Harlequin bugs are reddy orange & black spotted and are related to the stink bug family. They are small (about 9mm) shield-shaped and have a pair of wings that overlap making it look like an X on their backs.
Harlequin Adult (right), Harlequin Nymph (left)-James Castner, University of Florida
The nymphs are smaller and round and have the same coloration. Eggs look like small white marshmallows with black markings on them.
Eggs-James Castner, University of Florida
Habitat and Lifecycle
Harlequin bugs are found in all of the warmer states and usually not found north of Colorado. They overwinter as adults and emerge in late spring. They lay their eggs in rows (up to a dozen per row) on the undersides of host plants. Nymphs emerge and feed until they become adults in the summer months. Adults and nymphs both feed on the hosts. There can be more than one generation per year.
Damage on cabbage-James Castner, University of Florida
Diet and Damage
Cole crops, horseradish, mustard and radishes. If these bugs are present and they run out of food they will attack tomatoes, beans, beets, fruit trees and many weeds. They are sucking insects and the leaves of plants become mottled, browned and eventually will wilt and die.
1) Hand Pick
In the fall or early spring is usually the best time to do this. Destroy any egg masses you find on leaves. They are quite easy to see.
2) Plant a Trap Crop
Plant cole crops earlier then you normally would and monitor for the pest. When they appear, cover the crops and destroy the adults every morning.
3) Sabadilla Dust
Use this only as directed and use caution when using. If there are beneficials in the area it will kill them too.
5) Soap Sprays
Insecticidal soap sprayed directly on nymphs and adults will kill them.