Dollar Spot Fungus: Cause, Treatment, and Prevention


What Causes Dollar Spot Fungus?

Also known as Sclerotinia homoeocarpa, the dollar spot is a fungus that is always around and ready to spread. Dollar spot is a disease that affects both warm- and cold-weather grass. Though, in a strange twist, this fungus is more common on well-looked after commercial and domestic lawns than in the wilderness.

Dollar Spot Seasons

The ideal conditions for dew are when the mornings are cool (above freezing) and damp. Dew forms when warmer humid air condensates onto the cooler turf. Dollar spot flourishes on this water sitting on the leaves and when the days are warm, between 60 – 70°F (15 – 21°C).

The most active period for dollar spot is from the middle of spring to the middle of fall, though this will vary with climate zones. Irrigation, plastic sheeting, and other artificial means of controlling the temperature and moisture of the lawn can recreate the same seasonal growing conditions for the fungus.

Why Is It Moving Across My Lawn?

The dollar spot fungus can be active and waiting on the tips of grass. Mowing weakens the grass and opens a path for the fungus to make its way in. The remaining cuttings will carry the fungus up into the mower, which will then spread the fungus across the whole lawn.

The cut grass also struggles further as it needs to use stored energy as it tries to grow the tips back. If the weather is windy or wet, cut leaves get blown around, there the rain then transmits the fungus from the dead grass to the turf.

A golf cart’s wheels are another efficient way of spreading the disease. Golf carts are often driven over dollar spots, which are then transferred to the tires, then to the tire tracks on the turf.

The weight of a golf cart also puts extra stress on the grass-weakening its immunity and making it easier to infect. Even the constant traffic of golfing shoes is enough to spread the fungus around a course.

Identification: What Are Some Indicators of the Dollar Spot?

The dollar spot fungus begins on the leaves of grass during periods when morning dew forms and the low sun is not adequate to evaporate the water. As the fungus feeds off the dew, it creeps from one blade of grass to another in a white web.

These webs consist of hypha, a thread-like fungus, which is collectively known as mycelium or mold. Webs are easy to spot when dew clings to them, but smaller webs are harder to catch.

An infection will settle into the tips of your cut grass, and as it eats and grows, webs of fungus will continue to spread across your lawn.

Simple Signs of Dollar Spot

If you do not see a cotton-like web, it can be because there is not enough twinkling dew to highlight it, or the web was cut away by a lawnmower. But when your lawn is infected, it will develop one- to three-inch diameter discolored patches.

These fungus patches are irregular in shape, about the size of a tennis ball, and can connect to a neighboring patch or jump to other areas of your lawn. Infected grass starts by discoloring to a reddish-brown to tan at the tips.

The infected area will expand and grow from a small tan spot to a white or yellow patch, which is sometimes in the shape of an hourglass.

Is it Dollar Spot or a Brown Patch?

Brown patches on lawns are inevitable and are caused by pet urine, extreme weather, insects, and a range of other reasons. But most brown patches from other triggers are either in larger forms or located over fewer but far more separated locations.

Dollar spot is a fungus that tends to grow near other dollar spots and will start showing up at the tips of the leaves. The size of each spot is around that of a saucer or smaller, and the spots tend to grow in number but not size.

Should I Treat Dollar Spot?

Dollar spot fungus will kill the grass if it gets down to the roots, but you should get a fair warning before it develops that far. This disease can and will kill turf if given the resources and the time.

To some, a dollar spot can look like a seasonal fungus that comes and goes as the wind blows. The mistake is to think that if you leave it alone, the dry air of the summer or the cold of the winter will kill it off.

The main problem with dollar spot is that it is hard to tell how far it has spread until the grass discolors. By this point, you may have spread the virus around every part of your lawn by doing what you thought was good maintenance.

Can I Ignore Dollar Spot?

You can ignore the fungus, and it may shrink in the winter, but you cannot rely on the dollar spot to go away on its own.

This disease will come back, either from dormant spores left from an earlier season or carried from a bird for nest making. But is hard to know how deep the fungus has crept without closer inspection.

If the fungus reaches too deep, it will permanently scar the lawn, which will then need reseeding or new sod. Also, the deeper the fungus gets, the further it can spread undetected and the harder it is to kill.

How to Get Rid of Dollar Spot Fungus

Once the fungus has made a home for itself on your grass, it will become harder by the minute to stop it. You should try to verify that it is dollar spot fungus, find the proper action, and kill it off as fast as possible.

Materials

Step-by-Step Guide

  1. Measure – Start by working out the square footage of your lawn. You will need the surface area so that you can buy an approximate amount of product to cover all the grass. You will need around two fluid ounces of fungicide per 1,000 square feet.
  2. Aerate – A few laps of your lawn in aerator shoes will boost the oxygen to the roots, dry out the soil, and allow fungicide to get in beneath the turf.
  3. Prepare for Dispersal – If you are using a liquid fungicide, you need to mix the solution in the sprayer with the right amount of water. For granule fungicide, you need to pour the pellets into the disperser.
  4. Application – Wear gloves and a respirator when spraying liquid fungicide. Spray in a fan-like motion as you walk over your lawn. You should be able to see the fungicide glistening on the leaves when you are done.
  5. Trouble Spots – It is worth spending a bit more time on areas with an excessive number of patches. Shaded areas and dips in the turf will be combating low immunity and puddling, so try to give those places more attention with a hand spray bottle.
  6. Reapplication – Wait at least two weeks before going back over your turf with the sprayer. If it looks like a brand of fungicide is not working, switch to another make.

How to Prevent Dollar Spot Fungus

As with many turf diseases, it is possible to reduce or end the need for a rescue mission if you take the correct measures. Dollar spot has weaknesses, and the many methods of prevention are simple and inexpensive.

Fertilize

Be serious about fertilizing your lawn. Grass relies on nutrients and nitrogen to support its immunity and to grow back from the damage caused by foot traffic, mowing, and the weather.

Too much nitrogen is bad since this can burn the grass, again weakening it and leaving it open to infection. Short root grasses suffer more from a lack of water and nutrients, so you need to pay even more attention to what you feed your grass.

Rake

Warm weather grasses can develop a lot of thatch. But mowing is enough to cause a build-up of dead grass around your lawn, which makes a perfect breeding ground for a dollar spot fungus to survive.

Rake any dead leaves, grass, and sticks away. Anything blocking the sunlight from hitting the turf robs the grass of the energy it needs to fight disease and prevent it from perishing.

Mow

Stay within the ideal cutting height for your grass. Most grass prefers a cut of between two and four inches, but the cutting setting can be set to below one inch on sports pitches. Short grass often struggles more with low immunity.

Aerate

Aerating shoes help both the roots and the tips of the grass. These spiked shoes poke holes a few inches into the soil as you walk around, opening channels for air to reach the roots. This process also improves drainage and prevents irrigation water from pooling on the surface.

Test

Use a lawn tester kit to help you get the water, the pH, and the fertilizer levels right in the soil. A poor combination of these three will allow dollar spot fungus to attack your grass in its weakest state.

Other Remedies

Avoid using home remedies since these can end up doing more harm. Vinegar, salt, and bleach will all alter the pH levels of the soil, burn the grass, and make it harder to pinpoint dollar spots.

Stick to using commercial products when dealing with fungus infestations such as dollar spots.

Graham Walsh

I want to share everything I know about home improvement in order to help you. Whether you're a home enthusiast or an industry professional, I have the information that you need.

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