Spring and early summer applications of the new selective herbicide Rescue in areas of golf course rough could prove the most effective for the control of dense invasive Ryegrass, according to Syngenta Technical Manager, Dr Simon Watson. “Rescue application whilst the rough is still sufficiently open for effective spray targeting and whilst plants are actively growing should have the greatest effect,” he believes.
New research and on-course user trials are assessing spring Rescue treatments in rough and semi-rough this season to achieve the best possible control. Experience last summer and autumn highlights application can prove difficult in long dense rough. “Control proved slower than some greenkeepers had expected, especially on heathland courses where mature grass growth had ceased in dry weather,” he reports. “Rescue applications are best made when target weed grasses are actively growing.”
Dr Watson highlights that as an environmental management tool Rescue is proving highly successful in opening up rough and semi-rough to allow native grasses, wildflowers and biodiversity to flourish. “Where greenkeepers are looking to open up rough areas to make ball location easier and speed up play, a spring application this year could prove an instant winner with players,” he adds.
Rough is an extremely important area of the golf course for wildlife, according to STRI Ecological Consultant, Dr Kelly Harmar. “However, not all rough is of equal biodiversity value,” she reports. “Thick rough on nutrient rich soils tends to be dominated by coarse grass species and supports a lower proportion of wildflowers; this lack of botanical variation also limits the diversity of wildlife that the grassland can support.”
Dr Harmar warns chicks of ground-nesting birds can die of exposure if nests in thick rough do not dry out after rainfall.
She believes that Rescue can be usefully employed to create a mixed sward containing finer grass species, including Fescues and a greater diversity of wildflowers. Removing the undesirable grass species, such as perennial Ryegrass, serves to thin the sward and open up gaps for colonisation by wildflowers and finer grasses. “Wildflower seed requires light to germinate and will not thrive if sown into thick grassland rough. Management of the rough to encourage finer grasses can let in the light and increase biodiversity,” she says.
“The use of the selective graminicide Rescue as a management tool, particularly when used in conjunction with cultural practices, clearly has the potential to improve biodiversity in rough grassland and to raise the whole environmental potential of golf courses.” It is vital however, that the user has full grasp of the grass species within the target sward before treatment.
STRI trials undertaken in areas of rough at Loch Lomond Club in Scotland achieved an average of more than 80% Ryegrass control from a single application of Rescue in the autumn. Furthermore the Yorkshire Fog, which had been particularly dominant in some of the areas, was significantly smaller and more compact. “The treated plots generally had a greater proportion of finer grasses when assessed the following spring,” added Dr Harmar.
The results were replicated in a similar trial at the Mid-Herts Golf Club, recorded an average of more than 90% Ryegrass control, and with no other adverse change in the botanical composition of the sward.
Wait for active growth
Rescue needs the target plant to be vigorously growing for the herbicide active to be taken down to the roots for a really effective kill, advises Dr Simon Watson. “For treatments on fine turf areas it is also beneficial to have good growing conditions to enable rapid recovery of the fine grass species and help get the playing surface back to the best possible condition as quickly as possible.
“If the turf is under stress from drought or nutrient deficiency at the time of application the recovery is going to be slower and other weed grasses may have an opportunity to get in,” he warns. Good growing conditions will also aide any over seeding necessary to quickly establish and fill the gaps left by controlled Ryegrass.
Dr Watson advocates Rescue application when growth rates are increasing, rather than slowing down. Recording the amount of clippings being boxed off greens during mowing is a good indication of when growth is actively taking-off, he adds.
Syngenta www.greencast.co.uk or www.greencast.ie