Brian Clark of Close House Hotel and Golf Club continues his Greenkeeper's Diary Column aimed at keeping Golf North East readers up-to-date with greenkeeping goings-on.
In the middle of the summer we greenkeepers are hoping that the greens are in their optimal condition, but unfortunately sometimes nature is there to prevent this. This month I would like to briefly describe some of the more common diseases that can occur, especially on greens, so the next time you are out playing and your greens may happen to have patches on them you might be able to identify what it is.
The weather this month has been very warm and moist and this is ideal conditions for the spread of diseases on golf course greens.
Anthracnose is most common on Poa annua grass in the UK and Ireland but has been noted on Agrostis and Fescue. This pathogen can cause two types of disease depending on the prevailing weather conditions. Foliar blight is one of these diseases but can often be mistaken for drought, the grass turns a tan-yellow colour in irregular patches. Basal rot is the other and begins as yellowing of older leaves on individual plants. The youngest leaf may become brick red in the later stages of development. The plant easily pulls from the turf and a black rot is visible at the base of the stem. Basal Rot also occurs during the late summer and is normally most damaging during August and September, although sometimes symptoms are also seen through the autumn and winter.
Brown patch occurs on close mown turf patches for especially greens where water soaked grass has developed. The patches become tan to dark brown. In humid conditions a brown/grey ring may develop around the edge of the patch. On higher cut grass a light brown patch forms. Individual leaves may have lesions that are tan in the centre and bordered with a brown edge. This is not as common as other diseases but golf greens can be susceptible to it.
Dollar spot lesions on leaves are a pale, bleached colour. They are bound at either end by a darker reddish-brown band separating the affected tissue from the healthy green tissue. Small (dollar size) spots of bleached turf occur on close mown grass. The spots may join to form large areas of affected turf. White mycelium, which looks like hairs may be present on affected areas on dewy mornings, which disappear as the leaves dry.
The term 'fairy ring' is used to describe a number of turf grass diseases where soil-borne fungi cause certain symptoms to develop on the surface of the sward. Fairy rings are caused by the activity of many fungi classified as basidiomycetes.
Fusarium Patch can be a devastating disease on fine turf surfaces as the patches may be many inches in diameter and adversely affect the playing surface as well as its aesthetic value. Symptoms begin as a darkened water-soaked appearance to the grass. The patches enlarge and may develop salmon-pink to orange-brown rings of conidia around the outside of the patch. This is the most common disease found on greens through out the uk, and a warm wet summer like we are having is ideal for fusarium to spread.
Leaf spot is a severe infection which may thin the sward, cause dieback and leave patches with weak turf, affecting the aesthetic value and the playability of the turf. Symptoms depend on the grass species and the pathogen involved. Generally a yellowing or paling of the leaf blades may occur, accompanied with spots or lesions developing.
Red thread the symptoms depend on the grass species and severity of attack. Symptoms often start as small mostly circular patches of dead leaves interspersed with live plants. The patches may also have a pink tinge, Closer inspection will reveal pale pink to red needle or horn-like outgrowths. Although this doesn't affect the playing quality of the green it does affect the aesthetic appearance of the green.
Take-all patch symptoms begin as a slight reddening or bronzing of bentgrass usually in a ring during summer months. As the bentgrass dies resistant grass species or broad-leaved weeds invade the centre of the patch. Patches can measure from a few centimetres in diameter to over a metre. Symptoms may fade in late autumn and winter. This is becoming increasingly common in newly constructed bentgrass greens, and is more widespread than it was a few years ago. There is no current cure for this although it will grow out over a period of a few years.
I hope this brief description of these diseases is interesting, we as greenkeepers try to minimise the risk of disease to greens with our annual maintenance program. Removing the thatch layer from a green is a necessity, as the thatch layer will allow the turf to hold moisture and this provide optimum growing conditions for many of the diseases above. Thatch layers are reduced by techniques like hollow coring, scarifying and tining. There are several chemcial's on the market combat some of the diseases above, although these are expensive but are a necessity in a greenkeepers budget.