Lawn Grubs

Lawn Grubs admin February 21, 2023

LAWN GRUB CONGTROL

How Common are White Grubs in Colorado Lawns?

Grubs are Now Very Problematic in Colorado

Grub damage to Colorado lawns typically becomes noticeable in September and October. However, when an infestation occurs, we can trace the problem back to July, when adult beetles lay their eggs in the soil. These adult beetles specifically choose moist or wet soil for egg-laying, as the eggs can become unviable if the soil dries out for as little as 24 to 48 hours.

July and Proper Lawn Watering is The Key to Grub Control

As summer temperatures continue to increase yearly and more lawns are watered with automatic irrigation systems, conditions have become favorable for Japanese beetles to thrive. Here’s how this occurs:  Without irrigation, the heat and dryness of a typical Colorado July would cause most lawns to dry up and turn brown.

Grubs in the Soil

Lawn Insect Control Services Colorado
Grubs can often be found within the top few inches of soil. The damaged sod will often pull up like a freshly laid piece of sod, because the grubs feed on the roots of the grass.

Severe Grub Damage

This lawn in Boulder was destroyed from a major grub attack. Unfortunately this lawn had to be sodded to repair the damage.

The Lifecycle of Japanese Beetles

ADULT BEETLES EMERGE FROM THE  SOIL (JUNE)

In late May through early July, adult Japanese beetles emerge from the ground and begin searching for food and mates. These beetles can fly up to one mile and feed on a variety of plants, with their favorites being roses, grapes, and linden trees. Younger scarab beetles are often unnoticed during this time because they do not typically attack ornamental plants.

LAYING EGGS IN THE SOIL (JULY)

In July, female beetles lay up to 60 eggs each in the soil over a span of 2–3 weeks. The eggs hatch approximately two weeks later, depending on soil moisture and temperature. During this period, the white grubs are very small and primarily feed on grass roots throughout most of August.

GRUBS CAUSE THE MOST DAMAGE IN LAWNS (SEPTEMBER – OCTOBER)

From late August through October, depending on external temperatures, the white grubs undergo molting stages, transitioning into second and then third-stage larvae. As they grow, these grubs consume grass roots rapidly, and lawn damage typically becomes noticeable during this time.

GRUBS DIG 3+ FEET DEEP INTO THE SOIL TO OVERWINTER (NOVEMBER – MARCH)

As temperatures drop in autumn, lawn grubs burrow deeper into the soil, where they will overwinter below the frost line.

GRUBS RETURN TO THE SURFACE AND HAVE A SHORT FEEDING PERIOD (LATE APRIL)

In the spring, usually by late April or early May, the lawn grubs move back up to the shallow soil to feed on grass roots for a brief period. Most of the lawn damage observed in the spring is a result of their feeding in the previous fall, rather than spring feeding.

GRUBS PUPATE AND BECOME BEETLES (MAY)

In late spring, the white grubs stop feeding and transform into pupae, entering a stage where they are resistant to chemical insecticides. By late June or early July, the beetles emerge from the pupae and crawl out of the soil, completing their life cycle.

Grub Life Cycle
Illustration by K. English, NYS IPM

How to Kill Grub Eggs Using Only Your Sprinkler System

Dry July!

You read that correctly: you can effectively kill grubs by watering your lawn properly. Here’s how it works: grubs lay their eggs in moist soil, and if the soil dries out for even just 24 hours, the eggs will perish and become unviable.

Every-Other-Day Watering is Wrong!

The 1-2-3-2-1 lawn watering technique involves skipping watering on two consecutive days every weed during the month of July.  This watering technique is specifically designed to  aligns with the time grubs are laying their eggs. This method is based on logical reasoning and scientific principles, and the two consecutive days without watering are essential for reducing grub pressure.  When a soil completely dries out this alone can successfully destroy the grub eggs.

Lawn Watering Can Stop Grubs

Three-day-per-week watering is not the same as every-other-day watering. To kill grub eggs, the lawn needs a full 48 hours of dryness. The 1-2-3-2-1 lawn watering technique is designed to provide deep hydration while ensuring the soil dries out just enough to disrupt the grub life cycle, making it the best approach for July watering.

Daily Watering Keeps Grub Eggs Alive

Many homeowners still water their lawns seven days a week, which not only wastes water but also provides ideal conditions for Japanese beetles to lay their eggs. In fact, watering a lawn every other day does not allow enough time for the soil to dry out and can fail to kill off grub eggs.

When Necessary Apply This Insecticide

Due to the rapid increase of grub pressure in Colorado lawns we do suggest a preventative insect treatment of Acelapryn during the month of August.  This is a fail safe way to protect your lawn and avoid potential damage. Taking proactive steps can save you from losing significant areas of your lawn to grub infestations.

July is Egg Laying Season

To effectively combat grub eggs, allow the soil to dry out. Don’t make the mistake of watering your lawn every day in July—this will only promote their survival.

Lawn Grub Control and Prevention

How to Identify Grub Damage in Lawns?

The Pull Test

Identifying the symptoms of lawn grub damage is relatively straightforward, making it easy for even non-professionals to recognize. The simplest method is to examine the affected area of the lawn by gently tugging on the green grass adjacent to the damaged section. If the grass pulls up easily, like a fresh roll of sod, it indicates damage. This is because grubs feed on the grass roots at or just below the soil surface.

Look for Grubs

Once you confirm that grub damage is present and the grass roots have been consumed, carefully sift through the top inch of soil until you find a white grub. If you discover grubs, it’s clear they are responsible for the damage. However, if no grubs are found, the lawn may be experiencing other issues, such as drought stress or damage from spider mites.

Checking for Grubs

Suspect grubs in your lawn? Here’s how to check: Gently pull back a small section of sod in any damaged area. If you find white larvae underneath the grass, you must take immediate action to protect your turf!

Why do Organically Treated Lawns Rarely Suffer from Grub Damage?

2 Main Reasons

There are two main reasons why lawns treated organically by Organo-Lawn rarely suffer from grub infestations.

We Water a Lawn Correctly

First, Organo-Lawn insists that all its customers should follow a specific watering schedule for their lawns called the 1-2-3-2-1 technique. This watering practice gives the lawn two consecutive days without watering which allows the soil to completely dry out.  When the soil is dry the grubs typically do not lay eggs in soils that are not moist or wet. 

Beneficial Bacteria Kill Grub Larvae

Second, Organo-Lawn’s lawn care programs are designed to promote healthy soil that supports beneficial bacteria and nematodes. One such beneficial bacterium, Bacillus popillae-Dutky, is particularly effective at killing grub larvae. By building a thriving ecosystem in the soil, Organo-Lawn helps ensure the presence of Bacillus popillae-Dutky, which in turn protects the lawn from grub problems.

Grub Damage to a Lawn

This lawn in Boulder was attacked by white grubs. It is easy to tell if a lawn has a grub problem because the grass will pull up easily like it is a newly laid piece of sod.

Which Insecticide Do We Recommend to Kill Grubs?

If you are one of the unlucky homeowners and your lawn is damaged by grubs, Organo-Lawn recommends a special insecticide treatment called Acelepryn. This grub control is not organic but it is on the EPA’s reduced risk list.

We Also Recommend a Sprinkler Audit

In addition to the lawn grub treatment of Acelepryn, we always recommend an inspection of the sprinkler system to make sure the lawn is being watered according to the 1-2-3-2-1 lawn watering principals

EPA's Reduced Risk Listed

Acelepryn is on the EPA’s reduced risk list and will control grubs for up to 3 months after the grub treatment has been applied to a lawn.


Acelepryn Label PDF
Acelepryn SDS PDF

Professional Lawn Grub Control Services

 Boulder (303) 499-2000 or Fort Collins (970) 225-9425

DO YOU SUSPECT GRUBS?
SCHEDULE A LAWN EVALUATION

A Closer Look at Grubs
and the Damage They Can Cause to a Lawn

Early Signs of Grub Damage to a Lawn

Grub damage can be deceiving—it often looks like a dry, thirsty lawn at first. But if the grass pulls up easily like loose carpet, it’s a sign that grubs have been feeding on the roots. Early detection and proper treatment can help restore the lawn before the damage becomes severe.
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Early Signs of Grub Damage

Early signs of grub damage are appearing—subtle thinning, yellowing patches, and grass that feels slightly loose. Catching it now means there's still time to take action with proper lawn care and grub control before the damage becomes severe.
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Moderate Grub Damage to a Lawn

Moderate grub damage is starting to show, with thinning grass and weak spots that may peel up easily. Treating the lawn now with proper care, overseeding, and soil recovery techniques can help restore its health before the damage worsens.
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Localized Grub Damage to a Lawn

Localized grub damage is visible in small patches where the grass is thinning and losing strength. While the rest of the lawn may look healthy, addressing these spots early with proper treatment and overseeding can prevent further spread and restore the turf.
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Severe Grub Damage

Grubs have done extensive damage, killing off large areas of grass and leaving the soil exposed. At this stage, the best solution is to reseed or lay new sod to rebuild the lawn and prevent further issues.
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Severe Grub Damage to a Lawn

grub-damage-lawn
Severe grub damage has devastated this lawn, leaving large dead patches where the grass can’t recover. With the roots completely gone, overseeding or sodding will be necessary to restore healthy growth and bring the lawn back to life.
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Size of a Cranberry Girdler Grub

grub-compared-to-dime
This tiny but destructive pest is a cranberry girdler grub, shown next to a dime for scale. Though small, these grubs can cause significant damage by feeding on grass roots, leading to weakened and dead turf. Early detection is key to preventing lawn damage.
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White Grub of the Japanese Beetle

The white grub of the Japanese beetle is a hidden threat beneath the soil, feeding on grassroots and weakening the lawn. These C-shaped larvae can cause significant turf damage before emerging as adult beetles to attack plants above ground. Early detection is key to prevention.
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Japanese Beetles From Egg to Adult

From egg to adult, the Japanese beetle goes through a destructive life cycle. Grubs hatch underground, feeding on grassroots before emerging as beetles that devour plant leaves. Understanding their stages helps with targeted control to protect your lawn and garden.
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Japanese Beetle Adult

The adult Japanese beetle is a highly destructive pest, known for its metallic green and copper-colored shell. These beetles feed in groups, skeletonizing leaves and damaging a wide variety of plants. Controlling them early can help protect your lawn and garden from severe infestations.
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Adult Japanese Beetle on Leaf

An adult Japanese beetle caught in action, feeding on a leaf and leaving behind its signature skeletonized damage. These pests can quickly destroy plants if left unchecked, making early intervention essential for garden and landscape health.
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Japanese Beetles Damage on Leaf

Japanese beetles feasting on grape leaves, leaving behind their telltale skeletonized damage. These invasive pests can quickly weaken vines and reduce fruit production. Early control measures are key to protecting your grapes from infestation.
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Lawn Grubs Control Services - FAQs

How to Prevent Lawn Grubs Without Using Chemicals?

Taking control of lawn grubs can be simple and chemical-free by allowing the soil to dry out during July. Japanese beetles lay their eggs in lawns from late June to early July, and these white grub eggs are highly sensitive to a lack of moisture. Just one or two days of dry conditions can effectively kill the grub eggs. By turning off your sprinkler system for about a week in July during the egg laying period, you can eliminate the eggs’ viability. While the lawn may turn brown temporarily, it will bounce back swiftly with three deep waterings over three consecutive days.

Learn the 1-2-3-2-1 Lawn Watering Technique

If you follow the 1-2-3-2-1 lawn watering technique, your lawn will have sufficient time to dry out between watering sessions, further enhancing its resilience. Additionally, remember that grubs can be targeted by beneficial bacteria such as Bacillus thuringiensis and protozoa like Ovavesicula popilliae. By nurturing a living soil rich in microorganisms, you can create an environment that naturally combats these pests. With these strategies, you can maintain a healthy, vibrant lawn while steering clear of harmful chemicals.

Sprinkler Audit

Sprinkler Services
By far the most effective grub control is a properly programmed sprinkler system. Organo-Lawn offers sprinkler audits for our full season customers.

Additional FAQs - Grubs and Lawns

  • Grubs are the larval stage of beetles, such as Japanese beetles, June bugs, and chafer beetles. They feed on grassroots, causing turf to weaken, turn brown, and even peel away like loose carpet. Severe infestations can lead to dead patches and attract animals like birds, skunks, and raccoons that dig up the lawn to feed on them.

Grubs thrive in moist soil, which is why overwatering can create the perfect conditions for them to hatch and develop. Allowing the soil to dry out for at least 48 hours between watering cycles disrupts the grub life cycle by making the environment less hospitable for eggs and newly hatched larvae.

The 1-2-3-2-1 watering method is ideal for keeping your lawn healthy while discouraging grub infestations. This technique spaces out watering so that the lawn receives deep, infrequent hydration rather than frequent, shallow watering. The goal is to let the topsoil dry out for 48 hours between watering days, which helps kill grub eggs.

Yes, but recovery depends on the severity:

  • Mild damage: Aerate and overseed affected areas to promote regrowth.
  • Moderate damage: Apply compost and reseed to restore weakened spots.
  • Severe damage: If large areas of turf are dead, sodding or total lawn renovation may be necessary.

Preventative Control  

    1. Proper lawn watering where the lawn is not watered for 2 consecutive days during the month of July which will dehydrate the grub eggs, therefore killing them.
    2. Chemical treatment like Acelapryn, which can be applied in August to kill grub larvae while they are still young and before damage to the lawn has occurred.

Curative Products

    1. Chemical treatment like Acelapryn, which is applied after grubs have been discovered in the lawn, which is usually in the fall and/or early spring. This treatment will target and kill active, feeding grubs but must be watered in properly to be effective.

Japanese beetles (Popillia japonica) are invasive pests that damage plants in both their larval (grub) and adult stages. As grubs, they feed on grassroots, causing turf damage. As adults, they skeletonize leaves by eating the tissue between the veins, damaging lawns, gardens, and agricultural crops.

Native to Japan, these beetles were accidentally introduced to North America in the early 1900s. With few natural predators, their populations have spread across the United States, causing significant damage to turfgrass, ornamental plants, and crops.

Japanese beetles feed on over 300 plant species, with favorites including:

  • Roses
  • Grapes
  • Linden trees
  • Birch trees
  • Crabapple trees
  • Beans
  • Corn
  • Zinnias
  • Grubs are active in spring and fall, feeding on grassroots.
  • Adult beetles emerge in late June to early July, peaking in mid-summer when they feed on leaves and flowers.

Preventative Treatments 

Apply grub control products (like Acelapryn) in April or August to kill the larvae (Grubs) before they cause too much damage to lawns.

Biological Control

Use beneficial nematodes or milky spore disease to target grubs naturally.

Proper Watering 

Follow the 1-2-3-2-1 method to allow soil to dry out for 48 hours, disrupting grub development.

Handpicking

Remove beetles by hand in the early morning and drop them into soapy water.

Row Covers

Protect valuable plants with fine mesh netting.

Neem Oil

A natural insecticide (Lalguard) that deters beetles from feeding.

Companion Planting

Plant geraniums, garlic, or chives to repel them.

Traps

Use sparingly, as they may attract more beetles than they catch.

Insecticide Treatments

Liquid Acelapryn is an excellent chemical control and Lalguard is an excellent natural control. 

Completely eliminating Japanese beetles is difficult, but integrated pest management (IPM) using cultural (proper lawn watering techniques), biological (milky spore), and chemical methods (if necessary) can reduce their numbers and minimize damage over time.

By understanding the life cycle and control strategies of Japanese beetles, you can better protect your lawn and garden from these destructive pests.