How to Identify (and kill!) White Grubs

April 5, 2013 | Common Garden Pests

If you are a gardener chances are you have been out digging or rotottilling and have noticed white specs standing out against the dark brown of soil; the hated white grub.  And if you’re not a gardener chances are you have seen a June bug repeatedly knocking it’s head against your porch light on a warm summer night.  This seemingly unintelligent guest was also a white grub weeks prior.

White grubs belong to the Scarabaeidae family, and are usually referred to as scarabs.  Though some scarabs are not destructive during their beetle stage, they all have wreaked havoc on the roots of turf grass and ornamental plants in their larval stage.  Their damage can be sometimes overlooked, especially if the turf is watered and mammal pests like moles, possums, skunks and raccoons don’t start showing up to dig up your lawn and feed on the grubs.

So, you know you have white grubs but why do you need to know which white grubs you have?  If you plan on treating naturally it can be helpful to know what specifically you are dealing with or you may wish to know for your general edification.  For instance, milky spore will kill Japanese beetle larvae, but if you have a yard full of European chaffer you are probably wasting your money treating with milky spore.  Sending specimens off to a lab usually takes a week or two for results, and then they charge you for something you could have done with a little knowledge and a magnifying glass or field microscope.

If you decide to treat with beneficial nematodes (which kill all types of white grubs) we recommend Heterohabditus bacteriophora (Heteromask), but Steinernema feltiae (Scanmask) will also work.

Identifying White Grubs

First you will need some type of magnification, we recommend just a normal magnifying glass.  You will also need tweezers or forceps to hold your specimen still.  You will be looking at the rastral patterns on the grub, located on the underside right above the anus.

Oriental Beetle (Anamala orientalis) arrow

Oriental Beetle Raster

Then use these pictures of the five most common white grubs in North America to identify your grub.

Japanese Beetle Rasteral Pattern

Japanese Beetle


May-June Beetle Rasteral Pattern

May-June Beetle


European Chaffer Rastral Pattern

European Chaffer Beetle


Oriental Beetle Rastral Pattern

Oriental Beetle


Asiatic Garden Beetle Rastral Pattern

Asiatic Garden Beetle

Here is an actual example of the Asiatic Garden Beetle.

Asiatic garden beetle

Asiatic garden beetle rasteral pattern

It is important to compare what you are seeing against all of the drawings before making a determination.  Or, if you don’t feel like taking the time or have difficulty in determining whether you have Japanese beetles or one of the other four varieties, you could just treat with Heteromask.  25 million treats 1315 square feet, and 50 million treats 2630 square feet.  It is best (and most economical!) to treat just the areas effected by the grubs and the immediate surrounding areas.  Without a source of food (aka pest) the nematodes will die off and the treatment will be wasted.  There are two windows to treat for white grubs, early in the spring or late summer/early fall.  As always, if you have any questions please give us a call!

Happy Gardening.