UPDATE June 25, 2018 - New Imdacloprid labels indicate that this product can not be used on Linden or any Tilia species due to toxicity to pollinators.
I think this week I have talked more about Japanese Beetles either on the phone, email, social media, or in person than anything else. Everyone seems to be fighting these coppery colored monstrosities that seem to be more prevalent this year than anyone would hope. The last two winters have been mellow and it's led to their overwintering survivability. I know some may not like this – but we need a real winter, a winter that is actually cold. *Runs and hides*
So many people want to know what to do about them – how in the world do I get rid of them!?! To be honest there aren't a huge number of options.
One option is a bucket of water with a few drops of dish soap. Knock them in (best time is late afternoon or early evening when they are less active) and then they drown. Just make sure to dump the bucket once they are dead – otherwise the smell is not so pretty and yes that is based on personal experience. Sometimes you get so busy and you put the bucket of doom filled with Japanese Beetles off in a corner of the yard and forget.
Avoid Japanese Beetle traps. All they do is attract more to your yard. The reason you get so many Japanese Beetles is that they release an aggregation pheromone that tells others where the party is. The traps utilize that some concept, but by the time they arrive in your yard they get distracted by much tastier options. Fun trivia – Japanese Beetles can fly 10-15 miles.
There are chemical control options available, but there is something that needs to be kept in mind. The commonly used product carbaryl (often sold as Sevin) is highly toxic to pollinators such as honey bees and can still negatively impact them for more than one day after treatment is applied (information from from Purdue University Extension on Protecting Honey Bees From Pesticides which is available on their website). All of the recommended chemicals to control Japanese Beetles - acephate, acetamiprid, befenthrin, carbaryl, cyfluthrin, imidacloprid, permethrin, and spinosad are considered moderately to highly toxic to pollinators (most are highly toxic) and it is best to avoid application to plants that are in bloom and actively visited by pollinators. If you do choose to use chemical controls make sure that the plant you are applying to is listed on the label as well as Japanese Beetles. If controlling Japanese Beetles on food crops such brambles or grapes – make sure to follow the harvest-restriction date on the label. Always READ and FOLLOW the label and do not apply at rates higher than listed. If you need additional information about chemical controls you can contact your local Extension office.