T urf Disease By Season IDENTIFICATION
Causes ses Of T urfgras grass Dis iseas ease e & I Introd oduct uctor ory y Definiti finitions ons The most important cause of an infectious abnormality on turf that either kills the plant or destroys it’s aesthetic value is a Path thogen. ogen. Most pathogens are parasites that obtain nutrients from a host. Obli ligat gate Parasit rasites s survive only on a live host or living tissue. Saprophyte ophyte Parasit rasites s survive only on dead organic matter. Organisms that are mostly obligate but can live under certain conditions as saprophytes are classified as Facul ulat ative ive Sap aprophytes. phytes. Organisms that live most of the time as saprophytes but that can, on occasion, become obligate are classified as Facula ulative tive Oblig bligat ates. es.
The he D Diseas ease e T Triangle gle In order for disease to occur three conditions are necessary (1) A susceptible host (2) An active pathogen (3) Favorable environment If any of the three conditions are missing, disease will not develop Diseas ease e Progresses ogresses In 4 Stag ages 1. A disease pathogen enters the plant. 2. The pathogen inhibits it’s host without producing visible symptoms. 3. The interaction between pathogen & susceptible host. 4. Stage when pathogen reproduces for self-preservation.
Snow Mold Snow Mold Early March
Snow Mold d affects all cool season turf grass species in areas where there are extended periods of snow cover. In areas without prolonged snow cover Snow Mold damage is mostly cosmetic and will recover once the turf begins actively growing. Infection and disease progress is favored by cold (32 -36 degrees F) wet conditions. Extended periods of snow cover provide ideal conditions for establishment and spread. On taller mown turf, matted grass blades provide a similar insulating environment, but outbreaks normally are not severe without prolonged snow cover.
Snow Mold Recovery FIRS RST T WEEK K OF MARC RCH 10 DAYS S LATE TER
Red Thread The New Spring Scourge
Red d Thread ad in recent years has become one of the most troublesome late spring diseases affecting ryegrass & fine fescues in particular. Optimum weather conditions for development are air temperatures in the 68 to 75 degree ranges in conjunction with prolonged wet conditions and extended long dew periods. Symptoms initially appear as small (3 to 8”) circular patches of off - colored turf with a pinkish cast. Inspection of the leaf blade reveals red threads growing from the blade tip These threads are structures called scle leroti otia that enable the fungus to survive in the turf and upper layers of soil. The disease may spread by water or mechanically transmitted from lawn by infected mower blades.
Cult ltural ural M Managem ement ent O Of R Red ed T Thr hrea ead Normally maintaining adequate nutrient levels, especially nitrogen, would control the incidence and severity of the disease. However in recent years we have seen increasing pressure from red thread even on high maintenance properties with proper nutrient levels. Fertilize on a timely program to maintain proper nutrient levels Use a controlled release nitrogen source to avoid spikes and lulls. Do not irrigate late in the day which can leave the grass blade wet overnight. Disinfect mower blades with isopropyl alcohol and clean underside of mower deck whenever possible after cutting a highly infected lawn.
Chemica cal l Control ol F For R Red T Thread Due to the favorable weather conditions during mid spring when cool season turf is at it’s finest , a preventative red thread program is usually not employed. However in recent years the incidence and severity of a once easily controlled aesthetic disease has become a serious early season problem to many LCO’s. Recent research has shown excellent control using the Strobilurin chemical class that are labeled for residential turf such as Insignia (pyraclostrobin) Compass (trifloxystrobin) Headway (azoxystrobin + propiconazole) Other options include the DMI chemical class such as Banner Maxx (propiconazole) & Bayleton (triadimefon) As well as the Benzimidazole class containing only Clearys 3336 (thiophanate methyl) that is labeled for residential.
Necr croti otic c R Ring ing S Spot ot
Necr crot otic ic Rin ing g Spot as well as Summer Patch have been for years mistakenly classified as Fusarium Blight. Necrotic Ring Spot can occur midspring and again in early fall affecting established turf that is 2 to 5 years old and especially sod since Kentucky Bluegrass is one of the most susceptible species. The pathogen survives as dormant mycelium in infected turf and thatch and becomes active during cool wet periods in the spring. Symptoms begin as scattered light green patches 1 to 3 inches in diameter and then may grow to a foot or two turning dull tan to reddish brown. Larger patches may exhibit a frogs eye pattern with an apparently healthy green patch of grass that is partially or completely surrounded by a ring or crescent of dead turf. Diagnosis by leaf lesion is very difficult with NRS since they may not be present and if so not distinct.
Cult ltural ural C Control l O Of N Nec ecrotic tic R Ring Spot Sp Maintain thatch levels with scheduled aeration programs built into your yearly contracts with fall being the optimum window. Excessive thatch will benefit with an aeration in both spring & fall. Irrigation schedules should be set up to encourage deep rooting. Water deeply and infrequently to promote a healthy root mass. Disease conditions increase as mowing heights decrease. Maintain 2 ½ to 3 inches through the growing season without cutting more than one third of grass blade with any one mowing. Always apply a high quality controlled release nitrogen source to inhibit surge growth that weakens root mass.
Che hemica cal l C Control l O Of N Nec ecrotic tic R Ring S Spo pot Preventative fungicide applications for NRS are difficult without a previous history of disease prone turf Initial symptoms can be mistakenly overlooked in the spring due to favorable growing conditions that can mask a shallow root system caused by the disease. Once stressful weather conditions appear the symptoms become much more evident. Curative controls include Headway (Azoxy+Propiconazole) Banner Maxx (Propiconazole) Note that the DMI chemical class at high rates can slow down plant growth resulting in slower recovery. Eagle (Myclobutanil) is one fungicide in the DMI class that claims minimal side effects on plant growth. Systemic fungicides used on NRS should be watered in before they dry so the material has a chance to get to the shallow root zone.
Dollar Spot
Dolla lar r S Spot on residential turf normally begins to appear as weather conditions progress from late spring (cool and wet) to early to mid summer (hot and humid) conditions. It is not uncommon to have initial outbreaks occur in the same areas that experienced red thread pressure earlier due to the weakening of the plant. First stages begin as small spots of blighted turf that develop into circular straw colored areas 2 to 3 inches in diameter. When dew is present a white co-webby growth of mycelium may be seen in the affected areas. On residential cut turf these areas may be much larger and irregular and range from 6 to 12 feet in diameter. Upon close inspection an hourglass effect will be present towards the middle of the blade with thin brownish lesions at both ends of the hourglass.
Doll llar r S Spo pot P Progresse ressed d S Stage
Doll llar r S Spo pot
Mycelium Path thogen ogen Transp anspor orte ter
Cult ltural ural M Manageme ement nt Of D Doll llar Sp Spot Maintaining adequate nutrient levels will generally check severe outbreaks of the disease. Studies have shown that the dollar spot pathogen is a very weak parasite that primarily attacks the older yellowing leaves of the plant as compared to the younger vigorously growing green leaves. Therefore by providing consistent nutrient levels using a high quality slow release nitrogen source young growth will be encouraged while minimizing the aged leaves that serve as a food base for the disease. Mow at the recommended height of 2 ½ to 3 inches frequently enough so that no more than 1/3 of the leave blade is removed at any one time. Avoid irrigating at any time that will leave the grass blade wet overnight encouraging transmission of fungal mycelium.
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