Ever decreasing amounts of plant-protection products are being used in field crops; however, the quantity alone does not determine the risk for the environment, as discussed in a new Agroscope study on the use and risk of plant-protection products in Swiss field crops.
Plant-protection products (PPPs) protect crops from weeds (with herbicides), from fungal diseases (with fungicides) and from pest insects (with insecticides). However, they can also cause undesirable side effects in humans, animals and the environment. A comprehensive authorisation procedure and agricultural policy measures aim to reduce both the quantity of PPPs used as well as their potential risks. Agroscope has now produced a detailed analysis of trends in PPP use in field crops and the associated risk potential for surface waters over the last ten years.
Calculating PPP use and risk potential
Since 2009, 300 farms have recorded the amount of PPPs they use, as well as when and in what crops. From these figures, the Swiss-wide use of plant-protection products per crop was extrapolated for field crops. The model SYNOPS was used to calculate the risk posed to surface waters, both with and without considering the use restrictions for reducing aquatic risks imposed by the product authorisation.
Main findings of the Agroscope study
During the evaluation period, between 328 and 476 t of herbicides were used each year in Swiss field crops, with the amount of active substances used falling by nearly 31% between 2012 and 2018. Between 99 and 146 t of fungicides were used each year, nearly 27% less in 2018 than in 2009. Insecticides – frequently highly effective in low doses – were used in far lower quantities than herbicides and fungicides, except for paraffin oil in potato crops. The amount of insecticides used fluctuated over the years, with no clear trend. In addition to changes in the authorisation of PPPs and the increase in organic and extensified (‘extenso’) farming (which dispense with fungicides and insecticides), the decline in the total area under cereal cultivation was also a reason for the decrease in the amount of active substances used in field crops throughout Switzerland.
The area-weighted risk potentials (the quotient of environmental concentration over toxicity, extrapolated for the area occupied by all field crops) were highest for the herbicides, followed by insecticides and finally fungicides. The trends of the risk potentials were constant for herbicides, decreasing for fungicides and increasing for insecticides. Where the effects of the use restrictions for reducing aquatic risks were taken into account in the calculation, a sometimes distinct reduction in all risk potentials and an overall decreasing trend for all three groups of active substances were observed. Equally, the choice of active substance can have a major effect on risk potential. In 2014, for example, a sharp increase in risk potential for insecticides compared to 2013 was recorded, due to the authorisation of an active substance for the control of pollen beetle in oilseed rape. Nevertheless, this increase was greatly reduced by the use restrictions associated with product authorisation.
- The amount of PPPs used in field crops throughout Switzerland and the risk potential for surface waters have decreased in recent years.
- The use restrictions imposed by product authorisation have decreased the risk potential for surface water – in some cases substantially.
- Without considering the use restrictions, only the risk potential for fungicides decreased, while the risk potential for insecticides increased and that for herbicides remained constant.
- The choice of active substances had a major impact on risk potentials, since active substances differ from one another in terms of their behaviour in the environment and their ecotoxicity.
- The risk potential of PPPs for surface waters does not correlate with the quantity used: some active substances, although used in small quantities, were risk-dominant; others, although used in large quantities, had a low risk potential.
- Targeted support of the farms in terms of the use of lower-risk active substances can make an important contribution to reducing risk potential.