Harlequin Bug

Getting to Know Him

The harlequin bug is a very beautiful and a very tough bug.  They seem to resist almost anything, so early control is the key.   The harlequin bugs overwinter as an adult.  In the spring they need nitrogen to lay eggs.  The weeds that they enjoy are bittercress, shepherds purse, peppergrass, wild mustard, wild arugula and watercress.  You will find the Harlequin Bug on any member of the brassica family.  Once the brassica are depleted they will gravitate to asparagus, beans, corn, okra, and tomatoes.  Harlequin Bugs destroy your plants by using their sucking mouthparts.  They  are from the stink bug family.


Fall cleaning of the garden and tilling are your first defense. By getting rid of the debris in your garden the harlequin bugs have no place to hide.  We have multiple seasons so turn under your crop residue as soon as you are finished with your crop.  Do not plant brassicas in the same place during the year, rotate them, so the harlequin bugs can not find them or feed on them.  Turning over the garden in the fall and planting with a cover crop will get rid of any remaining pests and their eggs.

Beneficial Insects

One bug that acts as a beneficial insect in this instance is the  sow bug or pill bug.   At night the pill bug will climb up the base of the plant and feed on the eggs of the harlequin bug.  If you mulch your garden with straw the pill bugs will live in there and decompose material. The pill bugs eat the harlequin bug eggs at the same time.  Make sure to compost the straw at the end of the brassica season in a very hot compost pile to destroy any eggs that may remain.

Cover Crops

Cover cropping helps keep plants less vulnerable against bare soil, so that seedlings blend in with the landscape. The harlequin bugs have a harder time finding the young plants.

Row Covers

Using row covers will keep you protected from these pesky critters.  Fortunately if you are using row covers on members of the brassica family they do not need to be removed all season.

Trap Crop and Delayed Plantings
Mustards are a great trap crop.  Plant them earlier than your other brassicas.  and spray them with an organic OMRI approved insecticide to control the harlequin bugs.

Biorationals to Control the Harlequin Bug


Are made from the seed cases of  the pyrethrum flower, a species of chrysanthemum flower. It is the safest around food.

Diatomaceous Earth (Silicon Dioxide)

Ground up fossilized one celled diatoms that pierce the exoskeleton of many pests. It is used as a drench only in a powdered form.

Beauveria bassiana

This is a natural soil occurring fungi that is found in soils. It acts as a parasite to insects.  Once the droplets touch the targeted insects, they attach to the insects skin and germinate by sending out structures or hyphae that penetrate the insects body.  The insects die within 3 to 5 days. The dead insects body can be a source of spores as well. This should be done in the cooler parts of the day.


This is a plant from Central America and Mexico that is from the lily family.  The seeds are used for the insecticide.


Spinosad is made of spinosyns A and D, they are substances that are made by aerobic fermentation.   The species that is being fermented is Saccharopolysora spinosa of the actinomycete species. They were found in the Caribbean in soil samples in 1982. They are the filamentous bacteria that are in the soil that give it that sweet earthy smell.  Spinosad works by ingestion, activating the nervous system of the insect, causing loss of muscle control.  The insect dies of exhaustion because of the continuous activation of motor neurons.  This usually happens within one to two days.

Kaolin (Surround)

Kaolin clay is a particle film barrier  and can offer some protection for the organic grower.  Kaolin clay is an anti-caking agent used in toothpaste and other ingredients.  It was accepted onto the OMRI list in 2000.  It acts as a barrier between the pest and the plant by forming a film.  Make sure to spray kaolin on the underside of the plant leaves as will as that is where the harlequin bugs like to lay their eggs.


Insecticide that combines pyrethrins and canola oil.  Make sure to use this in the early morning or late evening.  Anything made with oil should not be applied on days that are over 90 degrees or it may harm your plants.


4 Responses

  1. i don’t think you should hurt them if you do. i’m only 8 and i already know what happens to them. bye.

  2. don’t put poison on the bugs

  3. Are they poisonus or not

  4. Kill those nasty Harlequins! They are my bane!

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