learning and memory processes. In addition to individual exposure to the plant protection products, the fish embryos were also exposed to various concentrations of an insecticide-herbicide-fungicide mixture that has been found in small streams in Germany. The exposure caused clear and specific changes in their behaviour: If the concentration of the mixture was low, the fish embryos exhibited behaviour that would normally be triggered by the herbicide alone. At higher concentrations of the same mixture, however, this behaviour was not reinforced, but replaced: The fish larva now behaved in the same way as when exposed to the fungicide.
"The work also demonstrates that mixtures of co-occurring plant protection products have the capacity to alter organismal behaviour at environmentally relevant concentrations. This supports the concept that, to better protect animals in the environment, chemical regulations should set acceptable exposure levels based on cumulative risk”, says Prof. Tamara Tal, UFZ ecotoxicologist and co-head of the study.
"The effects that we were able to measure in these animal models suggest that the actual ecological effects of plant protection products are much more far-reaching than previously assumed", says Martin von Bergen.
The researchers are therefore calling for the integration of more relevant behavioural tests for low-concentration chemicals in the risk assessment frameworks for plant protection products. This would help to identify critical substances and better protect non-target organisms, thereby contributing to the preservation of biodiversity in agricultural landscapes.
The research work was carried out as part of the Sens4Bee project funded by the Federal Ministry of Agriculture, Food and Regional Identity (BMELH), a grant from the Helmholtz Association and with the support of the Novo Nordisk Foundation.
Publication
Uthoff, C., Herold, N.K., Alkassab, A.T., Engelmann, B., Rolle-Kampczyk, U., Pistorius, J., Schweiger, N., Finckh, S., Krauss, M., Thum, A.S., Jehmlich, N.,Tal, T., von Bergen, M.: Cross-taxa sublethal impacts of plant protection products on honeybee in-hive and zebrafish swimming behaviours at environmentally relevant concentrations; Environment International, September 2025, https://doi.org/10.1016/
Further information
Cassandra Uthoff
UFZ Department of Molecular Toxicology
cassandra.uthoff@ufz.de
Prof Dr Martin von Bergen
Head of UFZ Department of Molecular Toxicology
martin.vonbergen@ufz.de
Prof Dr Tamara Tal
UFZ Department Ecotoxikology
tamara.tal@ufz.de
UFZ press office
Susanne Hufe
Phone: +49 341 6025-1630
presse@ufz.de