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Four-Lined Plant Bug

Four-Lined Plant Bug

Poecilocapsus lineatus

Insectalso: Fourlined plant bug

A fast-moving plant bug that peppers the leaves of herbs, perennials, and shrubs with neat dark spots in late spring and early summer. It is especially fond of mint, basil, and many flowers, and although the damage looks alarming, it is mostly cosmetic and the bug is active for only a few weeks.

🔎 How to spot it

Adults are bright greenish-yellow, about a quarter inch long, with four black stripes down the back and an orange head; they drop or dart away quickly when disturbed. The young nymphs are bright red with black dots. The damage is distinctive: small, round, sunken dark or translucent spots about one sixteenth inch across, often in groups, that can merge and drop out to leave a shot-hole look easily mistaken for a leaf-spot disease.

🥀 Damage it causes

Feeding punctures kill small patches of leaf tissue, leaving the spots that may turn brown or fall out as holes, and heavily hit leaves can curl, brown, and distort. The damage is concentrated on new growth at the tops of plants. It is mainly cosmetic and rarely threatens plant health, though it can disfigure herbs and flowers grown for their looks or harvest.

🛡️ Prevent it

Watch for the first nymphs and spotting in late May and early June, the only period the insect is active, since early detection limits injury. Cut back and clean up old stems in fall, where the eggs overwinter inside the stems, to lower the next year numbers. On lightly affected plants, simply tolerating the brief damage is often the best choice.

🧯 If it is already here

Because the bugs are quick and the season short, handpicking is tricky, but pinching off and destroying the first spotted leaves and any visible red nymphs helps. For valued herbs and flowers, insecticidal soap aimed at the nymphs gives some control if applied early while they are small. Once the few weeks of activity pass, no treatment is needed and plants push out clean new growth.

💡 Good to know

The neat round spots are so uniform they are routinely mistaken for a fungal leaf spot, but the timing, the lack of fungal specks, and the presence of fast green-and-black bugs or red nymphs give it away. There is one generation a year, eggs are laid in slits in plant stems, and the whole episode is over by midsummer.

🌱 Plants it attacks

289 plants in the library can be attacked by this pest

African Blue BasilAfrican MarigoldAgapanthusAgeratumAgrimonyAlice du Pont MandevillaAloe VeraAmethyst Falls WisteriaAnemoneAngelique TulipAngeloniaAniseAnise HyssopAnnabelle Smooth HydrangeaAnnual VincaApeldoorn TulipApple MintApril Tryst CamelliaArizona Sun Blanket FlowerArp RosemaryAshwagandhaAugust Beauty GardeniaAutumn Joy SedumBachelor's ButtonBarbara Karst BougainvilleaBay LaurelBecky Shasta DaisyBee BalmBenarys Giant ZinniaBengal Tiger Canna🥬Bibb LettuceBlack Currant🥬Black Seeded Simpson LettuceBlack-Eyed PeaBlack-eyed Susan VineBlood OrangeBlue Bird DelphiniumBlue Bird Rose of SharonBlue FescueBocking 14 ComfreyBonesetBorageBrunneraBurning BushButtercrunch LettuceButterfly Blue Pincushion FlowerButterfly Marguerite DaisyButterfly WeedCafe au Lait DahliaCaladiumCalendulaCalibrachoaCalifornia Giant ZinniaCalifornia PoppyCampanulaCarawayCardinal FlowerCarolina GeraniumCarolina JessamineCatnipChamomileChervilChocolate MintCinnamon BasilClimbing HydrangeaClimbing Prairie RoseCocktail Vodka BegoniaColeusCommon ChivesCommon FlaxCommon MallowCoral Drift Groundcover RoseCosmosCreeping PhloxCuban OreganoCulantroCuminCupani Sweet PeaCurly ParsleyCurry LeafCurry PlantDavid Garden PhloxDelft Blue HyacinthDenim n Lace Russian SageDillDusty MillerDutch Master DaffodilEastern Red ColumbineElecampaneEndless Summer HydrangeaEnglish LavenderEnglish Shelling PeaEnglish ThymeEpazoteEvening PrimroseFanal AstilbeFeather Reed GrassFenugreekFeverfewField Pea

For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.