We first saw a Japanese beetle (Popillia japonica) in our Racine, Wisconsin backyard a few years ago. They were devouring our rose bush. So, after reading about the use of geraniums as a trap crop (since geraniums are toxic to Japanese beetles), we planted a geranium next to our rose bush and the beetle problem seemed to go away.
This year, however, we — like many others in Racine — are finding these destructive pests all over the place. Oddly, they are not destroying the rose bush so far, but squadrons of Japanese beetles are busily turning our birch leaves, our crabapple leaves, and our neighbor’s grape leaves to brown lace.
So I have begun researching these pests on the Web, beginning with a PDF pamphlet from the USDA called “Managing the Japanese Beetle: A Homeowner’s Handbook.”
The publication says that Japanese beetles are a serious problem:
Today, the Japanese beetle is the most widespread turf-grass pest in the United States. Efforts to control the larval and adult stages are estimated to cost more than $460 million a year. Losses attributable to the larval stage alone have been estimated at $234 million per year—$78 million for control costs and an additional $156 million for replacement of damaged turf.
Grubs in lawn
Japanese beetles (Popillia japonica Newman) spend most of their life cycle — about 10 months of the year — underground as grubs. This is the larval stage, after the eggs hatch in the ground about 3 inches deep. The young grubs feed on grass roots until late autumn, growing to about an inch long, and then burrow down a little further (4 to 8 inches deep) and stay inactive all winter. In the spring, they go back to feeding on grass roots some more until transforming into pupae and then emerging as adult beetles in late spring or early summer.
The adults feed on a wide variety of plants during summer, with the females slipping away from time to time to lay eggs in the soil — about 40 to 60 eggs for each female. Then the eggs hatch, and the year-long cycle starts all over again.
(The above illustration and the grub photo are both taken from USDA Japanese beetle publications.)
So: How to get rid of the beetles?
One thing the USDA pamphlet makes clear is that Japanese beetles are here to stay. Since first being found in the United States near Riverton, New Jersey in 1916, they have been spreading westward like many other immigrants. Completely getting rid of these beetles is unrealistic. We have to learn to control, manage, and live with them — and it doesn’t look like this will be easy.
A Journal Times story by Racine County UW-Extension horticulture educator Patti Nagai this past Sunday notes the popular method of brushing the beetles downward into a bucket of soapy water. This will kill them, but is probably not a practical solution for our 40-foot birch tree — and it also ignores any eggs already laid in the lawn, as well as grubs already hatched.
Nagai also lists a number of insecticides, but my first instinct is to avoid insecticides as much as possible for fear of harming bees, butterflies, earthworms, birds, and fellow humans.
Milky spore, nematodes
Biological beetle control, however, sounds complicated and bizarre. For example, the USDA details the application of nematodes — microscopic parasitic roundworms — which grow their own bacterial lunch in the grubs’ bodies, killing the grubs in the process. One particular type of nematode, our friend Heterorhabditis bacteriophor, is apparently effective in controlling white grubs in lawn along with similar pests. You can buy beneficial nematodes on the Internet, spray them onto your damp lawn in the evening, and they’ll go to work injecting the grubs with bacteria. Still, the notion of spreading parasitic pinworms all over my yard makes me almost as uneasy as chemicals do.
Another funky-sounding suggestion is to kill the grubs with milky spore disease — but according to the USDA, it can take 2 to 4 years for enough milky spore disease to build up, and it works best when your whole neighborhood uses it. I’m not sure I’m ready to mount a door-to-door milky spore campaign.
Bag-A-Bug, Japanese beetle traps
There are Japanese beetle trap systems, such as Bag-A-Bug, which use “the Japanese beetle’s own natural sex attractant together with a proven floral lure” to attract the insects.
Unfortunately, according to the Japanese beetle page at UW-Extension Cooperative Extension, “the presence of beetles on or near a plant will attract more beetles. Consequently, use of Japanese beetle traps often attracts more beetles, and results in subsequent damage to plants.”
Consumer grub control products
The Scotts Company offers Scotts® GrubEx®1 Season-Long Grub Killer which employs 0.08% Chlorantraniliprole to kill grubs via one spreader application at some point from May to July (see also the “Preventing Grub Damage” video).
We’re now into August, so I don’t know if I’m too late for it this year. A Michigan State University Turfgrass Science article — “Home Lawn Grub Control Products 2011” — says to apply “between April 15 and May 15 for best results” because “it takes quite a bit longer to move down to where the grubs will be.”
That same article notes Bayer Advanced 24 hr Grub Killer Plus (9.3% trichlorfon) as something which will kill active grubs in the spring or fall. This sounds super — until you start reading about trichlorfon and birth defects, cancer, its toxic effects on birds (regurgitation, imbalance, trembling, slowness, lack of movement and wing-beat convulsions), groundwater contamination, and so on.
That’s what I have learned so far. I’ll keep searching and add anything else here which seems worthwhile or at least entertaining.
If you have Japanese beetle control methods or related insights you would like to share, please leave a comment below.