God love July.
It might be the best month for small talk. Of vacations…of sweet corn…and of something with far less appeal.
“About ten days (now)," says Mark Thoms, manager of the Earl May off 22nd Street in West Des Moines. "We’ve been seeing them really strong right now.”
Thoms can’t get away from talk of the Japanese beetle—not right now.
Whether it’s with us on TV, or with the customers who flock to his Earl May store.
“You can see them walking in with their little baggies full of the Japanses beetles and sometimes they’ll have some of the foliage with it,” he laughs.
I get it. I’ve worked HARD on my gardens and look at this! From the tops of the trees to the roots of the lawn, they’re wreaking havoc in Iowa.
"It really does justify this title as THE worst insect pest we have,” says entomologist Dr. Donald Lewis of the Iowa State University Extension.
Wow! Even the Iowa State BUG guy is slamming the Japanese beetle! Even the people who sell pesticides want to see them go, because even they've got them!
“We knew last year (that this year) would be bad—as it was last year," Thoms says. "And sure enough, they are (bad) right now.”
And get this, the top-selling treatment for them—the pheromone trap—is not recommended. The garden centers sell beetle traps, but with a loud warning.
“It has a lure, it’s gonna lure your Japanese beetles to this trap," thoms warns. "And they will fall down into the trap. So with that, that’s an invitation, right?”
Right--one that works TOO well. You’ll draw in every beetle in town!
“That is a disadvantage for the trees in the garden," Lewis explains, "because you have attracted in more beetles than the traps will be able to hold.”
Dr. Lewis compares it to emptying the ocean with a bucket. Instead, you're better off targeting only those beetles that are already in your yard and on your plants.
Experts advise using a two-pronged approach.
First, use a systemic spray early on to soak the ground around the plants and then later to spray the leaves themselves. The plants will take up the poison and dispatch it to the beetles when they chew the leaves, killing them.
Second, spray any visible beetles directly with a contact pesticide such as Eight. This will kill them quickly. You can also opt for a more organic contact killer such as Bonide's widely-available Japanese beetle killer with pyrethrin.
“You can spray your edibles," says Thoms, "your fruits, your strawberries, your raspberries that you have—and stop seven days prior to harvest.”
You’ll want to save ornamentals, like your hibiscus (Thoms says these might be the beetles' favorite of all), but with trees, there’s another option: do nothing.
“We see those trees year after year turn brown," says Lewis, referring to the many linden trees on the Iowa State campus which are feasted on by the beetles. "The crabapple tree behind me turns brown every year, and every year they come back.”
The trees will turn brown and ugly but they’ll be back—just like the beetles.
(Thoms and Lewis also recommend applying "grub control" lawn fertilizer--that's step #3 of the Scott's 4-Step Lawn Care program--in September and early June to kill Japanese beetle grubs, which eat the roots of your grass and can ruin a lawn.)