Diseases of Diseases of BentgrassBentgrass, , UltradwarfUltradwarf Bermuda and Bermuda and moremore
Alan WindhamPlant Pathology University of Tennessee
Abiotic Problems
Diagnosing Abiotic Problems
Often associated with stress related to weather phenomenonMay be related to cultural problemsMay be related to fertilizer or pesticide inputs
Abiotic (non-living cause of disease)
What gives you a clue?
Signs or SymptomsLack of signs or symptoms that would indicate a pathological problem point to an abiotic cause
• No mycelium• No fungal fruiting bodies• No spores
Nothing indicates that this is a disease
Roots are healthy; foliage is bleached but no sign of fungal infection
BentgrassBentgrass roots roots stained with acid stained with acid fuchsinfuchsin; no sign of ; no sign of any root pathogensany root pathogens
Root tip is composed of:
Root cap-protects root as it moves through soilMeristematic region where cell division takes placeZone of elongation where cells grow to their normal size
Root Cap
Bentgrass Root Tip
Meristematic
Region
(zone of cell
division)Zone of elongation
Anatomy of a root
Root CapMeristematic regionRegion of elongation
Root growth most Root growth most abundant in abundant in aerificationaerificationchannel where Ochannel where O22level is highest.level is highest.
Value of core aerification
Profile Problems
Zone of high organic matter; often anaerobic; smells like a sewer; will not support root growth
Severe layering problem
Black layer developing
Washed portion of plug; organic mat holds water and thus heat
Multiple black layers
Pathological root problems
Pythium oospores stained with acid fuschinA pythium infection in the meristematic region can slow or stop root growth
Discolored roots + fungal structures = trouble
Bentgrass root with a discolored center (stele) due to ETRI fungal infection
Root galls may = Root knot nematode
A nematode infestation usually impairs root function and may lead to secondary problems from infections from other pathogens.
Galls on bentgrass roots caused by root knot nematode
Root knot nematodes
Female root knot
Root knot nema in root gall
Root knot nematode eggs
Female root knot nematodes may produce 300-500 eggs in egg masses
Anthracnose
Caused by ColletotrichumcerealeGrass is thinnedFungus visible on foliage, crown of plant Bentgrass
Setae- hairlikestructures associated with fruiting bodies (acervulii)
Anthracnose
Crescent shaped spores
Anthracnose
Appresoria – infection structures, visible in crown and root tissue
Anthracnose
Infection mats
Anthracnose
Infection mats in leaf sheath
Rhizoctonia Diseases
Brown patch – cool season grassesLarge patch –zoysia and bermudaYellow patch – bentgrassWaitea patch- bentgrass, Poa annua
Brown Patch
Warm weather disease of a cool season grass
Brown patch control
Untreated Heritage
Heritage applied at 28 day intervals; UT Plant Science Farm
Large patchThis Rhizoctoniadisease is active at green up on zoysiaand bermuda
Yellow Patch
December 2007Creeping bentgrass
White mycelium forms “smoke ring”
Rhizoctonia cerealis
Right angle branching
Waitea patch
Described by Dr. Frank Wong, UC Riverside, on Poa annua
Southern Blight
Southern blight causal fungus Sclerotium rolfsii
Occurs during very hot weather; fungus produces abundant white mycelium
Sclerotium rolfsiiFungus produces spherical structures called sclerotia (pl)
Southern blight-tall fescue
Pythium Diseasescreeping bentgrass
Poor color from pythium root decline
Pythium blight- fungus has followed movement of water on green
Pythium blight of an ultradwarf bermuda?
TifEagle
Pythium on Tifeagle
Abundant white mycelium; also water soaked foliage
Pythium reproductive structures-oogonia
Rapid Blight Caused by a primitive fungus-Labyrinthula. Salinity usually is a problem when rapid blight shows up. Could be found on courses that use treated wastewater for irrigation source.
Labyrinthula cells dispersed when diseased tissue was macerated