How to Grow: Japanese Beetle Controls

Watch this video to learn about the life cycle of Japanese beetles and how to control them organically using sprays, hand picking and traps.


If you’re a gardener east of the Rockies you know about this pest the Japanese beetles. They plague gardens and feed on over 300 different types of plant. Now if you’re West of the Rockies, watch out. They might be coming your way.

Japanese beetles are tough to control because they love everything. Just let me give you a list of some of the plants they’ll feed on; apples, plums, cherries, grapes, hollyhocks, potentilla, hibiscus, zinnias, basil, and it goes on and on. So if you’re growing almost anything in your yard, you probably have Japanese beetles. Where they’re native in Japan they’re not really a big issue because they have parasitic flies that keep them under control. We’ve tried to introduce those in the Northeast over the last hundred years but they really haven’t gotten established so every year you see a lot of these adult beetles flying around.

The key to controlling Japanese beetles is to know something about their lifecycle. Japanese beetles start as c-shaped white grubs in the soil and in the spring they slowly move up through the upper levels of the soil till they get to a place, usually in early summer, where they’ll pupate. They emerge as this little guy right here that will be flying around feeding on everything. Their whole purpose in life is to eat and mate. What a life. Then they lay eggs all around the plants where they were feeding. The eggs hatch into C-shaped grubs and they spend the winter in the soil. The key is to control the grubs. Let me tell you how to do that.

The Japanese beetle grubs may be more or less severe depending on the weather. During really cold winters or really dry summers you’re going to have less grubs and therefore less beetles. But you can also enhance that effect too with two organic controls. One is called beneficial nematodes. Just like this product I have right here. This one’s called NEMA globe. Nematodes are microscopic little, wire worm-like creatures that use water channels in the soil to go on a seek and destroy mission. They actually parasitize the grubs. You would want to spray these on your lawn areas in May or June and then maybe again in September because that’s when the grubs are most likely to be in those upper level soil surfaces. That’s how they can find them and kill them. The key with this, of course, is to water the soil really well. That’s how they move around is through water channels. So do it right after a rain or water the area early and then afterwards after you spray them to keep it nice and moist. They really reduce the population so you have less adult beetles later on the summer.

Another product you can use is Milky Spore powder. This one works well in warmer areas because it over winters in the soil unlike the nematodes that you have to spray every year. The Milky Spore powder is a powder that will live in the soil and kill those grubs when it comes in contact with them. Both of these products work really nice to control those grubs and reduce the overall Japanese beetle population. Spraying nematodes or Milky Spore powder is a great way to reduce the grubs, especially around the plants, and their feeding because that’s what Japanese beetles do. They lay their eggs around where they feed.

But what about the adults. I’ve got a nice idea for you. Japanese beetles don’t like soapy water so what you can do is early in the morning when they’re still sluggish, go over to the plant and just knock them into the soapy water just by rustling the plant. Their response is to just drop right into the water and that will kill them. Of course you can crunch them too and you can hire a local kid to come over and pay for their first year of college tuition by paying them a dollar a beetle. Maybe not that much. But this is a good way to come out every morning and religiously reduce that population of Japanese beetles.

Another thing you can do to control Japanese beetle adults is to use the Japanese beetle traps. You’ve all probably seen these out in yards. A lot of these traps have a bad reputation because people think that they attract more beetles than they actually control. The key is to use them correctly. What you want to do with the Japanese beetles traps is keep them 100 to 200 feet away from your garden and ideally have about three or four of them per half acre lot so that you have a perimeter control of the Japanese beetles as they fly in. Also, keep them low to the ground because that’s the cruising altitude of Japanese beetles. Keep them a foot or two off the ground is ideal. When they’re that far away what they’ll do is with this pheromone they’ll lure the Japanese beetle in, they drop into the trap and you kill them. If you put them too close to the garden they’re going to go after your plants and not the trap and you get more damage. You can see how effective this is when you look inside you’ll just see our whole bag or a whole container filled with dead Japanese beetles.

For sprays you can use to control Japanese beetles, I’m an organic gardener so I stay away from the chemical sprays which certainly are effective. But even in the organic world certain broad-spectrum sprays like pyrethrum and spinosad are not that great to be used because they can kill honeybees as well. There is one spray that I’ve used, if you don’t mind your plants looking a little whitish, it’s called kaolin clay. This is a fine potter’s clay that you spray on the leaves of grapes or fruit trees. What it does is create a dusty film like you can see here on these leaves and the Japanese beetles don’t like to land on it or feed on those leaves.

So if you’re controlling the grubs in the soil, you’re hand picking them using traps, or even some of these sprays these are all great ways to control Japanese beetles in your yard.

Go here for more on controlling Japanese beetles.

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