"Climate change – the impact"
“Pest”-ered by climate change? By Steve Isaac, Area Manager for Scotland & Ireland, STRI This is the latest in a series of articles on the impact of predicted climate change on golf courses in Scotland. Let‟s just remind ourselves of the main climatic effects we are likely to see over the decades through to 2080, as published in the Government bodies for climatic research (The Hadley Centre and The Tyndall Centre) document entitled “Climate Change Scenarios for the United Kingdom”. Average temperature increases by approximately 1.5ºC-3.5ºC. Each decade the warming may vary across the UK by 0.1ºC-0.3ºC for the low CO2 emissions scenario compared to 0.3ºC-0.5ºC for the high emissions. Summer temperatures will increase more in the southeast compared to the northwest. There will also be more „extreme‟ high temperature days, e.g. the probability of the Scottish Highlands receiving one day with a temperature of 23ºC will increase from 1% to 15% by 2080. This increase in temperature will increase the „thermal growing season‟ for plants thus continuing the trend of recent years. Each degree of annual warming causes a lengthening of the thermal growing season of about three weeks in southern areas and of about one and a half weeks in northern areas. Clearly this will have implications for grass growth and subsequent maintenance operations. Winter rainfall will increase. For the low emissions scenario it is thought that the increase will be between 10-20% whereas for the high emissions scenario an increase of 15-35% can be expected. Summer rainfall is predicted to decrease. For the low emissions scenario the UK is predicted to be 35% drier in the summer whereas for the high emissions a decrease of 50% can be expected. Higher temperatures and lower summer rainfall is predicted to reduce average soil moisture by 40% for the high emissions and 20% for the low emissions. Finally, high winds may increase during the winter months but this predication is rather uncertain. As the life cycle and well being of most pests and diseases is related to climate, what impact will these predicted changes have on the incidence of damage through pest and disease attack on our golf courses? Increased disease attack? There is already evidence that we are seeing more pests and diseases on our golf courses. The wet and sometimes humid weather we have experienced through the summer and the milder winters is an ideal breeding ground for familiar diseases such as fusarium patch, but it also encourages other beasties to become more active. There are a number of diseases that appear more often in wet conditions: Fusarium patch disease (Microdochium nivale). Anthracnose (Colletotrichum graminicola). INSERT PHOTO 1 Take-all patch (Gaeumannomyces graminis). Yellow tuft (Sclerophthora macrospora). Most Greenkeepers will be familiar with the first three on this list but yellow tuft is becoming a fairly regular visitor to golf greens, generally restricted to low areas that retain more surface water. The visual symptoms are 2 pence piece sized yellow spots of bent or annual meadow-grass, the result of increased tillering and often a reduced root system. The Sclerophthora fungus causes this physiological growth response. When the ground dries the disease disappears with no real damage. Fusarium and take-all seem to be occurring more often on green surrounds, where there is more thatch and longer grass that holds surface water longer than the close cut greens. We have also seen an increase in take-all attacks on Poa annua, this from a disease that all the UK textbooks consider to be restricted to bent grasses. There has been more red thread (Laetisaria fuciformis) throughout the golf course, being seen on Poa annua as well as ryegrass and fescues. In some cases we have seen the apparent anachronism of active red thread and fusarium scars on the same piece of turf at the same time! As one is generally considered to be a symptom of nitrogen-deficiency and the other of possible excessive fertility then the climatic conditions must be over-riding other environmental influences. More brown patch (Rhizoctonia solani) is being reported, brought on by the warm, wetter summer weather. Fusarium and red thread are often seen year round, whereas previously the former was considered an autumn/winter disease and the latter only a summer one. Take-all activity is evident through much of the spring to autumn period now, not just confined to the months of July and August as often recorded in texts. Type 2 and superficial fairy rings pop up late autumn and late winter/early spring, again outside their “usual” seasons of activity. There have been more reports of rust diseases on turfgrass and dollar spot has been identified on grasses other than fescues. Not only are we seeing more outbreaks of disease but certain diseases are showing different symptoms to that commonly recorded in the past. For example, the classic symptoms of fusarium patch disease have been augmented by variations to type, e.g. summer outbreaks of 50 pence piece sized orange spots that cover putting surfaces, and expansion of seemingly controlled scars appears the most common means of disease development through the autumn and winter months rather than new outbreaks of disease to previously clean turf. INSERT PHOTOS 2 AND 3 A greater variety of disease? In addition to seeing more of the well-known diseases over recent wetter years, there have also been confirmed reports of unusual fungal disease incidence. These too are a consequence of climate change and tend to be more difficult to control as initial diagnosis of the problem is not always accurate and delayed treatment can make control more difficult. So, let‟s run through some examples of “new” diseases that have appeared in the UK over the last 5-6 years. In recent times we have occasionally seen small patches of white leaved grass to golf greens. These have, generally, appeared after periods of humid weather, seemingly doing no long-term damage but causing the plants to bolt (abnormally elongate). This phenomenon has been seen to perennial ryegrass cultivars on sportsfields as well as to annual meadow-grass on golf greens. The MAF Plant Health Laboratory in New Zealand has isolated Rhizoctonia solani and Fusarium fungi from affected grass tillers. Many Fusarium fungi are known to produce excessive gibberellins, which are growth hormones and this could be the cause of the abnormal growth. The best thing about all of this is the name the New Zealanders have given to the condition, “Mad Tiller Disease”, though in the UK it has been referred to as “Ghost Grass”. INSERT PHOTO 4 In the summer of 1997, the turf to the surrounds of some golf greens in southeast England were affected, the grasses reddened and the infected area increased notably day by day. The infection attacked the leaf and crown, effectively killing the whole plant. The causal fungus was isolated at STRI and identified as Curvularia sp., an unknown disease at that time. Fortunately, for those of us north of Hadrian‟s Wall, this fungus is unlikely to cause damage in temperatures less than 30 o C. In the summer of 1998, the turf on greens at a golf course in the Midlands of England was lost in irregular patches. Bipolaris sp. was identified as the fungus causing the damage. This is similar to Drechslera sp., which is commonly found causing leaf spots and can develop into “melting out”. In August 1999, a sample was sent to the Pathology laboratory at STRI of diseased Poa annua. The lab identified Fusarium culmorum as the causal agent, the fungus that develops symptoms referred to as “fusarium blight”, which is a foliar blight, crown and root rot of turfgrasses worldwide. Curvularia sp. and Bipolaris sp. are normally found living on dead and decaying plant material but under hot, humid conditions they are capable of quite severe disease damage. Relieving turf stress is the key to controlling both as there is no approval for any chemical control. Pests are on the up as well There has been quite a lot written about nematodes in the turf management press over the past 2-3 years. Nematodes are microscopic round worms, generally between 0.5 mm and 2.0 mm in length. Ditylenchus radicicola and D. dipsaci, the stem nematode, was identified in early 1998 affecting turfgrass vigour, it‟s activity favoured by warm soil temperatures but restricted by dry or waterlogged soil conditions. Stubby root nematode attacks the root on the outside, the root reacts by swelling to protect itself and this results in a poorer root system. The root knot nematode, Meloidogyne sp., is reported to be causing extensive damage to creeping bentgrass swards in the UK and Ireland. Nematode effects on turf can result in poor colour, the grass looks in a stressed condition, and damage usually occurs in irregular patches. There is no chemical control but managing stress to retain good turf vigour can limit nematode damage significantly. The direct damage done by nematode attacks is not all you need to be concerned about, as it can lead to other problems. For example, the fungus that causes anthracnose in annual meadow-grass needs a senescent area of grass root/stem to infect and damaged areas left by nematodes may provide entry points. We are all aware of the increased worm casting activity in wetter conditions but insect larvae that feed on grass also seem to be on the increase. Every year, we are warned about a plague of leatherjackets by one of the companies that sell a chemical that controls them. Fortunately, these dire warnings do not seem to have come to fruition as of yet, but there do seem to be more incidences of Bibio sp. larvae, with fever fly, frit fly and St. Mark‟s fly all in evidence. INSERT PHOTO 5 Chafer grubs are a major problem in some areas of England, with no effective chemical control. More worrying for us North of the Border is that they are heading our way. Chafer grubs damaging turf were unheard of in Scotland, thought to be due to our colder winters. Infestations severe enough to cause damage have yet to be seen, but the chafer grub has arrived with one individual identified on a course last year. Beyond our shores, there have been reports of a mite damaging Bermudagrass. Not of concern to us now, but if the UK climate is warming we may be looking to use such grasses in the future, at least in southern England. When you hear reports such as this, however, it does beg the question is this a “new” pest problem or is it simply the correct diagnosis for turf damage that has been noted but unexplained for years? A final example, just to show how tropical the UK climate is getting. A year or two ago a termite colony was identified in a house in Devon! Be afraid… Every Greenkeeper is aware of the increasing lack of a chemical option for pest and disease management. In many ways this is a good thing in that it ensures best practice is cultural-based and that reaching for the bottle (pesticide, not whisky) has to be considered the last resort. However, if our climate is changing as predicted then the environment will increasingly favour fungal growths and pests that can cause damage. Sometimes cultural management may limit damage to an acceptable level, but this “acceptable” level is likely to be higher than that currently considered tolerable. Golfers must be prepared for this possible scenario. Be very afraid… For those who are still sceptical over the whole issue of “Global Warming”, the changing nature of disease and pest activity on UK golf courses is compelling evidence that the climate is changing. Just run through the list of environmental conditions that favour many of the diseases listed: Humid atmosphere. Moist turf surface. Mild temperatures. High temperatures. Ring a bell? Yes, exactly the sort of conditions we can expect from the climate change predictions. This is not a situation that is likely to happen, the reports already coming in of diseases and pests occurring in the UK that had only previously been seen in warmer climes, e.g. southern Europe and the warmer States of the US, suggests that it is happening. Scotland may not see the worst of it, but we should all be prepared just in case. As part of the turf management project, selected Clubs will be keeping records of disease incidence and worm casting and a set of best practice guidelines for pest and disease management will be produced. In the meantime, we should all be reassessing our strategy towards this issue and ensuring that adequate cultural control measures are being employed as you can guarantee that a severe outbreak of any of the diseases mentioned will be far more disfiguring and damaging to putting surfaces than any remedial measure taken to limit attacks. References Dr. Kate Entwistle, Turf Diseases…What‟s New?, International Turfgrass Bulletin, 204, April 1999, pp. 26-27. Dr. Kate Entwistle, Any New Summer Diseases, International Turfgrass Bulletin, 206, October 1999, pp. 26-28. Dr. Kate Entwistle, Turf Doctor‟s Notes: Is Ditylenchus a pest on Your Turf?, International Turfgrass Bulletin, 209, July 2000, pp. 33-34. Dr. Ruth Mann and Sue Hockland, Nematodes - The Unseen Terror, Greenkeeper International, May 2002, 28-32. Dr. Kate Entwistle, New Diseases are Developing: Fact or Fiction?, Greenkeeper International, December 2002, pp. 40-42. This work was commissioned by The Scottish Golf Environment Group, in conjunction with the Scottish Golf Union and Scottish Executive, as part of an effort to raise awareness of the impacts of climate change on golf course management. Steve Isaac works from Blairgowrie ( 01250 875805 or e-mail email@example.com) and his colleague Richard Windows is based in Glasgow ( 0141 632 0805 or e-mail firstname.lastname@example.org).