Harlequin bugs are becoming more common in Colorado. Found only in southern Colorado a few years ago, they can now be seen hundreds of miles north of their former limit. Harlequin bugs are a type of stink bug and an important pest of cabbage and related plants.
The bugs are flat, about 3/8 inch long and black with bright red markings. They lay white, cylinder-shaped eggs with rings like barrel hoops in masses on the undersides of leaves. There may be three generations each year.
Harlequin bugs first cause a cloudy, white spotting of foliage. Plants may wilt and turn brown from large numbers of insects removing the sap. In Colorado they feed on cabbage, broccoli, horseradish, cauliflower, collards, mustard, turnip, radish and cress.
The insects can be tough to control although pyrethroids such as permethrin are registered for use on vegetable crops. Home gardeners can also hand pick and crush egg masses. They overwinter as adults under crop debris so fall garden cleanup is important.
For more information, see the following Planttalk Colorado™ script(s).