Plant protection products—fungicides, herbicides, and insecticides—are essential for safeguarding crops against pests, diseases, and weeds. However, a new study reveals that these chemicals can significantly alter the behavior of non-target organisms like bees and fish, raising concerns about broader ecological impacts. Researchers from the Helmholtz Centre for Environmental Research (UFZ) conducted a cross-habitat study analyzing these behavioral changes, published in the journal Environment International, highlighting the need for more comprehensive risk assessments for plant protection products.
The Problem with Plant Protection Products
While regulations govern the use of these products, non-target organisms inevitably encounter them, potentially experiencing harmful effects.
“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,” explains UFZ biologist Prof. Martin von Bergen. “Rainfall gradually washes plant protection products into the surrounding waters. They don’s simply remain and only affect the area where they are applied.”
The research team focused on behavioral changes as indicators of potential harm, recognizing that these products don’t always cause death but can still negatively impact individual health, population dynamics, and overall biodiversity.
Model Organisms and Research Approach
To effectively study these effects, the UFZ team used model systems representing terrestrial and aquatic habitats: the honeybee (Apis mellifera ) for pollinators and the zebrafish (Danio rerio ) for aquatic animals. This approach allowed for controlled experiments to isolate the effects of various 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 behavior 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.
The researchers exposed these models to concentrations of plant protection products found in their natural habitats and meticulously documented any changes in their behavior.
Observed Behavioral Changes
The results revealed significant behavioral disruptions in both bee and fish models.
Bees Under the Influence
Honeybees treated with insecticides exhibited reduced foraging activity and altered nectar processing habits. Fungicides and herbicides, on the other hand, resulted in less intensive brood care behavior. These changes can impair colony performance and the valuable pollination services bees provide.
“Such behavioral 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.
Fish in Contaminated Waters
Using a zebrafish embryo model, the researchers developed a behavior-based screening method to test chemicals for neuroactivity effects. This method enabled the rapid detection of altered learning and memory processes. Interestingly, exposing fish embryos to a mixture of insecticides, herbicides, and fungicides—commonly found in small streams in Germany—caused distinct behavioral changes.
At low concentrations, the fish displayed behaviors typically triggered by herbicides alone. However, at higher concentrations, this behavior was replaced with a behavior similar to that seen when exposed to fungicides.
“The work also demonstrates that mixtures of co-occurring plant protection products have the capacity to alter organismal behavior at environmentally relevant concentrations,” says Prof. Tamara Tal, UFZ ecotoxicologist and co-head of the study.
Implications for Risk Assessment and Biodiversity
The findings suggest that the ecological effects of plant protection products might be more extensive than previously understood. The study underscores the need for more sophisticated risk assessments that incorporate complex behavioral tests, especially when dealing with low concentrations of chemicals.
“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 von Bergen.
The researchers are advocating for a shift in regulatory approaches, recommending that acceptable exposure levels be determined based on cumulative risks from the mixtures of chemicals commonly encountered in the environment. Integrating more relevant behavioral tests into the risk assessment framework is crucial for better protecting non-target organisms and preserving biodiversity within agricultural landscapes.
