Why is my grass turning yellow and dying?

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So you’re wondering “why is my grass turning yellow and dying?”. My lawn has suffered in a similar way and I have found the following five, less obvious reasons can be the cause.

  • Lawn rust
  • Dry patch
  • Chafer grubs
  • Leatherjackets
  • Pet urine

Read on to learn how to remedy these issues and get your lawn back to it’s best.

Is lawn rust causing my lawn to die?

Lawn rust – A foliar fungal disease that attacks patches of lawns.  The fungus spreads via airborne fungal spores.

Symptoms

  • Grass begins to turn a yellowish-brown colour.  On closer inspection, the grass blades develop pustules with dark brown deposits.  
  • The grass will shrivel and discolour.
  • The grass rarely dies completely and will usually recover.

Cause

  • Various fungal species.
  • Usually more common in late summer and autumn, especially during wetter weather.

Remedies

Once the disease has taken hold, it will be difficult to reverse damage within that growing season.  For lawn rust, prevention is the best form of cure. Therefore, earlier in the season, try the following:

  • Improve air circulation.  Ensure that mowing clippings are cleared from the lawn surface to ensure good air circulation.
  • Do not overfeed lawn.  If you feed the lawn earlier in the season, closely read and follow the dosage.  Over-feeding the lawn will cause the grass to produce lots of lush fresh growth which will be susceptible to attack from fungal spores.

Is Dry patch turning my lawn yellow?

Dry patch is a condition that causes patches of soil within the lawn to repel water and therefore slowly kill the grass growing through it.  Yellowish patches will appear within a sea of healthy green lawn. This is a frustrating condition for the gardener as regular watering of the lawn can have little positive effect.

Symptoms

Yellowish patches appearing within a healthy lawn, even after regular watering during dry, hot periods of the summer.  The patches will slowly turn brown and die.

Puddles of water forming on the grass.  On closer inspection, the soil under the puddle will be completely dry.

Cause

Not a lot is understood about the actual causes of dry patch however, it is thought to be a consequence of fungal spores lying on the soil surface.  The water-resistant residue will cause water to either run-off the soil onto neighboring healthy grass, or the water will just sit on top of the affected area.  

The water will not penetrate the soil and therefore the roots of the grass will not receive the water necessary to grow.

Remedies

  • Rake and scarify the lawn.  Again, prevention is the best form of cure.  Scarifying the lawn will break up the top structure of the soil, thus aiding the water to penetrate the soil and reach the roots later in the season.
  • Spiking the area.  Use a garden fork to pierce the soil to improve drainage to the roots.
  • Applying a wetting agent.  Wetting agents increase the ability of the soil to pass the water down to the roots.  These can be purchased from many horticultural suppliers and garden centers.
  • Reduce lawn compaction.  In the autumn or early spring, use a garden fork to gently aerate the soil.  Once the fork prongs are within the soil, pull back on the fork handle slightly to lift a small patch of the turf.  This un-compacts the soil and allows room for good grass root growth over the coming growing season.

Are Chafer grubs turning my lawn yellow? 

Chafer grub in lawn. http://www.forestryimages.org/browse/detail.cfm?imgnum=5343065 
David Cappaert
Chafer Grub in lawn. Photo courtesy of David Cappaert.

Chafer grubs are larvae that live underneath the surface of the soil.  The grubs will eat the roots of the grass, thus slowly decreasing the vitality of the grass itself or completely killing small patches of lawn.

Identification

Chafer grubs are small c-shaped larvae with whitish-blue bodies and brown heads.  They have six legs and are approximately 2cm in length.

Symptoms

  • Small patches of yellow grass, which will likely slowly die over the course of the season.
  • Patches significantly develop in autumn and into spring.

Cause

Chafer beetles laying their eggs in the lawn soil.  This usually takes place in early summer.

Remedies

  • Apply nematodes.  Nematodes are a natural organism that can be applied to lawns in a liquid solution.  The nematodes will move through the soil and be ingested by the chafer grub, slowly killing the grub once it has done so.

Applying nematodes will require the soil to be damp before and after the application.

  • Re-turf or re-sow the affected areas during spring-autumn.  This isn’t quite a remedy as it doesn’t resolve the underlying issue of the grubs but it will certainly replenish the state of your lawn quickly.

Are Leatherjackets turning my lawn yellow?

Leatherjacket larvae.
Leatherjacket larvae. Photo courtesy of Rasbak.

Leatherjackets are the larvae of the crane fly aka the Daddy Long Legs.  The larvae live within the lawn soil.

Symptoms

One of the most effective ways of finding if leather jackets are causing your soil to turn yellow and eventually die is to soak suspected patches of the lawn with water and then cover this patch with a large piece of opaque sheeting.  Leave the sheet on the lawn overnight (Note – you may need to pin or weigh the sheeting down in the corners to ensure that the sheet remains in place). When you uncover the sheet the next morning, you will find a number of greyish brown larvae/grubs.

You may also lift a shallow section of the soil to see if the larvae are present.  A depth of 5-10 cm should be sufficient.

Cause

Leatherjackets will eat the soft stems of the grass.

Remedies

Applying a species of nematodes called steinernema feltiae to the lawn will help keep levels of the larvae in check.  Nematodes should only be applied when:

  • The general soil temperature is warm i.e. any time during spring, summer, and early autumn.
  • The soil is moist.  If the soil is not moist, hose the lawn down but don’t saturate it.
  • Follow the instructions on the packaging containing the nematodes.
  • You will likely have to lightly water the lawn to help the nematodes penetrate the immediate soil surface.

Is pet urine causing my lawn to die?

Symptoms

Multiple, small circular patches of yellow grass develop on the grass.  This gives a “scorched” effect to the ground.

Cause

Urine contains large amounts of nitrogen.  Although, grass requires nitrogen to grow strongly, too much nitrogen can cause scorching and dead patches.

Remedies

There are a number of ways to help reduce the side-effects of your pooch ruining your lawn.

  1. Water the lawn to dilute the nitrogen.  If possible, try to remember roughly where your dog urinated and use a hosepipe to dilute the nitrogen.  A little water should be able to achieve this. If it is difficult to keep track of where your dog urinated, perhaps use a lawn sprinkler once an evening (this may be difficult on larger lawns).
  2. Try to train your dog to urinate in one particular area of your lawn or garden.
  3. Don’t apply additional fertilizers to a lawn that your dog uses.  This will help maintain the nitrogen levels to a minimum.
  4. Introduce urine resistant varieties of grass into your lawn.  Fescues and ryegrass are better at coping with the high amounts of nitrogen but aren’t completely resistant to urine damage.
  5. Add herbal remedies to your dog’s food.  There are some herbal remedies, such as Premium Care Grass Burn Spot Chews, that can be added to your dog’s diet that can reduce the potency of its urine.  

Conclusion

“Why is my grass turning yellow and dying?”. As we can see, there are a number of reasons for a lawn to develop yellow/dead patches.  Some of these, such as pet urine, are more obvious than others. Following the steps above can save a lot of time in identifying the culprit, applying the correct remedy, and thus get your lawn looking back to it’s best.

Nobody said that it was going to be easy, but a healthy-looking lawn is more than worth it.