How to find out if your garden grubs are friends, foes … or a meal

grubs square

A member of our gardening group found these grubs, about the size of a quarter, in his garden. The post prompted a discussion on whether a planter’s friend or foe. Photo courtesy: Jeff Galios

Recently, a member of our Facebook gardening group found new residents in his garden: grubs.

Jeff Galios is known as our group’s pepper guru, and he found the fat, white, quarter-sized grubs in a planter. His post set off a discussion about these small critters, which are the immature (larval) form of a beetle and can live in your soil for as long as a year.

We set to work consulting the literature on whether grubs are good or bad for our gardens, and we found out the answer isn’t so simple. Before you can deem your grubs friend or foe, you need to do a little detective work.

Step No. 1: Find out what type of grubs are growing in your soil.

The coconut rhinoceros beetle is an invasive species to Hawaii and should not be kept in any capacity. The problem is, its grubs look very similar to the oriental flower beetle, which has been in Hawaii since 2002.

One difference between the two is that oriental flower beetle grubs wiggles on their backs, while coconut rhinoceros beetle grubs wiggle on their sides. Both will curl up into a C-shape when first exposed to air, so you may have to wait a bit for them to start wiggling. If you suspect that you have coconut rhinoceros beetle grubs, call the state Department of Agriculture’s pest hotline (643-PEST) immediately.

Step. No. 2: Weigh the pros and cons of grubs in your soil.

Assuming your grubs belong to a beetle other than the coconut rhinoceros beetle, you can begin weighing the pros and cons of their presence in your garden.

• The downside:

Grubs feed on plant roots and so you may not be aware of them until you see their damage. An infestation of grubs under your grass can result in the affected area becoming spongy, allowing the sod to be rolled back like a piece of carpet.

You’ve got an infestation if there are more than 10 grubs per square foot in your soil. There are organic and chemical methods around to control their populations. If you have pets, you might want to go with something organic. Consult your local garden shop for suggested products.

grubs soil

Grubs could make a welcome addition to your compost pile. Just read up before adding them. Photo courtesy: Jeff Galios

• The upside:

Similar to a worm composting bin, you can add grubs to your compost pile to speed up the decomposition of your organic materials. Just like worms, the tunnels grubs dig through the compost pile allow air and moisture to penetrate and accelerate the decomposition process.

If you already have a compost bin with worms, you probably shouldn’t add grubs. The leachate (liquid runoff) from grubs tend to be too acidic for worms; the two of them only seem to coexist when there’s a small number of grubs.

If you are trying to decide between grubs and worms in your compost pile, consider the following:

• Grub compost bins can decompose organic material faster, as they eat anything organic they come into contact with, while worms consume the bacteria generated by decaying materials.

• Worms can tolerate compost piles in various stages of dampness, while grubs need a relatively dryer medium. This is something to consider especially if your bin is kept outdoors.

• Grubs mature and will eventually leave your bin/pile. Hopefully once mature, they will lay eggs to keep the process going indefinitely. If you plan on keeping your bin indoors, you may want to go with worms, unless you are OK with mature beetles crawling around your kitchen.

Step No. 3: Go for grub with grubs. Or not.

According to, there are an estimated 1,462 species of edible insects, including — you guessed it — grubs. If you have the stomach to munch on them — fried, grilled, roasted or stewed — you can count on a meal that’s high in protein, calcium and phosphorous.

Lost your appetite? Maybe your pets are hungry for them. Grubs are a delicious meal for birds and if you have a pond or aquarium, your fish will enjoy nibbling at them as well. As you might guess, grubs are also popular live bait used in fishing.

As spring approaches, possible damage from grubs will become visible so keep your eyes open and begin weighing your options.

As for Jeff, from our gardening group, he decided to keep his grubs around, letting them complete their larvae cycle. Many fellow gardeners jokingly urged him to try eating one. He said he was tempted to throw one on the grill but chickened out. In either case, I’m sure friends of his will be closely analyzing the food at his next barbecue.



Fernando Pacheco is a blogger for being 808, a content specialist at HMSA and a media jack-of-all trades. He’s dedicated to seeking a healthier lifestyle for himself and his family. Join him on his journey on our blog and on social media! Chat with him directly on Twitter.



  • did you find out what type of grub these are?


    • My apologies for the late reply. This article was written a year ago and I had to follow up with the gardener who had discovered the grubs. Here is his reply:

      “I really don’t know what they were. i had em in a soil potted container for a long while but never saw them emerge. so i figured i might as well dump em out in my garden. figured the compost will be good for the plants. they were still alive so i let them be. i still dont know what species they were but sources tell me they could be Japanese garden beetles.”


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