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Diseases Part 4

Diseases Part 4

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Fairy Ring:

various basidiomycota

• Destroys turfgrass uniformity

• occasionally kills a band of grass at the

active edge of the fungus

• mycellium may cause hydrophobic spots

• mushrooms are unsightly and can “hide”

golf balls

• all grasses are susceptible


Symptoms

• Donut shaped rings or partial rings of

luxuriant, green grass 2’ to several feet and

larger

• over stimulated band is roughly 6” to 12”

wide

• green color and rapid growth are a result of

nitrogen release from organic matter being

decomposed by the fungus


Symptoms

• Grass is adversely affected to varying

degrees ranging from simple asthetic

problems to death of the grass

• edge of ring may “sprout” mushrooms

• “textbook” cases are a result of buried

organic matter

• can be serious problem on new sand based

turfgrass especially golf greens


• Edaphic

Fairy ring “phonetics”

• Type I - dead or

severely damaged

• Type II - dark green

rings

• Type III - little

damage/stimulation

mushrooms present

• Lectophilic

• Type A- little

damage/stimulation

mushrooms present

• Type B - dark green

rings

• Type C - dead or

severely damaged


Activity

• Survive as spores or mycellium

• most active during warm weather

• many cases are perennial (ie. Comes back in

the same spot year after year)

• can cause type I, II, or III symptoms


Control

• If possible remove all old soil and replace

followed by fumigation

• Prostar and Heritage have some activity

• better if injected, wetting agents may help

• in new sand-based greens, use adequate

organic matter, off-site mixing, wait a few

months (if you last that long)


Fairy ring on a Finnish soccer

field

• This field illustrates edaphic fairy ring caused by

high soil organic matter and liberal use of raw

chicken manure for fertilizer.

• Note the dark green color at the edge of the ring.

This is a response to the nitrogen released as

protein in the organic matter is digested by the

fungus and excess N is released.


Fairy Ring with fruiting-bodies


Edaphic fairy ring on

bermudagrass

• Fairy ring is not always circular but can

occur as an irregularly circular arc. When it

reaches the fruiting stage mushrooms are

produced at the active edge of the disease.

• Fairy ring frequently occurs in the same

area year after year.


Lectophilic fairy ring on a

bermudagrass putting green

• This green is low in nitrogen so the ring is

very pronounced. New sand based greens

are especially susceptible to fairy ring

because of reduced competition from other

organisms. Usually the problem disappears

as the soil in the green matures.


Type C symptoms in a

bermudagrass putting green

• Also low in nitrogen this green is exhibiting

what is often termed type C lectophilic fairy

ring. The grass is being killed at the active

edge of the ring.


Hydrophobic spot left by fairy

ring activity

• Although fairy ring usually doesn’t kill

grass it can cause problems in it’s aftermath.

This photo shows a hydrophobic spot left

behind after the active fairy ring

disappeared.


Gaeumannomyces graminis

• bermudagrass decline

• St. Augustinegrass take-all root rot

• also been observed as pathogen of

zoysiagrass

• associated with disease of in

centipdedegrass

• can be confused with brown patch


Gaeumannomyces graminis

• Primarily a root pathogen, has progressed

significantly when secondary foliar

symptoms appear

• starts as small “weak” spot in turf,

progresses to large, irregular, thinning

patches

• leaf symptoms range from chlorosis to

necrosis


Gaeumannomyces graminis

• Patches typically have healthy swards of

turfgrass intermixed

• roots are short and rotted, stolons can be

lifted easily

• likes hot weather and wet to saturated

conditions

• stressed turfgrass is much more susceptible


Gaeumannomyces graminis

• No effective chemical

• raise HOC

• irrigate properly and correct poor drainage

• improve air circulation

• some systemic fungicides (Banner,

Bayleton, Rubigan, Fungo, Cleary’s 3336)

may help as preventative


Microscopic view

Gaeumannomyces graminis

• This picture shows hyphopodia, an organ

characteristic of Gaeumannomyces

graminis, attached to grass tissue. The

hyphopodia

is a modified hypha that

attaches itself to plant tissue and directly

penetrates cells.


Gaeumannomyces graminis on

St. Augustinegrass

• The common name for this disease on St.

Augustinegrass this disease is “take-all

patch”.

• The general thinning shown here is

characteristic of this pathogen. Note the

intermixing of health, dying, and dead

swards of grass. These are secondary

symptoms associated with root rot.


Take-all patch is sometimes

confused with chinch bug

damage

• This shot looks like chinch bugs but is

actually take all patch. A simple float using

a coffee can with both ends cut out will

readily reveal the presence of chinch bugs.


More take all patch


Gaeumannomyces graminis on a

bermudagrass putting green

• In bermudagrass the common name for this

disease if bermudagrass decline. Like St.

Augustine it is characterized by thinning

and an intermixing of healthy, dying, and

dead swards of grass. Also, as with St.

Augustinegrass, the symptoms on the

surface are secondary symptoms associated

Courtesy Monica Elliott

with root rot.


This photo shows the intermixing

of grass in various states of

health


Bermudagrass decline is only a

problem at low heights of cut.

• This disease is peculiar to putting greens in

bermudagrass and is often worse around the

edge of the green where clean up passes

(especially triplexed) create additional wear

and compaction. This speaks to the

secondary nature of this disease. It typically

occurs on older greens with other problems

and in the hot humid weather of July and

August.


Primary root rot caused by

Gaeumannomyces graminis

• As mentioned the surface symptoms are

secondary. The primary symptom is root

rot. This photo contrast a healthy

bermudagrass root on the right (it is white

and fleshy) and a diseased root on the left

(spindley, brown, dark water soaked

lesions).

Courtesy Monica Elliott


SAD virus

• St. Augustine Decline virus

• incurable, remove and replant with resistant

cultivar

• small chlorotic spots which give leaves a

stippled appearance

• Texas east to Mississippi


Yellowing and stippling

associated with SAD virus


• Non-pathogenic

Slime mold

• produces gray, and sometimes other color,

fruiting bodies on grass leaves

• mow it off


Slime mold fruiting bodies on

grass blades

• At the fruiting stage slime mold “crawls” up

onto the grass and produces the symptoms

in this photo. It can be gray, yellow, or pink,

with gray seeming to be the most common.

• It is non-pathogenic and does not require

treatment.


Slime mold on mulch


Slime mold on mulch


Spring dead spot

• Significant problem in the transition zone

• Fairly complex combination of

– Disease (Leptosphaeria korrae, causes necrotic

ring spot in cool season grasses)

– colder than normal weather

• Usually comes back in same spots in bad

years

• soil moisture and fertility involved


• Mild to hot weather

Red thread

• looks like wilt and often exacerbated by

misdiagnosis

• broad spectrum


Red thread is easily confused

with wilt

• Closer inspection will reveal red mycellium


Red thread and a dull mower

• Multiple problems can occur on the same

turfgrass simultaneously. This picture shows

tall fescue mown with a dull rotary mower

giving it the whitish cast associated with

“mower disease” but also has a patch of red

thread developing. Dull mowers predispose

turf to numerous problems.


Shredding

at the tip

Close up of tall fescue Vascular bundle mown

ripped from the leaf

with a dull rotary mower

• Note the tearing and shredding at the end of

the blade. A vascular bundle has been

ripped out of the leaf for a considerable

distance.


Other diseases

• Spring dead spot (Ophiosphaerella spp.)

• Snow mold

• fusarium blight

• bacterial wilts

• algae (not really a disease)

• moss (ditto)


Disease Models

• Methods of predicting when disease

outbreaks are likely to occur

• Typically are conservative (I.e. tend to over

predict disease outbreaks

• Good tools but should not be relied upon

exclusively for decisions on fungicide

applications


Brown patch environmental

favorability index (EFI)

• Developed in Maryland

• Uses mean relative humidity & minimum

temperature

• Scaled from 0 to 8

• value of 6 or greater fungicide application is

recommended


Mills/Rothwell dollar spot model

• Predicts outbreaks based on maximum daily

temperature & relative humidity

• Treat with fungicide if:

– maximum daily temperature exceeds 77 o

F and

– relative humidity exceeds 90% and

– this combination occurs for 3 or more

days in a 7 day period


Pythium blight forcaster

• Risk is high if:

– maximum temperature exceeds 86 o F and

– minimum temperature exceeds 68 o F and

– relative humidity is 90% or greater for 14

or more consecutive hours


Trends in modeling

• Newer models are being

developed which consider the

length of time the foliage is wet.

• Still have a ways to go in this area

but modeling should gradually get

better as soon as we can find two

pathologist who can agree on

anything other than proper

spelling of Brown patch!


Overview of turfgrass diseases in

Florida


Common ornamental diseases

• Crown gall - Agrobacterium tumefaciens

• affects over 40 families

• gall with rounded irregular shape up to

several inches

• spread by water (is a flagellate rod)

• enters through wounds

• clean nursery stock


Crown gall

Tomato Ligustrum Pecan seedling

University of Georgia Plant Pathology Archive, University of Georgia, Bugwood.org


Mushroom root rot

• Clitocybe tabescens southeast US & tropics

• Armillaria mellea temperate, finer soils

• attacks almost anything anything except

monocots and ferns

• secondary wilt , mycelium between bark

and wood and honey colored mushrooms


Mushroom root rot

• remove soil in for 3’ radius and replace,

drench with bordeaux mix or ferban

• Fallow land for several years after removing

oaks

• Dig 3’ deep trenches between infected

plants and other susceptible species

• Large, important specimens may be

candidates for “surgery”


White mycellial mat between

cambium and wood


Powdery mildew

• Caused by several ascomycetes

• results in significant loss of foliage

• stunting, dwarfing, and reddening of leaves

which may occur prior to appearance of

white mycellium

• mild damp weather, mainly spring and fall

• bayleton, domain, rubigan, chipco 26019


Powdery mildew on

poinsettia


More powdery mildew


Camellia mosaic

• Viral disease of the foliage

• white to yellow spots on foliage, kind of an

“infectious varigation

• buy clean stock

• good sanitary practices


Camellia mosaic

showing

characteristic

mottling of the leaf


Coconut lethal yellowing

• MLO which plugs vascular tissue

• lethal disease of approximately two dozen different palm

species

• yellowing of leaves followed by browning

• spread by leaf hoppers

• Susceptible species

– Cocos nucifera (coconut palm),

– Adonidia merrillii (Christmas palm),

– Phoenix dactylifera (date palm)

– Pritchardia spp. (loulu palms)

– Caryota mitis & rumphiana (fishtail palms)

• replant with dwarf Malaysian or other resistant variety or

suppress with antibiotics


healthy palm diseased


• Injecting palms with

oxytetracycline

suppresses the disease

but the effect is

temporary

Coconut palms with

lethal yellowing


Damping off

• Can be caused by several genera of

phycomycota and ascomycota fungi

• major killer of numerous plants in the

seedling stage

• can kill pre of post emergent

• use treated seed and treat seed bed

• Banrot, Truban, Alliette


Fire blight - Erwinia spp.

• Major bacterial disease of pear, apple,

raphiolepis, pyracantha, photinia, spirea,

and others in the rose family

• rapid blight of the apical leaves and twigs

• leaves shrivel and die, but remain attached

• prune infected branches 12” below affected

area, use good sanitation


Fire blight in apples


A blighted branch


This disease is potentially

devastating in some crops


Juniper blight

• Attacks shrubs and trees in the juniper,

cypress, and jew families

• branch tips brown progressing to base

(mites cause browning base to tip)

• moist warm weather worse on young plants

up to about 5 years old

• full sun, well drained sites, use copper spray


Phytophthora (spp.) root rot

• Azaleas, camellias, pines, other ornamentals

• roots rot, possibly some stem rot

• secondary rapid wilt and death of shoots

• warm, wet soils 68oF to 95oF, frequent rain

• soil drench with Subdue or Banrot

• Crown and fruit rot in apples and pears

• Bud rot in palms

• Damping off in seedlings


Primary and

secondary

symptoms of

Phytophthora

root rot

primary reddening of the

cambium

Secondary

decline in

the tops


Phytophthora and Thielaviopsis

Bud Rots

• Typically occurs in the rainy season

• Starts as discoloration of the youngest fronds

• No new fronds will be produced but older fronds

will remain green initially

• Fungus usually enters through an injury

• Very common on freeze damaged buds (may also

be bacterial in this instance)

• Older palms it may be too late when symptoms

appear

• Young palm may be salvagable if caught early


Phytophthora and Thielaviopsis

Courtesy Monica Elliott

Bud Rots


Phytophthora and Thielaviopsis

Bud Rots

• Phytophthora is much more common

• Cultural controls helpful

– Avoid overhead irrigation

– Keep foliage dry

– Avoid standing water

– Good sanitation practices

• Before applying fungicide get lab diagnosis

• If you are not sure apply a mixture of two

fungicides

– Preventative bud drenches for young palms in

containers when conditions indicate


Pine tree decline

• Slash pines in sandy soils, under irrigation,

and higher fertility situations

• cause not completely understood

• some success with injection of fungicide

and microelements

• eliminate irrigation and elevated fertility in

root zone of pines


Pine tree decling

• These pines, adjacent to a tee, are

receiving too much water and

fertilizer


• Palms

• incurable

Ganoderma zonatum

butt rot

• remove soil and fumigate

• plant something else


Ganoderma produces decline in

the bud and “conks” on the

Courtesy Eric Knudsen

trunks


Conks are usually honey colored

• By the time the conks appear it is too late.


Conks are usually right at the

base of the palm


Hypoxylon rot

• Usually attacks weakened

trees

• Rot of hardwoods and some

shrubs such as Camellia

• Dislodges bark and causes

thinning in crown

• Surgery on valuable

specimens, or remove plant

• Don’t confuse with lichens


Various leaf spot diseases

• Ascomycota, bacteria, a few algae

• degrades foliage, may cause loss of new

growth

• various shapes and colors of spots

• identify and use appropriate control if

necessary


Leaf spotting organisms

fungal bacterial algal


Tar spot on maple


Exobasidium camellias & azelias


• Avoidance

• exclusion

• eradication

• protection

Disease control tactics

• host plant resistance

• therapy


Some pest can be

hard to diagnose

without local

knowledge

• This is damage is

caused by deer

feeding in the winter.


Fungicide Categories

• Contact – work on leaf & stem surface to

prevent penetration by fungus

• Systemic – are absorbed into plant tissue

and are translocated (primarily in xylem)

• Local systemic – absorbed but only move a

short distance, don’t move in vascular tissue

• Mesostemic – new category strongly

attracted to plant surface and are absorbed

by waxy layers


Comparison of fungicide categories

Contact Systemic

• Protective

• Not translocated

• New growth is not

protected

• Typically for foliar

diseases only

• Broad spectrum

• Little possibility of

resistance developing

• Typically not used for

root pathogens

• Protective & curative

• Translocated

• New growth is

protected

• For foliar and root

diseases

• Specific mode of action

• More possibility of

resistance developing

• Effective on root

pathogens


• Family

• Aromatic hydrocarbons

• Dithiocarbamates

• Benzonitrile

• Phthalimides

• Triazines

Contact fungicide families

• Examples

• (Common names)

• Chloroneb, ethazol, PCNB

• Thiram, mancozeb, maneb

• Chlorothalonil

• Captan

• anilazine


• Family

• ergosterol biosysthesis

inhibitors (EBI’s) also

known as (DMI’s)

• Benzimidazoles

• Acetanilide

• Phosphonates

Systemic fungicide families

• Examples

• (Common names)

• Fenarimol, cyproconazol,

triadimefon, propiconazol,

tebuconazol, myclobutanil

• Benomyl, thiophanate-methyl

• Metalaxyl

• Fosetyl-Al


• Family

Local-Systemic fungicide families

• Dicarboximides

• Benzamide

• carbamates

• Examples

• (Common names)

• Iprodione, vinclozolin

• Flutolanil

• propamocarb


• Family

• strobilurin

Mesostemic fungicides

• Examples

• (Common names)

• Azoxystrobin, trifloxystrobin

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