They have emerged. They are eating your roses, raspberries, birch trees, linden trees and more. Here’s the basics:
Japanese beetles emerge at this time of year to eat and mate. They lay their eggs in the sod, and the grubs eat grass roots, causing brown patches in yards. When they emerge as adults and find their favorite plants, they emit a pheromone that attracts more beetles.
The best method of control is to catch them by hand and drown them in soapy water.
Sometimes beetles react to a shadow by lifting their legs and letting themselves fall to the ground. Take advantage of this by holding a cup of soapy water directly under the beetle, move your hand over it to create a shadow and let them fall into the soapy water themselves. If that doesn’t work, grab ’em by hand and drop them into a soapy demise.
There’s not much that can be done for beetles on high branches that are out of reach, but you can apply a ground-level insecticide from mid-July until September to control the grubs for next year. You’ll probably still see some when they emerge from elsewhere, but at least there will be fewer of them.
Learn more: University of Minnesota Extension | Japanese Beetles.