RESEARCH STA Victoria recently funded a trial to assess the efficacy of various herbicides for the removal of perennial ryegrass from an established couch grass sward. Pictured are the plots 11 days after the September treatment
In
transition Throughout 2020, the Sports Turf Association of Victoria engaged AGCSATech to conduct a trial to assess various chemical options for the removal of perennial ryegrass oversown into a couchgrass surface. Senior agronomist
hroughout the southern and temperate regions of Australia, perennial ryegrass (Lolium perenne) continues to be one of the most popular turfgrass species utilised for winter sports turf surfaces. Within these regions, the summer periods are often hot and dry, more suited to growing warm-season grasses such as couchgrass (Cynodon dactylon) and kikuyu (Pennisetum clandestinum). However, the cooler months see warm-season grasses go into varying degrees of dormancy due to reduced ambient and soil temperatures. During winter, this loss of colour, reduced growth rate and lack of recovery potential can result in the deterioration of warm-season grasses. This is most obvious in high traffic areas such as goal mouths, ground access points and centre corridors. On many premier and tier one municipal sporting facilities, ryegrass is utilised to overseed warm-season grasses which 44
provides an actively growing surface which can protect the couchgrass throughout the cooler months. This improves both turf recovery and visual aesthetics. Overseeded playing surfaces also present well for television and spectators. As temperatures increase during spring, the ryegrass is then chemically removed or allowed to transition out naturally as warm weather and soil temperatures increase the stress on the ryegrass. The natural decline in the ryegrass and the improved couchgrass growth results in a transition back to couch. GRAPHIC: COURTESY OF SYNGENTA
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Bruce Macphee provides a summary of the key findings.
Figure 1. Temperature, rainfall and soil temperature data for the duration of the trial. Treatment applications (September and October) highlighted in red
AUSTRALIAN TURFGRASS MANAGEMENT 23.5
The Sports Turf Association (STA) of Victoria funded a trial to assess the efficacy of various herbicides for the removal of perennial ryegrass from an established couchgrass sward. The objective was to provide information on the most effective options for ryegrass removal and the ideal timing for the transition back to a warm-season surface for summer sports. There are several herbicides registered for the selective removal of perennial ryegrass (C3) from couchgrass (C4) surfaces. The trial was established at Evergreen Turf, Pakenham (southeast of Melbourne) in January 2020 with Santa Ana hybrid couchgrass installed using solid turf which was allowed to fully establish prior to being oversown with the ryegrass.
TREATMENTS The treatments consisted of seven herbicides and an untreated control with three replicates of each treatment. The treatments were divided into an early application (September) and a