ask-ruth-pictureDear Ruth,

Something is attacking my greens. I’ve never seen them before, but my neighbor says they are harlequin bugs. They are orange, white, and black and look kind of like a stinkbug.

Freaking out,

Dave in Fairview, NC

 

 

Dear Dave,

Your neighbor’s right! These distinctive black, orange, and white bugs could almost be called pretty ~ if they weren’t so tenacious. I had never encountered them until about ten years ago when my kohlrabi took a major downward dive. The plants seemed to die in just a few days, but in truth the harlequin bugs were probably sucking the lifeblood from the plants long before I noticed they had invaded.

harlequinbugsHarlequin bug, Murgantia histrionica, is a shield-shaped true bug and is most prevalent in the southeast. It damages plants by
sucking sap from the leaves, stalks, flowers, and fruit with its needle-like piercing mouth parts. Their black & white eggs are barrel shaped and have a circular lid. The adults and nymphs look alike at a glance ~ they both sport the distinctive harlequin bug colors, but the nymphs are smaller and wingless. The nymphs molt several times before they become a winged adult (adults are about 3/8” long). Plants in the brassica family (broccoli, cauliflower, cabbage, collards, kale, mustard, wild mustard, turnips, etc.) are among their favorite foods, but harlequin bugs will also attack other plants when their favored foods become scarce. During milder winters they have been spotted ~ in all stages of their life cycle ~ as far north as Virginia.

Linda Blue, Buncombe County Extension Agent and longtime OGS volunteer-extraordinaire, has this to say about harlequin bugs, “Unfortunately, as far as I know there are no good organic controls for harlequin bugs – difficult even with synthetic chemicals. Other than hand removal to a container of soapy water, one could try something like pyrethrum, but you’d have to directly contact the insects with the spray.”

I asked a few farmers at the tailgate market what they do. Anne Grier of Gaining Ground Farm recently sprayed Neem Oil for harlequin bugs; she reported that it wasn’t very effective; she had a less than 25% knockdown result. Alex Brown of Full Sun Farm said that Pyganic (a pyrethrin spray) doesn’t work on harlequin bugs. He suggested trying Molt-X. I googled Molt-X, and it does list “true bugs” on the label and it is OMRI approved for Certified Organic growers with restrictions. I first heard about Molt-X last spring ~ when Meredith McKissick of Crooked Creek Farm used Molt-X for cabbage maggots and she got a bonus outcome ~ her arugula was undamaged by flea beetles. Intrigued that Molt-X may be the solution, I did a price check on the internet. Surprise! The pint size container was listed at $149. Although it takes a miniscule amount to do the trick, the expected shelf-life on the pricey insecticide is 15 months. That cost may be beyond the means of most gardeners to protect a handful of plants…it would be more cost-effective to buy greens at the tailgate markets!

A gardener at Monticello (Thomas Jefferson’s home) suggested this routine for harlequin bugs. Spray plants thoroughly with Safer Soap to soften the insect’s shell. Then 3 days later, spray with pyrethrins. The bugs will be more vulnerable to the pyrethrin
because of the Safer Soap. As Linda pointed out, the spray must contact the insect. Home gardeners may have an advantage here. Since farmers are often using tractor-mounted sprayers, the product may not reach into all the nooks and crannies of the plant. A home gardener can use a hand sprayer and reach most areas of the plant (be sure to include the undersides of leaves).

harlequinbugs1According to one study, harlequin bugs are able to “sequester glucosinolates from its host plants for use in defense against predation [by birds].” That means they can accumulate the stinky-factor from cruciferous plants and use it to make themselves
distasteful to birds. Bummer. We can’t count on birds to control this bug!

Last year harlequin bugs turned up in my garden and then returned with a
vengeance this year. Between the dry weather and those bugs, by mid-August my garden looked fried. They really love collard greens, and I sacrificed my collards to the harlequin bugs hoping they would leave the kale alone. It worked until they decimated the trap crop (collards) and moved on to the kale. Here’s the catch: If the harlequin bugs are left undisturbed while they eat the trap crop, they are constantly reproducing and their numbers are growing exponentially ~ until the plants and garden
floor can be positively writhing with creepy harlequin bugs in various stages of their life cycle. This larger population will be much harder to eradicate.

Parasitic wasps & parasitic flies can be purchased for release in the garden, or you can try to attract native ones by growing flowering plants that produce nectar or pollen. They will parasitize the bugs and help control bad bug populations. Plant beneficial insect plants (umbral plants like Bronze Fennel, Dill, & Queen Anne’s Lace) to attract parasitic wasps and flies, and other beneficial insects to your garden area.

Conclusions for garden scale control of harlequin bugs.

  1. Keep your garden and surrounding area free of debris/weeds all year long. Debris/weeds will provide habitat for the bugs during the season and protection for bugs over the winter.
  2. Harlequin bugs are difficult to control, so be proactive. Pay attention as soon as you see one single bug. Scout for eggs and bugs. Eggs hatch more slowly in spring when temperatures are colder. Squish eggs and hand-pick the bugs off your plants and drop them into a jar of soapy water. Bugs will be easier to catch in early morning when they are moving more slowly. Act early and destroy bugs before they have wings and before they reach their reproductive stage.
  3. Plant resistant varieties ~ NC State Plow Sharing, Sept. 2001 suggests: Cabbage – Copenhagen, Market 86, Headstart, Savoy Perfection, Drumhead, Stein’s Flat Dutch, and Early Jersey Wakefield; Collards – Green Blaze; Cauliflower – Snowball X and Snowball Y; Radish – Red Devil, White Icicle, Globemaster, Cherry Belle, Champion, and Red Prince
  4. If you spray, remember that the spray must contact the bug to be effective. Try Safer Soap, pyrethrins, or sabadilla. Spray very early in the morning or late in the day in order to prevent leaf burn and avoid contact with honey bees.
  5. Remove or till in any plant material or crop residue left over after harvest. Till affected area after the weather turns cold to reduce populations.
  6. As always, maintain healthy plants by providing adequate water and fertilization. Healthy plants will be less susceptible to insect damage

Good luck with these bugs Dave, and thanks for writing,
Ruth

Ask Ruth © 2013 Ruth Gonzalez & Organic Growers School

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Ruth Gonzalez

Ruth Gonzalez

Ruth Gonzalez is a former market farmer, current gardener, and local food advocate. She has written numerous local food and gardening articles, blogs about local food, and writes the “Ask Ruth” Gardening Column for Organic Growers School. In her job at Reems Creek Nursery, Ruth offers advice on all sorts of gardening questions, and benefits daily from the shared wisdom of local gardeners. She has a special affection for clouds and finds delight in the natural world at every turn. Read more from Ruth at her blog: http://tailgatemarketfanclub.wordpress.com/