Took this pic of Japanese Beetles doing the two things — the only two things — they do: fornicate and destroy — on some jewelweed plants yesterday.
Reminded me of when we were kids and would help Grammie Quarteroni drown as many as we could on you grapveines, and we would end up with quart cans of drowned beetles, but more were always ready to replace them.
Apparently, the status quo is still in place.
Like zombies rising from the grave, in late June, Japanese Beetles emerged from our lawns. Unlike zombies, the Japanese Beetles went for our plants. We’re safe, but our gardens are getting eaten!
It may seem as though Japanese Beetles will eat any green leaves, though Cornell University’s Cooperative Extension service reports the beetles prefer grape leaves, roses, and shrub willows. Vegetable gardeners may also find Japanese Beetles on beans, lettuce, kale, raspberries and rhubarb.
Japanese Beetles chew up leaves, leaving large leaf veins in place. Depending on the number of beetles involved, leaves can become skeletons in a few days. Sadly, the smell of beetle-eaten leaves attracts more beetles. And, of course, Japanese Beetles sniff their way toward other Japanese Beetles. One leads to two, two lead to three, and three lead to a beetles party.
As adult Japanese Beetles chow on your plants’ leaves, their offspring hatch out in the soil and nurse on your plants’ roots. Female beetles lay eggs within a short distance of where they’re eating. The grubs dine on the roots of your lawn. In big numbers, grubs can do significant damage by late fall, though your lawn might not show it until spring.
Responsible pest management
Insecticidal chemicals can kill Japanese Beetles, but these are quickly falling into disfavor. Chemicals usually kill far more insects than just the ones causing trouble. It’s a bad idea to kill pollinating bees and flies, and predatory insects just to stop a beetle infestation. (Predatory insects don’t harm your plants, but they may kill insects that do harm plants. Ladybugs are, perhaps, the best-known in this class.)
Many gardeners carry a container of hot, soapy water to the garden and knock beetles off the plants into the water. They remove more tenacious beetles by picking them with their fingers and dropping them in the container. During peak season, you can revisit an infested plant or planting bed several times a day and find more beetles each time.
Suzanne Wainright, aka Buglady Suzanne or The Buglady, teaches garden pest control to nursery and public garden operators and landscapers all over the United States. She suggests your Japanese Beetles may not be such a big problem. “Homeowners tend to overreact the moment they see bug damage,” she suggests. “Plants and insects evolved together; plants can handle being chewed. Many can lose up to a third of their leaf mass without suffering.”
If you decide to treat against Japanese Beetles, The Buglady encourages you to use biocontrols rather than chemicals. “Neem oil (a natural plant extract) kills adult Japanese Beetles. It breaks down fairly quickly and rain washes it away, so you have to apply it often.
“To control grubs, try beneficial nematodes instead of chemicals. Nematodes on the market kill grubs of all types — even good grubs — but they won’t affect other beneficial insects.” Nematodes are microscopic worms, many varieties of which already live in your soil. Companies such as Biologic, a Pennsylvania-based business, raise and package nematodes you can spray on your lawn.
Buglady Suzanne is enthusiastic about a new product that has just become available to homeowners. “BT Galleriae kills adult beetles and grubs that swallow it. It’s a naturally-occurring protein that pokes holes in the bugs’ stomachs.”
You can apply BT to leaves where adults are feeding. Or, apply it to your lawn in autumn so grubs consume it before they get large and hard to kill. Keeping the Japanese Beetle grub population down protects against turf damage and keeps your grass healthy.
Buglady Suzanne points out that killing grubs in your lawn won’t solve your adult Japanese Beetle woes. “The beetles are very mobile. The ones on your plants didn’t necessarily begin life as grubs in your own lawn. They’ll find their way to you from all over your neighborhood.”
What of the well-advertised, popular remedies for Japanese Beetles? They probably do more damage than good. “The idea of planting ‘trap crops’ (plantings specifically to attract beetles away from your main garden) isn’t so good because you’re feeding the beetles,” Suzanne observes. “The well-fed females will lay a lot of eggs.”
Pheromone traps also deserve a bad rap. They capture hundreds of beetles without decreasing the numbers eating your garden plants. The pheromones attract female beetles, so you’ll have even more hungry insects on your plants and you’ll end up with a lot more grubs in your and your neighbors’ lawns if you set up traps.
Suzanne specifically discredits Milky Spore: bacteria advertised to kill Japanese Beetle grubs. She says it can take several years for Milky Spore to build up to lethal levels in your soil — if the package even contains the correct bacteria. Milky Spore products at garden centers, while labeled as Japanese Beetle deterrents, have not necessarily contained Japanese-Beetle-killing germs. “Milky Spore is a joke; look for BT Galleriae to control Japanese Beetles,” Suzanne encourages.
Daniel Gasteiger speaks enthusiastically about gardening and real food. His book, Yes, You Can! And Freeze and Dry It, Too, teaches how to preserve produce. He blogs about gardening at http://www.smallkitchengarden.net.