Three More Bad Bugs for Northern Gardeners

Yesterday, we posted about three of the six insects University of Minnesota entomologist Jeff Hahn thinks northern gardeners should watch out for. So, here’s the rest of the list.

Japanese beetle on rose

Even the Minnesota Landscape Arboretum has been battling Japanese beetles.

Japanese beetles. Not surprisingly, this was Hahn’s pick as the baddest bad insect this year. For the past month or so, gardeners have been picking, squishing and spraying to keep them from eating their roses, geraniums, raspberries and many other plants. Here’s the good news: Their typical active period is six to eight weeks, so this will not last much longer. When you talk with gardeners, it seems that JBs are everywhere, but they are not. For instance, parts of south Minneapolis do not have them. Outside of the Twin Cities, the infestations are spotty. Beetles in St. Cloud: yes; in Northfield, no. The way to identify them is to look for 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.

Four-lined Plant Bug. This is another insect that won’t be around for long (if it has not already left). The four-lined plant bug is less than one-third of an inch long, yellow green in color with four black stripes down its back. The bugs hatch in May and feed on many types of plants. One sign of the bug is dark, round damage to plant leaves. These are sites where the bug has been sucking nutrients from the plant. The damage generally will not kill a plant, but rather leave it looking scraggly. Like many pests, physical removal is a good control option. If you have a plant that is infested this year, remove and destroy the plant debris because that is where the eggs are for next year’s bugs. A variety of chemical options are also available.

Variegated Cutworms. We seem to have a bumper crop of cutworms this year, which many homeowners noticed not as worms but as eggs attached to the side of their houses. Cutworms come in a lot of colors, all unattractive. The variegated ones are dark brown with several yellowish, diamond shaped spots on top of the body. Cutworms damage plants by chewing on the foliage. Oval-shaped holes between the veins of leaves are a distinctive sign of cutworms. Larvae will feed for six to eight weeks, then pupate in the soil, before emerging as an adult moth. According to Hahn, cutworms may produce two generations a year here.