Reducing the negative impacts of pesticides

Ensuring that pesticides do not endanger public health or the environment is a key objective of the European Commission. Due to spray-drift, the effects of pesticides are often observed outside of crop fields, where they affect non-target plants, fungi and insects as well as humans. New research discusses the effects of pesticides on non-target species and demonstrates that employment of “best practice techniques” could completely avoid non-target effects by 2010.

In the Netherlands, land is used intensively to produce food and non-food crops such as flower bulbs. The climate favours fungal infection, which increases the need for fungicide in potato and fruit production. Consequently, annual pesticide-use is high compared to other European countries. Non-target organisms, including plants, fungi and insects, are damaged by pesticides as a result of spray drift, leading to a loss in biodiversity in rural areas.

Since 1991, policy in the Netherlands1 has achieved a reduction in pesticide use of more than 50 per cent. The focus is now to reduce spray drift and its effects. Best practice techniques, such as leaving unsprayed, crop-free borders around fields and using sprayers that have low-drift nozzles can be effective. Much research has focused on the impact of these measures on water contamination. However, Dutch researchers have now estimated the side-effects of pesticide drift on terrestrial biodiversity and the potential to reduce these effects in the future.

The researchers modelled the relationship between distance from pesticide-treated fields and amounts of pesticide deposited, via drift, in non-target areas. To measure the level of impact spray drift had on non-target species they examined the percentage areas in which the EC50 (the concentration of a pesticide where 50 per cent of the organisms die) was exceeded. Using these models they analysed three drift scenarios: (i) the recent past (1998); (ii) the present (2005) and (iii) the near future (2010).

It was demonstrated that in the recent past (1998) the EC50 was exceeded for herbicides in 59 per cent of areas adjacent to treated fields, affecting non-target plants. Insecticides and fungicides effected non-target insects and fungi in almost 30 per cent of these areas, at the EC50 level. In 2005, herbicides still affected non-targets in 41 per cent of areas adjacent to treated fields, despite the use of low-drift nozzles and the introduction of unsprayed boarders. In the future scenario (2010), if non-crop boarders were increased to 2.25 m for potatoes (compared to 1.5 m in 2005) and 1m for other crops (compared to 0.5 m in 2005), it was predicted that pesticide impacts could be cut to zero.

A new Thematic Strategy on the Sustainable Use of Pesticides has been adopted and European policy framework directive for sustainable pesticide use is under development2. This study suggests that increasing unsprayed buffer zones around crops is critical to the success of any new strategy to prevent the harmful impact of pesticides.

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