Turfgrass Diseases Update
Dave HanAssociate Professor & Extension SpecialistAuburn University /Alabama Cooperative
Extension System
STMA Conference, January 2011
Disease DiagnosisA process of elimination
1. Start with a list of possibilities based on turf species and time of year
2. Look for clues and patterns3. Rule out diseases, narrow the list of
possibilities4. Repeat steps 2 and 3, if needed5. Send sample to a diagnostic lab
Turfgrass Diseases(Partial) List of Possibilities
Bermudagrass• Dollar Spot, Spring Dead Spot,
‘Helminthosporium’ Blight, Fairy Ring, Large Patch, Curvularia blight, Pythium Blight
Bluegrass• Brown Patch, Dollar Spot, Fairy Ring,
‘Helminthosporium’ Blight, Pythium Blight, Summer Patch, Other root diseases
Ryegrass• Brown Patch, Gray Leaf Spot, Rust,
‘Helminthosporium’ Blight, Dollar Spot, Fairy ring
Tall fescue• Large Patch, Dollar Spot, Rust,
‘Helminthosporium’ Blight
Large Patch / Brown Patch / Zoysia Patch
Causal Agent: Rhizoctonia solani
Time of year: Spring and Fall(warm season grasses) Spring, summer and fall (cool season grasses)
Hosts: All grasses
Large PatchZoysiagrass
Large patchZoysiagrass
Large PatchSt. Augustinegrass
N. Tisserat, KSU
Large patchZoysiagrass
Large / Brown Patch Conditions Favoring Disease
Wet, humid weather Turfgrass going into or coming out of
dormancy Large Nitrogen applications when
turfgrass is not actively growing (too early in spring or too late in fall, or in summer heat stress)
Excessive thatch, poor soil drainage, low air movement, over-watering
Traffic, other stress
Large Patch Control Cultural Control
Reduce thatch, dethatching and aerification may be needed annually
Mow at optimum height Irrigate during fall and spring only as
needed to prevent drought stress
Large Patch Control Chemical Control
Preventive applications work best Use minimum of 2.5 gal/1000 sq. ft.
Don’t water in. Preventative Fungicides:
• Azoxystrobin (Heritage)• Flutolanil (Prostar) • Triadimefon (Bayleton)• Pyraclostobin (Insignia)
Can use contact fungicides for curative applications• Recovery will depend on growing conditions
Fairy Ring Caused by a variety of Basidiomycetes
(mushrooms and puffballs) that degrade thatch and can result in turfgrass death• Production of waxy materials that result in
hydrophobic soils• Production of ammonia and cyanide
Appear as circles or arcs from several inches to many feet in diameter.• Spread from a few inches to 2 feet per year,
slow spread
All grasses
Fairy RingZoysiagrass
Fairy RingP. ryegrass
Fairy RingP. ryegrass
Fairy Ring Control Management to reduce thatch helps reduce
symptoms Physically breaking up hydrophobic layer,
apply surfactants may help speed recovery Deep watering with root feeder Suppression of fairy rings with fungicides often
in combination with surfactants is needed• Azoxystrobin (Heritage) • Flutolanil (Prostar) • Pyraclostrobin (Insignia) • Combination products
LEAF SPOT AND CROWN ROT
Typical symptoms (pictured is bermudagrass; can occur on any grass)
“Helminthosporium” Leaf spots Caused by several
different fungi All turfgrasses All cause generic
leaf spots, and ‘melting-out’ if bad enough
Can rot sheaths and crowns
Most prevalent in spring and fall
“Helminthosporium” Leaf spots
Maintain balanced fertility - avoid high N Irrigate deeply in the morning Raise mower height during disease
outbreaks Fungicide:
• Mancozeb (Fore, Dithane, etc) • Azoxystrobin (Heritage) • Chlorothalonil (Daconil) • Propiconazole (Banner) • Trifloxystrobin (Compass) • Thiophanate-methyl (3336)
Pythium Blight
Can advance rapidly in warm, humid weather
Grass often dies in streaks, following equipment or water trails
Wash equipment thoroughly
Improve aeration and drainage
Rusts
Puccinia and Uromyces spp. Rust is a problem on zoysiagrass*,
ryegrass*, bermudagrass, tall fescue Time of year: spring or fall - spores are
blow long distances by wind Rust infected turf may appear dull
yellow or light brown from a distance Disease favored by shade, low fertility,
drought stress and infrequent mowing
Rust Control Maintain recommended fertility levels and
soil moisture to maintain growth Increase air circulation by pruning trees
and shrubs Mow frequently, remove clippings Fungicides often not needed:
• Heritage (azoxystrobin) • Chlorothalonil • Mancozeb • Banner (propiconazole) • Bayleton (triadimefon)
Fungicides
Contact:• Require good coverage to be effective• Coat the plant surface and prevent fungi
from getting in Local penetrant
• Can get inside leaves and move a little, but not throughout plant
Acropetal penetrant• Moves upwards (upwardly systemic)
True systemic• Moves up and down
Contact fungicides
Form protective barrier on leaf
Barrier must be complete for effective protection
How to get complete barrier?
– Small droplets– High pressure– Small nozzle opening– Large spray volume
Local penetrants Can move some through leaf Helps with distribution Still not truly systemic Good spray coverage still
critical With all contacts, reapplication
intervals are relatively short: 5-14 days
Barrier breaks down due to mowing, rain, UV exposure, etc.
Systemic fungicides
Most move upwards only (acropetalpenetrant)
Move through Xylem
Longer intervals
Also have contact activity
Pythium fungicides Pythium is different Need separate set of fungicides (for the
most part) Contacts:
• Chloroneb (Teremec) Ethazol (Koban) Systemics:
• Metalaxyl (Subdue 2E), Mefanoxam (Subdue MAXX), Propamocarb (Banol), *Azoxystrobin (Heritage)
Phosphites, Organic Phosphates• Fosetyl-Al (Signature), Phosphite
salts (Alude, Vital, Magellan)
What fungicides can do
Protect turf from infection by pathogenic fungi
Kill fungi that are on or in turfgrass tissue
Stop fungi on or in turfgrass tissue from growing
Some are systemic and can get into roots
Arrest the spread of a disease
What fungicides can’t do
Grow grass! For turf to recover from disease
damage, must have good conditions for regrowth or reseeding
New Fungicides
DMI (Demethylation inhibitors)• Tebuconazole - Torque (Cleary)
Golf course only for now Limit use on bermudagrass
• Triticonazole – Trinity (BASF), Triton (Bayer) Good tolerance during summer stress for
cool season grasses
New Fungicides
Strobilurin (QoI inhibitors)• Fluoxastrobin – Disarm (Arysta)
Labeled for dollar spot control
The Label Is the Law
Reading the Label