I live in Aurora CO in 2018 my Rose of Sharon was infested with Japanese beetles. I collected as many as I could and killed them with dishwashing detergent. There were almost no flowers. This spring I sprayed the lawn and soil around the shrub for lawn insects. The Rose of Sharon is just starting to bloom and I found several fornicating Japanese Beetles and earwigs in the blooms. Is there anything I can do to get rid of the Japanese beetles other than pick them off by hand to prevent them laying eggs? Spray with concentrated dishwashing detergent? or other pesticide?
Thank you I found links to Japanese Beetles on Roses from Michigan State Univ.
Denver County Colorado new control means for japanese beetles
Japanese beetles are particularly fond of roses which includes the Rose of Sharon.
There are insecticidal products available to spray/kill the beetles. However, some chemical insecticides are harmful to bees and butterflies. CSU Extension fact sheet 6.501 discusses the various methods that gardeners are trying to control the beetles. https://extension.colostate.edu/topic-areas/insects/japanese-beetle-5-601/ Please review the chart toward the bottom of the fact sheet which lists the insecticides.
Some of the products listed as less harmful to bees/butterflies are beetleGone, beetleJus, Sevin or Carbaryl, Acelepryn, Merit and GrubEx. Each of these products has a different persistence cycle - many will have to be repeated throughout the growing season.