Not exactly an answer but Harry had the best photos of them all and a lovely personality to match. Preventing Japanese Beetles

JB's release chemicals called pheromones into the air. These pheromones attract other beetles. Try to get rid of Japanese beetles early by dropping them into a bucket full of soapy water... I personally would not smash them and let them lay around in your garden etc....Might attract other beetles????

JB's traps??? seems to be a debated subject though...???

Some people have success with Milky Spore to kill the grubs in the lawn... But JB's can still fly in from your neighbors yards etc.

http://www.gardeningknowhow.com/plant-problems/pests/pesticides/what-is-milky-spore.htm

I do not use chemicals so other then that I can not help...

Ditto Jim's comments. Do not squash them, just knock them in a bucket of water with some liquid dishwasher soap. JB are my worst enemies in the garden, just hate them..lol.

The trouble with most sprays is, that are contact killers only for JB's, no residual kill. The only spray that I've found to have residual kill/repellant effect is called Demand CS & it along with all they other sprays are not good for bees so you want to use them sparingly. What I do is spray 2 or 3 times in peak JB season (mid-July to Labor Day in my area) & live with them the rest of the year.

Yes it is approved for ornaments but not for food crops on the labels I have seen. Also need to adjust the water pH with something like Indicate5 when you mix.

bruin, if you decide to begin using insecticides, please purchase an appropriate respirator & gloves. Rosemania dot com has a selection of PPE so you can get an idea of what you should be using. If you spray insecticide regularly, that tends to lead to spider mite outbreaks so you would also need a miticide. Many of us would rather knock the beetles into a bucket of water. Your garden, your choice.

Most likely many of us have been gardening long enough to know that they don't work. All insects quickly become immune to what you use. What the world has managed to accomplish is eliminating natural predators. We have done irreparable damage to our environment in many ways not simply the use of insecticides. The information is out there if you care to look at reliable sites.

I'm but a small part of this world but have chosen to be part of the cure. If only the rest of the world could join us.

ps. Have you ever view the photos of the air quality in China. Shall my children's, children be wearing masks to enter the outdoors. So a bit over the top for here but ya get the picture. I'm sorry for the comment but you asked.

Where are you? You already got them? So early?

So sorry to hear you have gotten them already. Is this the normal time of year for them to come out? I wonder if it is because of the warm winter that we had that they will be out early this year. I normally don't see them until late June.

In northern California, your beetles may not be same as the ones we call Japanese Beetles in the east that have just gone on their westward expansion and crossed the Mississippi.

What I think are Japanese beetles showed up in my front yard ~5 yrs ago, Front yard has ground cover, rock, backyard lawn with roses against the fence this winter. I am in Silicon Valley. I used neem this winter and don't remember seeing any since. My beetles have red backs.

Below are pictures of my Japanese Beetles, which as Ann said, I don't believe to be what you in California have....at least I hope not. Here they start in June, and for 2 1/2 to 3 months, come by the thousands (literally) on a daily basis. There is no way to knock them all in soapy water, etc...so they multiply and multiply uncontrollably. They ravage berries, roses, crepe myrtles, hibiscus, althea, corn, etc.

Your beetle looks like this Hoplia Beetle Management Guidelines--UC IPM

Oh yours don't look like the Japanese beetles we get over here. Good luck treating them!

Your welcome

I just saw 2 beetles on my roses today that look just like Bruins. Ive never seen them here before. I shooed them away lol. I hope this isnt the start of something.

~sjn

I mentioned the decline of Japanese beetles to Marci Martin--she thinks the birds in Connecticut have learned to eat them. Makes sense--there are many birds of all types that visit my yard--my neighbor even took a photograph of a Great Blue Heron standing on my roof!

I guess alabama birds haven't acquired a taste for them yet. We have all types of birds on the couple acres we keep as our "yard" and herons, geese and various ducks on the ponds in our pasture but our beetles haven't declined at all

Perhaps the best birds for taking care of the beetles are the "LBJs," the little brown jobs that don't get the attention of bigger and more distinctive birds. Though we also have chickadees and mourning doves as a constant presence in our yard.

I'm not sure I've ever seen a chickadee around our place, but we do have plenty of dove and many other types of birds, unfortunately that includes lots of mockingbirds who love to harass our dogs...brave birds they are! Back to the OPs beetles, though. Very glad they are not the same as we have, and hopefully, the hoplia beetle has more natural predators and doesn't reproduce as prolifically as our Japanese beetles do!!!

Bestest, cheapest JB control I've ever seen...about 3 years ago a flock of starlings descended upon my yard in the spring and began marching across, plunging their beaks into the soil and snorking up these big, white grubs. ( They were HUGE, like fried dumplings...the grubs, not the starlings. :D

That summer - not a single japanese beetle!

The trick, of course, is how to come up with a squad of hungry starlings.

We had Starlings in our yard today eating grubs... :-)

Four different scarab beetles (inc. the big not-JBs)

The big white grubs (inch long) aren't JB grubs. but for (at least) two other beetles including the ones that look like JBs on steroids). JB grubs are around 3/4 of an inch long and skinnier. Also white-ish, but when you squish them on a stone there's not that much there. The big grubs have massive innards.