Figure 1. Adult Japanese beetle on rose. Photo by Amanda Bachmann.
Profile & Behavior
Japanese beetles (Popillia japonica) are present in a few areas of South Dakota. So far, they have a foothold in the southeast corner of the state and appear periodically in the Brookings area. Sporadic populations can show up in other parts of the state, and are thought to be brought in on infested nursery stock or otherwise accidentally moved by people. The adult beetles feed on a wide range of trees, shrubs, and herbaceous plants. Japanese beetle larvae (grubs) are pests of turf, where they feed on the roots.
Japanese beetles are fairly distinctive, with a shiny metallic green and brown shell. Adult beetles are ⅜ - ½ inch long, with white tufts of hairs on the edge of their abdomen (Figure 1). They cause damage by chewing on leaves and heavy feeding can result in the skeletonization of the leaves.
When deciding on management options, consider the number of beetles present, what they are consuming, and the value of those plants. Small populations can be hand-picked and dispatched in a jar or bucket of soapy water. Japanese beetles use an aggregation pheromone that attracts their friends to the party, so catching populations early is useful. There are traps available that use this pheromone in addition with food scents to lure in beetles, but use these with caution. Research from other states determined that the traps actually attract more beetles than what are trapped. If the trap becomes full (or doesn’t kill the beetles), the beetles will be attracted to your yard and then feed on the plants around the trap. There are many general use insecticides available to kill Japanese beetles; however, they should be used with caution to prevent negative impacts to pollinators and other beneficial insects. For plants, such as roses, that are very susceptible to Japanese beetle cheesecloth or netting can be used to cover the plant during peak beetle flights.