The harlequin bug (Murgantia histrionica (Hahn)) is striking with its orange and black or red and black colors. It is a true bug. The harlequin bug prefers vegetables in the Brassica family, such as cabbage and broccoli. It will eat other vegetables and fruits if there are not enough Brassica vegetables around.
Lifecycle of the Harlequin Bug
Female harlequin bugs lay a cluster of about twelve eggs on the underside of a leaf. The eggs look like white kegs with two broad black hoops and a black spot on top. Depending on the temperature, the eggs hatch in four to twenty-nine days.
The nymphs hatch and feed for four to nine weeks. They go through five or six instars, or molts, before reaching sexual maturity.
One harlequin bug generation is about fifty to eighty days. The bugs overwinter as adults and emerge in the spring.
Damage Caused by Harlequin Bugs
Harlequin bugs are piercing-sucking feeders. They bite the leaf and suck the sap out of the leaf where they are feeding. These leave behind silver empty cells and silver trails in the leaves. High levels of harlequin bugs result in wilted leaves, browning of leaves, and premature leaf drop. The plant can die if enough leaves are attacked.
Control of Harlequin Bugs in Vegetable Gardens
Integrated Pest Management (IPM) is the best way to control harlequin bugs. Here are some things that work.
Handpicking the Harlequin Bug
The easiest way to control the harlequin bug is to handpick the pest off your vegetables and drop them in a jar of soapy water. The bugs will drown. Look under the leaves of infected plants. Remove any eggs you find and drop them in the jar, too.
Removing Badly Infested Plants
If you have a badly infested plant, it is best to remove it. Pick any bugs off and drop them in a jar with soapy water, then either eat what is left of the plant or place it in a plastic bag and put it in the trash. Do not compost the plant or you will spread the harlequin bug.
Sanitation
Adult harlequin bugs overwinter in plant debris, In early spring, they emerge hungry and ready to eat. Sanitation will help keep their numbers low.
- Destroy old cole crops and mustard plants in the fall.
- Remove weeds, especially mustard plants and ground covers, in the spring before the harlequin bug numbers explode.
- Plant a trap crop of horseradish, kale, mustard, or rapeseed and destroy it before your vegetables are big enough for the bugs to feed on.
Biological Controls
Parasitic wasps will lay their eggs in harlequin bugs and the larvae eat the bug from the inside out. General predators such as the green lacewing, assassin bugs, minute pirate bugs, and spiders also eat harlequin bugs. Many general garden predators can be purchased at online nurseries. However, you will do better if you attract beneficial insects to your garden. They will be there waiting when harlequin bugs start eating your plants and will keep the numbers of harlequin bugs low.
Chemical Controls
Pesticides are not generally recommended to control harlequin bugs. Insecticidal soap will kill nymphs it touches but does not have residual value, so the ones who hatch after you spray are not affected. In organic gardening, pyrethrins are allowed. They, too, have low residual value.
Harlequin bugs prefer vegetables in the Brassica family but will eat other vegetables and fruits if they are not available. The best way to get rid of them is handpicking. Good sanitation and encouraging beneficial insects are the best ways to combat an infestation of harlequin bugs.
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