Techniques for ImprovingFungicide Performance1. Maintain healthy turf2. Get an accurate diagnosis3. Select the best fungicide4. Time applications properly5. Put the fungicide where the pathogen is6. Provide uniform coverage of the target site7. Prevent fungicide resistance
apply in 1 to 2 gallons per apply in 2 to 3 gallons perapply in 5 gallons per 1000 ft2 ORwater-in with 1/8” of irrigation Proper placement is crucial Where is the pathogen attacking?
Conditions Favoring Spring Dead Spot Development • high soil pH • any factor that restricts root growth • soil compaction • excessive thatch • wet soils • any factor that reduces winter hardiness • excessive nitrogen in fall • potassium deﬁciency • wet soils
Damage is most severe on north-facing slopes...
Regular aeriﬁcation reduces spring dead spot development
Recovery from spring dead spot is very slow....
Speeding Spring Dead Spot Recovery• avoid use of certain herbicides in spring - dithiopyr (Dimension) - pendimethalin (Pendulum) - prodiamine (Barricade) - oryzalin (Surﬂan) - triﬂuralin + beneﬁn (Team Pro)• aerify or spike affected areas every two weeks• apply light and frequent irrigation• apply 1 lb N per 1000 per month from May to Sept
Keys to Successful Control of SDS• commit to implementing program for at least 3 years• map affected areas in spring for treatment• select an effective product• apply preventatively in fall when soil temperatures are between 60˚F and 80˚F• water-in immediately with 1/8” to 1/4” of irrigation
Comparison of fungicides for spring dead spot control in bermudagrass athletic ﬁelds, 2004 6 Heritage WG Rubigan 5 Eagle Banner Maxx UntreatedDisease Incidence (%) 4 3 2 1 0 Field #4 Field #5
Certain fungicides increase the density of dormant bermudagrass
Density differences are due to control of fungi that attack dormant bermudagrass leaves.
Impact of Fertilization Programs and PreventiveFungicide Applications On Spring Dead Spot inHybrid BermudagrassL.P. Tredway, M.D. Soika, and E.L. ButlerDepartment of Plant PathologyNorth Carolina State University NC STATE TURFGRASS PATHOLOGY
O. herpotricha O. korraeSpring dead spot is caused by three Do these species respond to species of Ophiosphaerella management practices similarly?
Research Objectives: Spring Dead Spot Management1. Determine the effects of nitrogen source and fall fertilization practices on spring dead spot development in bermudagrass fairways/athletic ﬁelds2. Evaluate fungicides for preventive control of spring dead spot in inoculated plots3. Compare and contrast the response of O. korrae and O. herpotricha to the above management practices
Bermudagrass Establishment and Inoculation• 10,000 ft2 plot established with ‘Tifway’ sprigs on Appling ﬁne sandy loam• 5’ x 10’ plots inoculated with O. korrae and O. herpotricha in October 2004• at each inoculation point, 10 cc of infested ryegrain was placed underneath a 2”-deep cup- cutter plug
Experiment 1: Nitrogen Source and Fall FertilizationNitrogen Sources (Main Plots) Fall Fertilizers (Subplots)• 1 lb N applied 4X per year • applied in Sept and/or Oct each 1. ammonium sulfate year 2. calcium nitrate 1. dolomitic lime (10 lb, 1 app) 3. sulfur coated urea 2. elemental sulfur (2 lb, 1 app) 4. urea 3. gypsum (10 lb, 1 app) 4. potassium chloride (1 lb, 1 app)- Split-plot, randomized complete block with 4 replications 5. potassium chloride (0.5 lb, 2- Treatments initiated in May 2006 apps)- Applied to same plots in 2006, 2007, and 6. potassium chloride (1 lb, 2 2008 apps)- entire study fertilized with 0.33 lb P and 0.66 lb K at time of each N application
Impact of Nitrogen Source on O. herpotricha 90Spring Dead Spot Index (diameter*incidence) Sulfur Coated Urea a a Calcium Nitrate a a 75 Urea Ammonium Sulfate 60 a a 45 a a a a b a b a 30 ab bb ab 15 bb b b c c 0 2007 2008 2009 Waller-Duncan k-ratio t-test
Impact of Nitrogen Source on O. korrae 30Spring Dead Spot Index (diameter*incidence) Sulfur Coated Urea Calcium Nitrate a a 25 Urea Ammonium Sulfate a 20 a a a 15 a a a a b a 10 ab b ab 5 a ab a b a b b c 0 2007 2008 2009 Waller-Duncan k-ratio t-test
Calcium Nitrate Ammonium Sulfate Urea May 2009
Prevention of Spring Dead Spot with Fungicides• signiﬁcant fungicide effects were Rubigan (6 ﬂ oz, 1X) Untreated detected in 2007 (p=0.0017) and 2008 (p=0.0098), but not in 2009 (p=0.1264)• a signiﬁcant fungicide x species interaction was detected in 2007 (p=0.0042) due to low index values induced by O. korrae• no signiﬁcant fungicide x species interaction was detected in 2008 (p=0.1111) or 2009 (p=0.0727)
Conclusions: Fertilization Programs and PreventiveFungicides for SDS Management• Spring dead spot pathogens exhibited a differential response to nitrogen sources • O. korrae was effectively suppressed by calcium nitrate • O. herpotricha was suppressed most effectively by ammonium sulfate• Fall applications of potassium, dolomitic lime, gypsum, and elemental sulfur had no effect on either spring dead spot pathogen• Spring dead spot pathogens responded similarly to preventive fungicide applications
Large patch rarely causes long-term damage to bermudagrass.
‘Helminthosporium’ leaf spot caused by Bipolaris cynodontis
The most common leaf spot fungus in bermudagrass
Chemical Control of Leaf Spots• Prevention is key• Monitor frequently during conducive weather• Applications most effective during early stages of disease development• Contact fungicides - mancozeb (Fore & others) - chlorothalonil (Daconil & others)