Thursday, August 24, 2006

Natural Predators For Japanese Beetles

We are plagued with Japanese Beetles every year and they take over our Rose of Sharon bushes hardly allowing them to bloom since they eat the buds.

One year I picked them off and put them in water and felt so bad about it. Instinct told me that something could possibly benefit by leaving them. We now leave them. The bushes are not good to look at and certainly not nice to be around. They last 4-6 weeks with an interest in about 300 species of plants. Fortunately for us, they seem to congregate mainly on the Rose of Sharons.

Some birds love to eat Japanese beetle, so attract them to your landscape with birdbaths, feeders and nesting boxes that are nearby where you have beetle problems. Don’t chase away starlings! These birds may be considered pests, but again, they have a great purpose when it comes to Japanese beetles. They eat the adult beetles and the grubs in the ground.

Another great natural enemy is the Spring Tiphia wasp, which was imported into America from China to control the beetles. The female wasp goes into the soil and lays her eggs right on Japanese beetle grubs, killing up to 85 percent of the grubs in a lawn. Sounds way better than poisonous chemical insecticides! Plant forsythia, peonies, and firethorn to attract these beneficial wasps.

After they are done feasting, they lay eggs that produce grubs that winter over and become beetles next year. There are many critters that dig these grubs up and eat them. Sometimes I find one while digging in the garden and I put it in the bird feeder as a juicy morsel for some fortunate bird. If you've got turf grasses, these guys will kill it. Fortunately we don't want a lot of grass since it doesn't serve much purpose for wildlife, so that's not been a concern.

My friends and neighbors have tried sprays and the bags that you hang around the garden to collect them, but their bushes don't appear to look any better than ours during this time period. The beetles release a substance that attracts more beetles and these bags have that substance in them. However, I've read online at various places that the bags seem to attract more beetles than they collect, so they're mostly being promoted now by places that sell them.

Patience is something I get to practice while waiting for the beetles to have their fill and be finished with our bushes and then the bushes seem to bloom profusely. It seems that the beetles have given them determination to shine after the battle is over.

Related Articles
Japanese Beetles And Birds
Japanese Beetles Life Cycle
Japanese Beetles Rise Again - Go Natural
Battling Japanese Beetles
Japanese Beetle-Proof Your Roses


Beatriz Moisset said...

Another wasp that feeds on Japanese beetles is the blue winged one, Scolia dubia ( There are also some tachinid flies that lay their eggs on Japanese beetles ( (

pathfinder027 said...

Rather than let the beetles have their way, I pick them off my beans and raspberry plants and drop them in a weak solution of soapy water. Beetles, like ants, leave pheromones to attract more of their kind. If you pick them off as they come, there are fewer beetles that follow, due to less of a pheromone trail. I also spread milky spore powder in my lawn, which attacks and kills the grubs. They don't seem to bother my roses or my rose of Sharon, as long as the pole beans are growing nearby.

sharingsunshine said...

That's what I did the last year we had them (the soapy water) but it really grossed me out to do that and I felt so guilty! LOL I have noticed that there are lots of holes in the yard about the time they begin making their way to the surface. We have skunks and they seem to love digging for them and I have seen the raccoon digging also and have heard that opossums eat them too, so I'm sure they've been helping out.

One point you make is about the pheromone trail. Those bags you get to hang up in your yard have that in them so they attract Japanese Beetles to the area. We promoted the info to our neighbors that they are now NOT recommended because they create a worse problem. I haven't seen any of those hanging in the yards of our close-by neighbors, so I'm sure that has helped also.

Here's some info from Perdue University: "Avoid Japanese Beetle Traps: There is no doubt that Japanese beetle traps catch large numbers of beetles. However, they usually do not reduce damage to plantings. Research has shown that these traps attract many more beetles than are caught. Therefore, susceptible plants along the flight path of the beetles and in the vicinity of the traps are likely to suffer more severe damage than if no traps were used."

Randi said...

Chickens really love Japanese beetles! You can catch the beetles easiest in the evening, when it's a bit cooler and the beetles are slower. Use a jar containing ice cubes and tap the beetles off leaves into the jar. The ice slows them down even more. When you're done, offer the sleepy little things to your chickens, ice cubes and all.

sharingsunshine said...

That's a great idea, Randi! I did the soap thing one year and felt so guilty. Am glad I found out the birds will take care of them. We have a lot of birds since we've been feeding them and creating habitat for them since we moved in here in 2000. Lots of new babies coming behind .... especially right now. I love it!

S. said...

You have to put the bags away from their favorite plant. If they're attracted to the plant and the bag, they won't go in... they hang around the plant and some go in... If they're attracted to the bag by a cement wall their only option is to go in.

Draw them away from the plant you want to save.

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