Technical Case studies
Amey undertakes large scale planting schemes as part of road construction and sports facility contracts, and Clive Parker, Senior Consultant (Horticulture & Arboriculture) for the Consulting and Strategic Infrastructure division, says that protecting young trees is vital.
Christmas trees before ...
harmless components. Mature trees, which have brown bark, will not absorb glyphosate, but sprayer operators should avoid any wounded areas on trunks as entry direct to the cambium can result in damage. Immature green bark may also allow some glyphosate uptake, making whips especially susceptible to damage. Any green area can absorb the product and
potentially cause damage, so care should be taken around low hanging branches that leaves are not sprayed. Avoid buds over winter as droplets can lodge in the axils and be absorbed into the plant. Using a guard or hood over the nozzle of the sprayer should minimise accidental damage. An alternative method is to use a hand-held
weedwiper, taking care not to let the rope wick touch any part of the tree. As droplet size is important in minimising
drift into the foliage, care should be taken that the correct nozzles are chosen to produce nothing finer than a medium spray (BCPC definition) or CDA drops of 200-300 microns, and that the correct pressure for the application equipment is adhered to. Low pressure or low drift nozzles are recommended. Tree shelters fitted around young trees help
provide protection against vermin and adverse weather conditions. Where trees are fitted with solid shelters, there is no need to use a spray guard or direct the spray away from the tree, but spiral shelters or those with holes do not provide sufficient protection and should be treated as if there was no shelter.
Timing
Early spring application: Perennial weeds grow from root reserves, with sugars rising in spring. Glyphosate uptake is therefore not as efficient as late summer or autumn treatments when the sugars are flowing down to the roots for winter storage. When planning weed control programmes,
Pre planting l/ha
Post planting- annual/perennial Grasses & Broadleaved weeds l/ha
Roundup ProBio
Roundup ProVantage
5 3.75
4 3
and after glyphosate treatment
this factor needs to be taken into consideration. Where early spring treatments are carried out, then a second application for complete control of perennial weeds may be necessary in the summer. Winter application: Weather conditions have minimal effect on glyphosate applications. Cold weather, leading to leaves moist with dew in mornings and light frosts, plus slower growth, do not present a problem. As Roundup ProBio and Roundup ProVantage
are rainfast in just one hour on annual grasses and couch, and in 4-6 hours on other weeds, a catchy day when only the morning is likely to be dry, can be considered a spraying day. It is possible to spray on frost in the morning
as long as leaves will dry later - frost is only a problem if it continues for days and causes the weeds to stop growing and become flaccid. Spraying can also be carried out on the dew/mist in the morning as long as the day will stay dry; although operators should avoid spraying in the evening as increasing dew leads to run-off. Use a medium-coarse spray to avoid driftable fines. Plants can often take months to develop full
symptoms in cold conditions, but will be controlled if winter spraying guidelines are followed.
Weed growth stages
The best time to kill perennial broad-leaved weeds is around flowering. Perennial grasses, like couch, should have 4-5 actively growing leaves, each with 10-15cm of new growth. Annual grasses and broad-leaved weeds need to have at least 5cm of leaf growth or two expanded true leaves before they will take up the herbicide. Poorer uptake also occurs during the rapid stem extension phase, as the flowering stem is extending, and should also be avoided, if possible.
www.monsanto-ag.co.uk
Post planting- Scrub: hazel, oak, Sycamore, willow, tough weeds l/ha
5 3.75
Post planting- heather Peat soils, (mineral soils) l/ha
4 (6) 3 (4.5)
Post planting- Rhododendron (with 2% Mixture B) l/ha
7.5 (6) 10 (8)
“How we do it depends on the nature of the scheme - some ornamental plantings will be mulched with bark or woodchip, but glyphosate is an essential part of the armoury.”
Mr Parker points out that adhering to recommended rates is important to prevent damage to trees, and adds that using residuals is necessary in some planting situations, again in a carefully planned tank mix with glyphosate.
“We like to take a holistic approach, but recognise that alternative controls such as mowing close to trees can be harmful. Amey uses a team of environmentalists and one of the priorities is to ensure that products work and are safe. We always have to consider other methods of weed control, however, as restrictions on chemical products become tighter.”
Where Amey hands over the ongoing maintenance of the site to the groundsman or another contractor, training is provided to ensure that appropriate weed control measures can be used. “Where the site is a school, there is also the opportunity to educate pupils about tree care,” says Mr Parker.
He comments that the first two to three years after planting are crucial, after which the young trees become virtually self- managing.
Solar farm planting
Tree plantations are increasingly in demand for their ability to screen sensitive sites, and contractor Amenity Land Solutions has recently completed a project at a solar farm in Shropshire.
Contracts manager Dave Harvey explains: “Using the tree shelters to protect the trees themselves, we spray with glyphosate post- planting for up to twelve months. There are very few other products that can be used on young trees and, whilst Kerb will tackle grass, it won’t control other weeds.”
With trees planted in triple rows 300mm apart, a standard knapsack with a 60 or 80deg nozzle can safely work around the trees.
“There’s insufficient space to use guards, which also run the risk of dripping when the sprayer is switched off.”
The contract, for a Belgian specifier, lasts for twelve months before the local authority takes it on, and includes planting white clover between the panels to minimise maintenance requirements.
Open guards Close planting PC APRIL/MAY 2015 I 123
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