Harlequin Bug

By Stephanie Rukowicz

The harlequin bug is a type of stink bug, much more colorful than the brown ones you might find around your house. An invasive species, it is a common insect pest of crucifers in the southern part of the U.S. but in recent years has been reported in PA as well.

2016 brought my first encounter with harlequin bugs. First eggs were sighted on kale around the same time I was noticing leaf miner damage to spinach and beet leaves (early May). At the time, I wasn’t sure what had laid the eggs, but noted their distinguished geometrical grouping and pattern.

 Uncapped (already hatched) eggs.

Side view of eggs, note black striping along side.

As the season progressed,the harlequin bugs made themselves known. Mostly laying on and inhabiting my kale plants, I attempted hand control by picking eggs and both adult and baby bugs, which helped but did not eliminate the population. I noticed as I pulled and destroyed severely infested plants that bugs and eggs could also be found on closely neighboring tomato plants. The warmer winter of 2015/2016 may have played a role in my new familiarity with this insect pest. Also, two plots in our garden use a radish cover crop, possibly providing a nice winter home for adult bugs.

Harlequin bugs on the underside of a collard leaf. Adult top left, youth middle right.

Later this season, I also spotted Harlequin bugs in the Parks and Rec vegetable garden at Columbus Square Park. Is this a new issue for South Philly? I wonder what next year’s gardening season will be like and if we need a more concentrated effort to control this pest population.

Collard leaf with damage from harlequin bugs,
browning and spotting. Also showing
concurrent damage from cabbage lopers
(holes and munching around leaf margins).

2014 Penn State Extension update:

“Early in the season populations and damage are often low and you may be tempted to ignore them. But, with two to three generations in a season, by the time fall crops begin to mature their numbers may be one hundred times as high, causing serious damage. Harlequin bugs reproduce quickly, developing from an egg to an adult in about 48 days. Adult males may live up to 25 days and females up to 41 days. During their adulthood they can mate repeatedly laying multiple egg masses of 12 eggs every 3 days. That means a single female can produce 164 eggs. My advice – don’t ignore harlequins bugs; put together a plan to keep their numbers low.”

Recommended cultural controls:

“Host-free periods without brassicas can help limit the population. Remember brassica cover crops, like forage radish, are known hosts. Harlequin can also feed and reproduce on wild weedy mustards (Shepherd’s purse, wild mustard, pepperweed), pigweed (Amaranthus spp.), lambsquarter (Chenopodium spp.). Keeping these weeds under control in fields and on field edges will limit habitat. Leftover crop residue in the field provides a protected host area for over-wintering adult harlequins. Remove or disk in residue to destroy overwintering sites. Trap crops have been recommended, but I would suggest that you need to rapidly kill the bugs in the trap crop, or destroy the trap crop and follow it with a host-free period, for this to work well. Plant an early crop of horseradish, mustard or kale and try to kill the harlequin bugs concentrated on this favorite host. One grower has successfully controlled harlequin by frequent vacuuming.”

Beneficial Insects and flowers in the vegetable garden.

Always on the quest to improve my garden and learn more about "organic" methods to prevent insects from devouring my plants, I recently searched for flowers to intertwine with my vegetable garden to increase beneficial insects.

After reading and finding lists, I found many of the suggested plants are already growing in my garden. A pleasant surprise to say the least.  I have in the past planted basil, sage, bronze fennel, dill and parsley without thinking about insects. The herbs were planted to eat not deter insects. A neighbor told me to plant marigolds to control aphids around the tomatoes. I found the marigolds did indeed keep the aphids down so I interplanted them again this year. 

The parsley and dill draws a beautiful black swallowtail butterfly every year so I plant parsley and dill just for them. When I see the yellow striped catepillar I know the plants will be soon deleafed and the caterpillars gone to come back as a beautiful butterfly.. 

Below is a partial list of plants suggested for drawing beneficial insects to the gardens and those I have planted. 

Annual Flowers and Herbs  

Basil (Ocimum basilicum) -- The flowers attract bees and other beneficial insects. A few sites offered the aroma of the leaves may deter aphids.

Calendula (Pot Marigold) -- Edible, orange or yellow flower petals.  Attracts bees, butterflies and hoverflies.

Cosmos -- Attracts lacewings, hoverflies and parasitic mini-wasps. 

Dill (Anethum graveolens) -- The leaves are used in recipes, and the flowers attract lacewings, ladybugs, hoverflies and parasitic mini-wasps.  The black swallowtail butterfly also enjoys this herb in my garden.

Marigold (Tagetes sp.) -- The flowers attract butterflies and hoverflies, and the roots produce a secretion that kills root-eating nematodes in the soil. 

Parsley (Petroselinum crispum) -- The flowers attract hoverflies, tachinid flies and parasitic wasps. 

Zinnia (Zinnia elegans) -- A wonderful flower for attracting, hoverflies, parasitic wasps and butterflies.  

Perennial Flowers and Herbs

Photo by Bruce Marlin NW Center for alternative pesticides 

Bronze Fennel  (Foeniculum vulgare 'Purpureum') --Bronze foliage. The flowers attract lacewings, ladybugs, hoverflies, parasitic mini-wasps and butterflies.

Chives (Allium schoenoprasum) -- Attracts butterflies and bees. Seeds will self sow all over the garden, deadhead religiously.

Garlic Chives  (Allium tuberosum) -- The flowers attract bees and beneficial insects. The leaves have a nice, strong garlic flavor. Reading information on this herb I found it repels aphids on roses. 

Lemon Balm  (Melissa officinalis) --  The tiny flowers attract hoverflies, tachinid flies and parasitic mini-wasps.  The leaves make a nice lemon flavored tea.

Sage  (Salvia sp.) -- There are many forms of sage, including culinary. They all attract bees and butterflies. Culinary sage is used with pork, and the leaves can be fried.

Yarrow (Achillia sp.) -- Attracts ladybugs, hoverflies and parasitic mini-wasps. A favorite in my garden that doesn't need alot of water.

For more information on insects, check out the Penn State Entomology site:

http://ento.psu.edu/extension/factsheets

Another Extension site worth visiting on this issue is http://umaine.edu/publications/7150e/

Additional Information http://www.motherearthnews.com