Japanese beetles are a common pest in Michigan.  You may have seen these small beetles feeding on leaves in your yard or garden.  They are responsible for the destruction of the foliage of many plants in Michigan gardens, especially rose bushes.  The harm they cause doesn’t stop there; as grubs, they feed on the roots of turfgrass.  The adult form of a Japanese beetle is about the size of a fingernail with an iridescent copper-colored body and a green thorax and head.

Beginning in August/September, the beetles start their life-cycle as grubs in your soil. Then, the following June/July, they emerge as adult beetles and start feeding and reproducing.  Females lay around 50 eggs in their lifetime and the next generation hatches in just 45 days.  When the soil temperature falls below 60 degrees, the grubs burrow into the soil for the winter.  As soil temperatures increase in the spring, they work their way up to the surface and begin feeding on turf roots.  In late summer and fall, these areas will be large dead patches in your yard.

There are a couple of different natural control options for Japanese Beetles.  Neither option harms beneficial insects, humans, or animals.  The first is a bacterial disease called milky spore, which kills the grubs.  You can most likely purchase milky spore from your local garden supply store. Some grocery stores such as Meijer also carry milky spore.  You apply it throughout your yard or garden in teaspoon amounts every 4 feet in rows 4 feet apart and then water the powder into the soil.  While the grubs are feeding, they ingest the milky spore, die, and decompose, releasing new spores into the soil.  It’s best to apply the milky spore in the spring or summer as the grubs are feeding.

A second option is to remove the beetles by hand.  To remove the beetles by hand, go around your garden and hand pick the beetles off of the plants.  Carry a bucket of soapy water with you and place the beetles in the water where they will drown.  It can be a tedious job, but it should be done daily to actually control the pests.  Japanese beetles tend to form in groups, so removing the beetles daily helps control swarms of beetles which destroy leaves quickly.


Sheena Wilson has  a Landscape & Nursery Management degree from Michigan State University and 10 years experience in the landscape and gardening business.  If you have specific questions you want Sheena to answer, you can leave a message below or send an e-mail to info@canopylandscapes.com and put “Ask Sheena” in the subject line.