They're swarming and it's a timing thing. The numbers will go down soon as they don't live long, but you want to do some serious sexual interruption here, if you can, to cut back on the next wave of bugs.

A modern UV zapper (or two) left on at night without other outside lights, or right beside an outside light that's inconvenient to shut off, can be a somewhat effective remedy. You supply the birth control and the chickens continue to eat organic food. Everyone wins!

Work both stages. You may be surprised at June Bug grub density. This sounds like a long term project.

>> Pray the nematodes have taken care of the grubs ... in the fall when they are due to hatch next.

You have Fall rains after a long-ish dry spell, don't you? That might be your Fall trigger.

Research shows that those "bug zappers" kill more beneficial insects then the ones we want killed.
Now is not the time to try to control the grubs since they are becoming the adult beetles you are seeing. These adults, at least the ones your chickens don't eat, will be mating and then will lay eggs that will hatch in August. The time to apply any grub control is late July to early August just before those eggs hatch when the grubs are small and easier to control.

Here is a link that might be useful: About Scarab Beetles

Thank you both for your replies.

A bug zapper had not occurred to me. I do not own one and I understand how it would be indiscriminate in killing bugs, good and bad.

I appreciate the link to the beetle info. So, applying nematodes in July for a greater chance of success as well as cost effectiveness seems the way to go.

Look up "Milky Spore" powder. It's a bacterium that only kills grubs but not the adult beetles. I currently have cutworms in my lawn and stumbled upon this product. I've never used it but as per the reviews I've read this product is organic and won't harm beneficial insects or any animals. I purchased it anyway and have it on stand-by in the event I ever need it. It's been around for some time so I'll assume it's safe to use but do some more research and decide for yourself. If the nematodes don't take care of the problem this might be an organic alternative.

In my yard, out in the country in east Tennessee, skunks are voracious and indiscriminate grub eaters.

As I understand it, Milky Spore is specific to Japanese Beetles.

Milky Spore Disease, "Bacillus popilleae" is a bacterium that the grubs of Scarab beetles ingest, eat, and which then settles in their digestive system and causes them to stop eating which causes them to die. It is effective in young grubs, fairly newly hatched to a few weeks old and after that not. The bacterium stays viable in the soil for many years. Contrary to some misinformation I have seen of late this bacterium does not move around in the soil and does not "attack" any grubs, the grubs must find and ingest the bacterium, When a grub that was infected by the bacterium dies, more of the spores are spread around that area waiting for another grub to ingest them.

It's worth noting that Milky Spore takes up to 3 years to build up and become an effective grub control. That is why you often hear conflicting reports about how effective they are. The good news is that once you build up a nice community of the bacterium, it lasts for a decade or more.

The better short term solution is to apply beneficial nematodes.

Interesting. If it takes up to 3 years to become effective then I better get started.

Milky Spore Disease is effective as soon as it is put down, however, because the bacterium are not everywhere, and because they do not move around in the soil, many grubs may not eat any. The bacterium gets spread around in soil as the grubs that do ingest some die (the grubs do move around) and the spores are put back into the soil. The longer the disease spores are in the soil and the more grubs ingest some and die, the more effective they become which is why some people think it takes 3 to 5 years before MSD becomes effective.