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Understanding Grubs: Lifecycle, Treatment, and Timing

Despite their small size, grubs are one of the most destructive forces facing your lawn. They can turn large sections of a beautiful lawn into lifeless, brown turf. Grubs have several factors working in their favor, not the least of which is how they go unseen until most of the damage is done. 

These tenacious lawn pests launch their assault underground, eating away at the most vital part of grass — the root system.

The good news is you have several ways to detect and defend your lawn against grubs. We’ll give you several strategies for setting up that defense and proactive measures if you already have an infestation. And if you’re wondering about the sneakiest way grubs destroy lawns, we cover that, too.

This Grub Article Covers:

What are Grubs?

Grubs are soft-bodied larvae of various beetle species. These c-shaped insects live underground and survive by eating the roots of grasses and other plants. Their life expectancy is roughly one year, with four unique life stages we’ll investigate in detail because they are crucial to defeating grubs.

Also, not all grub species are created equal. So, knowing the traits of Eastern Connecticut grubs helps choose the proper management options.


Types of Grubs

Common types of grubs found in Connecticut:

  • Japanese beetle larvae: Metallic-green-bodied, they are a major turf pest found across the eastern U.S.
  • June beetle larvae (aka white grubs): These plump grubs reach up to 2 inches long and are the offspring of various June beetle species.
  • European chafer larvae: Introduced from Europe, they’re common in the northeastern U.S. and eastern Canada.
  • Oriental beetle larvae: Smaller than Japanese beetle grubs, these tan-colored larvae are spreading across the U.S.

Despite various strengths and weaknesses, they all destroy lawns by devouring grass roots. A lawn cannot thrive with the roots under attack because they deliver water and nutrients to the surface grass blades.

Now, let’s get into the first stage of a grub defense strategy.


Signs of Grub Infestation

It’s impossible to stop a lawn pest if you don’t know what to look for that indicates a grub infestation:

  • Brown, dead patches of grass (often mistaken for a drought issue and noticed too late)
  • Animal activity — birds, skunks, raccoons, etc., digging up grubs to eat. 
  • Spongy or loose turf. When the roots are being decimated, the turf loses its anchor to the soil, creating a loose feel as you walk across damaged sections.
  • Grubs might be seen on the lawn surface when soil is disturbed.

Once any of these signs are spotted, there’s no time to waste. The only way to stop further damage is to address the grub problem, or else these hungry larvae will grow worse.

Prevent that with free grub prevention with any of our lawn care programs (*first year).


The Life Cycle of Grubs

One reason we relish being lawn geeks is because turfgrass is such an impressive plant. When properly cared for, it rewards us with lush beauty the entire family can enjoy, and neighbors can’t help but notice. 

Even when grubs attack the life-blood (roots) of grass, the lawn strives to survive. Signs may only become apparent when the grass can no longer outlast the damage. 

To avoid that disastrous stage, we need to get to know these creatures and their four life stages.

Egg Stage

Adult beetles typically lay their eggs between June and August. Any tiny soil opening is prime real estate for beetles to lay dozens of eggs. It only takes 14 days for those little lawn monsters to hatch. They can hatch sooner when conditions (warm and moist) are ideal for them.

Larvae Stage

This is a grub’s “Frankenstein stage,” when it does the most damage to grass roots. They start slow but quickly get out of hand, chewing up roots deeper and deeper, choking off all the vital resources to the lawn’s surface. The damage soon becomes visible, but now you’re playing catch-up.

Pupa Stage

This could be seen as the grubs’ “hibernation” season. Mature grubs creep back toward the soil surface, forming a protective “dirt cell.” Now protected, they transform into pupae to await the evolution into full-grown beetles. There’s no feeding during this period. 

Adult Stage

After the three prior cycles complete, grubs become beetles. They rise from the soil in late spring to early summer. Though no longer grubs, the destruction often continues as adult beetles start munching on enticing plants and trees on your property. They don’t fly away for a happy ending, either. They are actively mating, continuing the destructive cycle as more eggs are scattered across your lawn, producing more grubs.

Grub Life Cycle Diagram

Why are these four life cycles so important to understand? They reveal vulnerabilities for the most timely intervention (during the larval stage). This window gives you the best opportunity to keep your lawn from suffering extensive damage.

However, this life cycle also provides viable options for treatments even when you’ve missed the larval cycle. All you have to do is to learn easy ways to identify grub damage.


Identifying and Assessing Grub Damage

No need to be a grub expert to spot the damage they cause or assess what course of action is needed. Below are key points on grub activity that make it simple to spot, and tips for evaluating the severity of activity detected.

Early detection means turf protection. Remember, you’re unlikely to ever see an actual grub on the lawn surface. So, watch for yellowing or browning, thinning, and grass that doesn’t look healthy (aka unappealing). 

Notice irregular patches of turf that you could mistake for a drought problem and any holes in the lawn from animals clawing their way to find grubs to eat.

Animal activity may elude your attention, but the evidence will remain, so scout it out by walking your property regularly. Walking can also alert you to the spongy feel of loose grass being detached from the soil by grubs.

Ok, you’ve found signs that grubs have invaded your property. What next?

Once you know the severity of an infestation, you can plan treatment options. You need to take a “grub headcount” with a little digging. Use a special tool (cup cutter) or a small shovel to remove one square foot of soil at roughly three inches deep. Sort through this soil sample to count the grubs (photo below – they’re white with brown heads)

Five to ten grubs per square foot tells you treatment is needed. Over ten? Take immediate action because you likely have a severe infestation. One caveat…

Though highly unlikely, you may have randomly picked the one spot in your lawn where grubs happened to congregate. So, test several areas to be certain your grub count is consistent. The same principle holds if the first soil test reveals no grubs.

After you’ve inspected the soil samples, replace the soil and clump of grass to keep from having divots in your lawn.

The next step? Proven grub treatments.

Treatment Options for Grubs

While it’s great to have multiple treatment options to eradicate this problematic pest, each option has pros and cons. We’ll start with useful forces of nature we can harness.

Biological Controls

There are more beneficial insects in Connecticut than harmful ones. We can use that to your advantage. In the case of grubs, we can draft into service nematodes like the beneficial Heterorhabditis bacteriophora. These creatures are microscopic worms built to kill grubs by moving through the soil, tracking down grubs, and infecting them via natural openings.

Pros: See effective grub control without synthetic chemicals. Eco-friendly and safe for people, pets, and other beneficial insects.

Cons: Ideal soil conditions are needed for maximum effectiveness. Continuous grub control will likely require annual reapplication.

Another proactive natural measure is milky spore disease (Paenibacillus popilliae). This laser-focused bacteria is specifically the enemy of Japanese beetle grubs. It is deadly to this grub species using spores that will remain in the soil for years.

Pros: Once established, it provides long-lasting grub control. It’s perfect for property owners who’ve identified Japanese beetle grubs.

Cons: Not nearly as effective in controlling other grub species, and it can take at least two years for spore levels to rise to necessary volumes.


Chemical Treatments

Preventative insecticides with formulas including chemicals such as imidacloprid, chlorantraniliprole, or clothianidin are effective when applied in spring and early summer. Grubs ingest the insecticide while feeding on grass roots

Pros: It can stop grubs before they damage your lawn. Residual control can extend from two to four months to help stay ahead of grubs.

Cons: Not as eco-friendly as natural treatments and can be less effective against late-season grubs (another reason to regularly check for grub activity).

Curative insecticides like trichlorfon or carbaryl are applied when grubs are active, killing them on contact.

Pros: Provides faster control of active grub infestations, and no grub is safe when treatment is timed properly, regardless of the life stage.

Cons: Repeated applications are needed and can harm beneficial insects.

More environmentally-friendly treatments ahead, but a quick note on cures versus prevention…

Human nature nudges people to wait to act only when there’s no choice. Prevention is the better option, not just with grubs but with any home or property task. Yet, our nature works against our own best interests because it’s proven that people underestimate future risks.

And MRI studies show people often view their future self as… basically a stranger — someone they’re not really responsible for. That’s one reason preventative measures are put off. It’s how grubs get openings to destroy half a lawn versus being stamped out when their numbers are manageable.

Organic Alternatives

Natural insecticides containing azadirachtin (neem), spinosad, or Bacillus thuringiensis galleriae (Btg) can provide grub control with lower environmental worry.

Pros: Created from natural sources, they have lower toxicity and some organic treatments are specifically designed to fight grubs.

Cons: Effectiveness may not be as consistent or long-lasting as synthetic insecticides.

Cultural Controls

The best defense against grubs leans into broad strategies instead of individual tactics. Proper mowing, watering, fertilization, aeration, and efforts to increase helpful insect populations create the healthiest lawns. Healthy equals resilient turf that’s ready when grubs do show up.

Pros: Decreases the need for pesticides while promoting overall lawn health. An integrated approach doesn’t limit your pest control options.

Cons: It requires a diligent approach and even a healthy lawn faces an uphill battle in the event of an unchecked infestation.

All the above options work best in unison. Relying on one or two only leaves more openings for grubs.  A comprehensive lawn care approach is the number one way to avoid costly grub damage. The bonuses are a beautiful lawn and lower environmental impact as synthetic insecticide use is lessened.

Just don’t forget how crucial timing is.

Timing of Grub Treatments

Now that you have guidance on the various types of grub treatments, add optimal timing to the strategy.  Below are the ideal months for preventative and curative measures.

Preventative Treatments: Early summer to mid-summer (June – July). Why? The timing catches adult active beetles laying eggs, which will hatch surrounded by soil treated with the insecticide. Applying too early (April – May) means the treatment can diminish before grubs hatch.

Curative Treatments: Late summer to early fall (August – September). Kills on contact, so it’s effective at this stage with grubs feeding near the surface. Applying too late (past October) can give pests time to bury deep for the winter and escape. Too early (June – July) can miss late hatchers.

See the handy guide below for month-by-month grub treatments:

One-Year Grub Treatment Guide

  • April-May: Monitor for grub damage, but avoid preventative applications (it’s too early).
  • June-July: Apply preventative treatments to stop grubs before they hatch.
  • August-September: Perfect for curative treatments if grub damage is present. Can also utilize more preventatives.
  • October: Final chance for curative treatments, whereas preventatives would likely degrade before next season.
  • November-March: Treatment is ineffective for these five months with grubs bunkered deep underground.

Remember, monitoring is your best ally for a head start versus grubs. These sinister lawn pests can only thrive if they elude detection!

Long-term Grub Management Strategies

Some of the top scientific advances have been achieved by attacking problems from as many angles as possible. Grub management is no different. So let’s look at detailed angles that give homeowners an edge over this pest. 

Integrated Pest Management (IPM): This strikes grubs from all sides using biological, cultural, and chemical controls—natural and synthetic. Pests struggle to fend off multi-pronged attacks and defensive moves. 

Biological Controls: In addition to Heterorhabditis bacteriophora and milky spore disease, Entomopathogenic fungi (like Metarhizium anisopliae) is another bio-agent that disrupts grub life cycles.

Cultural Controls: Core aeration alters egg-laying beetles’ preferred habitat, while proper irrigation avoids drought stress that invites grub activity. Grub-resistant endophytic grass can be overseeded.

Chemical Controls: Insecticides are a must in certain scenarios but should be used with caution and precision. Preventative treatments work well when applied in early summer, while curative insecticides are fast-acting during active infestations. 

Lawn Maintenance: Thick, healthy lawns help keep grubs at bay. Best practices for healthy lawns include mowing at the recommended height for your grass type, using sharp blades, deep and infrequent watering, soil testing to inform fertilization, and overseeding thin grass.

Soil Health: Healthy soil makes for healthy turf and helps repel grub infestations. Improve your soil by adding compost, adjusting pH levels when necessary, and addressing drainage issues.



There’s no magic solution to ridding the world or your yard of grubs forever. Science saves the day, though, with an impressive array of solutions proven to protect your lawn from serious grub damage.

You have those tools at your disposal now, along with specific times to utilize them.

Hopefully, we’ve also put the finest point possible on having a healthy lawn year-round. Strong, thriving lawns can usually overcome any obstacle, from dry weather to disease and even relentless grubs.

Want access to free professional grub control? All our lawn care programs include grub control & it’s FREE with your first year of service. Act now to rid yourself of grub worries. 

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