ID #1007

What is causing the dead or brown spots in my lawn?

From leatherjackets to Labradors—there are many reasons why you could see dead or brown spots appearing in your lawn. Fortunately, most of the problems, especially when caught early enough, can be fixed easily and the spots should disappear.

Consider if any of the following could be the cause behind your brown spots:

  • Crane Fly Larvae
    Crane flies look like giant mosquitoes and lay their eggs in the grass in the summer or early fall. The larvae can grow to an inch and a half long and are also known as “leatherjackets” due to their leathery brown skin. They munch on the roots of the grass, as well as the rest of the plant, and any damage to the lawn is usually seen in the spring. Birds can also damage the lawn then as they scratch looking for the larvae.

    Usually the grass is strong enough to overcome any damage done by a small number of larvae. If you suspect leatherjackets are dining in your yard, carefully dig out a patch of lawn about 12 inches square and two inches deep and count the number of larvae you see. If there are less than 25, your lawn will likely be able to overcome the stress of the larvae, but if there are more, you should consider treatment, such as beneficial nematodes or insecticide or renovating your lawn. One other way to help suppress crane flies is to stop watering your lawn after Labor Day. Get more information about what to do about leatherjackets munching your lawn.
  • Dry Spots
    Stick a screwdriver into the brown patch of grass to see if it’s harder than the green lawn next to it. If so, lack of moisture may be why the patch is brown. If your sprinkler isn’t obstructed in any way, then dryness could be caused by a number of reasons including the poor condition of the soil in that area, excessive thatch, or a fungal growth in the soil.
  • Fertilizer, Weed Killer & Gasoline
    Putting too much fertilizer on your lawn can often be more damaging than putting on too little or none at all. Excess fertilizer can cause brown spots or streaks, or can even cause a brown cast over the entire lawn. Fertilizer can also “burn” if it’s applied directly to wet grass and isn’t washed off right away.

    It’s very difficult to try to spray just the weeds in your lawn if you’re using a product like Roundup® that contains glyphosate, which will kill not just your weeds, but your grass, and most other plants, too. Also, if you’re using a sprayer that drips or you’re spraying on even a slightly breezy day, you can easily end up with not only dead weeds as planned, but a lot of brown, dead grass spots, too.

    If most of your dead spots occur where you normally fill your mower with gasoline, then the problem could simply be spilling excess gas on the lawn, as petroleum products can kill grass.
  • Dull Mower & High Spots
    A mower in poor condition or with a dull blade may tear or crease the grass instead of cutting it cleanly and the tips of the grass may fray and turn brown. Also, if your yard is bumpy or uneven you may have high spots where you continually scalp the grass shorter than in other areas, causing it to turn brown. Getting your mower tuned up and your blade sharpened and smoothing out the high and low spots in your yard could make a big difference!
  • Dogs
    If the brown spots in your lawn are surrounded by dark green rings, then a dog or dogs may be the cause. Dog urine has a high concentration of nitrogen and salts which can suck the moisture out of the grass blades causing them to turn brown. But the lower concentration of nitrogen found on the outer ring of the spot can actually help “green up” your lawn.

    Solutions to this ongoing problem are to encourage your dog to use an area of your yard that doesn’t have grass, or to immediately wash off the dog urine on the grass blades with water, which will also help dilute the salts and nitrogen concentration. Be very wary of products to feed your dog that claim to eliminate the brown spots in your lawn as these products may cause urinary system problems in your pet. According to the Colorado State Extension service, “There are no dietary supplements that have been scientifically proven to reduce either the incidence or severity of dog spotting in lawns.”

    Check out other Urban Legends about dog urine damaging lawns and what to do about it.

Tags: brown spots, crane fly larvae, crane fly maggots, dead spots, dog, dry spots, dull mower, fertilizer, gas, high spots, lawn problem, leatherjackets, weed killer

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