Harlequin bugs mate on Lisa's Brussels sprouts. Knock them off into soapy water.
Harlequin bug eggs laid on the underleaf of Colleen's kale. Pick the group off and destroy (squish) them.
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Harlequin bug eggs hatching on Denise's kale. Pick off and destroy.
Harlequin bug nymph eating its way to adulthood.
Harlequin bugs (Murgantia histrionica) are members of the Stinkbug family. All stages of this pest emit a disagreeable odor when disturbed. Studies show they are able to sequester toxins from the plants they feed on into their bodies for defense against predators.
HOST PLANTS - PLANTS THEY LIKE
These pests are mobile and have a large range of host plants although it seems their favorite in our garden is red Russian kale. They are crucifer-eating specialists (kale, broccoli, Brussels sprouts, collards, etc) but once that food source becomes scarce they will move to squash, corn, beans, asparagus, okra, and tomatoes. Certain weeds act as hosts such as wild mustard, shepherd's purse, peppergrass, bittercress, and watercress.
DAMAGE
Rutgers observes: "Adults and nymphs pierce stalks, leaves, and veins with needle-like mouth parts and extract plant juices from cabbage, cauliflower, collards, mustard, Brussels sprouts, turnip, kale, kohlrabi, radish and horseradish. If infestations are heavy, harlequin bugs may also feed on asparagus, bean, beet, corn, eggplant, lettuce, okra, potato, squash and tomato. Damaged plants develop irregular cloudy spots around the puncture wound. Young plants may wilt, turn brown, and eventually die while older plants become stunted or deformed."
Download the complete PDF file: Rutgers Cooperative Extension Harlequin Bug Fact Sheet
CONTROL
These bugs usually inhabit the underleaf of a plant although they can be spotted on stems and sometimes on top of the leaf. Several adults were snuggled down where new leaves emerge on the brassicas.
Handpicking is probably the most effective way to control them in our garden. The adults can be quick to drop to the ground making spotting them difficult among the debris. Having a little container of soapy water to knock them into rather than trying to catch and squash them is probably a less frustrating and more palatable way of disposing of them. The eggs are easily picked off and crushed. The nymphs are not as agile (or experienced?) as the adults and can be crushed easily between two fingers.
One successful predator noted in a California study is the lowly pill bug (the roly polys of our childhood). They are abundant in our Garden and can be effective predators of harlequin bug eggs. Pill bugs are known to us as mostly harmless co-residents who helpfully feed on decaying vegetation, but the California study proved they have another side -- at night they climb into plants in search of harlequin bug eggs and other eggs of the stinkbug-family!
For more info on this unwlecomed critter:
Sustainable Options for Managing Harlequin Bugs | ATTRA
2014 UPDATE
The Sand Wasps have made nests in our Garden! They were encouraged to come by the sand between the bricks we laid for our walkways after Hurricane Sandy. The females sting the stinkbugs (Harlequins & Squash bugs) and drag them into a nest in the sand. Then they lay their eggs on the bug, which is still alive but helpless. The paralyzed insect provides sustenance for the next generation of Sand Wasps. These solitary wasps crashed the Harlequin bug population in our Garden! For the story and photos, see Sand Wasps to the Rescue!
2018 Sept 1
Where are our Sand Wasps? The Harlequins are all over some of our kale. The hot weather has encouraged them to proliferate.😞
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