Grub Damage Vs Fungus: How to Identify Your Problem?

A beautiful, lush lawn is every homeowner’s dream. However, this dream can quickly turn into a nightmare when your lawn is plagued by grub damage or fungus. Both of these problems can cause unsightly patches and unhealthy grass. Proper identification of the issue is crucial for successful treatment and restoring your lawn to its former glory. In this comprehensive guide, we will discuss the differences between grub damage and lawn fungus, how to identify each problem, and the best treatment and prevention methods.

Grub Damage

A. Grub Lifecycle

Here are the types of grubs commonly found in lawns:

  • White grubs: These are the larvae of various beetles, such as Japanese beetles, June beetles, and European chafers.
  • Billbugs: The larvae of this weevil species are often mistaken for white grubs due to their similar appearance.

Here are the grub feeding habits and lifecycle stages:

  • Grubs feed on the roots of grass and other organic matter in the soil.
  • Grubs go through three primary stages: egg, larva, and adult beetle.
  • Grub damage is most severe during the larval stage, as this is when they consume the most roots.

B. Symptoms of Grub Damage

  • Irregular brown patches: Grub damage often appears as irregular, brown patches in the lawn. These patches may initially be small but can expand and merge as grubs continue to feed.
  • Spongy lawn texture: Damaged roots can cause the lawn to feel spongy or soft underfoot.
  • Increased presence of birds, moles, or other wildlife: Grubs serve as a food source for various animals, leading to an increased presence of these creatures in your yard.

C. How to Confirm Grub Infestation

  • Examining the soil and grass roots: Peel back the turf in a damaged area and look for grubs in the soil. Grub-damaged roots will appear short, chewed, or missing.
  • Performing a grub count test: Dig a square foot section of turf about 2-3 inches deep and count the grubs. If more than 5-10 grubs are found, treatment is typically necessary.

Lawn Fungus

A. Types of Common Lawn Fungi

  • Brown patch: Caused by the fungus Rhizoctonia solani, brown patch appears as irregularly shaped brown or yellow patches in the lawn.
  • Dollar spot: This fungal disease, caused by Sclerotinia homoeocarpa, presents as small, round, straw-colored spots about the size of a silver dollar.
  • Fairy ring: Caused by various fungi, fairy rings appear as dark green circles or arcs with mushrooms or puffballs often present around the perimeter.

B. Causes of Lawn Fungus

  • Excessive moisture: Over-watering or poor drainage can create damp conditions that many fungi thrive in.
  • Poor soil drainage: Compacted soil or heavy clay can hinder water drainage, promoting fungal growth.
  • Over-fertilization: Excessive nitrogen in the soil can lead to an imbalance, making the lawn more susceptible to fungal diseases.

C. Identifying Signs of Fungal Infection

  • Discolored or irregular patches: Fungal infections often cause discolored, irregular patches in the lawn.
  • Presence of fungal fruiting bodies: Mushrooms, puffballs, or other fungal structures may be present.
  • Distinctive patterns or rings: Some fungal infections, such as fairy rings, create circular or arc-shaped patterns in the lawn.

Comparing Grub Damage and Lawn Fungus

A. Key Differences in Appearance

  • Irregular vs. circular patches: Grub damage typically results in irregular brown patches, while fungal infections often cause more circular or arc-shaped patterns.
  • Root damage vs. surface-level symptoms: Grub damage affects the roots of the grass, while fungal infections generally impact the surface-level appearance of the lawn.

B. Differences in Lawn Conditions

  • Soil moisture and drainage: Grub infestations are not heavily influenced by soil moisture, whereas fungal infections are more common in areas with excessive moisture or poor drainage.
  • Fertilizer usage: Over-fertilization can contribute to the development of fungal infections but is less likely to be a factor in grub infestations.

Treatment and Prevention

A. Grub Control Methods

  • Chemical treatments: Insecticides can be applied to the lawn to target grubs. It is important to follow the manufacturer’s instructions for proper application and timing.
  • Biological controls: Nematodes, a type of microscopic worm, can be introduced to the soil to target and kill grubs naturally.
  • Cultural practices: Proper lawn care, such as mowing at the correct height, watering deeply but infrequently, and aerating the soil, can help reduce the risk of grub infestations.

B. Fungus Control Methods

  • Fungicides: Chemical fungicides can be used to treat fungal infections in the lawn. Be sure to follow the product’s instructions for proper application and timing.
  • Improved lawn care practices: Avoid over-watering, mow at the correct height, and aerate the soil to reduce the risk of fungal infections.
  • Soil amendments: Adjusting the pH of the soil or adding organic matter can help create a healthier environment for grass, making it less susceptible to fungal infections.

C. General Prevention Tips

  • Proper irrigation and drainage: Water your lawn deeply but infrequently to encourage deep root growth and reduce the risk of fungal infections.
  • Appropriate fertilization: Follow a balanced fertilization program and avoid over-fertilizing to minimize the risk of fungal infections and other lawn problems.
  • Regular lawn maintenance: Mow at the proper height, aerate the soil, and detach as needed to promote a healthy, dense lawn that is less susceptible to pests and diseases.


A beautiful lawn requires consistent care and monitoring. Accurate identification of problems, such as grub damage or fungal infections, is essential for effective treatment and maintaining a healthy, lush lawn. By following the prevention tips and treatment methods discussed in this guide, you can protect your lawn from these common issues and enjoy a vibrant, green outdoor space.


  • Nathan Collins

    Having spent years working in the landscaping industry, Nathan Collins has cultivated a wealth of knowledge about the natural world. He is committed to helping others appreciate the beauty in their backyards, whether it's through identifying rare rocks and minerals or crafting the perfect landscape.

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