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Invasive Insect: Harlequin Bug

Harlequin bugs have expanded their invaded range and can now be found in Pennsylvania. If not controlled, they can pose a serious problem.

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Updated:

May 22, 2024

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Figure 1. Harlequin bug adults. Photo by Sue Muller via the Maryland Biodiversity Project under the CC BY-NC 4.0 DEED license.

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Native to Central America, the harlequin bug (Murgantia histrionica) spread extensively across the southern regions of the United States following the Civil War. Historically, distribution maps indicated that the harlequin bug was mainly found in the southern states. However, its range has expanded significantly, and it is now commonly found as far north as Pennsylvania. This pest is particularly notorious for causing considerable damage to cabbage and other cruciferous crops, posing a significant threat to agriculture. The expansion of the harlequin bug's habitat underscores the adaptability and resilience of this pest.

Description and Identification

The harlequin bug is an insect from the stinkbug family Pentatomidae. Their life cycle is complete between 50 to 80 days. They are small with a shield-shaped body typical of stink bugs. Its distinctive appearance features a black body adorned with bright red, orange, and yellow markings arranged in a harlequin-like pattern, giving it its name (Figures 1 and 2). Just like any stinkbug, it emits a foul odor from scent glands when threatened. The eggs are oval-shaped (barrel-like) and typically laid in clusters on the underside of plant leaves (Figure 3, left). They are usually white with black bands. The nymphs (immature) resemble adults in coloration but lack fully developed wings, undergoing molts before reaching adulthood (Figure 3, right). Adults can survive winter conditions by hiding on crop residues.

Harlequin bug adults - Note the orange and black coloration and squarish shaped body — Figure 2. Harlequin bug adults. Photograph by Mike Raupp (UMD), used with permission.

Two photos. left photo is of egg masses - they look like black and white horizontally striped cups. Right photo is immature harlequin bugs - they are small, rounded and mostly orange in color with three small stripes of black on their back — Figure 3. (Left) Harlequin bug egg mass. (Right) Harlequin bug immatures. Photos by USGS Bee Inventory and Monitoring Lab via Flickr, under a PDM 1.0 DEED license.

Host Plants

The harlequin bug (Murgantia histrionica) primarily targets plants in the Brassicaceae family. Some common hosts include cabbage, broccoli, cauliflower, kale, brussels sprouts, collard greens, mustard, turnip, and radish. However, they can also be found on other plants such as asparagus, beans, beets, cotton, eggplant, fruit trees, okra, peppers, sunflowers, and tomatoes, and weeds such as wild mustard, shepherd’s purse, pigweed, and lambsquarter.

Damage

Harlequin bugs are agricultural pests that cause significant damage to crops. These insects pierce plant tissues with their needle-like mouthparts to feed on sap, leading to characteristic symptoms such as wilting, stunted growth, and yellowing of leaves (Figure 4). Additionally, their feeding can create wounds that serve as entry points for pathogens, increasing the risk of secondary infections. Left uncontrolled, harlequin bug infestations can result in substantial yield losses, making them a significant concern for farmers and gardeners alike.

Harlequin nymphs (orange and black coloration) feeding on a large leaf — Figure 4. Harlequin bug nymphs feeding on turnip crop. Photo by Geo Lightspeed7 via Wikipedia, under a CC BY-SA 4.0 license.

Management

Monitoring

It’s important to regularly inspect plants for signs of harlequin bug activity, such as feeding damage and the presence of eggs or nymphs. This can help detect infestations early and guide management decisions.

Cultural Control

Removing and destroying crop residues in the fall can help limit the survival of adults during the winter months and reduce damage in the following year.

Physical Control

Handpicking adult and nymph harlequin bugs from plants can be effective for small-scale infestations. Additionally, barrier methods such as row covers can prevent adult harlequin bugs from reaching susceptible plants.

Chemical Control

The use of broad-spectrum insecticides, like acetamiprid, carbamates, and pyrethroids can be used to control harlequin bugs. Kaolin clay (OMRI listed) can be used to protect the plants. The use of insecticidal soaps and neem oil can also be efficient. Following the recommended rates and application intervals specified on each insecticide label is important to ensure effective and safe usage. Additionally, it's important to prioritize personal safety by wearing appropriate personal protective equipment when handling and applying pesticides. By adhering to these guidelines, you can maximize the efficacy of pest control measures while minimizing risks to human health and the environment.