If the large brown beetles that come to the light at night look like the top left of the adults on this page below, then they are "June bugs" more correctly called June beetles.
http://ohioline.osu.edu/factsh...
The nematode is supposed to get both kinds. Milky spore, where it works, only gets Japanese beetles. This next link is the nematode - not endorsing this particular product, it's just the first one that came up when I searched for Heterorhabditis bacteriophora. It lists the target pests and those include both Japanese beetles and June beetles:
http://www.buglogical.com/bene...
Neither of these is likely to work as well as an insecticide but for a biological control this is the one that was recommended by an entomologist at a talk I attended on white grubs.
