Is That Dead Patch in Your Lawn Grubs? How to Tell — and What to Do

Every August and September, we start getting calls from Bergen County homeowners who are watching sections of their lawn turn brown and die — and assuming it's the summer heat. Sometimes it is. But a significant number of those calls turn out to be grub damage, which looks almost identical to drought stress on the surface but has a completely different cause and a very different solution. Here's how to tell the difference, and what to do about it.

What Are Grubs and What Do They Do?

White grubs are the larvae of several beetle species — most commonly Japanese beetles, masked chafer beetles, and European chafer beetles — all of which are common across Bergen, Passaic, and Morris County. Adult beetles lay eggs in lawns during July, and by August those eggs have hatched into C-shaped white grubs that feed voraciously on grass roots just below the soil surface.

Because they're attacking the root system, the damage appears from the top down — the grass simply loses its ability to take up water and nutrients and starts to die in irregular patches. By the time the damage is visible, the grubs have been feeding for weeks.

How to Tell Grubs From Drought Stress

The quickest test: grab a handful of grass in the dead patch and tug. If the turf peels back like a loose carpet with virtually no resistance — roots detached, soil exposed — you almost certainly have grubs. Drought-stressed grass, even when brown and crispy, still has an intact root system and won't peel away easily.

You can also dig a small section of sod and check the soil beneath. Finding more than 5–6 grubs per square foot is considered a damaging infestation. In heavily affected yards in Glen Rock, Wyckoff, and Ridgewood — where Japanese beetle pressure is significant — we sometimes find 20 or more per square foot.

Preventive vs. Curative Grub Treatments

There are two types of grub treatments, and understanding the difference is important for setting realistic expectations.

Preventive treatments are applied in late May through early July — before eggs hatch. They use systemic products that are taken up by the roots and ingested by newly hatched grubs as they begin feeding. Preventive treatments are highly effective (90%+ control) and are the backbone of our grub control program. The tradeoff is that you're treating before you see damage, which requires some faith in the process.

Curative treatments are applied when active grubs are present — typically August through September. They work faster but are less reliable than preventive products, especially against larger, more mature grubs later in the season. If you're finding active damage, a curative treatment can stop the infestation from spreading, but some turf loss may already be unavoidable.

Will Damaged Areas Recover?

It depends on the extent of the damage. Lightly affected areas with some remaining root structure can recover on their own with proper watering and fertilization. Heavily damaged sections where the turf has completely detached will typically need to be overseeded or resodded. Fall is the ideal time for that recovery work — which is one reason we recommend scheduling a grub treatment in spring so you're not doing turf repair in September when you should be overseeding on a healthy lawn.

The Bottom Line for Bergen County Homeowners

• Japanese beetle grub pressure is significant throughout Bergen, Passaic, and Morris County — preventive treatment is worth it for most lawns.
• The preventive window is narrow: late May through early July. After that, only curative options are available.
• If you're finding dead patches in August, do the tug test before assuming drought damage.
• Grub control is included in our full-season lawn program — you don't need to think about timing separately.