Should You Use Japanese Beetle Traps? Here's What Experts Say

If you're trying to keep beetles from ruining your garden, a trap can make things worse when used incorrectly.

Some insects, such as butterflies and other pollinators, get a warm welcome when they visit gardens. However, there are plenty of other bugs that you don't want to spot around your yard, and Japanese beetles are some of the most destructive pests of both ornamental and edible plants. These insects usually appear in May or June, snacking on vegetation into August. When you first spy the beetles munching on your roses or raspberry plants, putting out a trap might seem like a good idea. However, some experts and researchers say these devices aren't necessarily the best way to keep Japanese beetles at bay. In fact, a trap could even make your pest problem worse.

japanese beetle on green leaf
Blaine Moats

The Problem with Japanese Beetle Traps

"Japanese beetle traps, like other insect traps, are used mainly for determining how bad the infestation is and for eliminating several beetles at once," explains Ryan Smith, an entomologist and owner of Ant and Garden Organic Pest Control in Beaverton, Oregon. There are two types of scents that these traps use: a pheromone that attracts males and a floral scent that brings in males and females.

"However, [the traps] can be a problem if you're living in a residential area surrounded by neighbors with gardens and yards," Smith says. "Studies show that Japanese beetle traps can lure these insects that are as far away as five miles. So, with the use of Japanese beetle traps, you might be bringing more of these pests into your backyard."

The Best Way to Use Japanese Beetle Traps

Still, not all experts say you should avoid traps. "Actually, there are no reasons to avoid using Japanese beetle traps, if you know how to use them properly," says Nicholas Martin, an entomologist and founder of Pest Control Hacks. The beetles are "avid travelers that seek food sources and cover large distances to feed. You should place the traps away from flowering bushes and plants that may attract these insects more than the trap," he explains. At least 30 feet away is the standard recommendation, but the further, the better to make sure most beetles end up in the trap and not on the plants you're trying to protect.

Once you've set out a trap, you may notice that it will fill up rather quickly. To help the trap continue to be effective, you need to empty it frequently. If it overflows, all those beetles will probably find their way to your plants instead of staying in or around the trap.

Japanese Beetle Trap Alternatives

"To get rid of Japanese beetles in your garden, you can start by picking them by hand, especially if there's not that many," Smith says. If you aren't squeamish, you can crush the beetles or just drop them into a container of soapy water to kill them. Smith also offers the following homemade solution to spray on any beetles you see. It will kill them without harming your plants.

DIY Japanese Beetle Insecticide

  • 1 tsp. dishwashing liquid
  • 1 cup vegetable oil
  • 1 cup rubbing alcohol
  • 4 cups water

Mix your ingredients, put them into a spray bottle, and spritz the concoction onto the bugs. The beetles will continue to appear over several weeks, so you'll need to check for them often before they can do much damage.

Leaving the Japanese Beetles Be

Scientists and backyard gardeners alike have observed that Japanese beetles are more plentiful some years than others, so if you don't have a very heavy infestation, sometimes the best course of action is to just leave them alone. Yes, the bugs can certainly be a nuisance, but they don't usually cause enough damage to kill well-established plants. And even though these insects are not native to North America, they provide a food source for many species of wild birds and mammals, which naturally help keep Japanese beetle populations in check.

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