Jim Dill
Pest Management Specialist Hi, I’m Jim Dill. I’m the pest management
specialist with the University of Maine Cooperative Extension and I want to talk to you a bit
about Japanese beetles. Here in the state of Maine, depending on where you live and
weather conditions, Japanese beetles start coming out at the end of June. Give or take
a week on either side of that, and you’re going to be able to look outside and find
Japanese beetles just about everywhere. What we want to do first is talk a little
bit about the biology. When the adults come out sometime around the end of June or beginning
of July, the first thing they do is look for a food source. Once they start feeding on
the food source, their priority is finding a mate. When they find one, they begin mating
and lay their eggs about 10 days later. In most parts of the state, the Japanese beetle
is laying eggs in the turf by the middle or end of July. The larvae hatch a couple weeks
later, so by about the middle of August you’ve got larvae feeding on the roots of your grass.
When we talk about management, there are two different strategies to work with. One is
controlling the adults, and the other is to deal with the larvae. One of the things I
suggest is to fill a container with water and put in a little dish washing liquid. Once
you’ve got a few drops in, it breaks the water’s surface tension so the beetles fall
in and drown. Then all you do is place the bucket underneath the plant and start tapping.
Yes, a lot of them will fly away – that’s just the nature of them.
The next method of controlling them works great, especially if you have kids. For some
reason, kids just love to get out there with a regular old car vacuum or hand vacuum. Just
charge it up and vacuum up the beetles. Admittedly, once you’ve done this, you probably want
to dedicate the vacuum to doing this, because it gets a little messy inside. Once you’ve
vacuumed them up, you’ve got them trapped in there, so you open it, dump it into soapy
water and the adults drown. There are several organic materials available
to the homeowner, including spray pesticides that work quite well. A couple of them contain
some type of insecticidal soap, which actually smothers the adult beetles. You can also use
something containing Neem, which is an anti-feedant – it prevents the beetles from feeding.
Once you spray it on, they will stop feeding and eventually leave the plant alone and die
due to its toxic effects. I’d be remiss if I didn’t talk about this
last thing, and that is Japanese beetle traps. Everybody asks, “Should I use Japanese beetle
traps?” Of course, the big joke is, “Yeah, give them to your neighbor, put them in his
or her yard and all the beetles go over there.” Well, that’s not so far from the truth.
What happens is there are three things that act when you’ve got a Japanese beetle trap.
You’ve got the bright yellow color, and then there are two different lures we put
in there. One is a pheromone lure that attracts just the males, and the other one’s a floral
lure that attracts both males and females. So they go to fly into the trap, but they’re
not the best flyers in the world. They’re good, but they’re not the best at landings.
So if your trap is sitting in your rose bush, they go flying into it but miss and get all
over the roses. So even though your Japanese beetle trap will
be great, will work and will just be full of beetles, you want to take a stake and put
your trap at least 50 feet away from what you’re trying to protect. As I said, the
Japanese beetles come out here in Maine sometime around the end of June, start mating and lay
their eggs sometime from the middle of July until the end of July. What they look for
is a nice grassy area. The females go down and lay their eggs, and within 10 days, depending
on the weather and the temperature, those eggs hatch.
As soon as they hatch, the first thing they start doing is feeding on the roots of the
plant. If you want to try to control these stages of the Japanese beetle and don’t
mind using a synthetic insecticide, there are two or three of those available on the
market that can be used quite effectively. If you want to try to do it organically, the
only thing that really seems to help here in the state of Maine is using nematodes.
We use what we call the HB nematode. You can call your local extension folks and they can
tell you about it, or you can go online and Google it. The HB stands for the scientific
name, which is 20 syllables long or so, but all you need to say is HB nematode and it
will come up. A lot of the time they come in a little sponge. You soak that for an hour,
put the nematodes in a watering can, spray it out over 5,000 square feet and then those
nematodes attack the grubs. Whether you’re going to use nematodes or
some type of synthetic chemical in your lawn, the time to do that is from the middle of
August until the beginning of September. That way, you’ll get most of the more complex
grubs, because there are other things aside from the Japanese beetle out there that will
be hatched and susceptible at that stage. Of course, the last option you have is to
call in a professional certified pesticide applicator who can come in and treat your
lawn or shrubs.