This week, I’ve had a number of people tell me they spotted Japanese beetle. I was initially surprised, because I track degree days to predict adult emergence every summer and it seemed a bit early. According to the ISU Agronomy Mesonet, adults could be emerging in southern Iowa and I would expect adult emergence in central Iowa next week. See my recent ICM News article showing a degree-day map for 2018.
Last night, I attended a field demonstration highlighting herbicide resistance near McCallsburg, IA. I was constantly bombarded with beetles and flies. I finally got a good picture of one of the beetles and noticed it was the false Japanese beetle (Photo 1). Obviously, there is some confusion out there (even by a trained entomologist!), so I thought I could post a few pictures to help you confirm the identification. It is important to distinguish Japanese beetles (Photo 2) from other chafers because other species are not known field crop pests. The false JB is not a concern in corn and soybean.
They do resemble each other in the size and shape, and are in the same subfamilies of beetles called shiny leaf chafers (Rutelinae). True Japanese beetles are more iridescent with a metallic green head and thorax with copper-colored forewings. The false Japanese beetle is not quite as shiny (sorry, that is up for your interpretation!). Also, the white tufts of “hair” along the sides and tip of the abdomen are not as obvious.