In 2018, around this same time period, I wrote a BYGL Alert about the damage in my garden caused by the four-lined plant bug (Poecilocapus lineatus). I was a bit upset because of the amount of damage to a wide variety of plants. I SAID I was going to take action but of course, I never got around to it. Well, that's about to change this year! Once again there is significant damage to a wide variety of perennials including my mints, daisies, bee-balm, mums, salvia, obedient plant, verbena, 'Honorine Jobert' anemone, an assortment of hydrangea cultivars, and many more herbs and perennials. Some plants are more damaged than others, but none more than the oregano, the epicenter of my infestation. I have had some amounts of damage for many years, but never to this extent.
I teach pests of herbaceous plants quite often and I am usually pretty reserved about this plant. I usually don't get excited as it only has one generation per year and it's early enough in the season that you can prune, etc. That tune is going to change next time I teach this class! In addition, the damage is about to end! I am at war and I will have to take action this season or populations might continue to enjoy my plants.
As for the damaged plant parts, I will prune or shear them. New growth will cover what's missed. By summer, you won't be able to tell. Since the nymphs are still feeding and causing damage, I am going to spray with a pesticide labeled for ornamental plants that kills plant bugs. Contact insecticides listed for control of four-lined plant bug include carbaryl, bifenthrin, permethrin, lambda-cyhalothrin, acetamiprid, and cyfluthrin. If you do choose to use pesticides, be sure to read the label carefully and pay particular attention if you are going to use an insecticide on vegetables or herbs. Products labeled for ornamentals can't be used on vegetables.
Joe Boggs authored a BYGL ALert on April 23, 2019 mentioning that he spotted this pest beginning to feed in the Cincinnati area. You can read this article to find out more specific details about this pest.
Check back with me next year around this time to see if I really did get around to spraying this season.