The herbicide ethofumesate has been used to control the weedgrass annual meadow-grass in high quality managed amenity turf. Historically formulations of this chemical had label recommendations for this use (the 200 g/l EC formulations which are no longer available). Other formulations remain and the active ingredient is included in Annex 1
However, none of the approved formulations have label recommendations for use in managed amenity turf. A number do have label recommendations for the control of annual meadow-grass in amenity grassland and grass seed crops. The STRI has successfully applied for a Specific Off-Label Approval to use one of these products to help control annual meadow-grass in managed amenity turf (www.pesticides.gov.uk/psd_databases.asp).
Annual meadow-grass is a ubiquitous weedgrass that can, and frequently does, invade more desirable sports and general amenity grass swards. Where this occurs, problems with surface stability are common and the use of plant protection products and water increases, particularly for high quality sports surfaces.
Stability problems arise because annual meadow-grass forms a shallow-rooted but very dense and "thatchy" sward. This is part of the mechanism that allows the grass to out-compete other more desirable grasses. However, for sports this loosely attached layer of organic matter can easily detach and cause players to slip when turning or stopping. From a management perspective, annual meadow-grass is highly susceptible to turfgrass diseases, particularly microdochium patch (caused by Microdochium nivale).
As a result of this, use of fungicides tends to increase. This grass is also intolerant of drought conditions and water use increases to maintain acceptable appearance. This is generally combined with a need for more frequent and larger fertiliser applications. Once established, this grass needs very intensive maintenance to produce acceptable playing quality and appearance.
Where stress factors (disease, drought, cold, low fertility) cause problems, the surface provided by this grass will deteriorate rapidly. However, once these issues are addressed, annual meadow-grass is best adapted to exploit the improved growing conditions and reinvade before more desirable grasses establish.
Research has demonstrated that use of ethofumesate, particularly in perennial ryegrass dominated sports surfaces, can give very good control of annual meadow-grass. It is important to note here that perennial ryegrass is fairly tolerant of ethofumesate but this is not the case for all amenity grass species. The chemical can be very damaging to fescues, other meadow grasses and some bentgrasses. In perennial ryegrass swards ethofumesate is best used to slow or prevent establishment of annual meadow-grass during the establishment phase.
Alternative control measures
No chemical alternative exists for controlling annual meadow-grass in managed amenity turf. Some control can be achieved through careful management and physical means.
From an ongoing management perspective, annual meadow-grass ingress can often be slowed and established cover reduced by lowering water and fertiliser inputs. However, for high quality sports surfaces, particularly those subjected to intensive wear, this also reduces the performance of the desirable grasses. Under reduced inputs, these grasses are less able to withstand wear and more prone to diseases. This will in itself lead to unacceptable playing surfaces.
Physical removal and replacement of the top layer of playing surfaces has been used to good effect to control annual meadow-grass. However, this is a costly exercise. It will also have to be repeated regularly to control annual meadow-grass. In some cases, it is highly desirable to do this for reasons other than controlling weedgrasses. However, there are risks to bear in mind when replacing a surface, such as ensuring that the work does not damage the underlying construction and drainage.
For many sports, time limitations as to when this can be done also come into play. Where physical means are used, the efficacy in terms of controlling annual meadow-grass can be greatly improved by combining the physical removal of the surface with ethofumesate use. In this situation the chemical will prevent the initial establishment of annual meadow-grass, allowing a uniform sward of the desirable grasses to establish on the new surface. This creates a sward that will be more difficult for annual meadow-grass to invade in the future. The fully established desirable grasses will be better competitors against seedling annual meadow-grass plants that invade the sward after the effect of the chemical has worn off.
Please note: for off-label approvals conditions of use will not be given on the product labels provided by pesticide manufacturers. It is essential that anyone who needs to use a pesticide product in accordance with a Specific Off-Label Approval (SOLA) read the text of the SOLA Notice as well as the product label before commencing any spraying operation. Also, under the SOLA provisions all applications made will be at the user's own risk.
Andy Newell, STRI Head of Turfgrass Biology