The Four-Lined Plant Bugs of the Apocalypse

In a recent post I speculated about a possible fungal disease disfiguring some of my plants. Alert readers Brenda Coulter and Julia V correctly identified the problem as four-lined plant bug.

Four-lined plant bug
Four-lined plant bug


It’s odd how after they mentioned this bug, I started seeing it everywhere. This either says something about my limited powers of observation, or suddenly my four-lined plant bugs stopped using their invisibility cloaks.

Four-lined plant bugs have piercing mouth parts. They suck the chlorophyll out of the leaf cells, which sounds rather sinister. After that the cells turn brown or black and may fall from the leaf, leaving little holes. If there is enough damage the leaves may shrivel up.

Culver's Root damaged by four-lined plant bug.
Culver’s Root damaged by four-lined plant bug.

There is one good thing about four-lined plant bugs: they don’t stick around for very long. They hatch in May or June and mature over about six weeks. Then they feed for another month or so, mate, and die, leaving their eggs to overwinter. They have only one generation per year.

Healthy plants should recover from the vampire-like attentions of the four-lined plant bug. The damage is cosmetic, though it can look darn ugly.

In my garden it looks like these bugs have matured, so they should be around for another month or less. When they are gone I may cut back the damaged plants – primarily Culver’s Root (Veronicastrum virginicum) and Anise Hyssop (Agastache foeniculum). It doesn’t make sense to me to cut the plants back while the bugs a still feeding.

How the four-lined plant bug looks to your garden plants.
How the four-lined plant bug looks to your garden plants.

My hope is that everything will recover by August 1, when our garden will be part of the Wild Ones garden tour. If not, I’ll survive.

I considered using an organic insecticidal soap, but decided against it. My understanding is the soap can kill non-target insects, including beneficial predators. My garden has been remarkably free of insect pests for some years, which I attribute to a diverse and balanced insect population. In order to maintain that balance, I will tolerate some cosmetic damage, even some delayed or lost flowering.

Do you ever use insecticidal soaps? If so, at what point do you think it is warranted?

50 Comments on “The Four-Lined Plant Bugs of the Apocalypse”

  1. I would take your approach of creating a balanced garden. Your bug looks interesting does it provide food for any thing else? A few years ago I bought an organic insecticidal soap and after a few sprays decided its not for me as they are indiscriminate on invertebrates and I did not know what the affects were on birds and frogs who would usually eat the invertebrates. Are you opening your garden up?

  2. I haven’ t come across these bugs, my particular bug horrors are lily beetle and asparagus beetle. I thought at first the latter were an unusual sort of ladybird and was admiring their prettiness. Now my daily garden patrol is a killing mission. I squash them with my fingers; not for the squeamish. But no nasty sprays please. Obviously they upset the balance and kill the good guys as well as the plant- munching monsters.

    • Luckily I have yet to be afflicted by lily beetles, though I do have lilies. Do asparagus beetles attack plants other than asparagus? These four-lined bugs are a bit too quick to catch, but when I used to have Japanese beetles I would go out every morning and evening and push them into a mug of soapy water. Then I would watch them drown and make cackling noises.

  3. I don´t use any insecticidal soap in my garden either. We have a society in Denmark called ” poison free gardens” that I have joined. Both for sake of all the other insects in our gardens, but also for the sake of our groundwater.

  4. I have not encountered this bug and am glad you were able to at least identify it and its habits. My nemesis, the Japanese Beetle, will be arriving soon and destroy everything in its path. I try to capture them and feed them to the chickens which is my only satisfaction. I haven’t tried any insecticidal soaps but if they worked on these beetles I might be tempted. 🙂

  5. There is always something that wants to chew its way through our lovely gardens. At the little house in the big woods, it’s slugs and snails. Never heard of the four-line plant bug. And, yes, what a good decision not to use anything on them.

  6. Jim, I have used insecticidal soap, but mainly on my potted plants. I also found neem oil to be good. I nay used it to control aphids, though, and let natures take it’s course otherwise. Predatory insects do a remarkable job if you have enough, as well as particular plants that attract certain insects. Japanese bean beetles preferred the Amaranthus leaves over the beans, so as a result their leaves were almost see through while the leaves of the beans were almost untouched. The problem with neem oil is that you have to make sure you mix it with dish soap and keep the sprayer shaken or you can get brown areas on your leaves… But, in your case now, since the four-lined plant bug is almost run it’s course… Do they particularly like only certain plants? If they are only attracted to certain plants, you only have to spray those plants. Using a synergistic spray, like neem oil, makes the leaves taste bad and they won’t eat them… GREAT POST!!!

  7. I’m glad you have got to the root of the problem…..but what a pretty looking beetle, I haven’t seen one of those before. Good to hear there will be no long lasting damage! I hope all comes good for the garden tour, I’m sure it will.
    I avoid all sprays and chemicals and rely on natural predators which is ad hock

  8. Yes, I agree with Marian (and the others). I sometimes use Neem oil (organic) on houseplants, but that’s because houseplants don’t have the benefit of being outside and interacting with the beneficial insects. Oh, and beer traps for slugs in my vegetable garden. Otherwise, I agree–it’s worth the cosmetic damage to have an environmentally friendly garden. I hope these insects will exit your garden soon.

  9. This is a new bug to me, possibly because it is a mid-west native? Apparently, the four-lined plant bug is native to the US, which means that it should have natural predators that will keep it in check over the long run. Some of those birds that hang out in your garden might be happy to feed it to their babies. Since reading Doug Tallamy, I tend to only worry about non-native insects (like Japanese Beetles) that aren’t integrated into the local ecology. For these, I try to use manual controls (like brushing Japanese beetles off the plants they are eating into a container of water to drown them). I think your approach is a wise one.

  10. Interesting thread. I try and stay away from insecticides–especially if I would have to mix them (I don’t trust my skills on figuring out the ratios correctly). I am a live and let live kind of person for the most part and have been extremely lucky in that not too much has enjoyed my plants. Current insect obsession seems to be the roses…all the leaves now look somewhat lacy. But like another poster here I am too lazy and too busy to get after it.

  11. Don’t cut your plants back. If all they ate were the leaves, then why cut the stalk that will grow more leaves? I just had spider mites completely decimate my phlox leaves but they’re already growing back. Give them a couple of good drenchings of water enriched with liquid kelp and then just wait.

  12. Hello Jason, ants are a big problem here, they’ve turned the front border into a black fly factory and the ladybirds are no-where to be seen. I won’t spray the black fly, but I’ll probably put down ant bait just to control the population, which is getting out of control! Ugh, I hate ants.

  13. They can be a real p-i-t-a. They have a short life span but the eggs do overwinter in the duff and at the tips of plant stems (about 6 inches along the stem). They really like plants that have aromatic resins so as you can imagine that is a problem for those of us in Texas growing every type of sage available. They used to be rare here in the south but their population has exploded recently. It took me a year of serious effort to get rid of them. They are native but they were out of control in one of my beds. I went out each morning to capture the nymphs early in the season and then cleaned the bed meticulously that fall and trimmed everything that might host the eggs. I still have a few here and there but it doesn’t look like Manhattan at rush hour any more.

  14. Thank goodness they don’t stay long. I am also on a garden tour this year, in mid-July (unfortunately a few weeks before full-bloom time here). I’ve been using just a solution of dish soap and water and only on my John Cabet climbing rose bush. I worry that it might be bad for some beneficial bugs. But if I don’t put anything on it, the rose bush will be just bare by July. Everything else I just leave alone.

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