Pesticide free weed control   

A new benign technology for weed control involves application of hot water and foam. Obvious health and environmental benefits include eliminating pesticide exposure at source and preventing pesticide run-off into water courses. This new technology has advantages over earlier versions of the system and should allow broader uptake in the UK. 

Hot water and foam being applied along a path for weed control. Photo: Waipuna

A hot water based technology has been in the process of development for several years. Water heated by a boiler (in a van) is delivered through a hose and applied using a wand. An earlier prototype of the technology involved spraying hot water alone onto weeds. However, rapid cooling of the hot water required operators to saturate the ground to ensure weeds would be killed. In addition, the system had been developed in New Zealand and could not easily adjust to the hard waters of Northern Europe which blocked delivery nozzles. 
    Further research has found answers to both of these problems. The hot water is now mixed with an organic foam solution and retains heat for much longer allowing application speeds comparable to those of herbicide treatments. Wider nozzles prevent problems with hard water deposits.
    The organic foam compound or surfactant is produced from sugar extracts from maize and coconut (alkyl polyglycoside). The foam produces a thin film that prevents heat from immediately dissipating as the hot water is released. Treatment can now be accomplished twice as quickly.
    The producing company claims that the formulation degrades completely within 28 days and in Europe no permits are required for it as a weed control system. Trials have been conducted in Germany by Hohenheim University and by Bremen Airport. Early results are extremely positive and Bremen Airport has issued an endorsement. More advanced and scientific trials are under way in Germany and France. 
    Faced with the costs of analysing and treating water contaminated with pesticide residues in order to meet drinking water standards, the system is of particular interest to water companies and some have already shown interest. It is also of interest to municipalities and other bodies which need to control weeds in public areas such as roadside verges, pavements, boundaries and school playgrounds. A portable electric powered system has been developed for domestic use: the ‘Green Weeder’ is made from plastic in a wand shape that allows for spot treatment using only tap water and electricity to heat the water. 
    The system is very effective for control of annual weeds but perennial weeds may require repeat treatments or may have to be treated on a regular basis.
    The company involved, Waipuna, takes its name from the Maori word that means ‘pure water’. It is already operating in New Zealand, Australia, USA, Canada and many countries of Europe. The company bases its activities on the premise that the true costs of the use of pesticides are not internalised in pesticides costs and if they were, then alternative systems would be cheaper in comparison. Machines are currently being developed for organic orchards, sugar beet and for domestic use. Fresh injections of capital are allowing problems to be solved and new products to be developed to suit varying circumstances.

For further information visit www.waipuna.com or contact Gavin Porter on gporter@waipuna.com

[This article first appeared in Pesticides News No. 62, December 2003, page 11]