Your lawn, which was green, thick, and healthy last year, is now covered with yellow patches. Why, and what can you do about it? There are several potential reasons for this fading. The first thing to do when you notice yellow spots on your lawn is to call your Nutrite Expert to diagnose the problem so that appropriate actions can be taken immediately.

Why is my lawn turning yellow?

The most common causes leading to grass turf discolouration are disease, pests, environmental conditions, and inadequate lawn care. Although it can be alarming to see your lawn turn yellow, remember that “yellow” does not necessarily mean “dead”—your lawn can be dormant. Dormancy is a protection system that ensures the survival of your lawn when it is under significant stress, such as drought. Therefore, you will be able to save it once you choose the appropriate treatments.
A lawn scattered with yellow grass patches
A lawn scattered with yellow grass patches

Diseases causing yellow grass patches

In Quebec, there are no registered products to treat fungal diseases on residential lawns. Proper care of your lawn will ensure a healthy lawn.

Dollar spot

Signs

Clusters of small, round, sunken patches of yellow-coloured grass about the size of a silver coin will show up on your lawn. White mycelium, which looks like spider’s webs, can also be seen on the lawn in the early morning.

Solutions

  • Sharpen your mower blade and set the mowing height to 3 inches.
  • Where allowed by regulation, water the lawn in the morning (between 5:00 a.m. and 8:00 a.m.) rather than in the evening or at night.
  • Collect clippings to prevent the spread of the disease.
  • Aerate the lawn.
  • Fertilize the lawn with a nitrogen-rich fertilizer.

Red thread

Signs

Small red or pinkish threads appear on the tip of the grass blades as the nights are getting colder. This is a disease that affects the lawn damaged by the blade of your mower.

Solutions

  • Sharpen your mower blade and set the mowing height to 3 inches.
  • Where allowed by regulation, water the lawn in the morning (between 5:00 a.m. and 8:00 a.m.) rather than in the evening or at night.
  • Collect clippings to prevent the spread of the disease.
  • Aerate the lawn to decompact the soil.
  • Fertilize the lawn.

Leaf blight

Signs

This disease affects the leaves, crown, and roots of the turf and gives it a yellow colour. You may notice small dry yellow pathways caused by this disease as early as the beginning of spring.

Solutions

  • Sharpen your mower blade and set the mowing height to 3 inches.
  • Where allowed by regulation, water the lawn in the morning (between 5:00 a.m. and 8:00 a.m.) rather than in the evening or at night.
  • Ensure good drainage, the lawn must dry.
  • Collect clippings to prevent the spread of the disease.
  • Limit the thickness of thatch.
  • Fertilize the lawn.

Spring lawn disease or snow mold

Signs

If your lawn turns yellow after winter, the gray snow mold may be the culprit. It is usually caused by an excess of moisture from snowmelt. This disease can be detected by the gray-coloured circles it leaves on the lawn before it turns green.

Solutions

  • Rake the lawn.
  • Avoid watering the lawn.
  • Fertilize the lawn with a potassium-rich fertilizer in the fall.
  • Make the last mowing of the year at 5 cm.
  • Aerate the lawn.

Pests causing yellow lawn spots

Chinch bugs

Signs

Also known as hairy chinch bugs and lawn fleas, chinch bugs will appear around mid-July. Be particularly vigilant when temperatures are hot and dry since this is the time when they are likely show up and cause the most damage. You will notice their presence quickly as large patches of dry yellow grass will form and keep growing if no treatment is applied. These insects can destroy entire sections of your lawn. Not to be confused with drought.

Solutions

  • Call a Nutrite Expert to treat your lawn for insects quickly.
  • Apply insecticidal soap to affected areas.

Prevention

  • Sharpen your mower blade and set the mowing height to 3 inches.
  • Where permitted by regulation, water thoroughly in the morning or evening.
  • Fertilize the lawn so that it is nice and thick.
  • Overseeding to densify the lawn, especially in very sunny areas.

Read more

Sod webworms

Signs

The sod webworm is an insect that causes irregular patches of yellow grass, ranging from a few centimeters to several meters in diameter. The grass will be easily torn off if you pull on it. Sod webworm larvae could damage your lawn until the first frost in the fall if they are not controlled.

Solutions

  • Apply a control product in the fall when damage first appears.
  • Rake affected areas of the lawn and then overseed.
  • Aerate in the spring, then overseed and fertilize affected lawn areas.
  • Where permitted by regulation, water thoroughly in the evening or morning.
  • Treat with a preventive pest control product.

Read more

Grubs

Signs

Grubs cause irregular patches of yellow grass up to one meter in diameter and more. Your lawn could also be badly damaged by skunks that seek these worms to feed on them. Because the worms eat the roots, the grass will lose its grip on the soil and lifts out easily when pulled.

Solutions

To control infestation in the spring and fall:

  • Remove dead patches of lawn or infested areas.
  • Add quality soil and reseed or replant lawn.
  • Turn off lights that attract adults when they emerge in June and July.
  • Contact your Nutrite expert for a white grub preventive treatment.
  • Apply an over-the-counter insecticide to kill the larvae.

Read more

Other pests

Signs

Some less common insect species such as cutworms, marsh crane fly, and bluegrass grubs can also damage your lawn and cause yellow patches.

Solutions

  • If you can’t identify the pest affecting your lawn, call a Nutrite Expert. He will get you the right diagnosis.

Environmental conditions causing yellow lawn patches

Cold damages

Signs

If large patches of grass don’t turn green once spring comes, it might have been damaged by frost and ice. This means that, in some areas, the snow cover was not thick enough to protect your lawn from the cold.

Solutions

  • Rake the affected sections of lawn and then overseed.
  • Fertilize the lawn.

Severe or prolonged drought

Signs

The grass turns yellow evenly and gets very dry. It is important to know that the grass is not dead, but dormant, meaning that it stores all its energy in its roots to protect itself from the sun. As soon as the rain or cool weather returns, the grass will turn green again.

Solutions

  • Stop mowing the lawn.
  • Keep foot traffic to a minimum.
  • Try to water the lawn at least once a week in the early morning (according to the watering regulations).

Inadequate lawn care and other reasons responsible for yellow lawn

Lack of fertilizer

Signs

The lack of nutrients in the soil could very well be the reason behind a yellow lawn that won’t turn green after winter.

Solutions

  • Fertilize the lawn.
  • Aerate the lawn.
  • Apply lime to the lawn.

Dog urine

Signs

Urine will leave patches of yellow grass with a dark green outline because it is highly concentrated in ammonia.

Solutions

  • Dilute the urine by pouring water where your pet urinates.
  • Train your dog to urinate elsewhere.

Other stress factors

Signs

Since grass is a plant, several stress factors can induce discolouration, such as campfires, chemicals, objects left on the lawn for too long, foot traffic, etc.

 Solutions

  • Fertilize the lawn.
  • Aerate the lawn.
  • Apply lime to the lawn.

How to turn a yellow lawn green again?

The treatment to be applied to your lawn will depend on the cause of the problem. Generally, with a proper mowing height and adequate watering, you should get rid of your yellow grass patches. However, if you perform good lawn care, but yellow patches do not go away, here are your options:

  • Fertilize the lawn.
  • Apply pest control (treatments applied by experts).
  • Aerate the lawn.
  • Overseed
  • Add lime to the lawn.

Contact a Nutrite Expert. He will help you find the causes of your yellow grass problem and recommend the combination of treatment needed to solve it.

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