Weed Control - A firm line on hard surfaces

Taking care of sports surfaces and public areas means controlling weeds, and hard surfaces need special care to meet legislation. Monsanto Technical Manager Manda Sansom gives some practical advice on compliance and choosing the right equipment

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The wet spring followed by a few sunny weeks led to a significant greening up across the country, which unfortunately included weeds. Amongst the challenges for amenity managers and groundsmen in mid-summer is keeping hard surface areas tidy and weed-free.

"Whether it is to maintain presentation standards or ensure safe use of hard courts, MUGAs and play areas, effective weed control is as important on hard surfaces as it is on turf," comments Monsanto Technical Manager Manda Sansom.

"Tennis courts, for example, will be in high demand as summer continues. Weed control is important in keeping the flat playing surface for the high quality play that members or the public require, eliminating trip hazards and extending the life of the court surface itself."

Pavements, public walkways and paths in ornamental areas also require attention, but spraying on hard surfaces demands special care to meet with current legislation, Manda cautions.

"Restrictions to spraying on hard surfaces were introduced in 2012 to ensure pesticide run-off from non-porous hard surfaces to water courses is minimal."

"Adopting the new rules was designed to reduce run-off to drains and water bodies as required by the Water Framework Directive, but it also minimises the use of pesticides as required under the Sustainable Use Directive and saves money by reducing unnecessary herbicide use in overall spraying. Moreover, compliance is well within the reach of competent, qualified operators - the legislation brought into law is what we at Monsanto, the Amenity Forum and Amenity Assured Contractors consider best practice."

The rules apply only to spraying on non-porous hard surfaces, which include tarmac, bitumen, block paving/pavements, crazy paving, solid wall bases and concrete. All paving is included, irrespective of gaps being filled with permeable material such as sand.

Natural surfaces not intended to bear vegetation (such as bare soil), permeable surfaces overlying soil (such as sand or gravel) and railway ballast are not covered by the rules because pesticides can naturally percolate downwards rather than running-off.

Manda explains: "On hard surfaces, there is little or no absorption, posing a high risk of run-off to the nearest drain after the first 2-3mm of rain. It is particularly important to check herbicide product labels carefully to see if they apply to your intended target before use."

Good spraying practice

Hard surface weed control must be achieved with spot spraying, using weed wipers or sprayers, which can be automated with infra-red weed detection units or manually operated. Suitable applicators include ATV mounted units, knapsacks, CDA and specialist ULV applicators.

Ensure spraying takes place only when weeds are actively growing (normally March to October) and is confined only to visible weeds.

"By only treating the weed foliage itself rather than spraying the entire area, the potential run-off is reduced by 97% once it has dried on the leaf," explains Manda. "Run-off from treated leaf material is much reduced as most of the glyphosate enters the leaf within a few hours and only breaks down gradually as the plant dies and tissue rots."

Technique is also important, she points out: "Weed detection units are ideal on ATV equipment but, when spraying manually, it is important not to stop and treat each individual weed with the standard dilution as this will result in overdosing. The trigger/switch on the sprayer should be turned on and off whilst continuing to walk."

Weeds in a 30cm swath across the kerb edge, to include any weeds growing in the gutter on the road side, can be sprayed, but watch out for drains, Manda adds: "Whilst you should not overspray drains, you do not have to observe a 1m buffer around them."

Qualified operators

Operators wishing to apply herbicides to hard surfaces are required to attend a suitable course organised through the National Proficiency Test Council, leading to PA1/6 certification in hand operated spraying. A Certificate of Competence became compulsory when spraying any approved professional pesticide, even on privately owned land, on 25th November 2015 with the end of Grandfather Rights.

The right nozzle

Always check the product label for the manufacturer's recommended application rates and appropriate nozzles.

"When spraying glyphosate products using hydraulic nozzles choose those rated at 1.5-2.5 bar which produce an even distribution," advises Manda. "Be careful, because many nozzles are designed to work at 3 bar or more, which is outside the label specification for Roundup products. A medium or coarse spray is required to avoid damaging drift from fine droplets. Roundup ProActive and Roundup ProVantage formulations have low drift properties built-in, producing 33% less drift than standard glyphosates through flat fan nozzles."

Low pressure, even flat fan, anvil or deflector tips are the most suitable for a knapsack sprayer because the pattern is even, whereas standard nozzles designed for use on a boom must overlap each other for correct coverage. "There is no advantage in applying Roundup at any more than 250 l/ha and, indeed, results can actually improve in lower volumes. Since knapsack applications involve the operator carrying the necessary water on his back, there is little justification for choosing any other than the lower volumes. The lowest label water volume for Roundup ProVantage through a knapsack is 80l/ha," she says.

Application rate is a function of nozzle output, walking speed and swath width.

"Good calibration is essential for efficient use of herbicides and, although all operators have undergone training, it is still worth emphasising the need to recalibrate whenever the product, situation or nozzle type is changed."

Manda comments: "Many people underestimate the importance of nozzle height in accurate application. Most are designed to work at 50cm above the target, but the most comfortable working height for the operator is much more variable and is often around 35-40cm. The swath width is dependent on this height and halving it will also halve the swath width and double the application rate."

Hard surface spot treatment rules introduced in 2012 require that roads, pavements and other impermeable surfaces can only be sprayed in 30cm bands along edges or individual weeds.

Manda says: "Currently, there are no nozzles designed to spray 30cm bands, which means nozzle height needs to be reduced to achieve the narrower width. Double dosing is a real risk, unless the sprayer is recalibrated, because more dilute spray solutions will be necessary. The Green DT 0.75 deflector nozzle needs to be at only 15cm height to deliver a 30cm band width and, being so close to the ground, makes it hard to achieve accurate coverage."

A very simple way to keep the nozzle height correct whilst working is to attach piece of lightweight chain of the required length to the end of the hand lance and keep its end just at target height, she advises.

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