How to Identify, Control, and Prevent Harlequin Bug

The harlequin bug, Murgantia histrionica is named for its unique coloration and pattern. The harlequin bug is a member of the stink bug family and has a similar shape and size as other stink bugs. They also produce odors as a defense mechanism against predators. 

Harlequin bug is an invasive pest in North America. Originating from Mexico and Central America, it was introduced to the U.S. after the Civil War. They are commonly found in the southern United States and rarely north of Pennsylvania on the East Coast and Colorado to the west. 

Not only are they invasive pests, but they are also pests for cruciferous plants such as cabbage, kale, broccoli, mustard greens, and others, earning them the name ‘harlequin cabbage bugs’. If left unchecked, this pest can cause entire field crops to wilt and die. 

What is Harlequin Bug?

Harlequin bugs have a distinctive look with their black shield-shaped bodies, speckled with yellow, orange, and red patterns. This aposematic coloration is a form of self-defense to deter predators. They are approximately three-eighths of an inch in length and the female bugs are slightly larger than the males.

It’s no surprise that this bug has captured the imagination of many people who have named them ‘calico bug’, the ‘fire bug’, and ‘terrapin back’.

Life Cycle

Harlequin bugs are destructive pests because they can have up to three generations per year under favorable conditions. One generation or life cycle develops over 50-80 days as they undergo the egg stage, nymph instars, and adult stages.  

These bugs overwinter as adults to emerge in early spring every year. Adult females will mate and lay around a dozen black and white eggs per female on the underside of leaves. The eggs are a recognizable barrel shape standing on their end, marked by two rows of alternating black and white stripes and a black dot. Eggs hatch into nymphs from 4-29 days later depending on the temperature.

Nymphs typically go through five or six instars and become more brightly colored with each progressive molt. A newly hatched nymph cannot fly but will develop its wings during the last instar stage.   

Common Habitats

Adults overwinter in leaf litter and debris near their host plants. Annual weeds such as wild mustard, peppergrass, and shepherd’s purse can serve as overwintering hosts.

Harlequin bugs are not well adapted to cold winter temperatures so are more commonly a pest in the southern United States. Their population may be especially noticeable after mild winters. Adult bugs emerge as soon as the weather warms in early spring and can be found on the leaves of various host plants.

What Do Harlequin Bugs Eat?

Murgantia histrionica feeds on over 50 species of plants but has a strong preference for host plants in the cabbage family. Both adults and nymphs feed on plant tissue using their piercing and sucking mouthparts. The damage on leaves looks like light-colored, cloudy, or brown patches of dead plant tissue. 

Harlequin cabbage bug infestations on a large scale result in the wilting of leaves and stunting of the overall development of the plant. Entire crops may suffer if they are not able to bounce back from an infestation.

A harlequin bug may also feed on other host plants outside of the brassica family including ornamental plants like sweet alyssum and spider plants and fruiting plants like beans, tomatoes, and many others.

Control

While gorgeous to look at, these stink bug relatives can cause some serious damage to crops and especially to plants in the brassica family. We recommend using a combination of methods to control their population through an integrated pest management methodology to not bring harm to beneficial insects in your garden.

Organic or Chemical Control

Adults, nymphs, and eggs are easily spotted and destroyed. During the growing season, check your plants frequently, hand-picking and dropping adult bugs into a cup of soapy water to kill them. Check under the leaves of host plants and crush any harlequin bug eggs. Hand-picking or even vacuuming bugs can be effective ways to keep the population under control. 

Use insecticidal soap to cover the bugs completely. Or control chemically using insecticides such as pyrethrin. 

Some formations of pyrethrin are approved for organic use. Use these products early in the season and set up a schedule to apply every few weeks. Follow the instructions on the packaging carefully since it is a broad-spectrum insecticide.

Spinosad, another type of organic insecticide, is also effective against harlequin bug nymphs. 

Environmental Control

Harlequin bugs have relatively few natural enemies because of their self-defense mechanisms through their pungent odors and bright colors. There are several native hymenopteran wasps that parasitize the eggs of harlequin bugs.

These have been released as a form of biological control and researchers continue to study the effect they have. In a home garden, plant umbellifers to attract parasitic wasps that prey on harlequin bug eggs.

One method of environmental control for harlequin bugs is to grow a few trap crops, like fast-maturing mustards, near the main crop early in the season. Trap crops can help you identify and destroy the first wave of adults to mitigate against a large infestation later.

Harlequin bugs use pheromones to congregate on the best food source. Alternate trap crops with a period of non-host plant cultivation to further reduce the overall population of this pest. 

Prevention

A great way to control this pest is by eliminating opportunities for the harlequin bug to survive through the winter. This means cleaning up plant debris and residues from crops like kale or mustard right after harvesting. Remove annual weeds around susceptible crops. 

As the weather warms up, add floating row covers around plants to create a physical barrier against harlequin bugs. Floating row covers to prevent cabbage moths will mean that you will be well-equipped to prevent or control harlequin bugs as well. These covers prevent the sucking damage that occurs when a harlequin bug goes to feed as they never reach the plant.

Frequently Asked Questions