A good grub is hard to find, butt not impossible
I nearly ran my car off the road when I saw it. A monstrous grub looming toward me from a billboard, with the message that I should hire a landscape company to kill it before it killed my lawn. The heck with my lawn! That grub looked like it wanted to plop right off that billboard and eat a few Riverfront Trail bikers for a snack.
Grubs are the immature form of the insect class that most people know as beetles. There are so many insects in this class, officially called Coleoptera, that they comprise about 25 percent of the insects in the whole world. This means there are a LOT of grubs wriggling around out there. I try not to think about that when I’m going to sleep at night.
Grubs have to be one of the most unattractive, squirm-worthy forms of insects in the world. Seriously. They’re fleshy and moist and sometimes it’s hard to tell which end is the head and … bleaaaah … I’m gagging a little here.
Before I took the Colorado State University Master Gardener course, I truly thought that the only good grub was a dead grub. The truth is, some grubs are incredibly destructive. Others aren’t, and it’s difficult to tell the difference for those of us who aren’t trained entomologists.
The really, really sinister grubs don’t even live here. They’re the grubs that grow into the Japanese beetle, an insect famous for defoliating pretty much everything in its path. If you know anyone who lives in the Midwest or the East, they probably have horror stories. We briefly had a battle with Japanese beetles in Palisade that started in 2002, but experts were able to successfully eradicate the invasive insect within a few years, which prevented significant damage to orchards and vineyards.
Yes, some grubs live in the soil and feed on plant roots. Other grubs live in the soil and eat things that are already dead; they help compost organic materials. So these hideous things can sometimes be helpful. Hard to imagine, I know.
How do you tell the difference between a bad grub and a not-so-bad grub? I knew you would ask. Ugh. First, you have to wash the grub off if it’s really dirty so you can see it properly. You’d better have a magnifying glass ready. Oh boy.
Try to straighten the grub out and get a good look at its hind end. It’s absolutely no help that grubs are naturally shaped like the letter “C” and will probably try to curl up because you’re messing with it.
Now, determine which end is the grub’s butt and position your magnifying glass accordingly. You’re looking for the shape of the grub’s “anal slit” (not kidding) and the “raster pattern,” the design of hairs on the grub’s butt (totally not kidding). These characteristics identify the grub species. If you’re looking for some helpful photos of this for your own little grub-identification lab, just google “grub identification” images and you will be set.
My tactic when dealing with grubs is (honestly) to let out a little shriek of disgust, pick up the grub and throw it in the street. Squishing them is too gross. I should be more responsible and actually wash the grub off, get my hand lens and examine the pattern of hairs on its butt to determine if it’s a “bad guy.” Strangely, most of the time I just don’t feel like getting that intimate with a grub.
Doesn’t this sound fun? There’s no ifs, ands or butts about it, identifying grubs is a little complicated and quite frankly, disgusting. But I tell you this for the purpose of letting you know that just because you find a grub in your garden or lawn, it doesn’t mean you necessarily need to spend a ton of money on chemical treatments to eradicate them.
Take the time to find out if it’s a good guy or a bad guy and it could save you a significant amount of money. If you can’t figure it out, take one of the grubs to the CSU Extension office for identification. Even if you have one of the bad guys, you should still identify the species so you can effectively time the treatments and use the right chemicals or make sure the company you hire does so.