Development of zero and minimal herbicide regimes for controlling weeds on hard surfaces and determining their emissions

The ‘Best Practice Guidance Notes for Integrated and Non-chemical Amenity Hard Surface Weed Control’ document is launched on 18 March 2015 and is available to view and download here.

The aim of this project is to develop a weed control programme for pavements and roads (amenity use) which minimises risk to the environment (in particular, water quality) compared to using herbicides alone, while still controlling weeds to an acceptable standard. The impacts (inc. costs and benefits) of three programmes are being measured and new reactive specifications developed for municipal weed control. Methods available for controlling weeds fall into three categories:

  1. Chemical methods: herbicide (mainly glyphosate)
  2. Integrated methods:  combining chemical and non-herbicidal methods to minimise herbicide use and risks
  3. Non-herbicidal methods: thermal (flaming, infra-red, hot water, steam, hot foam) and mechanical  (wire brushing, sweeping, hand removal)

This project is comparing these three categories over a 5 year period to allow the different methods used to control weeds to be explored and evolve. Alternatives to herbicide need to be explored in order to minimise risks to surface and groundwaters, develop sustainable performance specifications for amenity weed control contracts and find alternative weed control methods to lessen the risk in the future of restrictions being imposed on herbicide use. Weed classification A new weed level classification system has been developed in the trial areas with a set of photographs to help assessors to estimate weed coverage and growth, quickly and accurately, enabling the contractor to decide when and where the treatments should be applied. Herbicide use Initial methods of non-herbicide control were based on a pedestrian operated infra-red heat treatment for pavement areas. Pavement edges and kerbs and channels were treated with a hand-held flame gun. A weed ripper (a powered steel brush) machine was also utilised. However, none of these treatments were suitable for all areas of the pavements and road gullies due to risks including damage to vehicles, garden borders and operator exposure to vibrating machinery. During 2012 an alternative Non-herbicide method of weed control was explored; a hot foam machine. The machine was used twice within the Non-herbicide and Integrated zones and proved to be effective on annual weeds but less effective on large perennial weeds. The speed of treatment was much improved over that of the weed ripper and could be operated in most weather conditions and used effectively near parked cars, street furniture and garden walls. The machine is being further trialled in 2013 and integrated better for tap rooted weeds with spot treatments of herbicide. To date the amount of herbicide applied in the Integrated approach has been kept under 50% of the allowable maximum dose. Weed growth The researchers have analysed the temperatures held by the plants after hot foam applications, which reach over 40oC; the temperature needed to permanently damage most weeds. Weed growth and coverage in 2012 was at least comparable, if not better in the Integrated programme compared to the Herbicide alone programme. Growth and coverage of weeds was more difficult to control in the Non-herbicide approach. Interestingly, there was a significant difference between the treatments for 3 of the weed species, with dandelion, procumbent pearlwort and annual meadow grass being less frequent in the Integrated treatment. Glyphosate runoff into drains EMR has also been monitoring glyphosate runoff in the trial areas. Meteorological data is being collected using weather stations placed in local schools within the experimental area. After an application of glyphosate, samples of runoff are collected from drains, following three subsequent rainfall events. As expected, glyphosate in drains was significantly higher in those treatments that had received herbicide and the Integrated plots had a smaller amount of glyphosate runoff than Herbicide only plots; due to herbicide only being applied to streets where it was required. Environmental impacts A life cycle assessment of the 3 treatment programmes was done by the University of Hertfordshire to allow an overall value of each environmental impact being produced. This included inputs into the 3 programmes applied from ‘cradle to grave’, including manufacture, fuel, herbicide, adjuvant and water consumption being assessed. It is noteworthy that the Integrated and Non-herbicide treatments had much higher energy consumption than using herbicide alone. Emissions and energy consumption for the three treatments were (smallest to largest): current practice Herbicide < Integrated management (restricted herbicide) < Non-herbicide (thermal and mechanical). However, the predicted aquatic ecotoxicity was greatest for the Herbicide treatment followed by the Integrated and finally Non-herbicide control.   East Malling Research – Project leader, vegetation analysis and herbicide emissions University of Hertfordshire – Economic and environmental impact assessments Kent Highways and Transportation – Specialist support, highways management, contract development Languard VM – Weed control specialist contractor Environment Agency – Ground water protection expertise For more information contact

Weeds on pavement
Foam treatment of weeds

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