Look Who's Back! Japanese Beetles

Our editor took the picture above yesterday in a nice rose garden in the eastern Twin Cities. In case you don’t recognize it (he was not very eager to have his photo taken), that’s a Japanese beetle feasting on these lovely roses. Below is a better photo from a couple of years ago where the beetle posed better.

Yes, they are back — and pretty close to on-schedule as Japanese beetles tend to emerge in Minnesota late June or early July. Japanese beetles are one of the most disheartening pests to afflict northern gardeners recently.

Japanese beetles overwinter in yards in the grub stage. After they emerge, they spend for six to eight weeks feeding, mating and generally wrecking havoc on roses, linden trees, geraniums, raspberries and many other plants.

For the past couple of years, beetle infestations seem to be worse in the Twin Cities, particularly on the St. Paul side.

Japanese beetles have a few look-a-likes, but they are fairly easy to identify. They are an iridescent green/gold beetle with five white tufts of hair on each side of the abdomen and two larger tufts on the tip of the abdomen.

For smaller infestations, the best bet is to pick or shake them off the plants (preferably in the morning when they are less active) and drown them in soapy water.  There are several chemical options for addressing beetles and their grubs, but at this point, you may want to just wait them out. They won’t be here for long — until next year.

Here’s a post we did in 2013 with more information on the beetles and another one on what works and what may not with Japanese beetles. The U of M has information on management of Japanese beetles.