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.”

News from the Edible Landscape Demonstration Garden

Success can come in small packages or sometimes in small bottles filled with smelly liquids. The garlic concentrate diluted with water (one part concentrate to three parts water) has been effective in deterring those pesky Japanese beetles from completely denuding the grape vines. Most of the damaged leaves have been removed and, with luck, the plants will push new growth before the end of the season. Score one for our side! Hand picking the harlequin beetles off of the curly kale seems to be keeping those critters in check. The plants are looking quite perky for this point in the season.

The cucumber harvest is well under way. We planted 'Pickle Bush' hybrid along two small trellises back in May. The resulting plants are flowering well and have produced enough cukes to make a batch or two of bread and butter pickles. A later planting of 'Marketmore 97' cucumbers are almost a foot high and should provide us with even more crunchy additions to late summer and early fall salads.

Cardoon in bloom

The dozen or so different types of beans are now in their glory. The long, red Chinese noodle beans climbing high on their tepee supports look wonderful at the back of the garden. The various shelling bean plants -- Calypso, Great Northern, Black Turtle -- are filled with pods, ready for picking. The string beans including 'Soleil', 'Masai' and 'Kentucky Wonder' are in flower. What a wealth of delicious eating awaits!


The cardoons are in full bloom at the moment. Their thistle-like flowers are bold and beautiful. It is worth considering planting this perennial for its ornamental qualities alone.

Come visit us in the garden soon! We love company!

News from the Edible Landscape Demonstration Garden

The sweltering heat of the last ten days has made work in the garden a challenge. Luckily, the staff at the Horticulture Center arrive at the crack of dawn and the gates are open shortly after 6am. July can be a cruel month for plants and humans alike. One can count on certain visitors to the garden, however... Japanese and harlequin beetles. Despite the fact that we saw zero grubs in the soil of the beds this spring, the Japanese beetles have swooped down on the grapes climbing the arbor and are feasting on their leaves. Bag traps are encircling the garden, fifty feet or more away from the beds. They are filled with bead bugs. But still they come to have breakfast, lunch and dinner. This week, we soaked the grapes with garlic spray, a potential deterrent to beetle activity. The scent was incredible, so strong that one's eyes would water. We'll see if that helps to solve the problem.
The harlequin beetles, so colorful but so nasty, have found the kale to their liking, but, interestingly, not all of the kale. They seem to like two cultivars -- Red Russian and Lanciniato. They ignore the curly kale. Go figure! The two favorites have been relegated to the compost pile.  Good looking white eggplant starts will be taking their place tomorrow.

The City Gardens Contest judging date has been set -- Friday, August 2nd. We're busy staking errant plants, deadheading blooming herbs and generally tweaking an already well manicured and beautiful garden. Please stop by for a visit and be sure to sign in at the visitors' box. If you're there at 6:30 am, we'll treat you to coffee!