In the first of two articles, STRI consultant, Michael Boyes, faces an old foe on the golf course as current conditions give silvery-thread moss a huge advantage
The legacy of the extended hot and dry weather of Summer 2018 can still be seen across many of our UK golf courses with lingering, although thankfully localised, areas of sparse grass cover evident on a number of the playing surfaces, despite extensive renovative programmes.
Unfortunately, our putting surfaces have not entirely escaped the impact of the prolonged oppressive conditions either and some thinning of the sward has occurred, particularly on south-facing aspects and raised areas of the profile.
Additional irrigation delivery, absolutely essential to keep the severely stressed turf alive under drought conditions, has contributed to the prosperity of our old foe moss, and in particular, Bryum argenteum (silvery-thread moss) which successfully invades the inevitable voids which result in the green’s sward.
The botanical phylum Briophata (which includes mosses and liverworts) are amongst the simplest of land-dwelling plants whose morphology, growth and survival characteristics differ significantly from the higher plants, such as the turfgrass species they coexist with in putting surfaces.
Mosses do not have root systems, instead anchoring to the surface with rhyzoids, and do not possess a vascular system (i.e. phloem and xylem) for water or nutrient delivery, which if present could have provided a pathway to facilitate control or eradication.
These opportunistic plants are able to survive drought conditions, dehydrate and remain dormant for long periods before rehydration allows photosynthesis to recommence. Bryum argenteum (silvery-thread moss) in particular, is known for a rapid uptake of water which categorises the plant as ectohydric.
Silvery-thread moss reproduces sexually via spores or asexually through displaced fragments, both of which can be spread via foot traffic, mowers or other turf maintenance equipment.
Factors which encourage the development of silvery-thread moss on greens
- Low heights of cut – Turf managers are under constant pressure to produce faster greens and often employ aggressive mowing practices which imposes undue stress on the grass plant causing a thinning of the sward.
- Reduced nitrogenous fertility – In an attempt to keep surfaces “lean and mean”, again often in pursuit of increased green speed, the density of the sward suffers facilitating the ingress and spread of moss.
- Increased irrigation – Liberal applications of irrigation contribute to keeping the top of the soil profile wet which is conducive to the success of moss development.
- Excess thatch accumulation – High organic matter levels can impede water infiltration, rendering the surfaces wet and conducive to the encroachment of silvery-thread moss.
- Removal of chemical controls – Historically chemical intervention for silvery-thread moss proved a particularly successful eradicant with the employment of some rather worrying mercury-based fungicide products, quite rightly now withdrawn. Other products such as chlorothalonil fungicide, ferrous and ferric sulphate, sodium carbonates such as baking soda and even dish washing detergent have been trialled with results found to be highly variable and often ineffective compared with the use of the most recently withdrawn herbicide carfentrazone.
Note: No chemicals, or indeed any other products, should be employed or even trialled unless legally authorised for the specific control of moss in fine turf.
In lieu of chemical controls we need to look at current management practices to structure renovation and routine maintenance programmes on the greens to develop a playing surface which is less conducive to moss encroachment and colonisation:
For guidance on how to deal with silvery-moss, read part 2 here.
Contact STRI for specialist advice on seasonal conditions at your sport facility on +44 (0) 1274 565131 or firstname.lastname@example.org
Borst, S.M., Scott McElroy, J. & Breeden, G.K. (2010) Silvery-thread Moss Control in Creeping Bentgrass Putting Greens with Mancozeb Plus Copper Hydroxide and Carfentrazone Applied in Conjunction with Cultural Practices. Hort Technology Volume 20, Issue 3, p.574-578
Gerlernter, W. & Stowell, L.J. (1998) Chemical and Cultural Controls for Moss, Bryum argenteum on Putting Greens. Unpublished
Happ, K. A. (1998) Moss Eradication in Putting Green Turf. USGA Greens Section Record September/October 1998 p. 1-5