4 Types of Fungus That Look Like Spiderwebs on Your Grass (and Possible Solutions)

Mariel Loveland
Written by Mariel Loveland
Updated June 10, 2022
Cobwebs on grass
Photo: Sam Tanner Lees / 500px / Getty Images

Highlights

  • Fungus can look like spiderwebs on your grass. 

  • An unhealthy yard can breed fungi.

  • Remedies include proper lawn care, fungicide, and fertilizer. 

  • Call a pest control pro if you have actual spiderwebs all over your yard.

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Those spiderwebs on your grass probably aren’t actually spiderwebs at all—they’re most likely some type of fungus. An unhealthy yard can breed fungi, whether it’s caused by overwatering, compacted soil, improper mowing, or over-fertilization. 

The best course of action is usually ramping up your lawn care. The healthier your lawn, the less of an opportunity fungus has to grow. In some cases, fungicide can help a persistent fungal disease.

A local lawn treatment pro should be able to tell you how to treat those pesky so-called spiderwebs all over your yard, but identification is the first step. Here’s what might be the problem.

1. Mycelium

Mycelium is a type of fungal growth that disappears as the day starts to get warm—but it will reappear without fail. It looks like tiny threads, and you may even notice some mushrooms growing out of the affected area. If you only see “spiderwebs” on your grass in the morning, there’s a good chance you’re looking at mycelium. So, how do you treat it?

How to Treat Mycelium

Mycelium thrives on moisture, so you want to give your lawn the best chance to dry out during the day. Water your lawn in the early morning, and make sure you’re using the correct amount of water for your yard. Bag your grass clippings rather than allowing them to decompose on your lawn (this also traps moisture). Don’t walk through the infected grass, which could spread the fungus to another area of your lawn.

2. Dollar Spot Fungus

Dollar spot fungus takes its name from the obvious silver dollar-sized tan patches it causes, specifically on golf courses. On home lawns, spots vary between 3 and 6 inches in diameter, and their size is determined by mowing height and the width of the grass blades.

Because of their round, randomly patchy appearance, these spots are commonly misidentified as damage from pet urine. But if you've got mycelium and these round patches, you've most likely got dollar spot fungus. Causes of this fungal lawn pathogen include over- or under-watering, mowing too short, heavy thatch, and poor lawn aeration. 

How to Treat Dollar Spot Fungus

If dollar spot fungus has already taken hold of your lawn, the best course of action is typically fungicide. Either a contact or penetrant fungicide can work, though certain dollar spot fungi may be resistant to the latter. A lawn care specialist should be able to prescribe an exact treatment plan. 

To prevent the spread, practice good lawn maintenance. You’ll want to minimize moisture with infrequent, early-morning waterings. Since infections usually develop during the growing season, applying nitrogen-based fertilizer at the start of the season can help keep dollar spot fungus at bay

3. Brown Spots on Lawn (Rhizoctonia Solani)

Large brown patches in the grass combined with early morning mycelium is a sure sign of Rhizoctonia solani. This fungal pathogen—which causes both large patch disease and brown patch disease—has near-identical strains that attack different grass species.

How can you tell the difference?

  • Brown patch disease, which is most infectious in hot, humid weather, creates discolored patches that are 3 feet or smaller in diameter.

  • Large patch disease, which is active in cooler conditions, can cause dead brown areas of up to 15 feet in diameter.

Both of these fungal lawn diseases are the result of over-watering and over-fertilizing. 

How to Treat Rhizoctonia Solani

You can use a fungicide on certain types of ryegrass or bentgrass, but the best way to treat brown patch or large patch disease is typically by increasing air circulation and watering properly. 

Aerate your lawn (especially if you’re dealing with compacted soil) and dethatch regularly. It’s also important to avoid excess nitrogen since this disease is often caused by over-fertilization. While the disease persists, don’t apply any fertilizer—especially if it’s nitrogen-rich, water-soluble, or quick-release fertilizer.

Rhizoctonia solani is a waiting game. With great lawn care, your lawn will recover, but it takes time. Prevent disease in the future by only fertilizing your lawn with a slow-release product when the humidity is below 86% and the temperature is consistently above 70 degrees Fahrenheit.

Cobwebs covered in dew
Photo: Cavan Images / Cavan / Getty Images

4. Pythium Blight

Pythium blight, also known as greasy spot or cottony blight, wreaks most havoc in hot weather and high humidity. This pathogen attacks lawns that have compacted soils and poor drainage. This disease progresses quickly and can decimate your lawn in just 24 hours. 

If you have what appear to be spiderwebs in your lawn in the early morning and the grass suddenly develops small, sunken, slimy spots up to 1 foot in diameter, your lawn is most likely infected with pythium blight. 

How to Treat Pythium Blight

Your best course of action will depend on the type of grass you have. Pythium blight can progress quickly, so contacting a local lawn care pro as soon as possible is essential. 

You can and should correct drainage issues, aerate to relieve compacted soil, and work to build good soil health for a robust, lush, green lawn that isn't as susceptible to pathogens.

What to Do if You Have Actual Spider Webs All Over Your Yard

Not all “cobwebs” on grass are actually mycelium—sometimes you do get actual spiderwebs on grass. Unless you have a significant infestation, which is rare, it's unlikely you'll even notice them.

There are a few telltale visual differences between mycelium and spiderwebs on the lawn. Mycelium has a more fluffy, cottony appearance, whereas lawn spiderwebs are conical and more traditionally web-like. Mycelium vanishes as the day gets warmer, but spiderwebs remain until something breaks their delicate filaments. 

Mostly, lawn spiders make their webs and hide in out-of-the-way locations where they eat the insect pests that damage your yard. So, even if you're a little bit scared of spiders, remember that they'll help you with your lawn maintenance. 

However, if you're concerned that your lawn has a serious spider or other insect problem, contact a local lawn pest control specialist for guidance.

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