turf disease management: can it be done without fungicides?
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Turf Disease Management: Can it be done without fungicides?
Lane TredwayAssociate Professor and Extension SpecialistDepartment of Plant PathologyNorth Carolina State University
What is sustainable?
capable of being continued with minimal long-term effect on the environment (American Heritage Dictionary)
capable of being maintained at a steady level without exhausting natural resources or causing ecological damage (Collins)
of, relating to, or being a method of harvesting or using a resource so that the resource is not depleted or permanently damaged (Merriam-Webster)
Which practice is least sustainable?
1. removing trees to increase sunlight and air movement
2. planting a variety containing resistance genes from grasses collected in Poland
3. planting a variety containing frog dermaseptin genes
4. applying the biofungicide Rhapsody (Bacillus subtilis)
5. applying fungicide Heritage (azoxystrobin)
6. applying a mixture of soda, beer, soap, ammonia, and mouthwash
Which practice is most sustainable?
1. removing trees to increase sunlight and air movement
2. planting a variety containing resistance genes from grasses collected in Poland
3. planting a variety containing frog dermaseptin genes
4. applying the biofungicide Rhapsody (Bacillus subtilis)
5. applying fungicide Heritage (azoxystrobin)
6. applying a mixture of soda, beer, soap, ammonia, and mouthwash
How do plant diseases develop?
Amount of Disease
Disease-Conducive EnvironmentSu
scep
tible
Host
Pathogen
The environment triggers disease development.
Fungal growth is driven by temperature and moisture.
How are turfgrass diseases managed?
Amount of Disease
Disease-Conducive EnvironmentSu
scep
tible
Host
Pathogen
How are turfgrass diseases managed?
Disease-Conducive Environment
Pathogen
Plant a disease-resistant
species or variety
25% Disease
How are turfgrass diseases managed?
Remove trees to increase sunlight and air movement
Pathogen
10% Disease
Plant a disease-resistant species
or variety
How are turfgrass diseases managed?
Apply a fungicide to suppress pathogen
growth
2% Disease
Remove trees to increase
sunlight and air movement
Plant a disease-resistant species
or variety
Establish a threshold. How much damage is acceptable?
0% 5% 10%
Host
Pathogen
Environment
Host
Disease management begins at planting.
Host
Turf Species Vary in their Disease Susceptibility
Kentucky bluegrass - summer patch, dollar spot, leaf spot, rust
perennial ryegrass - dollar spot, red thread, Pythium blight, gray leaf spot, brown patch, rust
tall fescue - brown patch
fine fescues - dollar spot, summer patch, red thread
Varieties vary widely in their susceptibility to certain diseases.
Most land/grant universities evaluate turf varieties.
Host
ntep.org
Healthy, well-managed turf is very resistant to disease.
Host
Nitrogen has the greatest impact on turf growth.
EVERY turf disease is influenced by nitrogen.
AnthracnoseDollar SpotFairy Ring Pythium Root DysfunctionRed ThreadRust
Brown PatchPythium BlightGray Leaf Spot
Spring Dead SpotLarge PatchSnow Molds
Low Nitrogen High Nitrogen
Host
under-fertilizedwell-fertilized
Host
Over-fertilization produces leaves that are soft, lush, and easy to infect by the fungi that cause brown patch, Pythium, and other diseases.
Mowing has a tremendous effect on turf health.
Mowing practices influence gray leaf spot development.
Host
Mowing Height
0
10
20
30
40
50
1.5” 2.5” 3.5”Mowing Height
Gra
y Le
af S
pot I
ncid
ence
(%)
0
10
20
30
40
50
Collected Returned
Gra
y Le
af S
pot I
ncid
ence
(%)
Mowing practices influence gray leaf spot development.
Host
Clipping Collection
The environment drives disease development.
Does irrigation cause as many problems as it solves?
0
10
20
30
40
Light, Frequent Deep, Infrequent
1.5”3.0”
Summer Patch is Impacted by Mowing and Irrigation
Sum
mer
pat
ch in
cide
nce
(%)
Davis and Dernoeden, 1991
0
20
40
60
80
100
120
140
6/3
6/10
6/17
6/24 7/
17/8
7/15
7/22
7/29 8/
58/12
DewCure 2 oz Check
Reducing leaf wetness suppresses dollar spot.
Clarke, Rutgers University
Dol
lar S
pot I
ncid
ence
Pathogen
Suppressing pathogen growth and survival.
Are fungicides sustainable?
Environmental Impact Quotient (EIQ)What’s the real environmental impact?
http://www.nysipm.cornell.edu/publications/eiq/
Product Rate/1000 ft2 Interval EIQ/month
Heritage 50WG 0.2 oz 28 days 7.3
Rhapsody 5 oz 7 days 7.6
Bayer Fungus Control 2 lbs 14 days 28
Scotts Lawn Fungus Control 1.35 lbs 14 days 64
Daconil Ultrex 3.2 oz 14 days 538
Pathogen
flickr:kanickmoses
Toomany
fungicidesto choose from!
Get an accurate diagnosis!
Disease Management Utility
turffiles.ncsu.edu/diseasemgmt
Disease Management Utility on TurfFiles
turffiles.ncsu.edu/diseasemgmt
Soil pH impacts micronutrient availability.
Pathogen
Patch diseases are enhanced by high soil pH.
Spring dead spot Summer patch
Necrotic ring spotTake-all patch
NH4+
H+
Soil Root
soil pH decreases
NO3-
OH-soil pH increases
Nitrogen source influences soil pH
Biologicals
• a living organism is applied to the turf, which may inhibit disease through a variety of mechanisms
Biofungicides
• an inhibitory compound, derived from a specific microbe, is concentrated and applied to the turf
Composts
• stimulate activity of soil microbes
• some of which may be beneficial
• some may be harmful or pathogenic
What about biological control?
0
50
100
150
200
4 May 18 May 1 Jun 15 Jun 1 Jul 15 Jul
Rhapsody (2%) Rhapsody (3%) Untreated
Dolla
r Spo
t Inc
iden
ce
Rhapsody applied every 14 days
**
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