I'm assuming the nematodes would kill the JB grubs in the soil,so they likely would not harm caterpillars.

No easy way to eliminate them,that I know of.Those beetle traps merely attract more to your yard,so hand picking is the the best way to do it.

I have a birch tree which is my main food source for my cecropia caterpillars. The tree gets its share of JBs every year but this year has been really bad. I have spent oodles of time smashing beetles but always finding more. The ground was becoming littered with see-thru birch leaves. I was getting worried about running out of food for my cecropias. In desperation, I bought two JB traps at Lowes on Sunday evening. I was literally surrounded by JBs while trying to set these traps up, around 40 feet from my birch tree. In 18 hours, these two traps took in more beetles than I ever could have imagined (these are NOT "Bag-a-bug traps - they are another brand with a large clear bag). Monday evening I added two "Bag-a-bug" traps about 90 feet from my birch tree. I am very happy to report that I am finding very few JBs on my birch now.

I think the beetle trap solution works in my case because my yard is big enough so that the traps are far from my tree plus I don't have other plants I'm trying to protect (more leeway in where I can put the traps).

KC