Turfnet 2013 J Dempsey

Centre for Research in BiosciencesCommon cool-season turfgrass pathogensModes of infectionControl options Turf plant's defences Enhancement of defence responses

John Dempsey BSc(Hons)Centre for Research in Biosciences, Bristol, UK

1

Greenkeeper since mid 1980sCourse manager at Curragh Golf Course since 19932

BSc in Turfgrass science Myerscough college, UK

Final year research project-

The Effects of Phosphite on the Growth and Diseases Susceptibility of Agrostis stolonifera 3European Turfgrass Society2nd Conference Angers, France 2010

Centre for Research in BiosciencesCurrently carrying out postgraduate research for a PhD in turfgrass pathology

The mechanism by which phosphite reduces susceptibility to Microdochium nivale

Todays talk-Cool season turfgrass pathogensModes of infectionControl optionsTurfgrass defence mechanisms Ways to enhance or stimulate these defences6Disease - 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 qualityPlaying qualityWhat is a disease?

Disease triangleTurf managers need to focus on which factors we can successfully influence

Biotic and Abiotic factorsBiotic InfluencesAbiotic InfluencesFungiAir temperatureOomycetesSoil temperatureNematodesPlant nutrientsVirusesSoil aerationBacteriaWind dessicationInsectsSoil moistureOther invertebratesAir pollutantsVertebratesOperator damage

Identify the host plantGrass species

Identify the symptomsChlorotic, discoloured, rings, patches etc

Inspect the site Environment and any conditions which encourage the disease Patterns, is the turfgrass the only plants effected

Soil propertiespH, nutrient status, aeration

Management history

Staff knowledgeBackground information

Once data is collected identify the causal agent

Or submit samples for analysis

Common cool season pathogensFusarium patchPink snow mouldMicrodochium nivaleAnthracnoseColletotrichum cerealeBrown patchRhizoctonia solaniDollar spotSclerotinia homoeocarpa Red Thread Laetisaria fuciformisTake-all Patch Gaeumannomyces graminisLeaf spot / Melting out Drechslera, Bipolaris, CurvulariaRusts Puccinia spp. and Uromyces sppFairy ringsBasidiomycetesPythiumPythium sppYellow tuftSclerophthora macrosporaModes of infectionFungi and oomycetes consist of

Mycelium made up from a network of hyphaeHyphae -tubular filaments

Microdochium hyphae

Disease cycle

Survival

spores sclerotia infected debris (thatch) infected grass plantsalternate hosts.

Infection processFluorescent microscopy and stains

Using pot samples and infected greens

18

Inoculum in the soil conidia, myceliumInfection first in the crown and sheath areaMoves to the leaf and enters plant through stomata or appressoriaThe plant recognises the pathogen, this leads in induction of defence responses

19

Ascomycete fungus - Fusarium patch or Pink snow-mould

Most common pathogen in cool-season turfgrass

Microdochium nivale

Large class of fungi (15,000 species in 1,950 genera)22Microdochium nivale- Fusarium patch

Host All cool season turfgrass species

ConditionsPersistent humidity, moist surface, high N + pH

SymptomsOrange / brown spots initially that enlarge and coalesce.Active pale, slimy centre, dark margin, may have mycelium. Inactive pale and dry, no mycelium

Survival and spreadSurvives on infected plants and thatchSpread by conidia in water + wind, infected debrisInfects through stomata and wounds ControlMoisture control, correct fertiliser, avoid return of clippings, Chemicals iprodione, chlorothalonil, azoxystrobin, fludioxonilMicrodochium nivale- Pink snow mould

Uncommon unless in areas of prolonged snow cover

Hosts - All cool season grass species

ConditionsAfter prolonged snow coverSymptomsPink - bleached, dead areas, white / pink mycelia, no sclerotia

ControlPink - prevent Microdochium build up before snow. Same chemical control as Microdochium patch.

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 bentgrassYoungest leaf red - black rot at base - stunted roots

AnthracnoseSymptoms Foliar blight-

Mostly mid-summerleaves and shoot discolour, similar appearance to drought stress attacks the leaves and stems

ControlIndicates a problem with turf

Correct any compacted areasMinimise thatchAdequate fertiliserChemical preventative apps with combine fungicides more effective than curativeDMI/chlorothalonil

Host Rye, bents and Tall fescues mostly affected

ConditionsMost severe in warm, wet / humid. SymptomsCircular 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 spreadSurvives by bulbils and mycelium in debris and soil, spread by mycelium growing from plant to plant, infects directly or into wounds.

ControlCorrect fertiliser, good drainage, remove moistureChemical curative azoxystrobin or pyraclostrobin Brown Patch - Rhizoctonia solani

Host most grasses (Festuca, Poa, Agrostis, Lolium)

Conditionslow fertility, warm / humid, 20C, dewy morningsSymptomsHour glass lesions, small, circular, depressed spots initially, dead grass is dry and bleached Survival and spreadSurvives as stromata, and as dormant myceliumSpread by wind, water, equipment, debris and clippingsInfects wounds, stomata and by direct penetrationControlCultivar 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, iprodioneDollar spot - Sclerotinia homoeocarpa

Host - All cool season turfgrass species

ConditionsMild temps, low fertility Occurs in spring and becomes worse as grass enters dormancy More aggressive strains? Tolerance to nitrogen?SymptomsPink / red appearance, bleached leaves, red sclerotia (needles).Mild - only tips affected, severe - whole shoot killed. Survival and spreadSclerotia in thatch, spread by water, wind, equipmentinfects through stomata and cut leaf tips. ControlCultivar selection, correct fertiliser, chemical - azoxystrobin iprodione, propiconazole Red Thread Laetisaria fuciformis

Red Thread Laetisaria fuciformisHost - Bent grasses

ConditionsG. graminis always present in soil. Greens low in antagonists (sand, sterilized), increase in pH, poor drainage.

SymptomsSaucer shaped, depressed bronze areas of bent grass, resistant grass species in patch, black roots, presence of perithecia in stems

Survival and spreadSurvives in previously infected plants, spreads by ascospores (wind + water), soil and debris movement, equipment. Infects by runner hyphae into the root.

ControlTest 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 OctChemicals some broad spectrum but not greatTake-all Patch Gaeumannomyces graminis

Host Most turfgrass species

ConditionsWarm / humid, leaf wetness

SymptomsDepend on causal agent and grass speciesCurvularia - Mottled yellow green descending from leaf tip, red / brown margin. No lesions on Agrostis and more tan than brownDrechslera 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 spreadSurvive as conidia and in infected plants. Spread on wind, water, infected clippings, equipment. Infects through stomata or directly.

ControlCultivar selection, correct fertiliser, reduce surface moisture, Leaf spot / Melting out - Drechslera, Bipolaris, CurvulariaHost Many species, some affect numerous grasses others specialised

ConditionsWarm / humid, leaf wetness

SymptomsOrange / brown pustules on individual leaves.May have chlorotic halo around pustule

Survival and spreadComplicated lifecycle 5 spore typesUrediniospores produced in abundance cause epidemicsTeliospore overwintering spore, germinates to produce -:Basidiospore windborne can infect secondary host (eg P. graminis and Barberry)pycniospores and aeciospores formed on alternate hostaeciospores can only infect grass producing urediniospores again.ControlMost severe on slow growing turf.Usually indicates stress eg. drought, inadequate fertiliser, shadeRemove stress factors water well, feed if required, Increase mowing heightChemical no label recommendation in UK Rusts - Puccinia spp. and Uromyces spp.Fairy ring -Basidiomycetes Type 1Ring 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 2Ring of stimulated grassCaused 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 3Ring of fruiting bodiesCaused by many basidiomycetesBasidiomycetes do 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

Host Most cool season grass species

ConditionsWarm and very wetSymptomsSmall spots of yellow excessively tillered turf, poor rootingSurvival and spreadSurvives indefinitely in infected plantsoospores produce sporangia that germinate to produce zoospores. Zoospores swim to new host and infect meristem tissue.

ControlDrainage, remove water after floods, verticuttingMetalaxyl, phosphiteYellow tuft - Sclerophthora macrospora

Pythium - Pythium spp.Host Most but Perennial Rye, Creeping bent and Poa annua most affected

ConditionsHot, humid temps above 80 F Symptomssmall spots or patches of blighted grass thatsuddenly 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.ControlPreventative - Mefenoxam, propamocarb, azoxystrobin, pyraclostrobin, phosphite.Pythium blight develops most rapidly under humid conditions when air temperature is above 80F. As temperatures approach 90F, only a few hours are required to destroy a stand of grass.

FungicidesCultural practicesDisease resistanceBiological controlControl - General IPM

Control reliant on fungicides

Managing resistanceAvoid repetitive and sole use of a particular fungicide -or same mode of suppressionAlternate fungicides with differing modes of actionDont reduce Strobilurins in tank mixesUse as part of an integrated program of controlReliance on fungicides-

Expensive Inhibition of beneficial organismsLegislative controlsScope for alternative means of disease control

Environmental factorsSurface moistureTemperaturesHumidityPoor air movementLight quality

The environment is a key factor for disease developmentTurfgrass and pathogens are always present. Weather patterns and environmental effects are vital

Aerate

Sand topdressings

Reduce surface moisture

Increase air movement

Improve light quality

Improve drainage

Percolation

Sand rootzones

Aviva Stadium, Dublin

Croke Park, DublinManaging Sports surfaces to reduce disease

ManagementSurface and rootzone pHFertiliser programThatch reductionIrrigationCutting height etc

Any factor which give a pathogen the edgeMicroclimateRootzone constructionInfiltration and percolationAir movementLightTurfgrass speciesPlant factorsBreeding for resistance

Cultivar selection

Nutrition

Plant defences

Development of resistant cultivars

Plant resistance breeding

Seed choices

GM of turfgrassEnhance defence responses

Many diseases are also influenced by the nutritional status of the sward.A perfect balance is the goal. Both excessively high and low fertility can contribute to turfgrass disease pressureNutritional IPMMinimum Levels for Sustainable NutritionPACE TURF and Asian Turfgrass CenterPlant nutrition

Applications of ferrous sulphate reduced the incidence of Microdochium nivale - J Oostendorp and Dr. Andy Owen, Myerscough College

Silicon -Datnoff

Composts/compost teas Increase in fertilityIncrease in antagonistic fungi

Biological controls

Compost teas Trials Conducted by Josh Webber at Myerscough College

Sterile water Autoclaved Compost tea Compost teaCompost tea+mychorrizaeTrials Conducted by Josh Webber at Myerscough College Sterile water Autoclaved Compost tea Compost teaCompost tea+mychorrizaeTurfgrass defences

Turfgrass responses to infection70

Hydrogen peroxideNitric oxidePhenolsPhytoalexinsSalicylic acid

The HR is triggered by the plant when it recognizes a pathogen. The identification of a pathogen typically occurs when avirulence gene products, secreted by a pathogen, bind to, or indirectly interact with the product of a plant resistance (R) gene. R genes are highly polymorphic, and many plants produce several different types of R gene products, enabling them to recognize virulence products produced by many different pathogens. In phase one of the HR, the activation of R genes triggers an ion flux, involving an efflux of hydroxide and potassium outside the cells, and an influx of calcium and hydrogen ions into the cell. In phase two, the cells involved in the HR generate an oxidative burst by producing reactive oxygen species (ROS), superoxide anions, hydrogen peroxide, hydroxyl radicals and nitrous oxide. These compounds affect cellular membrane function, in part by inducing lipid peroxidation and by causing lipid damage. The alteration of ion components in the cell, and the breakdown of cellular components in the presence of ROS, results in the death of affected cells and the formation of local lesions. Reactive oxygen species also trigger the deposition of lignin and callose. These compounds serve to reinforce the walls of cells surrounding the infection, creating a barrier and inhibiting the spread of the infection.

71Turfgrass defence responsesSynthesis of Reactive Oxygen Species (ROS) O2, H2O2, NO

Hypersensitive response (HR)Programmed cell deathPhenolsPhytoalexinsSalicylic acid

Plants induced responses to infection

Short term defence response Long-term resistance - Systemic Acquired Resistance (SAR) When a plant cell recognizes particles from damaged cells or particles from the pathogen, the plant launches a two-pronged resistance: a general short-term response and a delayed long-term specific response. As part of the induced resistance, the short-term response, the plant deploys reactive oxygen species such as superoxide and hydrogen peroxide to kill invading cells. In pathogen interactions, the common short-term response is the hypersensitive response, in which cells surrounding the site of infection are signalled to undergo apoptosis, or programmed cell death, in order to prevent the spread of the pathogen to the rest of the plant. Long-term resistance, or systemic acquired resistance (SAR), involves communication between the damaged or infected tissue with the rest of the plant using plant hormones such as jasmonic acid, ethylene, abscisic acid or salicylic acid. The reception of the signal leads to changes within the plant, which induce genes that protect from further pathogen intrusion, including enzymes involved in the production of phytoalexins. Often, if jasmonates or ethylene (both gaseous hormones) is released from the wounded tissue, neighbouring plants also manufacture phytoalexins in response. 72

Hydrogen peroxide responseImportant component of stress response in plantsMeasure using a number of methodsHistological stains using fluorescent microscopy TMB (tetramethylbenzidine) DAB (diaminobenzidine)74TMB staining

DAB stainingHydrogen peroxide detection in gramineae inoculated with M. nivale, stained with TMB and DAB.

Phenolic compoundsMeasure using reagent and spectroscopy

A. Autofluorescence of phenolic compounds (yellow) in leaf close to the hyphae (blue)

B. Callose (light-green) in leaf cells after aniline blue stainingAnother important response pathogen challengeVisualise using fluorescent microscopy 76

Systemic Acquired Resistance Salicylic acid signal molecule for SAR

The systemic acquired resistance (SAR) is a "whole-plant" resistance response that occurs following an earlier localised exposure to a pathogen. Plants use pattern-recognition receptors to recognize conserved microbial signatures. This recognition triggers an immune response. SAR is important for plants to resist disease, as well as to recover from disease once formed. SAR can be induced by a wide range of pathogens, especially (but not only) those that cause tissue necrosis, and the resistance observed following induction of SAR is effective against a wide range of pathogens, which is why SAR resistance is sometimes called "broad spectrum." SAR is associated with the induction of a wide range of genes (so called PR or "pathogenesis-related" genes), and the activation of SAR requires the accumulation of endogenous salicylic acid (SA). The pathogen-induced SA signal activates a molecular signal transduction pathway that is identified by a gene encoding for defence responses.78Defence activatorsCivitasSalicylic acidHydrogen peroxideHarpinChitinPhosphite

Can defences be stimulated?Treatments to control diseases by priming the expression of plant defences

Civitas used to induce defence responses

Direct foliar applications

Salicylic acid Hydrogen peroxideHarpinHarpin is a plant elicitor, it binds to receptors on the plant leaf and triggers physiological processes within the plant triggering systemic acquired resistance.

ChitinForms part of the fungal cell wallSignificant in the activation of immune responses in plantsFound also in the outer skeletons of insects, crabs, shrimps, and lobsters.PhosphiteForm of Phosphorous (P) a major nutrient of plant growthTaken up as Phosphate - Phosphoric acid (H3PO4) Phosphite - Phosphorous acid (H3PO3)Phosphite not metabolised in plants

82

Trials running since Sept 2010

Treatments applied bi-weekly

Disease incidence and turf quality assessed monthly

Phosphite Phosphite/biostimulant Iprodione Iprodione/phosphite NPK Control

85 Phosphite Phosphite/biostimulant Iprodione Iprodione/phosphite NPK Control

86

Agrostis canina plots January 2012Agrostis canina canina plots January 2012

.88

December 2008ControlPhosphiteThese pictures here were taken 10 weeks into the treatments, the control is on the left and the Phosphite treated sample on the right.89Mycelial Growth on Amended PDA -4 days p.i.

90

Hyphal morphology Unamended 75g/ml Phosphite

Phosphite application significantly reduces Microdochium nivalePhosphite is rapidly assimilated and translocated by turfgrassPhosphite has a direct inhibitory effect on mycelial growthTracked Microdochium infection process defence responsesEnhance Inducible defence mechanisms - ROSSystemic Acquired resistance -phytoalexins and salicylic acidPhosphite research summary

Know your siteKnow your plantAccount for environmentReduce conditions for disease pressureMaintain a balanced nutritionConsider alternates to enhance fungicide program

Key points for todayIm on Twitter @J_J_Dempsey

Thanks for listening Any questions?95