How to combat Japanese beetles in your yard and garden
Beetles are the largest group of insects, but fortunately, not many native beetles are serious problems. Native beetles are either beneficial predators, or they are preyed upon by other beneficial species. The ones you need to worry about are exotic beetles with no natural predators. They can chew up or bore through trees and shrubs with nothing to stop them. Japanese Beetles are an excellent example of an exotic pest that has swept most of the eastern half of the United States. The metallic green beetles munch on flowers and leaves, and lay eggs in turf so their white larvae can feed on the roots of plants.
How can you stop them from consuming your landscape?
Physically remove the beetles and destroy them to slow them down. The presence of Japanese Beetles actually attracts more of their kind (This is why traps are not a good idea). Also, the more you remove, the less eggs they can deposit in the turf.Insecticides should be used with caution. Follow label instructions, and make sure the insecticide is recommended for your tree or shrub species. Insecticides can kill more than the intended pest. By killing beneficial insects, you will leave your plants open to attack by other pests.Other safer and less toxic methods are available for control. Bacterial milky diseases (sold as Milky Spore) are naturally occurring and attack only white grubs, and will not harm people, animals, or other insects. If applied in late summer it will slowly get the grubs under control. If left to do their thing, the bacteria will grow and spread out to provide long-term protection in your yard. Always read carefully and follow the directions on the box.Select healthy trees and shrubs to plant that are less attractive to Japanese Beetles. The beetles seem to enjoy nibbling on Norway and Japanese maple, linden, elm, pin oak, horse chestnut, sycamore, birch, willow, crabapple, mountain ash, cherry, plum, and roses. Trees and shrubs they don’t seem to prefer are red and silver maple, red oak, ash, tulip tree, magnolia, red mulberry, holly, burning bush, flowering dogwood, forsythia, privet, lilac, hydrangea, boxwood, cedar, juniper, arborvitae, spruce, and yew.
Contact your local Cooperative Extension office for more information.