They’re baaaack! Yes, it’s that time of the summer when these little foreign invaders, the japanese beetles (popillia japonica), invade our gardens and lawns and occasionally our homes. It seems to me that they’re a wee bit early this year, but then again, so is everything else.
So what is an enlightened gardener to do? Well, the conventional wisdom is that those traps that they sell are really only good for monitoring an infestation–or attracting them to the yard. They do not trap all the beetles. Folks joke about putting the traps on adjacent properties which is fine if your neighbors don’t object but I just don’t see that being practical in most cases. So the beetle traps are not really the answer we were looking for.
A good resource for a thorough understanding of the beetles can be found at this USDA pamphlet. It describes how they got here, how they can be controlled through integrated pest management, what chemical controls are effective if you choose to use chemicals, and which plants are most susceptible to damage, and some alternatives.
As for me, I’m fortunate that the birds keep the grub population in control and without grubs you can’t have a lot of beetles. So I normally don’t do anything about these beetles at all (secretly I think they’re kind of pretty, but that’s only because you are looking at the sum total of the population on my property at the moment).
If the population does get out of hand, I go out early in the morning or later in the afternoon–when they’re sluggish–and knock them into a cup of soapy water. When they’re dead, I spread them out for the birds to eat. Everybody wins.