The scoop on Japanese beetles and brown marmorated stink bugs

Gardeners — it’s time to gear up for the bug invasion. No, it wasn’t enough for us to have to battle with Colorado potato beetles, iris borers, cutworms, four-lined plant bugs, tent caterpillars, aphids, mites and sawflies. Now, as you probably well know, Japanese beetles are upon us. In a few short weeks they will be chewing up your plants and making out in your yard!

But that’s not all. It’s likely we will soon be seeing the brown marmorated stink bug (Halyomorpha halys), too. More on those in just a minute. First, let’s talk about Japanese beetles. I wrote about these critters last season, but questions come up about them all the time, so I’ll pass along the latest information from Jeff Hahn, an entomologist with the University of Minnesota Extension Service.

Hahn says it’s hard to know how bad this year’s infestation will be. But he figures if you were unlucky enough to have a yard full of Japanese beetles last year, you can probably look forward to the same, or worse, this season. Female Japanese beetles lay eggs in the soil beneath turf grass in the summer, so the mild weather this winter was a good thing for the grubs that spent months burrowed deep in the earth. The lack of snow cover might have reduced their numbers a bit. It’s hard to know right now. 

Because warm temps came so early this spring, we’ll likely start seeing Japanese beetles during the last half of June rather than early July. That means murderous thoughts will be on our minds at least through the middle of September. Trouble is, there’s no good way to kill these buggers. 

Can’t kill the boogie man

Those pheromone traps that you see for sale everywhere don’t work. Oh, they definitely attract beetles the way they say they will. But they attract so many beetles that they make a bad infestation worse. Please don’t buy these, and if your neighbor hangs one up, beg them to take it down. If you feel they won’t take that approach very well, steal the trap in the night and throw it away. Later, attribute the theft to “kids today.” 

You’ve probably heard about various turf grass treatments to get rid of Japanese beetles. Strategies usually involve using some kind of preventative insecticide to kill the larvae. Timing of the treatment is crucial because these chemicals only work at the early larval stage. They aren’t effective against older larvae. 

But timing isn’t the biggest challenge facing those who pin their hopes on treating turf to get rid of beetles. Adult Japanese beetles can and do fly miles to get to plants they like. So you can treat your grass all you want, but if all of your neighbors for miles don’t treat theirs, you’re going to have beetles on your plants. There’s no way around it. 

Why spray a bunch of potentially harmful chemicals that probably aren’t going to do much good anyway? Despite the stink (they smell terrible when they gather in groups), damage and general horror caused by Japanese beetles, the best approach to dealing with them is to walk around knocking them off plants into a bucket of soapy water. It’s gross, so wear gloves. If you’ve heard they bite, don’t be too alarmed. I’ve personally consigned thousands of these beetles to a watery death with nary a chomp, so they can’t be too vicious. 

Stink bugs

You may not have spotted one yet, but like Japanese beetles, emerald ash borer and other invasive pests that have found their way into the U.S. in recent years, the brown marmorated stink bug is likely to cause problems for a wide variety of plants once they become widespread. 

Like our native stink bugs, brown marmorated stink bugs are brown and sort of flat and triangular-shaped. Get in close though and you’ll notice that these new invaders have white markings on their abdomens and light-colored bands on their otherwise dark antennae. (Warning: True to their name, these bugs reek so it’s probably not such a good idea to hold them close to your nose for inspection.)

Brown marmorated stink bugs feed on many plants, but they particularly enjoy feeding on fruit trees, some vegetables and soybeans. Researchers are keeping an eye on this new pest and they’ll take any help they can get. If you come across one of these smelly critters contact Arrest the Pest at 651-201-6684 or 1-888-545-6684. 

Or, send an email: arrest.the.pest@state.mn.us. 

Meleah Maynard is a writer and Master Gardener. Email her a question or read her weekly gardening updates at her blog: everydaygardener.com.