A new study has shed light on commonly overlooked safety issues in fungicide products—issues related to substances present alongside active ingredients.
The research focused on Syngenta’s fungicide, Amistar, which is formulated with the main active ingredient azoxystrobin, also found in many similar products commercialized in Europe.
Amistar is routinely sprayed on flowering crops foraged by bumblebees without exposure-mitigation measures, as per Amistar’s current label specifications.
Amistar fungicide co-formulants account for between 10-20% of the product and serve the purpose of helping to activate and stabilize azoxystrobin. But residue left behind in the pollen, nectar or wax is thought to be significantly high enough to warrant further scrutiny.
Of these co-formulants, alcohols ethoxylates are of particular interest to researchers studying bee health, as adverse effects have been reported in other insect populations.
Previous regulatory testing of azoxystrobin as a whole performed on honeybees, and not bumble bees, found no ill effects. But the research is lacking in residue analysis studies looking at the exposure of bumblebees to adjuvants.
In new research conducted at the Royal Holloway University of London, scientists tested some ingredients of Amistar fungicide individually, including alcohol ethoxylates, for possible damaging effects on bumblebees.
One group of bumblebees was fed Amistar mixed with sugar water; two separate groups received a co-formulant mixture and alcohol ethoxylates neat, proportionately to formulation levels; and a control group was given pure water.
Different health parameters, including appetite, weight change and survival, to different stressors related to the Amistar diet variants were assessed over the course of 5 days across all the groups.
After 48 hours, 23% of bees given the integral Amistar fungicide product died, while bees given the Amistar ingredient of alcohol ethoxylates starved to death at a slightly higher rate (30%).
The authors observed a concurrent 50% decrease in appetite and 4% loss of body weight in both Amistar and alcohol ethoxylates-treated bees, amongst outcomes affecting ecosystems.
The remaining bees in the alcohol ethoxylates group showed significant damage to the gut lining, with a 302% increase in gut melanization (tissue necrosis).
Some caveats remain, such as whether the dose used in the study is transposable to real-life, full-field exposure levels to the fungicide, which can be difficult to ascertain.
Amistar fungicide was previously believed to be safe, with no label restrictions for bee populations because of its LD50-based regulation. By this token, a mortality rate below 50% is deemed safe. However, there is mounting evidence of harm on the health of bumblebees, too.
The study has raised the need to review safety testing for fungicides, especially the types of outcomes measured during the testing, integrating health effects on bees rather than just mortality.
If these results are reproduced and more evidence comes to light, there may be a call to introduce regulations on co-formulants that more accurately reflect their toxicity, to protect the health of bees and pollination.
