DISEASE

Disease Triangle 
Turfgrasses are susceptible
to more than 70 diseases, which develop from an interaction between a susceptible plant (host), a disease-causing organism (pathogen),
and an environment that favors the pathogen to infect and incite disease in the host
Disease Management Triangle
Disease management may also be conceptualized as a triangle. Following proper diagnosis, plant diseases may be managed or controlled by manipulating the host, the pathogens and / or the environmental conditions. Hosts may be manipulated by replacing a susceptible turfgrass species or cultivar with a resistant alternative

Hosts:
• All cool season turfgrasses.
• Bentgrass, annual bluegrass and perennial ryegrass are particularly susceptible

Diagnosis:
• Circular straw-colored patches of turf usually less than 10 inches in diameter, evident after snow-melt
• Orange, brown to black sclerotia form on leaves

Environment:
• Snow-cover is required for disease development
• Disease is severe when snow-cover exceeds 90 days

Cultural Controls:
• Avoid a fertility program that results in lush, fast-growing turf in late fall and winter
• Maintain potassium levels according to soil tests
• Use snow fence, hedges or knolls to prevent snow from accumulating excessively on turf
• Use dark-colored organic fertilizers or composts to melt snow in spring
• Physically remove snow in spring
• Prevent compaction of snow during winter
Hosts:
• Bermudagrass

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.

Environment:
• Disease is severe where average daily temperature in November is < 60°F (16°C).
• Poor surface and subsurface drainage
• Thatch > 1/2 inch think

Cultural Controls:
• Disease is more severe on soils low in potassium and on turf that receives excess nitrogen during late summer and fall.
• Maintain balanced fertility throughout the growing season.
• Maintain moderate to high levels of phosphorus, potassium and minor elements according to soil test.
• Improve surface and sub-surface drainage
• Limit thatch thickness
Hosts:
• Creeping bentgrass and annual bluegrass

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

Environment:
• Temperatures of 68° - 86°F (20° - 30°C)
• Disease is severe on turf subjected to drought stress, low mowing, shade or poor air circulation

Cultural Controls:
• Disease is more severe under low nitrogen conditions
• Maintain balanced fertility throughout the growing season
• Reduce shade and increase air circulation
• Mow at recommended height
• Avoid drought stress
• Avoid irrigation in late afternoon or in evening prior to midnight
Hosts:
• All common species of turfgrasses 

Diagnosis:
• Can be difficult to diagnose; microscopic examination of roots and crowns may be necessary
• Symptoms resemble other patch diseases or dormant turf
• Slow return from dormancy in the spring
• Later spring symptoms include patchy turf with yellowish-orange to reddish-brown discoloration
• Fall patches can be quite obvious with chlorotic tan and brown coloration

Environment:
• Daytime temperatures from 50° - 70°F (10° - 21°C) and
   nighttime temperatures from 45° - 55°F (7° - 13°C)
• Cool, wet weather
• Poor drainage and excessive irrigation
• Critical times for disease: early spring after snow melts and late autumn
• Highly maintained turf most susceptible

Cultural Controls:
• Improve drainage and do not overwater
• Promote good air circulation
• Increase mowing height
Hosts:
• Kentucky bluegrass, fine-leaf fescue and bermudagrass

Diagnosis:
• White, powdery masses of fungal spores scattered over surface of leaves
 
Environment:
• Disease is severe in shaded areas at temperatures of 60° - 72°F (15° - 22°C)
• High humidity is required for infection, but leaf wetness is not essential

Cultural Controls:
• Disease is more severe under excess nitrogen conditions
• Maintain balanced fertility throughout the growing season
• Reduce shade and increase air circulation
• Plant shade tolerant cultivars and species
Hosts:
• All cool season turfgrass
• Bentgrass, annual bluegrass and perennial ryegrass are particularly susceptible

Diagnosis:
• Salmon colored to red-brown patches of turf 1 to 8 inches or more in diameter; common after 60 days or more of snow cover

Environment:
• Disease is common after at least 60 days of snow cover, but pathogen can infect turf in absence of snow
• Disease is particularly severe when snow covers unfrozen ground

Cultural Controls:
• Disease is more severe on fast-growing, lush turf that receives high nitrogen and low potassium in late fall
• Maintain balanced fertility
• Use snow fence, shrubs or knolls as wind-breaks to prevent excess snow from accumulating
• Prevent snow compaction by machinery or skiers
• Melt snow in spring with organic fertilizers
• Physically remove snow in spring
• After snow melts, to prevent Fusarium Patch, decrease shade and increase air circulation to enhance drying of turf; avoid application of lime if possible
• Avoid irrigation in late afternoon or in evening prior to midnight
• Mow at recommended height
Hosts:
• Bluegrass, bentgrass, fescue, perennial, ryegrass, bahiagrass, bermudagrass, zoysia and buffalograss

Diagnosis:
• Round to oval chocolate-brown spots on leaves
• Spots may have tan centers

Environment:
• Temperatures of 77° - 95°F (25° - 35°C)
• Disease severity increases with increase in temperature
• More than 10 hrs. of leaf wetness per day for several days

Cultural Controls:
• Disease is more severe under excess nitrogen conditions
• Maintain balanced fertility throughout the growing season
• Reduce shade and increase air circulation
• Avoid irrigation in late afternoon or in evening prior to midnight
• Limit thatch thickness
• Mow at recommended height
• Use light-weight mowing equipment to reduce stress
• Plant resistant cultivars
Hosts:
• Only bentgrasses are highly susceptible

Diagnosis:
• Wilted to bronze or brown circular patches of turf up to several feet in diameter
• Roots along margins of patches are dark brown

Environment:
• Disease develops rapidly on cool, wet soils with pH > 5.5
• Disease can be more severe on sandy soils

Cultural 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 levels of phosphorus. potassium and minor elements according to soil tests
• Improve surface and subsurface drainage
• Avoid use of lime if pH > 5.0
• Avoid heavy, frequent irrigation

Get FREE estimates treatment for your lawn! 
Call 248-475-0989.

Our licensed and experienced team undergoes continuous training to keep up with the latest disease control methods.

Share by: