Effective Control of Pythium and Brown Patch Diseases of Cool-Season Turfgrasses. Bruce B. Clarke Rutgers University, New Brunswick, New Jersey USA

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1 Effective Control of Pythium and Brown Patch Diseases of Cool-Season Turfgrasses Bruce B. Clarke Rutgers University, New Brunswick, New Jersey USA

2 Diseases Caused by Pythium Damping-off of seedlings Pythium blight of foliage Pythium root rot, dysfunction

3 Pythium Blight Causal Agent(s): Pythium aphanidermatum and other Pythium species such as P. myriotylum, P. graminicola,p. arrhenomanes, and P. ultimum Hosts / Occurrence: All turfgrasses are susceptible with the cool-season grasses - creeping bentgrass, annual bluegrass and Kentucky bluegrass - being the most.

4 Pythium Blight Causal Agent(s): Pythium aphanidermatum and other Pythium species such as P. myriotylum, P. graminicola,p. arrhenomanes, and P. ultimum Hosts / Occurrence: All turfgrasses are susceptible with the cool-season grasses - creeping bentgrass, annual bluegrass and Kentucky bluegrass - being the most.

5 Pythium Blight Symptoms on Leaves small ( cm), bronzed, water-soaked patches a with slippery or slimy feeling when rubbed between the fingers white-gray cobwebby mycelium may be present with humidity is high symptoms may occur in streaks, sometimes with water draining channels

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9 Mycellium and oospores of Pythium ultimum

10 Pythium zoospore infecting turfgrass root

11 Pythium Blight Most likely to occur when temperatures exceed 29 0 C (day) and 20 0 C (night) and when the relative humidity is high. Typically occurs between June and September

12 Conditions Favoring Pythium Blight High soil salinity favors increased susceptibility High fertility generally favors increased disease Low soil moisture preceding abundant rainfall and high temperatures

13 Pythium Blight Cultural Control Maintain adequate soil moisture Reduce seed rates (spring and summer) Soil ph in a more acid range Balanced fertility Leach salts if they accumulate to high levels Reduce leaf wetness

14 Chemical Control of Pythium Blight I Phenylamides : Subdue MAXX (spray and seed treatment) II Phosphonates : Alliette Signature III Strobilurins : Heritage MAXX, Compass, Insignia IV Acylamine: benalaxyl (New QiL Chemistry cyazofamid)

15 Pythium Blight Control: 2007 Penn State University Treatments and Product Appl.rates Azoxystrobin 0.62 kg ai/ha Trifloxystrobin 0.31 kg ai/ha Pyraclostrobin 0.55 kg ai/ha Untreated Mike Fidanza

16 % Blighted Turf Percent Pythium blight Aug. 24, 2007 (21 Days after treatment) a b b b Agrostis stolonifera (fairway cm Bellewood Golf Course, North Coventry, PA. (Penn State University, State College, PA USA - Mike Fidanza)

17 Control of Pythium Blight on Lolium : Rutgers 2005 % turf area infested Trt and rate / 1000 ft 2 Sch. 13 Jun 30 Jun 25 Jul metalaxyl 0.37 kg ai/ha 14 day 7.3 a 3.0 ab 0.0 a Propamocarb 2.2 kg ai/ha 14 day 0.0 a 1.0 a 0.0 a Fosetyl-Al 9.8 kg ai/ha 14 day 0.8 a 0.0 a 3.8 ab Pyraclostrobin 0.55 kg ai/ha 14 day 0.0 a 0.0 a 0.0 a Azoxystrobin (WG) 0.31 kg ai/ha 14 day 0.0 a 0.0 a 0.3 a Azoxystrobin (WG) 0.62 kg ai/ha 21 day 0.0 a 1.3 a 11.3 c Azoxystrobin (ME) 0.62 kg ai/ha 21 day 0.0 a 4.5 b 10.0 c Untreated check b 24.3 c 32.7 e

18 Control of Pythium Blight with Selected Fungicides on Perennial Ryegrass : Rutgers 2010 Treatments applied in 4 gal water/m on a 14-day interval beginning on 18-June to 23-July.

19 Biology and Management of Pythium Root Rot Bruce B. Clarke 1 and Lane Tredway 2 Rutgers University 1 and N C State University 2 USA

20 Pythium Root Rot Pathogen: Pythium aristosporum, P. arrhenomanes, P. graminicola, P.volutum; others Grasses affected: All turfgrasses, but primarily Agrostis stolonifera and Poa annua

21 Root Rot Caused by Pythium species Pythium Root Rot Caused by an large number of Pythium species Occurs in poorly drained greens or during wet weather May develop at any time of year Symptoms usually in irregular patterns, sometimes in spots or patches Responds well to standard Pythium fungicides (metalaxyl)

22 Pythium Root Rot

23 Pythium Root Rot

24 Pythium oospores

25 Kerns and Tredway Pythium root rot reduces the plant s ability to absorb water and nutrients

26 Uninoculated P. torulosum P. volutum Kerns and Tredway

27 Roots Infected with Pythium Root Rot

28 Untreated pyraclostrobin (0.56 kg ai/ha) August 5, 2004 Kerns and Tredway

29 Management of Pythium Root Rot - Improve drainage, sunlight penetration - Improve soil conditions; deep tine aerification - Fungicides: contact fungicide drenches (avoid in high heat ), followed by metalaxyl or fosetyl-al

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31 Rhizoctonia Blight (Brown Patch) Causal Agent : Rhizoctonia solani Host : Bentgrass Ryegrass Fescue Agrostis sp. Lolium sp. Festuca sp.

32 Relative Growth of a Cool-season Grass / Pathogen System

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38 Conditions Favoring Brown Patch * Hot, Wet Weather * High Humidity * Excess Nitrogen * Thatch Accumulation

39 Brown Patch of Cool-season Turfgrasses: Disease Cycle C - growth of fungus from sclerotia or dead plant tissue C - colonization of lower leaves in turfgrass canopy (symptoms of disease may not be apparent!) C - colonization of upper leaves in turfgrass canopy with symptoms

40 Environmental Parameters Necessary for Brown Patch Development * RH >95% for 10 hours * Minimum Air Temp. > 15 0 C * > 2.5 mm Rainfall within 36 hours

41 DO NOT IRRIGATE 12 AM DEW AND GUTTATION WATER 6 PM 6 AM LEAVES DRY 12 PM DO NOT IRRIGATE

42 Brown Patch of Cool-season Turfgrasses Management Balanced fertility Improve air movement Decrease leaf wetness Correct subsurface drainage problems Reduce thatch Avoid high N fertility during periods of heat stress Improved cultivars for better disease and heat stress Proper mowing Ht. Use of fungicides

43 NTEP Agrostis Greens Test Brown Patch Ratings, Stillwater, OK USA a L-93 a A-4 A-1 a G-2 a Century a a Crenshaw LSD = 0.9 Penncross b 1 to 9, with 9=no disease, 1993 trial

44 Chemical Control of Brown Patch I DMIs: II Dicarboximide: tebuconazole, propiconazole iprodione III QoIs: azoxystrobin, trifloxystrobin, pyraclostrobin IV Organic Phosphate: tolclofos-methyl

45 Control of Brown of Brown Patch on Festuca arundinacea, Rutgers 1987 Treatments applied on 14-day interval beginning on 3 July,

46 Control of Brown of Brown Patch on Agrostis stolonifera, Rutgers 1990 Treatments applied on 28-day interval beginning on 11 July, Rizolex 75W = Tochlofos-methyl 75W, Chipco F = Iprodione 2F

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48 Improving Disease Control using Disease Predictive Models R. Latin Professor of Plant Pathology Purdue University

49 Decisions regarding fungicide application schedules may be based upon Calendar Damage thresholds Environmental-Based Disease Predictive models

50 Factors Involved with Disease Predictive Models Standard Factors Others Factors Air temperature Relative Humidity Rainfall/Irrigation Soil Temperature Dewpoint Evapotranspiration Leaf wetness Degree Days Temp base 50

51 Weather-based systems collect environmental data and process the data into usable information. Environmental data Hours Dew Air Temp RH Data Processor (computer in weather station on golf course) Disease Prediction Precip

52 Important environment-based models (Cool season grasses) Diseases Dollar spot, Pythium blight Brown patch Gray leaf spot Anthracnose

53 Brown Patch (Bent) 1. Low air temp > 15 C (for two consecutive days) 2. RH > 95% for at least 10 hours 3. Rainfall/irrigation of at least 2.5 mm within the past 36 hr Schumann, Clarke and Burpee, 2001

54 Predicting Pythium Blight Hall et al 1985 ( over predicts ) Based on air temp during 24 hr period only Min temp > 20 0 C < 18 hr = No risk Min temp > 20 0 C > 18 hr < 24 hr = Mod risk Min temp > 20 0 C > 24 hr = Severe risk

55 So In Conclusion: For - Calendar - Weather-based - Damage threshold methods Each has advantages and disadvantages. However, weather based disease predictive models offer the greatest opportunity to improve control and to potentially reduce fungicide usage.