ON COURSE
Reproduced by courtesy of the Golf Club Secretary November 2001

Anthracnose - Friend or Foe ? __________________________________________________________________ A course management column by A J Beggs BSc Hons, STRI Manager/R & A Agronomist

As our days begin to shorten and the leaves adopt their golden hues, our thoughts turn from producing the perfect putting surfaces to protecting them from winter damage.

Fungal attack is still our biggest concern and the fungus that causes Anthracnose (Colletotrichum graminicola) is becoming more common on golf greens across the country. At some Clubs it is now more common than Fusarium and is the major weakening effect on greens through the autumn and winter. It is the most regularly mis-diagnosed disease and this can be very damaging for those of you with an abundance of annual meadow grass (Poa annua) - the host species of the fungus.

Anthracnose can attack the turf at any time of the year but stressed annual meadow grass plants are particularly vulnerable during the autumn and winter months. Diseased plants show general yellowing and thinning as the fungus attacks and rots the crown. Individual plants can be easily removed from the turf and blackened bases can often be seen by the naked eye. The amount of damage depends on many factors (see below) but it is important to realise that the disease can be devastating if the condition and the factors that cause it are ignored.

As with all disease management, prevention is better than cure. However, unlike some other fungal diseases that respond well to chemical attack, Anthracnose often recurs after treatment. Its spread can be halted by fungicides but if the underlying causes of the disease are not corrected it will return more aggressively than before.

The following factors are known to contribute and encourage the disease :

1. Poor surface drainage - there are many possible causes of this including poor green construction, contour collection, trapped layers of organic matter or thatch in the upper profile, compaction, etc. Poor drainage induced by compaction is becoming more common as a result of increased use of sometimes small greens where pin space is restricted.

2. Annual meadow grass - the presence of annual meadow grass in itself is not a cause of the disease. However, the more of this grass a green has, the more likely Anthracnose will be seen.

3. Low fertility - Anthracnose is a disease that attacks turf in a state of low fertility. In this respect it is the opposite of Fusarium, which tends to attack the over-fed turf.

4. Over-irrigation - gross over-irrigation or an old system that fails to deliver in an accurate manner can encourage Anthracnose.

5. Low mowing - prolonged low mowing, particularly in late summer and autumn, can pre-dispose the turf to disease especially if annual meadow grass is abundant. It is a stress factor that can be avoided without compromising pace.

6. Dry Patch - the link between dry patch and Anthracnose is an interesting one. it is common to find autumn disease on turf previously affected by Dry Patch. Clearly Dry patch is not a cause but it may be a pre-cursor having weakened/stressed the turf through drought.

If your Club is familiar with the above issues, it may well be that you have or are likely to have a problem with Anthracnose. The following cultural initiatives may help :

• It is important that the Club makes the most of its inherent construction type, maximises the surface flow of water off putting greens and prevents surface flow onto them. It is also vital that it mitigates the damaging effects of play. This means effective and timely aeration, regular top dressing and the installation of extra drainage in some circumstances. Furthermore, do not be frightened of resting surfaces where necessary.
• Turf dominated by annual meadow grass will always be vulnerable to attack by the Anthracnose fungus. Those that manage for it are asking for trouble. Eradication may be impossible but good traditional greenkeeping should enable its presence to be minimised and thereby its vulnerability to Anthracnose.
• Aim to apply nitrogen in a balanced fashion through the growing season. Do not go for too long between applications and with warmer autumns and increased play there may be a case for Applying that final feed a little later than was the case twenty years ago. This is particularly true if managing perched water table greens with a sand dominated root zone.
• The importance of effectively removing excess moisture in the form of rainfall has already been emphasised. It is also vital that the Club does not over apply its own. If the Club has an automatic watering system ensure that it is operating effectively and supplement it as necessary with hand irrigation to achieve good coverage. The gross over-application of irrigation water to some areas of turf and not enough to others is a sure way of promoting the disease.
• Avoid low mowing for long periods. A good greenkeeper knows the heights of cut his swards will tolerate. Use local knowledge together with modern techniques, such as improved verticutting and brushing, to maximise pace without over stressing the turf.
• Use high quality wetting agents in a pro-active manner to prevent Dry Patch during the summer months. If the greens are particularly prone to this condition, there may be merit in working a root zone injection treatment into the summer maintenance programme.

Anthracnose is far more than a troublesome disease - it is a biological indicator of trouble ahead. We live in an age where golf is as popular as it has ever been and some of our older golf courses on heavier soils are struggling to cope. Increasing susceptibility to Anthracnose can be a sign that redevelopment or reconstriuction could be necessary. However, it may also be a sign that the current maintenance initiatives are inappropriate or insufficiently intensive. Whichever it is, do not disregard a disease that can be both a friend and a foe. Use the signs it is giving to the Club's advantage.

Reproduced by courtesy of the Golf Club Secretary November 2001