Pesticide products are composed of different ingredients. The active substance is declared as acting against the targeted 'harmful' organism (ie: glyphosate against weeds). Safeners and synergists are part of the ingredients that can be contained in, mixed together or applied in pesticide products (formulations) to enhance their efficiency. They can be a single substance or a mixture of several components. Although they are always mentioned jointly in the EU Pesticides Regulation, safeners and synergists serve a different function.
Safeners
A safener is a substance added to pesticide formulations to eliminate or reduce the harmful effects of the pesticide active substance on specific crops. These safeners are often applied to seeds or used in combination with herbicides. Their main function is to enhance the crops' ability to quickly break down herbicides through metabolic processes. This enhancement works by amplifying the biological pathways in the crops responsible for breaking down herbicides. The goal is to speed up the degradation of herbicides within the crop, preventing them from reaching concentrations that could be damaging. Safeners have primarily been developed for cereal crops such as maize, rice, and sorghum, particularly to protect against specific herbicides applied to crops before the plants emerge from the soil (pre-emergence herbicides).
Synergists
Synergists are chemicals that in theory lack pesticidal properties on their own but which can increase the activity of the active substance(s) in a pesticide formulation. There is little information available on synergists, most of it refers to insecticide synergists. A commonly used commercial insecticide synergist is piperonyl butoxide (PBO). PBO is applied before using specific insecticides (e.g. pyrethroid or neonicotinoid insecticides). It works by inhibiting the insects’ ability to break down the insecticide molecules, thus making them hypersensitive to the insecticide [4]. Without this substance, insects would be more likely to degrade the insecticide before they die, and recover from the poisoning. Problem is, the use of synergists can affect other insects.
Not intert ingredients
Evidently, safeners and synergists are not “inert” compounds. They can have unintended effects on living organisms and biological processes. For example, synergists could have harmful effects on honeybees, by inhibiting their defensive detoxifying enzymes and ability to resist the toxicity from insecticides. Therefore, a thorough risk assessment of their potential toxicity to non-target species is absolutely critical! However, a significant deficiency exists, as this assessment so far has been very diverse among EU member states and therefore largely insufficient.
Read more : Addressing the 9-years Gap: The Long-Awaited Proposal on Safeners and Synergists
