Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu
A few weeks ago some growers contacted me about a very small bug that was all over their organic fields of various vegetables. It took me awhile to find out what it was as it seemed recognizable, but did not fit any real pest I was familiar with. On one farm the nymphs were all over every vegetable and were feeding most heavily on eggplant—actually killed many plants. This small bug was the Twice stabbed stink bug, Cosmopepla lintneriana also known as the Wee Harlequin Bug or Two-spotted stink bug (fig. 1). It is a very small (5-7 mm) bug (fig. 2). The body is black with a red band crossing the width of the insect’s shoulders (pronotum) and a short red stripe along the midline. These markings are sometimes orange or yellow. The pointed back of the bug (scutellum) has two red spots near the tip of this triangular body part (fig. 1). The tips of the wings are clear or white when overlapped. The nymphs have a remarkably similar color pattern as the adults, but lack wings. It can be found throughout much of North America. It has a very wide host range that includes mostly weed species such as thistles, mints, goldenrods, ragweeds, pigweeds as well as vegetable crops such as crucifers, brassicas, tomatoes, eggplants etc. The bugs feed by sucking sap from the plant. Females lay eggs in clusters on host plants and guard them. Adults overwinter under leaf litter in the field or woods.
The odd thing was that there were literally hundreds of the nymphs crawling over everything in the one vegetable field. They even appeared under row cover in some areas of the field. The best I can figure is that the adults laid eggs on the weeds next to the tilled part of the field and when this area was tilled later in the season the eggs survived and were able to hatch and the nymphs suddenly appeared out of the ground. Organic controls did a poor job of controlling even the smaller nymphs. This bug has been an occasional nuisance in vegetable fields, why it is so prominent this year is unknown.
Figure 1 Twice stabbed stink bug adult
Figure 2 Twice stabbed stink bug adult on penny