Noticing something off with your lawn? Those brown patches and wilting grass might not be from the weather. Early detection is key to saving your turf, and it often starts with looking for the culprits beneath the surface. This guide will help you spot the 8 signs of grubs in lawn before they cause serious damage.
Grubs are the larval stage of beetles, like Japanese or June beetles. They live in the soil and feast on grass roots. If you catch them early, control is much easier. Let’s look at the telltale signs that grubs have moved into your yard.
8 Signs of Grubs in Lawn
Here are the eight most common indicators that grubs are damaging your grass. You might see one or several of these signs at once.
1. Spongy, Bouncy Turf
Walk across your lawn. Does it feel unusually soft or spongy underfoot, almost like a cheap carpet? This is a classic early sign. As grubs eat the roots, the grass loses its anchor to the soil. This creates a loose, bouncy layer of turf that you can often peel back easily.
2. Irregular Brown Patches
Grubs damage roots, which prevents grass from taking up water. This leads to drought-like symptoms. You’ll see irregular brown patches that appear during late summer or early fall. Unlike fungal spots, these patches won’t have a distinct ring or pattern. They just get bigger and browner.
- Patches often start small and expand rapidly.
- They don’t improve with watering.
- The edges of the patch will feel loose if you tug on the grass.
3. Increased Bird or Wildlife Activity
Are birds, raccoons, or skunks constantly digging up your lawn? They aren’t being vandals; they’re feasting. These animals love to eat grubs. If you see flocks of birds pecking at the grass or small holes dug overnight, it’s a major red flag. The animals have detected the grubs before you have.
4. Grass Pulls Up Like Loose Carpet
This is the definitive test. Grab a handful of brown grass at its base and give it a gentle tug. If it lifts away from the soil with little to no resistance, exposing bare dirt, the roots have been severed. You might even see the creamy-white, C-shaped grubs right there in the soil. They’re usually about an inch long.
5. Moth or Beetle Activity Earlier in the Season
Remember an influx of beetles buzzing around your outdoor lights in early summer? Or lots of brown June beetles flying low over the grass? Adult beetles lay eggs in your lawn, which hatch into grubs. A surge in beetle activity is a strong predictor of a future grub problem.
6. Increased Mole or Vole Activity
These underground pests don’t eat your grass roots. They eat the grubs. If you see raised ridges or tunnels crisscrossing your lawn, moles are likely hunting the grub buffet beneath. Controlling the grubs often sends the moles packing too, as their food source disappears.
7. Thinning and Wilting Grass
Even before distinct brown patches form, the grass may just look thin, weak, and wilted. It loses its lush, green vigor. This general decline happens because the compromised root system can’t support healthy top growth, even with proper care.
8. Check Under the Sod
The most direct method is to investigate. Use a shovel to cut a one-square-foot section of turf in a damaged area. Peel it back like a piece of sod. Look in the top 2-3 inches of soil. Healthy soil might have a few grubs, but more than 5-10 per square foot indicates a problem that needs treatment.
How to Confirm and Treat a Grub Problem
Once you’ve spotted the signs, take these steps to manage the issue.
Step 1: Confirm the Infestation
Do the tug test or sod check in several areas, especially at the edges of brown patches. Count the grubs you find. This helps you gauge the severity.
Step 2: Choose the Right Treatment
- For Active, Large Grubs (Late Summer/Fall): Use a fast-acting curative insecticide labeled for grubs. Water it in thoroughly according to the label directions.
- For Prevention (Late Spring/Early Summer): Apply a preventative grub control product. This targets the young grubs before they grow large and cause damage. It’s the most effective long-term strategy.
- Natural Options: Beneficial nematodes (microscopic worms) can be applied to the soil. They seek out and kill grubs. Milky spore is a bacterial disease that specifically targets Japanese beetle grubs over time.
Step 3: Repair the Damage
After treatment, you’ll need to repair the lawn. Rake out the dead grass in the damaged areas. Loosen the soil, add a bit of compost, and reseed or lay new sod. Keep the area consistently moist for the new grass to establish.
FAQ About Lawn Grubs
What time of year are grubs most active?
You’ll see the most damage from late August through October, as the grubs are largest and eating the most. A second period of activity can occur in the spring before they pupate into beetles.
How many grubs is too many?
A few grubs are normal. But if you find more than 5-10 per square foot, it’s time to take action. In healthy lawns, the grass can tolerate some feeding, but high numbers cause visible damage.
Will grass grow back after grub damage?
Yes, but it often needs help. The grubs destroy the roots, so the grass can’t recover on it’s own. You will need to reseed or resod the bare patches after the grubs are controlled.
Can overwatering cause grubs?
Overwatering itself doesn’t cause grubs, but it can create a favorable environment for the adult beetles to lay eggs. Consistently moist soil in mid-summer is attractive to them. Proper, deep but infrequent watering is best for lawn health and grub deterrence.
What is the fastest way to kill grubs?
A curative insecticide containing Dylox or Carbaryl will work quickly, often within days. Remember to water it in immediately to move the product into the soil where the grubs are living. Always follow the product label for safety and effectiveness.
Keeping a watchful eye for the 8 signs of grubs in lawn is the best defence. Regular monitoring, especially in late summer, allows for early intervention. With prompt action, you can eliminate the grubs and restore your lawn to its thick, green glory. A healthy, well-maintained lawn is also more resilient to pests, so good cultural practises are your first line of defence.