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