Centre for Research in Biosciences

1. Centre for Research in Biosciences • Common cool-season turfgrass pathogens • Modes of infection • Control options • Turf plant's defences • Enhancement of defence responses John Dempsey BSc(Hons) Centre for Research in Biosciences, Bristol, UK

2. Greenkeeper since mid 1980’s Course manager at Curragh Golf Course since 1993

3. BSc in Turfgrass science – Myerscough college, UK • Final year research project- • The Effects of Phosphite on the Growth and Diseases Susceptibility of Agrostis stolonifera

4. European Turfgrass Society 2nd Conference Angers, France 2010

5. Centre for Research in Biosciences Currently carrying out postgraduate research for a PhD in turfgrass pathology – The mechanism by which phosphite reduces susceptibility to Microdochium nivale

6. Todays talk- • Cool season turfgrass pathogens • Modes of infection • Control options • Turfgrass defence mechanisms • Ways to enhance or stimulate these defences

7. What is a disease? Disease - the malfunctioning of host cells and tissues that results from their continuous irritation by a pathogenic agent and leads to the development of symptoms (Agrios, 1988). Problems caused by a pathogen on amenity turfgrasses Visual quality Playing quality

8. Disease triangle Turf managers need to focus on which factors we can successfully influence

9. Biotic and Abiotic factors

10. Identify the host plant • Grass species • Identify the symptoms • Chlorotic, discoloured, rings, patches etc • Inspect the site • Environment and any conditions which encourage the disease • Patterns, is the turfgrass the only plants effected • Soil properties • pH, nutrient status, aeration

11. Management history • Staff knowledge • Background information • Once data is collected identify the causal agent • Or submit samples for analysis

13. Modes of infection • Fungi and oomycetes consist of – • Mycelium – • made up from a network of hyphae • Hyphae -tubular filaments

14. Microdochiumhyphae

17. Disease cycle • Survival • spores • sclerotia • infected debris (thatch) • infected grass plants • alternate hosts.

18. Infection process Using pot samples and infected greens Fluorescent microscopy and stains

19. Inoculum in the soil –conidia, mycelium • Infection first in the crown and sheath area • Moves to the leaf and enters plant through stomata or appressoria • The plant recognises the pathogen, this leads in induction of defence responses

22. Microdochium nivale Ascomycete fungus - Fusarium patch or Pink snow-mould Most common pathogen in cool-season turfgrass Large class of fungi (15,000 species in 1,950 genera)

23. Microdochium nivale- Fusarium patch • Host – All cool season turfgrass species • Conditions Persistent humidity, moist surface, high N + pH • Symptoms Orange / brown spots initially that enlarge and coalesce. Active – pale, slimy centre, dark margin, may have mycelium. Inactive – pale and dry, no mycelium • Survival and spread Survives on infected plants and thatch Spread by conidia in water + wind, infected debris Infects through stomata and wounds • Control Moisture control, correct fertiliser, avoid return of clippings, Chemicals – iprodione, chlorothalonil, azoxystrobin, fludioxonil

24. Microdochium nivale- Pink snow mould Uncommon unless in areas of prolonged snow cover • Hosts - All cool season grass species • Conditions After prolonged snow cover • Symptoms Pink - bleached, dead areas, white / pink mycelia, no sclerotia • Control Pink - prevent Microdochium build up before snow. Same chemical control as Microdochium patch.

26. Anthracnose - Colletotrichum cereale • Host – all grasses • Two forms- Basal rot Foliar blight • Symptoms Basal rot- Most frequent during spring, summer, and autumn affects crowns, stem bases, and roots mostly P. annua and Creeping bentgrass Youngest leaf red - black rot at base - stunted roots

27. Anthracnose • Symptoms Foliar blight- Mostly mid-summer leaves and shoot discolour, similar appearance to drought stress attacks the leaves and stems

28. Control Indicates a problem with turf • Correct any compacted areas • Minimise thatch • Adequate fertiliser • Chemical –preventative apps with combine fungicides more effective than curative • DMI/chlorothalonil

29. Brown Patch - Rhizoctoniasolani Host – Rye, bents and Tall fescues mostly affected • Conditions Most severe in warm, wet / humid. • Symptoms Circular patches on turf, tissues become dark and water soaked, infected spots turn brown and die. Typical appearance -‘Smoke rings’ may On taller grasses light brown patches form. Close inspection often reveals leaf lesions • Survival and spread Survives by bulbils and mycelium in debris and soil, spread by mycelium growing from plant to plant, infects directly or into wounds. • Control Correct fertiliser, good drainage, remove moisture Chemical curative –azoxystrobin or pyraclostrobin

31. Dollar spot - Sclerotinia homoeocarpa • Host – most grasses (Festuca, Poa, Agrostis, Lolium) • Conditions low fertility, warm / humid, 20C, dewy mornings • Symptoms Hour glass lesions, small, circular, depressed spots initially, dead grass is dry and bleached • Survival and spread Survives as stromata, and as dormant mycelium Spread by wind, water, equipment, debris and clippings Infects wounds, stomata and by direct penetration • Control Cultivar selection, correct fertiliser, keep turf well watered but with a dry surface, Chemical – avoid repeated apps of DMI, good risk of resistance build up, carbendazim, chlorothalonil, fenarimol, iprodione

33. Red Thread Laetisaria fuciformis • Host - All cool season turfgrass species • Conditions Mild temps, low fertility Occurs in spring and becomes worse as grass enters dormancy More aggressive strains? Tolerance to nitrogen? • Symptoms Pink / red appearance, bleached leaves, red sclerotia (needles). Mild - only tips affected, severe - whole shoot killed. • Survival and spread Sclerotia in thatch, spread by water, wind, equipment infects through stomata and cut leaf tips. • Control Cultivar selection, correct fertiliser, chemical - azoxystrobin iprodione, propiconazole

34. Red Thread Laetisaria fuciformis

35. Take-all Patch Gaeumannomyces graminis • Host - Bent grasses • Conditions G. graminis always present in soil. Greens low in antagonists (sand, sterilized), increase in pH, poor drainage. • Symptoms Saucer shaped, depressed bronze areas of bent grass, resistant grass species in patch, black roots, presence of perithecia in stems • Survival and spread Survives in previously infected plants, spreads by ascospores (wind + water), soil and debris movement, equipment. Infects by runner hyphae into the root. • Control Test irrigation water (consider acidifying), avoid liming, minimise fungicides, adequate fertiliser, reduce thatch Apply manganese in May and Jun, sulphate of Iron in Aug, Sept and Oct Chemicals – some broad spectrum but not great

37. Leaf spot / Melting out - Drechslera, Bipolaris, Curvularia • Host Most turfgrass species • Conditions Warm / humid, leaf wetness • Symptoms Depend on causal agent and grass species Curvularia - Mottled yellow green descending from leaf tip, red / brown margin. No lesions on Agrostis and more tan than brown Drechslera and Bipolaris – On Poa lesions red/brown to purple/black. On Lolium brown spots enlarge to lesions with grey center and brown margin. On Agrostis small red brown lesions that coalesce to cover the leaf – can look like drought stress. • Survival and spread Survive as conidia and in infected plants. Spread on wind, water, infected clippings, equipment. Infects through stomata or directly. • Control Cultivar selection, correct fertiliser, reduce surface moisture,

38. Rusts - Pucciniaspp. and Uromycesspp. • Host Many species, some affect numerous grasses others specialised • Conditions Warm / humid, leaf wetness • Symptoms Orange / brown pustules on individual leaves. May have chlorotic halo around pustule • Survival and spread Complicated lifecycle – 5 spore types • Urediniospores – produced in abundance cause epidemics • Teliospore – overwintering spore, germinates to produce -: • Basidiospore – windborne can infect secondary host (egP. graminis and Barberry) • pycniospores and aeciospores formed on alternate host • aeciospores can only infect grass producing urediniospores again. • Control Most severe on slow growing turf. Usually indicates stress eg. drought, inadequate fertiliser, shade Remove stress factors – water well, feed if required, Increase mowing height Chemical – no label recommendation in UK

39. Fairy ring -Basidiomycetes • Type 1 • Ring of dead grass bordered on both sides with stimulated grass growth. • Mostly caused by Marasmius oreades. • Control – self antagonism, wetting agent (very difficult to control). • Type 2 • Ring of stimulated grass • Caused by numerous fungi e.g. Agaricus spp., Lycoperdon spp. • Control – hide symptoms by fertilising and applying sulphate of iron, apply wetting agent. Azoxystrobin + wetting agent • Type 3 • Ring of fruiting bodies • Caused by many basidiomycetes

40. Basidiomycetesdo not directly affect the grass • Mycelial breakdown products coat soil grains producing a hydrophobic soil and grass dies from drought • Decomposes organic matter. • Basidiomycete growth releases nitrogen stimulating grass growth

41. Yellow tuft - Sclerophthora macrospora Host – Most cool season grass species • Conditions Warm and very wet • Symptoms Small spots of yellow excessively tillered turf, poor rooting • Survival and spread Survives indefinitely in infected plants oospores produce sporangia that germinate to produce zoospores. Zoospores swim to new host and infect meristem tissue. • Control Drainage, remove water after floods, verticutting Metalaxyl, phosphite

43. Pythium - Pythium spp. Host – Most but Perennial Rye, Creeping bent and Poa annua most affected • Conditions Hot, humid temps above 80 F • Symptoms • small spots or patches of blighted grass that suddenly appear. In the early stages the grass leaves appear water-soaked, slimy and dark. As the disease progresses, the leaves shrivel and the patches fade from green to light brown. • Cottony mycelium can usually be seen in mornings on the foliage. • Control Preventative - Mefenoxam, propamocarb, azoxystrobin, pyraclostrobin, phosphite.

44. Pythium blight develops most rapidly under humid conditions when air temperature is above 80°F. As temperatures approach 90°F, only a few hours are required to destroy a stand of grass.

45. Control - General IPM • Fungicides • Cultural practices • Disease resistance • Biological control

46. Control reliant on fungicides

48. Managing resistance

49. Reliance on fungicides- • Expensive • Inhibition of beneficial organisms • Legislative controls Scope for alternative means of disease control

50. The environment is akey factor for disease development Turfgrass and pathogens are always present. Weather patterns and environmental effects are vital Environmental factors Surface moisture Temperatures Humidity Poor air movement Light quality