Fungi 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.
Nothing gets in the way of a gorgeous outdoor aesthetic like an abundance of spiderwebs. However, those spiderwebs on your grass might not actually be spiderwebs at all; they’re most likely some type of fungus. Unhealthy yards breed fungi, whether caused by overwatering, compacted soil, or over-fertilization, and many of these types of fungi bear an unsettling resemblance to spiderwebs.
Whether you’re dealing with spiders or fungi, though, they have to go. Luckily, any vetted lawn care specialist can tell you how to treat those pesky so-called spiderwebs, but proper identification is the first step. Here’s a look at four possible web-making fungi and solutions to help you get rid of them for good.
Mycelia are fungal threads that disappear as the day starts to get warm, but they reappear the next morning without fail. These tiny web-like threads may even have 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.
How to Treat Mycelium
Mycelium thrives on moisture, so make sure your lawn can completely 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.
Note: While mycelium is what often gives the appearance of spiderwebs on your lawn, other fungal lawn infections, like dollar spot or brown patch disease, can also lead to fungal mycelium. If you have multiple lawn infections, treat each one separately for the best chance of ridding your lawn of all of them.
2. Dollar Spot Fungus
The Clarireedia jacksonii fungus causes dollar spot, which takes its name from the obvious silver-dollar-sized tan patches it causes, often seen on golf courses. These patches range in size from 1 to 3 inches in diameter. On home lawns, spots may vary between 3 and 6 inches in diameter.
The size difference is due to mowing height and the width of the grass blades. Since golf courses have closely mowed turf, they tend to have smaller fungus patches, while yards with higher-cut grass will have larger ones.
Because of their round, randomly patchy appearance, these spots are commonly misidentified as grass damage from pet urine.
When dew is present, you might see what looks like spiderwebs growing on the dollar spot fungus patches, which is most likely the fungal mycelium. Causes of dollar spot include over- or under-watering, mowing grass too short, heavy thatch (the layer of dead grass and other organic material between the healthy grass and the soil), and poor lawn aeration.
How to Treat Dollar Spot Fungus
If dollar spot fungus has already taken hold of your lawn, the best solution is typically fungicide. Either a contact or penetrant fungicide will work here, though certain dollar spot fungi are resistant to the latter. A lawn treatment specialist near you can prescribe an exact treatment plan to knock out dollar spot fungus and mycelium.
So what can you do on your own? Simply put, practice good lawn maintenance to prevent the spread of dollar spot fungus. Minimize moisture with infrequent, early-morning waterings and apply nitrogen-based fertilizer at the start of the growing season.
3. Brown Spots on Lawn (Rhizoctonia Solani)
Large brown patches in the grass combined with early-morning web-like 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
Use fungicide on certain types of ryegrass or bentgrass, but always combine fungicide with methods to increase air circulation and proper water distribution to truly curb the spread of brown patch disease. Aerate your lawn if you have deeply-compacted soil, and dethatch your yard regularly.
Don’t over-fertilizer, either, as it’s important to avoid excess nitrogen in your yard, which can speed up the growth of fungal infections and kill your grass. As a matter of fact, refrain from applying any fertilizer when the disease is active. If you must fertilize for other reasons, avoid nitrogen-rich, water-soluble, and quick-release formulas.
Beyond using fungicides and increasing air circulation, treating this fungus is a waiting game. Lawns can recover from Rhizoctonia solani, but it takes time. Once you’ve cured your yard, prevent future outbreaks by fertilizing your lawn with a slow-release product when the humidity is below 86% and the temperature is consistently above 70 degrees Fahrenheit.
4. Pythium Blight
Pythium blight, also known as greasy spot or cottony blight, wreaks the 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, pythium blight has most likely infected your lawn.
How to Treat Pythium Blight
Pythium blight moves quickly, transforming from a minor nuisance to a lawn-threatening agent of chaos in no time at all. Your first step here is to contact a lawn care pro near you for some heavy-duty professional treatment.
What can you do on your own?
Aerate the soil and remove thatch from the lawn, taking time to clear up any drainage issues in your yard.
Block off infected areas from foot traffic (the fungus travels on shoes).
Wipe down everything that comes into contact with the area, including tools, your lawnmower, and shoes.
What to Do if You Have Actual Spiderwebs All Over Your Yard
Not all webs on grass are actually mycelium threads or a lawn fungus like pythium blight. 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 cone-shaped and more traditionally web-like. Mycelium vanishes as the day gets warmer, but spiderwebs remain until something breaks them.
Mostly, lawn spiders make their webs and hide in out-of-the-way locations where they eat pests that damage your yard. So, even if you're not fond 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 insect problem, contact a local lawn pest control specialist for guidance.
Mariel Loveland contributed to this piece.
Frequently Asked Questions
Grass spiders, also known as funnel-web spiders, are the culprits here, building small webs directly into the grass to catch any insects that have the misfortune of crawling too close. They are often confused with wolf spiders, as the two species look nearly identical, but grass spiders are actually great helpers in maintaining your lawn.
Nearly all spiders carry venom, so in that sense, yes, grass spiders are toxic. However, grass spider fangs are incredibly small, so it’s difficult for them to penetrate human skin. In other words, babies, older adults, and anyone with thinner-than-average skin are at risk of grass spider bites, which can cause itching, redness, and swelling. Grass spiders don’t like to tangle with humans, though, so any aggression on their part is usually for self-defense.
Spider mites don’t have too much in common with actual spiders, but these insects can absolutely destroy a lawn. Spider mites feed on grass roots and blades and are extremely effective at draining nutrients from plants, which can quickly kill grass. These mites are ravenous, so talk to a pest control pro at the first sign of spider mites in your lawn.