Grubs are a common cause of sudden lawn damage in late summer and early fall in Minnesota. While the damage may appear quickly, the feeding has been happening below the surface for weeks.

Understanding how to identify grub damage, what causes it, and how to prevent it will help you protect your lawn long term.

How to Identify Grub Damage

Common signs of grub damage include:

• Brown patches that are gradually increasing in size.
• Grass that pulls up easily like loose carpet.
• Birds, raccoons or other animals digging in the lawn.

The key identifier is that the grass has little to no root system left. If you gently pull on the turf and it lifts easily, grubs are likely present. You can often find white C shaped grubs in the top few inches of soil, especially at the edge where green turf meets brown turf.

Biology and Cause of Grub Damage

Grubs are the larvae of beetles that live in the soil and feed on grass roots. As they eat, they damage the lawn’s ability to absorb water and nutrients, which leads to brown patches that grow over time. The most severe lawn damage typically occurs in late summer and early fall, though some feeding injury can also be visible in spring.

The typical annual life cycle in Minnesota looks like this:

• Late Summer: Adult beetles lay eggs in the soil.
• Early Fall: Eggs hatch into white grubs that begin feeding on grass roots.
• Winter: Grubs move deeper into the soil to survive cold temperatures.
• Spring: Grubs move back toward the surface and feed again.
• Early Summer: Grubs mature and emerge from the soil as adult beetles.

This life cycle repeats annually, which makes both prevention and timely treatments important.

Common Misconceptions About Grubs

• Every brown patch is not grubs. Many lawn issues look similar. Drought stress, heat stress and disease can all cause browning The defining factor with grubs is root loss and grass that lifts easily.
• Animals are not the problem. People often think that raccoons or birds caused the issue. In reality, animals are reacting to the food source.
• Once you have grubs you will always have grubs. Beetle populations fluctuate. Some years will be heavy pressure and other years will be little activity.
• If I see adult beetles I must have a grub problem. Adult beetles may not lay eggs in your lawn. Also, the grass can survive some level of grub feeding. So just because you see adults does not always mean grubs are a problem.
• Controlling the grubs will fix my lawn. Once the roots are eaten, the grass cannot simply bounce back. Time is needed for regrowth or in most cases repair is needed.
• Beetle traps often attract more beetles into an area than they remove, which can sometimes increase egg laying nearby.

What Can a Homeowner Do Once They Have Grub Damage

• Water regularly to support any remaining roots and encourage new root growth.
• Plan for overseeding and repair of damaged areas.

What Can bioLawn Do Once Grub Damage Is Present

When active grubs are identified, we can apply a curative grub control treatment. This application will stop grub feeding. Note that while this product stops new feeding, the grass may already be weak and may continue to turn brown for some time. Our curative treatment stops active feeding and also provides protection against newly hatching grubs later in the same season.

Once damage exists, bioLawn can also help with reseeding areas of the lawn to achieve recovery.

What Can a Homeowner Do to Prevent Grub Damage

Prevention is the best approach to grub control. Homeowners can mow at proper mowing heights and water deeply and infrequently to encourage strong root growth that will tolerate some grub feeding. Homeowners should also keep an eye out in late summer for excessive beetle populations and early signs of damage so grubs can be treated quickly.

What Can bioLawn Do to Prevent Grub Damage

For lawns with a history of grub issues or a concern about damage, we recommend a Preventative Grub Control Treatment. This treatment, applied in May or June, targets grubs as they hatch later in the season and prevents damage before it begins.

Final Thoughts

Grubs damage lawns by destroying the root system below the surface. By the time brown patches appear, feeding has often been occurring for weeks. The good news is that grub activity follows a predictable cycle each year. When you understand that cycle, you can either prevent the damage entirely or respond quickly before widespread turf loss occurs.

If you suspect grub activity in your lawn, proper identification and timely action make all the difference in protecting your turf long term. Reach out to our team if we can help.