Cool Stuff About Collard Greens

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We just celebrated Independence Day and August is not here yet, so why Collards? We don’t start them until August. Here in North Carolina we love our Collards. In fact, we are one of the top three collard producing states in the nation. Unfortunately, insects love them too. That’s why an NCA&T Farm research project is very exciting to those of us who love to eat collard greens, but don’t love fighting with the insects that love to eat them too.

I’m talking about the harlequin bug. The distinctive black, orange, and white harlequin bugs. Stylish but vicious, they suck the vigor right from the plants. The harlequin bug, (Murgantia histrionica), extracts the sap from the leaves, stalks, flowers, and fruit of Collards with its piercing mouth parts. Their black & white eggs are barrel shaped and have a circular lid. Plants in the brassica family (broccoli, cauliflower, cabbage, collards, kale, mustard, wild mustard, turnips, etc.) are among their favorite foods.

More and more, consumers are opting for produce that hasn’t been exposed to pesticide. Dr. Louis Jackai, Professor of Entomology at NCA&T, is conducting a pest management field trial of “trapping” Harlequin Bugs to protect collards. The project uses a mustard crop to decoy the harlequin bugs off the collards in order to reduce insecticide use.

Southern collards are planted in plots bordered by Florida Broadleaf and Old Crop Mustard crops. The plots I visited worked like a Harlequin Bug vacuum when the mustard crops were in bloom. The yellow mustard green flower blooms were wrapped up in harlequin bugs, while the collards just a few inches away were basically free of them. In the control plot a few meters away the same variety of collards planted without the mustard trap crop were wrapped up in harlequin bugs. Hmmm, that’s interesting.

What is happening? Collard and mustard plants contain a group of chemical compounds that attract insects, and the flower stage of the mustard crop produces it in abundance. As the mustard plants age and their pollinated flowers become pods, the bugs move from the mustard plants back over to the collards (about 45 days after transplanting) and the collards begin to see harlequin bug damage. If you are harvesting collards over time, a second planting of a mustard “trap” crop can keep the pests off and extend your harvest season.

Other tips for garden control of harlequin bugs in addition to trap cropping:

  • Keep your garden areas free of debris/weeds all year long to eliminate habitat.
  • Be proactive and scout and destroy eggs and bugs before they have wings and can reproduce.
  • Plant resistant varieties
  • If you spray, remember that the spray must contact the bug to be effective. Read and follow product label directions. Spray very early in the morning or late in the day in order to prevent leaf burn and avoid contact with honey bees.
  • Remove or till in any crop residue left over after harvest and again after the weather turns cold to reduce pest populations.
  • Maintain healthy plants with sufficient water and fertilization. Healthy plants will be less vulnerable to insect damage.

For more information on “trap” cropping take a look at the following website: http://www4.ncsu.edu/~dorr/What_is_Biocontrol/home_gardener_q_and_a.html  :

Minda Daughtry is Horticulture Agent for the Lee County Center of North Carolina Cooperative Extension.