There have been a few sightings of large masses of rose chafer adults in corn, soybeans and even other crops like strawberries. These adults are known to be pests in grapes and well, roses.
Even though the masses of adults look alarming, they are not going to do much damage to the corn and soybeans. They really are just there to hang out and mate with each other. If they do lay eggs in the soil of these fields, the grubs won’t be actively feeding until later in the summer when the crop is well advanced and able to tolerate it. Michigan has had these in the past and this year too and have not experienced economic impact because of their presence in corn or soys.