Grub Worms in The Garden – Are They a Problem?

Grub Worms. You find them in the garden, in your lawn, almost anywhere that there are a few inches of soil.  White or grayish, these little creatures can be anywhere from ½ inch in length to some that are as big as your little finger.  What are they?  Are they bad?   Are they dangerous?  Should I do anything about them?

Grub Worms - white grub

What Are Grub Worms

You are digging grub worms out of the soil.  Grubs are the larval stage of several species of beetles.  Some of these beetles are considered beneficial in the garden and some are considered pests.  It is hard to tell what beetle will emerge from the grub you have found in your soil.  However, in West Texas, the most prevalent grub found in soil in gardens and lawns is the white grub worm.

The white grub worm is the larval stage of what most people call Junebugs.  Junebugs are true beetles.  Beetles are distinguished from other insects by the hard case that folds over the back, protecting their abdomen and their hind wings.  This hard-shell are actually wings that have hardened to form this protective shield.

Grub WOrms - adult junebug

The Junebugs lifecycle takes place above ground and below ground.  Mid-summer, the females burrow a few inches into the ground and lay their eggs.  Approximately two and a half weeks later, the eggs hatch into the larval stage that we know as grubs.

The grubs are the larval stage in the Junebugs development.  The grubs overwinter in the soil, eating almost anything they can find as they burrow and move around.  This continual feeding includes the roots of most plants. Most of the destruction done by white grubs is during this feeding stage during the winter months.

Are Grub Worms Bad?

Of the 100’s of grubs that can inhabit the soil, the white grub is the one most seen and is the one that causes the most destruction.  White grubs will feed voraciously for months underground and can leave your turfgrass without enough root system to support healthy above-ground growth in the spring. 

If you have planted cover crops in your garden to enrich the soil, the white grubs can inhibit your cover crop from performing this function by eating away the roots that should be capturing nutrients to put back into your soil.

Grub WOrms - turf damage

From the standpoint of economics and aesthetics, grubs can be one of the most destructive winter pests you can have in your garden or turfgrass. 

When the grub pupates and matures into the brown Junebugs with which we are all familiar, they emerge from the soil and prepare to start the cycle over again.  Junebugs feed on the leaves of oak trees and walnut trees and may forage on other plants as well.  While not as destructive as the grub stage, they can cause some damage to plants.

Are Grub Worms Dangerous?

Grubs and Junebugs are not dangerous to humans or pets.  They are not toxic.  If these creatures are grown in sterile soil, they can be eater easily and provide a rich source of protein.  I am not advocating that you put grubs into your diet, but it is a fact that in some environments where grubs grow large, they make an excellent protein source for many cultures.

With that almost disgusting fact out of the way, you are safe handling these insects.  They don’t transmit diseases to humans or animals.  Neither the grubs nor the adult beetles have stingers, nor do they bite. 

Do Grub Worms Have Any Positive Function?

Grubs are part of the soil food web.   Grubs feed on organic material in the soil.  Many of the nutrients in this organic material is returns to the soil in the form of castings. Many birds and other insects prey on the Junebugs, providing spring and summer food sources.  Yes.  Junebugs and grubs do have a role to play in the natural workings of the soil biome.  The problem is the impact that they have on our human desires.

In a perfect system, other organisms in the soil and the predation of other creatures would keep the Junebug and grubs in balance with the rest of the system.  However, maintaining a well-balanced soil biome and garden habitat runs counter to our desires and ideas of the perfect landscape.

How Do I Know If I have A Grub Worm Problem?

The presence of grubs is a natural part of the soil biome.  You are never going to have a perfectly grub free turf or garden.  The problem arises when the natural predators of the grub and Junebug aren’t present and the Junebugs have free rein to lay eggs and for grubs to develop.  That leads to an infestation.

Grub Worms - grub infestation

Generally, if you find more than 6 to 10 grubs per square foot of garden or turf soil, you have an infestation.  An easy way to check doesn’t require anything more sophisticated than a shovel and a little time.  Turn over a shovel full of turf or soil in your garden and break that lump of soil apart carefully.  Count the number of grubs you find in the shovel full of soil.

Ideally, you should find no more than 3 to 4 grubs in the clump of soil.  Any more than that and you may have a problem.  It is also a good idea to count and record how many earthworms you find as well as any other creatures that you find living in your soi.   This is an excellent way to judge the health of your soil biome.

Ok.  I Have a Grub Worm Problem.  What do I do Now?

Controlling grubs organically requires a holistic approach to your soil.  Understanding that the soil biome is a complex system and that when it is in balance and working properly, infestations and disease problems are almost non-existent.  If you have an infestation or disease problems, it is a good sign that there is something wrong with your soil.  Gaining control of the situation requires recognizing that an infestation or disease is a symptom, not the real problem.

In many instances, the culprit behind a grub infestation is us.  The standard response to controlling grubs is to apply a systemic pesticide to the turfgrass or garden plants.  This system insecticide is distributed through the plant, the grub eats the plant roots, and the insecticide kills the grub.

grub worms - don't spray

What we often fail to realize is that it isn’t just the grubs that eat the plants.  All the other organisms in the soil also eat the plants or the decaying parts of the plants.  Systemic insecticides are non-specific.  Anything that eats the plant material will probably be affected as well.  This can leave your soil sterile and devoid of much of the life that keeps the soil biome healthy. 

Don’t forget the above ground beneficial insects that feed on the plants as well, especially bees.  Many bee species that feed on the nectar from flowing plants are susceptible to the systemic insecticides we spray to control grubs. 

How do I Get Control of Grub Worms without Chemicals?

First, you don’t get control.  You work to build a healthy soil biome.  This is not a control issue. You nurture the soil and let nature control the problem.  The goal is to regenerate the soil and encourage a rich and diverse soil biome that will take care of itself, saving you the trouble and expense of trying to maintain control.

The Steps to Natural Grub Worm Control

  • First and Foremost – Our philosophy is to never, ever use pesticides, herbicides, or synthetic fertilizers on your yard or your garden.  That should be your first step.  Just stop.
  • Feed the Soil, Not the Plants – Plants don’t just seek out the nutrients they need in the soil around their roots.  The plants exist as part of a dynamic and complex food web that exists in the soil.  From the smallest bacteria to the largest creatures such as earthworms, they all work together to produce and deliver the nutrients that your plants need.  Keep the soil healthy, and the soil will keep your plants healthy.
  • Don’t Till – Tilling destroys the soil biome.  Good soil doesn’t need tilling to properly infiltrate water, to incorporate organic matter, or to aerate properly.  Weill aggregated soil does all of this naturally and it is the soil biome that creates these soil aggregates. 

When an Infestation must be Controlled

If you have an infestation of grubs and you can’t wait for your soil biome to naturally respond, there are some natural things you can do to remedy the situation.  One of the best is to apply beneficial nematodes to your soil and let them mitigate the problem. 

grub worms - nematode

Nematodes are tiny worm-like creatures and are predators by nature.  You can purchase predatory nematodes that are specific to grubs.  These little agents of destruction will attack the grubs and reduce the infestation. There are some caveats to using grubs that you should understand

  • Timing is Everything – The application of beneficial nematodes for grub control should be made in late summer or early fall when the eggs of the Junebug are getting ready to hatch.  If you apply the nematodes in the spring, most of the grubs will pupate and be gone before the nematodes can do their work.
  • Conditions Must be Right – Nematodes need the right soil conditions to be able to move through the soil to find the grubs.  Soil moisture must be correct to allow the nematodes to do their work.   Follow the instructions that come with your nematode order to make sure that you get the best results.
  • Buy the Right Nematodes – There are hundreds of varieties of beneficial nematodes available.  Make sure that you get the nematodes that specialize in white grubs.  Talk to the supplier about your problem and your situation.  Most reputable suppliers will be happy to give you advice and direct you to the best solution for your grub problem.

The Long Term Solution for Grub Worms

In the end, the best method we have found for controlling grubs, as well as other pests and diseases, is to let nature take charge.  When we get out of the way and let nature regain control, the soil biome systems begin to regulate themselves.  This creates balance and ensures that the soil is healthy, which produces healthy turf and plants. 

Working with nature and understanding the processes works much better than trying to control nature and manage these complex processes, many of which even the best scientists in the world don’t fully understand. 

Feed the soil, not the plant.

Links and Resources

For more information about organic gardening, lifestyles, and living, visit our website at West Texas Organic Gardening.

If you found the information here helpful, you might also find these articles on our website of interest.

Organic Growing Myths

Toss Your Tiller

Building Healthy Soil

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