Beyond IPM (Part 3 of 3)

Weed management
Weeds that are present in a sports turf or fine ornamental lawn will generally only provide a very low health and safety risk due to reduced turf strength, potentially producing either a slippery surface or one which provides less traction (or grip) for a player. This could increase the potential for minor injuries from twists and falls, but the likelihood of injury would be very small. Moss and algae can pose a higher risk in some areas, especially some golf course sloping turf surfaces, due to the significantly slippery surface they can create under moist or wet conditions. [1]

The main issues to do with weed management are that of:

  • visual acceptability, which is a very subjective value judgement,
  • the competition effect weeds can have with desirable grass species,
  • the effect weeds might have on the playing performance of a turfgrass surface,
  • a reduced carrying capacity of a turf surface where a high quantity of weeds are present.

The negative effect weeds can have on playing performance is probably the main practical  reason why selective herbicides may need to be applied to a turfgrass surface.

Weeds create an environment in which ball reaction is not consistent, whilst some species also die back during the winter creating a thinner sward. [2] This can reduce the carrying capacity of a pitch and the quality of play due to a thinner more open sward and is a significant reason why weed management is important in turf surface management.

Correct turf management practices which reduce the potential for weed colonisation and spread are essential if selective herbicide use is to be minimised or even eliminated.

Examples of good practices include:

  • managing surfaces in accordance with carrying capacity measures so as not to overuse a surface which would then increase the amount of bare areas in which weeds can become established;
  • applying fertilisers which create a mildly acidic soil reaction, making surface conditions whihc are less desirable for many weeds;
  • apply optimum quantities of appropriate nutrients, and certainly not excessive amounts and also not including nutrients just because ‘it sounds good to have a range of nutrients available’; the aim being from turf nutrition is to maintain a relatively hard wearing and dense sward;
  • undertake correct mowing practices – not too long / too short; correct frequency; well set machines; boxing off / letting clippings fly as appropriate; so as not to overly stress the grass plant.
  • irrigate to create a deep rooted sward and not a shallow rooted one which will be less competitive to weed invasion.
  • aerate under correct soil moisture conditions to encourage a deep rooted sward which will be better placed to withstand any potential weed invasion;
  • maintain a dense sward and repair areas wherever possible to reduce exposed areas which would otherwise be an invitation for weeds to colonise;
  • overseed, using appropriate grass species, and at times when quick germination and rapid development is anticipated, so as to maintain a dense sward;
  • regular scarification and verticutting to stress or control trailing weeds such as clovers;
  • and don’t forget hand weeding, even on a large surface such as a football pitch, a little and often on a planned regular basis will soon keep weeds down – clearly this is going to be difficult or not possible where tight financial constraints are in place, but even a small effort can help.

Wider considerations
A key factor that must therefore be considered is the active management of the carrying capacity of the grass surface to ensure that the ecological capacity of the surface is not exceeded as this will reduce healthy growing conditions, increasing the likelihood that pesticides may be needed.

Carrying capacity can, however, have three different meanings and each of these should be considered when taking a systems approach to managing the wide range of turf surfaces: [3]

  1. Physical carrying capacity, which is the maximum amount of use or activity that can occur at any one time; this is more related to amenity grass surfaces;
  2. Perceptual carrying capacity, which is the maximum amount of use that can occur before overcrowding reduces the level of enjoyment or a minimum amount of use required to instill a sense of safety within users; this is more related to amenity grass surfaces;
  3. Ecological carrying capacity, which is the maximum amount of use that can occur without reducing the ecological attributes of a site; this is related to both amenity grass and sports turf surfaces. For sports turf surfaces it is often just referred to as ‘carrying capacity’ or ‘sustainable use’.

If pesticides are used, the first question should be ‘Why has the need arisen for their use?’
Other questions would include:

  • What impact will they have on the carrying capacity of a surface?
  • Will they improve the possibility of optimal carrying capacity being achieved?
  • Will the main positive impact be from an improvement in playing quality and/or visual appearance?
  • Are the thresholds which have been set for the use of a selective herbicide appropriate? The acceptable amount of weeds may be lower than actually needed: is there really that much practical difference between a 5% content and a 3% one? Or a 14% one and a 20% one? Weed content will also increase and decrease depending upon the time of year and period of growth for the weed.

Going ‘Beyond IPM’ requires challenging currently thinking and questioning the reason why a pesticide is needed for a specific situation. Objective justification is essential, and if the need is justified then so be it.

Have stakeholders been identified and consulted? How are they to be engaged with and what influence can they have on the decision-making process that relates to the management of the turfgrass surface?

What are the local issues that have to be taken into consideration before the use of pesticides can take place?

What impact might the use of pesticides have on resident and transient wildlife within the site boundary? Recording and monitoring wildlife and their activity levels within the site boundary is one part of IPM, but it plays a more prominent role in a systems approach to managing land areas. Should we not be thinking more widely than just the confines of the immediate turfgrass surface?

Weeds may support a diversity of invertebrates and this may be an area that has not been explored fully before considering pesticide use. For example, Stinging nettle (Urtica dioica) is traditionally a weed of some general amenity grass areas. However, this might be a position that is revised in some situations due to the abundance of invertebrates that feed on the plant. One detailed study found that 27 insect species relied on this plant as, more or less, their sole source of food, whilst 17 also used it as a food source along with other plant species.[4]

What the is the wider impact that might arise from the use of pesticides on the environment which is beyond the local area that surrounds the managed site?

IPM will consider the specific crop within a site, but not the wider implications. Are there any regional, national, international or global concerns that you may be able to assist or mitigate against by implementing a ‘Beyond IPM’ approach?

Series Conclusion
A sustainable approach to managing turfgrass surfaces will need to consider how ‘Beyond IPM’ can be integrated into applied management activities.

Integrated Pest Management has been a focus on addressing site specific situations, but we should be looking at a sustainable ‘Beyond IPM’ approach which requires a more insightful consideration for the longer-term impact of actions on the local ecosystem (plants and wildlife), as well as the environment which sits outside of the site boundary.

Users of pesticides should develop management plans that have already considered how unhealthy plant situations can be alleviated by cultural and physical means before resorting to chemical applications.

The impacts and consequences of pesticide use, not just within the site boundary but in the wider environmental context, need to be reflected on and evaluated prior to including pesticides as part of a responsible and sustainable management plan.

Sustainability is a contested and complex concept, however, by actively engaging with it, many concerns and values can be more fully addressed so that an acceptable outcome is found for all involved with the management of turfgrass surfaces.

References

[1] Baldwin, N.A. (1988) ‘Technical Note. Identification and control of algal slime on turf’, Journal of the Sports Turf Research Institute, Vol.64, pp177-180

[2] Adams, W.A. & Gibbs, R.J. (1994) ‘Natural Turf for Sport and Amenity: Science and Practice’, CAB International, p165

[3] Green, B. (1981) ‘Countryside Conservation. The protection and management of amenity ecosystems’ (2nd Edition), Unwin Hyman, p186

[4] Pollard, E., Hooper, M.D. & Moore, N.W. (1974) ‘Hedges’, The New Naturalist, Collins, pp109-110

Chris Gray, 1st September 2018