December 05, 2018 | Grass Seed

Pythium Blight Fungus in Turf: Control & Treatment

Pythium Blight Fungus in Turf: Control & Treatment

You can observe symptoms of this grass disease in many places – on golf greens, in lawns and so on because like many other spores, pythium’s ones can travel too. Symptoms of Pythium blight get apparent during humid, warm weather exactly when turf grass is wet for about 12 hours. The given disease is especially severe when daytime temperatures surpass 28°C and night ones don’t go below 20°C. The first symptoms include dark green to purple leaves aggregating into irregularly shaped or circular patches in turfgrass.  These patches can be 1-20 cm in diameter. There aren’t any distinct lesions on infected leaves. Patches of infected turf grass are capable of enlarging and coalescing, inflicting serious damage to golf courses, lawns, athletic field turf, etc.

What is pythium?

Pythium actually belongs to a group of organisms dubbed “oomycetes.”  Despite having much in common with fungi, Pythium, as well as other oomycete pathogens, act differently from fungi, therefore they need alternative methods of control.

Pythium aphanidermatum turns out to be the key species associated with Pythium blight in America. However, fifteen other species of this organism have been associated exactly with foliar blight symptoms.

Pythium life cycle

Pythium aphanidermatum, as well as other species of these organisms, survive mostly as oospores in turfgrass root zones and also thatch. However, as vegetative mycelium, they can be found in turfgrass leaves as well as roots. Under good conditions, mycelium is able to proceed with its surge, infecting a grass plant in a couple of hours. Apparently, infection of turfgrass leaves takes place via direct penetration from vegetative zoospores or hyphae.  Zoospores need free water for moving and infecting other turfgrass plants. Moreover, Pythium species are capable of spreading to other adjacent susceptible plants via mycelial surge. The infected material, such as thatch and soil can spread this stuff when moved to other areas.

Pythium blight appreciates wet weather and temperatures 13 – 18°C. However, it demonstrates the maximum severity in cloudy, rainy or humid weather, with temperatures 30-35°C. The highest frequency of foliar infection takes place under the circumstances of prolonged leaf wetness and high relative humidity.

High soil salinity turns out to be another factor, which favors pythium blight. The development of standing water greatly contributes to the spread of these organisms. High levels of nitrogen fertilization are able to enhance its severity by simply making a lush turf canopy. A calcium deficiency favors  pythium blight too.

Pythium disease treatment

Of course, like many other homeowners, you’re also eager to know how to get rid of Pythium. We’ve come up with a bunch of great tips. They will help you to effectively control this disease in many ways.

Pythium blight control: cultural practices

Cultural practices can be effectively employed with the aim of promoting an environment where the infection is limited by Pythium species. Irrigation appears to be a crucial cultural practice to closely watch this disease. It’s recommended to have your lawn watered early in the day. Thus, you will enable your grass blades to dry. It will diminish the likelihood of leaves staying wet overnight.

Providing good surface as well as subsurface drainage when creating new turfgrass sites, and also renovating areas where water can accumulate in established turf grass areas happen to be other crucial steps in Pythium blight control.

Other crucial management practices include getting rid of thatch. Thus, you’ll improve drainage, diminish drought as well s nutrient stresses on turf. What’s more, you’ll remove the sources of this disease.

A well-balanced system of turfgrass nutrition appears to be a key to controlling this disease. Excessive fertilization during hot times and nitrogen applications can worsen the disease severity. You require strictly monitoring the level of nitrogen applied to your lawn. It shouldn’t exceed 25 kilograms of nitrogen per ha in hot weather.

When employing nitrogen-based fertilizers, you’d better utilize slow-release sources. Alternatively, you can spoon-feed your grass with minor foliar applications of fertilizer in summer or spring when occurrence of this disease is most probable.

Besides this, it’s also crucial to avoid calcium deficiency. You require maintaining a bit acidic soil pH. By providing substantial airflow across golf greens as well as other areas of turf by pruning shrubs and trees you will ensure light penetration and also ramp up air movement, facilitating drying of the turfgrass foliage.

When mowing, stay away from areas of wet turf, with the temperature of more than 21°C. You need to wash your mowing equipment before you enter unaffected areas. Thus, you’ll minimize the spread of this disease in your lawn.

Chemical control: best fungicide

In terms of chemical control, you can effectively utilize fungicides against pythium blight. To be exact, you can use the following:

  • Dithiocarbamates
  • Aromatic hydrocarbons
  • Quinone outside inhibitors
  • Phosphonates
  • Carbamates
  • Phenylamides
  • Quinone inside inhibitors

Fungicides belonging to different chemical groups need to be combined or alternated within a control program to tame the further development of resistant populations of these organisms. By simply alternating between contact and systemic fungicides might postpone resistance development.


Pythium blight, alternatively dubbed “grease spot”, “cottony blight”, or “spot blight” was first reported in the previous century. To be exact, the first reports emerged in the 1930s. However, the given disease wasn’t officially recognized as an issue in some parts of the United States until 1954. Initially, it was considered to be just a disease of golf courses. However, it’s currently recognized as an issue of lawns as well as athletic fields.

The first fungicides employed to control it were dichlone, organic mercury compounds, captan, inorganic mercury, and cycloheximide. However, these fungicides were unable to ensure complete control of the disease. Metalaxyl appeared to be the first systemic fungicide employed specifically against pythium as well as downy mildew pathogens. It took place in 1979. Later isolates of P. ultimum from turfgrass plants and greenhouse-grown ornamentals have been discovered to exhibit the resistance of this disease to mefenoxam. It helped to create more advanced fungicides.