Stripes in the Garden: Handling the Four-Lined Plant Bug
- Monica Sabella
- Apr 16, 2023
- 2 min read
By Monica Sabella, Horticulturist, Journalist
A newb to vegetable gardening, imagine my surprise when I walked out to the garden and found a small black beetle with bright orange stripes trailing down its back creating havoc in my paradise.
Yes, it was the four-lined plant bug. With a pinching, sucker it was draining the life from my plants one nutrient at a time. Partnered with the other seasonal dangers and pests, my crops didn’t stand a chance against this monstrosity. So I started digging, into the books, that is, to find some knowledge about my enemy and uncover a secret to quell this beetle’s growing appetite.
Once a season, a new generation evolves. Over the course of a few weeks, eggs that were layed in two to three inch slits made within the host plant stems by the mother during the winter, will hatch. There are three nymph stages that follow until the bug grows to its final adult form, during that time it is eating during May and June.
Penn State Extension reports, “They generally feed on tender new growth with their piercing-sucking mouthparts. They extract the chlorophyll as they feed, and also inject enzymes, which results in the characteristic spots.”
The reason these critters are so hard to identify is that the symptoms of an infestation usually resemble a plant leaf disease. Small, round, sunken black spots roughly one sixteenth of an inch will dot the outside and inside of the leaves, sometimes merging together to form a blotch and blackening the leaves.
Assistant Professor Joe Boggs writes for Ohio State University, “Like many plant-feeding hemipterans, the bugs inject enzymes into the plant to cause cells to collapse. They then feed on the resulting ‘cell slurry.’”
The true bug’s right red color throughout its growing stages makes them easier to spot, but their speed and varied diet puts 250 plant species at risk, including woody ornamentals and herbaceous perennials. Herbs, vegetables, members of mint (Lamiaceae) family, Russian sage, blue-mist shrub, any new growth of shrubs like forsythia, deutzia, dogwood, and weigela are also susceptible.
Though unsightly, the damage isn’t necessarily deadly to your garden, Penn State assures. “On herbaceous plants such as herbs and perennial flowers, one of the easiest ways to deal with the damage is to wait until the pests have gone for the year, and then cut the plants back below the damage. They will regrow nicely, and no one will ever know how bad they looked in spring. This treatment can delay blooming of herbaceous perennials a bit.”
While Boggs writes, “Weed management is another important step in reducing localized four-lined plant bug populations. For example, I consistently see some of the heaviest damage on Teasel (Dipsacus spp.). The preference for these non-native weeds is so strong; I use the teasels to monitor localized four-lined plant bug population densities. Mowing to destroy teasel or other weeds showing feeding symptoms will eliminate them as repositories of bug eggs that will hatch next season.”
Some useful insecticides that have also proved to work wonders are labeled specifically for four lined plant bugs and include the ingredients acetamiprid, bifenthrin, carbaryl, cyfluthrin, flonicamid, insecticidal soap, lambda-cyhalothrin, malathion, permethrin, pyrethrins and piperonyl butoxide, and thiamethoxam.
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