Harlequin Bug Infestation in a Garden

Harlequin bug adult and nymph (Linda Tanner via Wikimedia Commons, CC BY 2.0)

Harlequin bugs are a type of stink bug that feed on the sap of plants, particularly those in the Brassica family such as broccoli, cauliflower, and cabbage. These insects are a significant pest for gardeners and farmers, as they can cause significant damage to crops. The harlequin bugs pierce the leaves and stems of the plants with their mouthparts to feed on the sap, which can result in wilted leaves, stunted growth, and reduced yields. In severe infestations, entire plants may die.

In addition to feeding damage, harlequin bugs can also serve as vectors for plant diseases. Their excrement, which can accumulate on the leaves of infested plants, can provide a suitable environment for the growth of plant pathogens. This can further exacerbate the damage caused by the bug infestation.


It is important to monitor your garden regularly and take action quickly if you suspect a harlequin bug infestation, as they can cause significant damage to crops.

  • Leaves may turn yellow and appear wilted, curled, or puckered.
  • Stunted growth, including smaller leaves and stems, can occur as the insects feed on the sap of the plants.
  • Reduced yields and smaller fruit or vegetable size can be a result of the plant’s energy being redirected away from fruiting and flowering to repairing damage from the bug infestation.
  • Leaves may have black or yellow spotting as a result of excrement from the insects.
  • Leaves and stems can become distorted and may have a rough, scab-like appearance.
  • The presence of small, brown egg masses on the undersides of leaves is a clear sign of a harlequin bug infestation.
  • In severe cases, entire plants may die.

What is a Harlequin Bug

It is important to be able to identify harlequin bugs in a garden in order to take appropriate control measures, as they can cause significant damage to crops if left unchecked.

  • The body of a harlequin bug is oval or shield-shaped, with a flattened appearance.
  • They are brightly colored, with black, red, and yellow markings, making them highly visible in a garden.
  • Harlequin bugs are approximately 1/2 inch in length.
  • They have long, thin antennae, typically as long or longer than the length of their body.
  • Their legs and head are black.
  • The bright coloring of harlequin bugs is a warning to predators that they are toxic and unpalatable.
  • Juvenile harlequin bugs are black with red markings and resemble miniature versions of the adult insects.

Treating a Harlequin Bug Infestation

It is important to monitor your garden regularly and take action quickly if you suspect a harlequin bug infestation, as they can cause significant damage to crops. Control measures may include the use of insecticides, handpicking and removing the bugs from the plants, and the use of row covers or other physical barriers to prevent the insects from accessing the plants. Crop rotation and planting insect-resistant varieties can also be helpful in reducing the risk of harlequin bug infestations.

It may be necessary to use multiple methods to effectively control harlequin bug infestations in a garden. For example, using a combination of physical barriers and insecticides may provide the most effective protection for your crops.


  • Choose an insecticide that is specifically labeled for use on harlequin bugs and the type of plant you are treating.
  • Read and follow the instructions carefully, including any precautions for use and any required personal protective equipment.
  • Apply the insecticide according to the label instructions, taking into account the timing and frequency of applications.
  • Consider using a systemic insecticide, which is taken up by the plant and distributed throughout its tissues, for longer-lasting protection.
  • It is important to rotate the use of insecticides to reduce the risk of the harlequin bugs developing resistance.

Hand picking and removing the bugs

  • Check your plants regularly for signs of harlequin bugs, and remove any insects you find by hand.
  • Place the bugs in a sealed container, such as a plastic bag, and dispose of them.
  • Consider using gloves to protect your skin from the bugs’ defensive secretions.
  • This method can be effective for small infestations, but may not be practical for larger infestations.

Physical barriers

  • Cover plants with row covers or other physical barriers to prevent harlequin bugs from accessing the plants.
  • Make sure the covers are securely fastened to the ground to prevent the bugs from crawling underneath.
  • Remove the covers when the plants are in flower to allow for pollination.
  • This method can be effective in preventing new infestations or reducing the severity of existing infestations.

Crop rotation and planting insect-resistant varieties

  • Rotate your crops so that plants from the Brassica family are not grown in the same location year after year.
  • Consider planting insect-resistant varieties of crops that are less attractive to harlequin bugs.
  • This method can help to reduce the risk of harlequin bug infestations and make them easier to control if they do occur.

Biological control

  • Encourage the presence of natural predators, such as birds and other insect-eating animals, in your garden.
  • Use biological control agents, such as parasitic wasps, to target the harlequin bugs.
  • Introduce beneficial insects, such as ladybugs, lacewings, and minute pirate bugs, which feed on harlequin bugs.
  • Maintain a diverse garden ecosystem with a variety of plants to provide habitat and food for natural predators.
  • This method can be effective in reducing the population of harlequin bugs over time, but may take time for the beneficial insects to establish and have an impact.