Herbicides

If other weed-control methods prove inadequate, herbicides can offer a cost-effective solution.

At times we can live with weeds, but a lot of the time we can not. In urban areas, weeds can be more than just a nuisance. By seeding and growing in pavement cracks they cause damage and uneven surfaces, pose a trip hazard, can be slippery and trap litter that then presents a fire risk and attracts vermin. It is argued that the resulting loss in civic and community pride leads to graffiti, vandalism and degeneration.
Weed infestations in planted areas and cropping situations are just as serious. Weeds compete for light, water and nutrients and so cause desirable plants or crops to become stressed with a subsequent lowering of quality, reduced saleability and little or no profit.
In sports turf, weeds disrupt the speed and bounce of the ball. On synthetic pitches, mosses, lichens and weeds damage the surface as well as causing dangerous playing conditions. And in water features, rivers and streams, weeds can choke other aquatic life, disturb the balance of the ecosystem and ultimately result in a stagnant, foul-smelling swamp.

Selecting a solution
The options for weed control are many. In a lot of situations the use of herbicides is likely to be the most cost-effective choice, but hand weeding, hoeing, hot-water treatment and flame guns are some of the options that should always be considered before grabbing the sprayer. The unnecessary use of herbicides is a waste of money and, more importantly, involves needless risk to operators, the public and other creatures and plants. It can also contribute to the build-up of resistance, making product selection more difficult and even threatening the use of such chemicals in the future.
Although weeds should never be tolerated in pavements, there are situations where some level of weed infestation can be overlooked. Sometimes a lack of funds for maintenance may mean that a certain amount of weed has to be tolerated in playing fields or shrubberies. It is important to spend time considering the type of weeds, where they are growing and cost implications of different methods of treatments given the level of infestation involved and location of the problem.
If it is deemed necessary to use herbicides, it is essential that the weeds are correctly identified. This can be difficult, especially in the early stages, but is vital if a suitable and effective product is to be chosen for their control.
As with all chemicals, a review should be made of previous incidents and experiences to determine what treatments have been used and to assess their level of success.
Control of Substances Hazardous to Health Regulations 1994 (COSHH) assessments should provide information relating to previous chemical applications. Find out from advisers or sales representatives whether such treatments are still appropriate and legal.
Always select the product that poses the least risk to humans, animals and the environment, but that has a good, well-documented track record for controlling the weeds concerned. It is also essential that the product is for use against the problem identified and is approved for use in the required situation. Check all the details including those relating to applications near water, timing of application and dosage. Make sure that appropriate equipment is available to apply the product and that it is in good working order. Only qualified, competent staff should apply herbicides, and appropriate personal protective equipment must be used.
Weeds on pavements and in non-crop areas can be treated with non-selective herbicides. This year Bayer Environmental Science is offering landscape managers and maintenance contractors a new product for use on service areas.
Called Pistol, the product is intended for the control of annual and perennial weeds on soft and gravel surfaces. It has two active ingredients. The first, glyphosate, controls weeds already at the surface. The second is diflufenican. This is a residual element and works by establishing a barrier through which weed seeds are unable to germinate.
Headland Amenity Products also has a new glyphosate formulation. Tangent is a non-selective, non-residual herbicide (450g/litre) and carries a no hazard classification. Absorbed by the foliage and translocated around the plant, Tangent is effective on annual and perennial grasses as well as broad-leaved weeds. It is approved for non-crop areas, paved areas, around trees and shrubs and for forestry situations.
Selective herbicides are used against weeds in turf and, by exploiting differences in physiology and biochemistry, control a range of broad-leaved weeds without damaging the grass. A new product in this sector is Nocweed. Available from Bayer Environmental Science, this herbicide contains MCPA, mecoprop P and dicamba. The actives have subtle differences in their modes of action to offer long-term control of a wide spectrum of weeds.

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