By Lloyd Phillips
Researchers in Australia have raised the alarm that the widely used crop protection fungicide ingredient, chlorothalonil, appears to have the unintended consequence of threatening beneficial insects and other non-target organisms.
The fungicidal compound chlorothalonil reportedly poses a major risk to the world’s populations of beneficial insects and other non-target organisms. This is according to the results of a study* conducted by researchers at Macquarie University’s School of Natural Sciences in Australia.
Chlorothalonil is reportedly a broad-spectrum fungicide designed to protect agricultural crops from fungal diseases, including Alternaria, Botrytis, and Septoria species, to control fungal pathogens on vegetables, fruits, nuts, cereals, to prevent diseases on turf grass and ornamental plants, and to act as a mildewcide in paints and surface treatments.
Although its use has been banned in 27 European Union countries and in Costa Rica in the years since 2019, chlorothalonil is still widely used in other parts of the world subject to varying degrees of control. In South Africa it is classified as a restricted agricultural remedy that may only be distributed through and handled by qualified pest control operators.
Study Reveals Concerning Effects on Beneficial Insects
In their studies using the common fruit fly (Drosophila melanogaster) as test subjects, the researchers in Australia found that, among other impacts, even low concentrations of chlorothalonil reduced these insects’ weight, delayed their pupation and resulted in fewer eggs.
In their paper, the researchers stated research is required to determine chlorothalonil’s impacts on other insect species.
However, it can be extrapolated from their recent research with the common fruit fly that “these findings emphasise the potential risks chlorothalonil poses to wider insect populations, even at low doses, and underscore the importance of assessing non-target effects in broader ecological contexts”.
The researchers pointed out that populations of beneficial insects and other organisms around the world are at great threat from various factors, including agricultural chemicals.
“Understanding the effects of agricultural chemicals is critical for developing sustainable pest management strategies that minimise non-target impacts and support ecological balance in agricultural landscapes.”
*Dissawa Darshika M., Boyer Ines and Ponton Fleur 2025. Chlorothalonil exposure impacts larval development and adult reproductive performance in Drosophila melanogaster. Royal Society Open Science. 12250136. http://doi.org/10.1098/rsos.250136
