The false Japanese beetle, Strigoderma arboricola, may be fairly common in soybean the third and fourth weeks of June. In contrast, the Japanese beetle, Popillia japonica, usually occurs during late July and August and is most likely to be found in Iowa soybean in counties along the Mississippi River or near Cedar Rapids.
False Japanese beetles are often noticed by fieldworkers because they have a tendency to land on light-colored clothing or get in ones hair. Adults are 8-12 mm in length. They are called sand chafers in Nebraska because of their preference for lighter soils and they may be abundant on heavy soils in Iowa.
False Japanese beetles feed on soybean leaves, eating large holes between the leaf veins. In addition to soybean, they feed on roses and a variety of flowering plants. There is one generation per year. The larvae feed on plant roots and larval development takes 160-164 days when feeding on bluegrass roots. Adult beetles have lived for 21 days in the laboratory. No economic damage to soybean has been reported in Iowa from false Japanese beetle.
False Japanese beetle is similar in appearance to the Japanese beetle. On the false Japanese beetle, the pronotum, or "neck" is shining black, often with metallic reflections and the sides may be reddish brown. The wing covers are metallic bronze and have numerous small parallel grooves. The abdomen has five tufts of white pubescence below the edge of the wing covers, and there are no white spots on the "tail." The distinguishing features of the Japanese beetle are a dark green metallic body, reddish brown wing covers, tufts of white pubescence below the wing covers, and two white spots on the tail of the beetle.
This article originally appeared on pages 123-124 of the IC-488(15) -- July 1, 2002 issue.