Technical
Going Dutch on Weed Control!
Dr Corné Kempenaar
re-invent the wheel, the UK can learn many useful lessons from the SWEEP
“Rather than
A review of weed control management practices in Holland indicates how methods are likely to change in the UK over the next few years, driven by European legislation
ong before the EU’s Sustainable Use of Pesticides Directive (or its Water Framework Directive) were conceived, and around the time of the EU Drinking Water Directive 98/83/EC, which limited, to one part per billion, the acceptable
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contamination by pesticides in drinking water, a team at the Plant Research International B.V. at Wageningen University and Research Centre in Holland, set to work to understand how pesticides find their way into water from hard surfaces, and what can be done to minimise their impact. Led by Senior Scientist and Head of Research, Dr Corné Kempenaar, the research was supported by the Dutch water companies VEWIN, Water Board Hollandse Eilanden en Waarden, and manufacturers of Round-Up glyphosate, Monsanto.
initiative”
The objective, of course, was to try to minimise water pollution, whilst obtaining acceptable levels of weed control on hard surfaces at an acceptable cost. Nearly 50% of Holland’s drinking water is derived from surface water, so the problem was a big one to solve. The research started in 1999. From 2001-2006, the team set up trials to monitor the effects that applications of pesticide on hard surfaces had, in terms of pesticide run off. Worst case scenarios were emulated on a 10x10 square metre hard surface, where run off could be gathered and analysed after applications of herbicide followed by simulated rainfall. Further trials used urban areas of one to ten hectares of paved surfaces, where
the run off into drains was analysed. Other methods of weed control, such as herbicide applied by weed wipers, very low dose applications of herbicide, spot treatment, sweeping regimes and heat- based alternatives were evaluated. The result of the research led to the development of a programme called SWEEP (in Dutch: DOB), which was so effective that it was formally adopted by Holland into law in 2007. It probably leads the world in defining a cost effective integrated approach to weed management, meeting, years ahead of time, the requirements of the EU Drinking Water Directive, the EU Sustainable Use of Pesticides Directive and the EU Water Framework Directive. So, rather than re-invent the wheel, the UK can learn many useful lessons from the SWEEP initiative, how it is operated and how it achieved success. Trials on hard surfaces indicated that pesticide run off, using Monsanto’s Roundup Evolution (equivalent to Roundup Pro Biactive in the UK) gave high levels of run off if rain followed soon after application. Within one to three days after application, run off was greatly reduced. So, as part of SWEEP, it has been agreed that the herbicide must not be applied if there is a 40% chance of rainfall, of more than 1mm per 3 hours, within 24 hours of application, as advised by the Dutch Met Office. Glyphosate runoff in SWEEP experiments was between 0.2% and 5.7%, much lower than assumed. It was also established that accurate low level doses of spot applied glyphosate can achieve good weed control in conjunction with good
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