Plant Diseases Chapter 4 Section VII of the Pest Bear & Affiliates Service Personnel Development Program 2005 Copyright @ 2005-2006, Central Fla Duplicating,

Plant Diseases

Chapter 4

Section VII

of the

Pest Bear & AffiliatesService Personnel Development Program

2005

Copyright @ 2005-2006, Central Fla Duplicating, Inc. All rights reserved

Select the disease you wish to learn about by “clicking” on the respective title in the Table of Contents on the following

page.


To properly understand the diseases affecting turf, you must understand five things about each disease:

1) Who the host or hosts are

2) What is the pathogen that causes the disease

3) How do you make a diagnosis of the disease

4) What environmental factors are favored by the disease

5) How can the disease be controlled using management cultural controls


Contents• Anthracnose

• Brown Patch

• Dollar Spot

• Fairy Ring

• Gray Leaf Spot

• Gray Snow Mold

• Helminthosporium

• Necrotic Ring Spot

• Nematodes

• Pink Snow Mold

• Powdery Mildew

• Pythium Blight

• Red Thread

• Rust

• Spring Dead Spot

• Stripe Smut

• Summer Patch

• Take-All Patch


Anthracnose


Anthracnose - Hosts

Creeping bentgrass

Bluegrass

Fescue

Perennial ryegrass

Bermudagrass

Centipedgrass

St Augustinegrass


Anthracnose - Hosts

Annual Bluegrass is particularly susceptible


Anthracnose - Pathogen

• Colletotrichum graminicola


Anthracnose - Diagnosis

• Grass turns yellow to brown in irregular shaped patches of turf

• Leaf lesions are yellow with black centers

• Brown to black hairs (setae) may be observed on leaves or crown with aid of 10x magnification


Anthracnose - Environment

Found in temperatures >78° F

More than 10 hours of leaf wetness per day for several days

Particularly severe on turf exposed to soil compaction and excessive thatch

Pathogen may cause crown rot in creeping bentgrass at temperatures of 60°-77°F


Anthracnose – Managementcultural controls

Disease will be more severe under low nitrogen conditions

Maintain balanced fertility throughout the growing season

Use light weight mowing equipment to reduce compaction

Limit thatch thickness

Decrease shade and increase air circulation to reduce wetness

Avoid irrigation in late afternoon or evening prior to midnight


AnthracnoseCompleted

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Brown Patch


Brown Patch - Hosts

• All common turfgrass species are susceptible to Brown Patch


Brown Patch - Pathogen

• Rhizoctonia solani


Brown Patch - Diagnosis

• Cool-season turfgrasses: circular patches of brown turf a few inches to several feet in diameter

• Leaves have gray, irregular-shaped lesions with thin brown borders

• Patches are surrounded by smoky-colored ring or mycelium on close-cut turf


Brown Patch - Diagnosis

• Warm-season turfgrasses: leaf sheathes at margins of patches are brown to black

• Dark brown lesions may be visible on stolons


Brown Patch - Environment

Night temperature > 60°F for cool season grasses and 50- 60°F for warm season grasses


Disease is severe at low mowing heights

Disease can be severe on poorly drained soils


Brown Patch– Managementcultural controls

Disease may be more severe on lush turf with excessive nitrogen and low phosphorus and potassium


Decrease shade and increase air circulation to enhance drying of the turf

Avoid irrigation in late afternoon or in evening prior to midnight


Mow at recommended height


Brown Patch Completed


Dollar Spot


Dollar Spot - Hosts

• All common turfgrass species are hosts for Dollar Spot


Dollar Spot - Pathogen

• Sclerotinia homeocarpa


Dollar Spot - Diagnosis

• Straw-colored patches of turf 1-3 inches in diameter

• White mycelium may be associated with patches when turf is wet

• Straw-colored lesions extend across leaf blades


Dollar Spot - Environment

Night temperatures > 50°F and day temperatures < 90 °F


Disease is severe on turf which is subjected to drought stress


Dollar Spot – Managementcultural controls

Disease may be more severe under low nitrogen fertility





Avoid drought stress


Dollar SpotCompleted


Fairy Ring


Fairy Ring - Hosts

• All common grass species are hosts for Fairy Ring


Fairy Ring - Pathogen

• Several species of “mushroom-forming” fungi


Fairy Ring - Diagnosis

• Circles or arcs of mushrooms or wilted, dead or dark green turf

• White mats of fungal mycelium may be found in thatch or soil associated with circles or arcs


Fairy Ring - Environment

Light to moderate textured soils are favored

Soil usually has a pH of 5-7.5

Low to moderate soil moisture


Fairy Ring – Managementcultural controls

Maintain moderate nitrogen fertility

Maintain moderate to high levels of phosphorus and potassium according to soil tests

Excavate ring and soil 12 inches deep and 24 inches beyond ring or arch and replace with new soil

Remove sod, cultivate soil 6-8 inches deep in several directions, add wetting agent to soil, reseed or sod


Fairy RingCompleted


Nematodes


Nematodes - Hosts

• All common grass species are hosts for nematodes


Nematodes - Pathogen

• More than 15 different species of nematodes attack turfgrasses


Nematodes - Diagnosis

• Irregular shaped light green or yellow patches of turf which may be several feet in diameter

• Leaves may be yellow or brown from the tip

• Roots may be thin, stunted or knotted


Nematodes - Environment

Soil temperatures of >40° F

Symptoms are often severe on turf growing in sandy or light-textured soils

Symptoms may be enhanced by drought and high temperatures of >80°F


Nematodes – Managementcultural controls


Maintain moderate to high levels of phosphorus and potassium according to soil tests

Have soil analyzed for nematodes prior to seeding or sodding

Use sod that is nematode free


NematodesCompleted


Pythium Blight


Pythium Blight - Hosts

• All common turfgrass species are susceptible to Pythium Blight


Pythium Blight - Pathogen

• Pythium aphanidermatum and other species of Pythium


Pythium Blight - Diagnosis

• Greasy brown patches of turf an inch or less in diameter, increasing to several inches and turning straw colored

• Grey-white, cottony mycelium observed in the early morning


Pythium Blight - Environment

Night temperature > 65°F


Poor surface and subsurface drainage


Pythium Blight– Managementcultural controls

Disease may be more severe under excessive nitrogen conditions


Maintain optimum plant calcium levels



Improve surface and subsurface drainage

Avoid mowing when surface is wetCopyright @ 2005-2006, Central Fla Duplicating, Inc. All rights reserved

Pythium Blight Completed


Gray Snow Mold


• All cool season grasses

• Bentgrass

• Annual Bluegrass

• Perennial Ryegrass

Gray Snow Mold - Hosts


Bentgrass, Annual Bluegrass, and Perennial Ryegrass are particularly susceptible

Gray Snow Mold - Hosts


Gray Snow Mold - Pathogen

• Typhula incarnate

• Typhula ishikarensis


Gray Snow Mold - Diagnosis

• Circular straw-colored patches of turf usually less than 10” in diameter, evident after the snow melts

• Orange, brown to black sclerotia form on leaves


Gray Snow Mold - Environment

Snow-cover is required for disease to develop

Disease is severe when snow cover exceeds 90 days


Gray Snow Mold – Managementcultural controls

Avoid a fertility program that results in lush, fast-growing turf in late fall or winter

Maintain potassium levels according to soil tests

Prevent snow from accumulating excessively on turf areas

Prevent compaction of snow and remove snow in the spring

Use dark-colored fertilizer to melt snow in the spring


Gray Snow MoldCompleted


Necrotic Ring Spot


Necrotic Ring Spot - Hosts

• Kentucky bluegrass

• Fine-leaf fescue


Necrotic Ring Spot - Pathogen

• Leptosphaeria korrae


Necrotic Ring Spot - Diagnosis

• Light-green to yellow patches of turf 3-5” in diameter

• Light-green turf turns brown to straw-colored

• Roots and rhizomes are brown to black


Necrotic Ring Spot - Environment

Initiates at temperatures <80 degrees F in moist soil

Severity of symptoms increases with drought and temperatures >80 degrees F

Disease may be very severe in compacted soils


Necrotic Ring Spot Completed


Spring Dead Spot


Spring Dead Spot - Hosts

• Bermudagrass


Spring Dead Spot - Pathogen

• Species of Leptosphaeria, Ophiosphaerella, and Gaeumannomyces


Spring Dead Spot - Diagnosis

• Circular patches of straw-colored turf up to several feet in diameter

• Evident after winter dormancy

• Roots at edges of patches are dark brown to black


Spring Dead Spot - Environment

Disease is severe when the average daily temperature in November is <60 degrees F

Poor surface and sub-surface drainage

Thatch is > ½ inch thick


Spring Dead Spot– Managementcultural controls

Maintain good potassium and low nitrogen levels in the late summer and early fall

Maintain a balanced fertility throughout the growing season

Maintain moderate to high levels of phosphorus, potassium, and minor elements according to soil tests

Improve surface and sub-surface drainage



Spring Dead Spot Completed


Red Thread


Red Thread - Hosts

Bentgrass

Bluegrass

Fine-leaf fescue

Perennial ryegrass


Red Thread - Hosts

Fine-leaf fescue, and Perennial Ryegrass are particularly susceptible


Red Thread - Pathogen

• Laetisaria fuciformis


Red Thread - Diagnosis

• Red-brown patches of turf 1-4” in diameter

• Pink-red mycelium grows from the tip of the infected leaf blades


Red Thread - Environment

Cool temperatures, 40-70 degrees F



Red Thread– Managementcultural controls

Disease is more severe with low nitrogen fertility

Maintain balanced fertilization throughout the growing season

Maintain moderate to high levels of potassium and phosphorus

Avoid irrigations in late afternoon or evening

Mow at least once each week and remove diseased portion of leaf blades


Red Thread Completed


Powdery Mildew


Powdery Mildew - Hosts

• Kentucky bluegrass

• Fine-leaf fescue

• Bermudagrass


Powdery Mildew - Pathogen

• Erysiphe gramminis


Powdery Mildew - Diagnosis

• White,powdery masses of fungal spores scattered over the surface of the leaves


Powdery Mildew - Environment

Disease is severe in shaded areas at temperatures of 60-72 degrees F

High humidity is required for infection, but leaf wetness is not essential


Powdery Mildew– Managementcultural controls

Disease is more severe under excessive nitrogen conditions

Maintain a balanced fertility program throughout the growing season

Reduce shade and increase air circulation

Plant shade tolerant grass


Powdery Mildew Completed


Helminthosporium Leaf Spot


Helminthosporium Leaf Spot - Hosts

Bluegrass

Bentgrass

Fescue

Perennial ryegrass

Bahiagrass

Bermudagrass

Zoysia

Buffalograss


Helminthosporium Leaf Spot - Pathogen

• Bipolaris sps.


Helminthosporium Leaf Spot - Diagnosis

• Round to oval chocolate-brown spots on the leaves

• Spots may have tan centers


Helminthosporium Leaf Spot - Environment

Temperatures of 77-95 degrees F

Disease severity increases with increases in temperature



Helminthosporium Leaf Spot– Management

cultural controls

Avoid excessive nitrogen and maintain a balanced fertility in the growing season


Avoid late afternoon or evening irrigation

Limit thatch thickness and mow at recommended heights

Use light-weight mowing equipment to reduce stress

Plant resistant grasses


Helminthosporium Leaf Spot Completed


Gray Leaf Spot


Gray Leaf spot - Hosts

• Most warm season turfgrasses

• St Augustine is particularly susceptible

• Ryegrasses and fescues may exhibit severe symptoms under prolonged warm, wet conditions


Gray Leaf Spot - Pathogen

• Pyricularia grisea


Gray Snow Mold - Diagnosis

• Round or oval gray spots on the leaves

• Spots surrounded by brown or yellow border

• Leaves may be blighted gray, usually from the tip downward


Gray Leaf spot - Environment

Night temperatures of >70 degrees F


Disease is severe in shaded areas or during periods of extended overcast weather


Gray Leaf Spot – Managementcultural controls

Disease is more severe under excess nitrogen fertility


Decrease shade and increase air circulation to enhance drying of turf

Avoid irrigation in late afternoon and evening prior to midnight


Gray Leaf SpotCompleted


Rust


Rust - Hosts

All common species of turfgrasses


Rust - Pathogen

• Several species of Puccinia and Uromyces


Rust - Diagnosis

• Red-brown powdery masses of spores on leaf blades or leaf sheaths


Rust - Environment

Temperatures of 68-86 degrees F

Disease is severe un turf subjected to drought stress, low mowing, shade, or poor air circulation


Rust– Managementcultural controls

Disease is more severe under low nitrogen conditions


Reduce shade and increase air circulation

Mow at recommended heights


Avoid irrigation in late afternoon and in evening prior to midnight


Rust Spot Completed


Pink Snow Mold


Pink Snow Mold - Hosts

• All cool season turfgrasses

• Bentgrass, annual bluegrass and perennial ryegrass are particularly susceptible


Pink Snow Mold - Pathogen

• Microdochium nivale


Pink Snow Mold - Diagnosis

• Salmon colored to red-brown patches of turf 1-8 inches or more in diameter

• Common after 60 days or more of snow cover


Pink Snow Mold - Environment

Disease is common after at least 60 days of snow cover

Pathogen can infect turf without snow cover

Disease is particularly severe when snow covers unfrozen ground


Pink Snow Mold– Managementcultural controls

Disease is more sever on fast-growing lush turf that receives high nitrogen and low potassium in the fall

Maintain balanced fertility

Prevent snow compaction and prevent snow from accumulating

Melt snow in spring with organic fertilizers

Avoid applications of lime

Avoid irrigation at night and mow at the recommended height


Pink Snow Mold Completed

•Return to ContentsCopyright @ 2005-2006, Central Fla Duplicating, Inc. All rights reserved

Summer Patch


Summer Patch - Hosts

Bluegrasses and fine-leaf fescues

Summer Patch - Pathogen

• Magnaporthe poae


Summer Patch - Diagnosis

• Circular patches of wilted straw-colored turf

• Usually less than 10 inches in diameter

• Leaves turn yellow or brown starting at the tip

• Roots are light to dark brown


Summer Patch - Environment

Day-time temperature >85 degrees F

High soil moisture

Poor surface or subsurface drainage

Low mowing height


Summer Patch– Managementcultural controls



Reduce compaction

Syringe turf with water when temperature >85 degrees F

Mow at recommended height

Prevent stress


Summer Patch Completed

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Take-All Patch


Take-All Patch - Hosts

Only bentgrasses are highly susceptible


Take-All Patch - Pathogen

• Gaeumannomyces graminis


Take-All Patch - Diagnosis

• Wilted to bronze or brown circular patches of turf up to several feet in diameter

• Roots along margins of patches are dark brown


Take-All Patch - Environment

Disease develops rapidly on cool, wet soils with pH >5.5

Disease can be more severe on sandy soils


Take-All Patch– Managementcultural controls

Disease is more severe under low or unbalanced fertility conditions

Fertilize with acid-forming sources of nitrogen such as sulfur coated urea

Maintain moderate to high levels of phosphorus, potassium and minor elements according to soil tests


Avoid use of lime if soil pH >5.0

Avoid heavy, frequent irrigation


Take-All Patch Completed


Stripe Smut


Stripe Smut - Hosts

• Bluegrass

• Bentgrass

• Fescue

• Perennial ryegrass

• Tall fescue


Stripe Smut - Pathogen

• Ustilago striformis


Stripe Smut - Diagnosis

• Yellow to black stripes from tips to base of leaf blade

• Black masses of spores form along the stripes

• Leaves turn brown from tips down and tips of leaves twist and curl


Stripe Smut - Environment

Infection occurs at 50-68 degrees F

Sever symptoms are evident during drought and temperatures of >75 degrees F

Symptoms are often more severe on acid soils and on turf with excessive thatch


Stripe Smut– Managementcultural controls

Disease is more severe on lush, overfertilized or thin, underfertilized turf



Apply lime if pH is <6


Mow to recommended heights


Stripe Smut Completed


Documents

Plant Diseases Chapter 4 Section VII of the Pest Bear & Affiliates Service Personnel Development Program 2005 Copyright @ 2005-2006, Central Fla Duplicating,