Fungus: The Boogey Man of Lawns - Scary, Invisible and Mostly Your Imagination


By Rick Orr
St Augustine lawn

Fungus: Often Accused Rarely Guilty

So many times I have heard "I have brown spots in my lawn, it must be a fungus". No, it's not a fungus, it's probably something else. Why? Fungi are such pathetic weak pathogens,  what little damage they do is cosmetic, sub-lethal, and temporary. Fungi are not invisible ninjas, moving silently in the shadows killing your lawn. Fungi are as delicate as a snowflake, so fragile, that they can be stopped by a puff of air or a ray of sunlight.

If Fungi are Harmless, Why All the Fungicides?

Golf courses and marketing drive the promotion of fungicides. A fungus on a golf green will cause an uneven putting surface and an ugly blotch on the green. Fungicides keep the green smooth and appealing. That same fungus on a St Augustine lawn mowed at 4" is barely even noticed, much less a reason for concern. But fungicide makers have learned that the homeowner is willing to buy fungicides to rid their lawn of the boogeyman - fungus.

Fungi and Your Lawn

Fungi must have perfect conditions to damage your lawn. Whatever those perfect conditions are, as soon as the conditions change - i.e. the sun rises, the wind blows, or leaves dry - the fungus is dead. It is no longer viable. It cannot damage your lawn any longer. Most fungi can do little more than damage a few leaves which are replaced by the grass plants within days. The average homeowner is more likely to mistake water stress for a fungus problem and think a fungus problem is normal.

Fungi are Beneficial

Fungi are part of the soil microbial community and are necessary for the enzymatic digestion of organic materials - composting. Their job as microbes in the soil is to digest dead dying tissue and recycle it into plant food. Under certain conditions - usually very temporary conditions - fungi can attack living tissue. But only while conditions remain perfect. St Augustine turf has few problems with fungus and the few that can cause problems are weak, sub-lethal, and temporary. There is no need to constantly treat fungus in a St Augustine lawn - it does more harm to the ecosystem of the soil than good for the grass.

Some Fungi are Worse than Others

In Pinellas, brown patch is the worse. Brown patch can cause "crop circles" in a St Augustine lawn that are quite ugly. It only occurs during specific weather conditions - the moist cool nights of fall and spring. Prevention is nearly impossible, curative treatments help to reduce damage and the lawn will recover and look great in a week. But even as ugly as brown patch is, it is not a lethal threat that will kill your lawn. It is merely ugly. A temporary ugliness.

You Got a Fungus - We got a Cure, for a Price

Many of the larger lawn spraying companies, like Trugreen,  sell fungicide as an add-on to their regular service. They have learned what the fungicide makers already knew - homeowners will buy fungicides to get rid of the boogeyman in their lawn. It's magical -  you had a fungus, we sprayed it and it went away. But in practice applying fungicides to a St Augustine lawn is very profitable to cure a minor problem that would have gone away with the change in the weather - anyway.

My Lawn is Sick, I'll Give it some Medicine

Many homeowners want to cure what ails the lawn by giving it a shot of medicine. The fact is diseases caused by fungi are minor, insignificant, and temporary problems in a St Augustine lawn. Save yourself some time and money and avoid fungicides as a cure for what ails your lawn. If you want to spend time and money to cure what ails your lawn, upgrade the irrigation system and buy a mower that will mow a lawn at 4". A better irrigation system and mowing at 4"  will have a greater positive impact on your lawn than the most expensive fungicide.

Rick Orr Owner-Staff Agronomist Barefoot Grassl/Creator of ILOVETURF.COM
Staff Agronomist at Barefoot Grass

Since 1995, Rick Orr has worked in Pinellas County providing turf management and pest control. Rick Orr is a graduate of VA Tech in Agronomy (Turf Ecology) and the creator of 

Since graduating from VA Tech in 1979, Rick worked in the green industry, mostly with golf courses, resorts, and large communities. Rick has obtained certifications in arboriculture, landscape, irrigation, and taught Environmental Horticulture at St Petersburg College. 

Currently, Rick is the Staff Agronomist at Barefoot Grass in Largo, FL. To learn more about Barefoot Grass Free Price Quote from Barefoot Grass for Home Pest Control and/or Lawn Care 

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