Geocoris spp.
Big-eyed bugs- Kind
- Wild — attract it
- Best for
- Background predation on nymphs
Pest
Tarnished plant bug
Lygus lineolaris
The short answer
A flattened, mottled brown bug about 1/4 inch (6 mm) long, with a small pale yellow triangle in the centre of its back. Adults and the fast-running green nymphs suck on buds, shoot tips and developing fruit. They inject a saliva that kills the cells around each bite. The dead spot does not grow while the tissue around it does, so strawberries come out cat-faced, and shoots and leaves turn spotted, holed and twisted. It feeds on hundreds of plants and breeds in the weeds around a garden. Control there means timing: count nymphs at strawberry bloom, keep weeds down before they flower, and never spray open flowers.
hero macro · adult on a strawberry flower
Adult Lygus lineolaris on a strawberry flower truss. Photo: pending.
Identification
Adults are about 1/4 inch (6 mm) long, oval and rather flat, mottled brown, bronze, tan or greenish, with darker markings and a small yellow or pale green triangle in the middle of the back. The University of Kentucky describes it as a yellow Y. They are good fliers and move about easily. This is the common plant bug of the central and eastern US. In the West, the closely related western tarnished plant bug, usually just called lygus bug, does the same damage. Insecticide labels often say "lygus bug" rather than tarnished plant bug.
Nymphs are bright green, and the youngest are yellowish. They can be mistaken for aphids, but they run quickly when disturbed. From the third instar they carry five black dots on the back: two just behind the head, two on the next segment and one in the middle of the abdomen. There are five nymphal stages. UC IPM notes a harmless lookalike, Calocoris, which is narrower and has two black dots behind the head.
Easily confused with
- Damsel bugsBeneficial — leave itDamsel bugs are slender and tan, with thickened, spiny front legs for grabbing prey; plant bugs are flatter ovals with a pale triangle on the back.
- Big-eyed bugsBeneficial — leave itBig-eyed bugs have a wide head with bulging eyes and shorter antennae; plant bugs have smaller eyes, longer antennae and a narrower head.
- AphidsAlso a pestYoung plant bug nymphs are pale green and aphid-like, but they move much faster than aphids do.
Damage symptoms
The damage comes from the saliva, not the sap loss. The bug injects a toxin that kills the cells around each feeding puncture, and the dead spot stops growing while the tissue around it keeps expanding. The first sign is usually small brown spots on young leaves, which become holes and distortion as the leaf grows. On strawberry, feeding on the seeds stops the berry developing around them, leaving a cat-faced fruit with large, hollow, straw-coloured seeds. UC IPM notes poor pollination causes similar misshapen berries, but with small, undeveloped seeds instead.
- Cat-faced strawberries: lumpy, misshapen fruit with hollow straw-coloured seeds
- Small brown spots on young leaves that turn into holes and distortion
- Shoot tips and flower buds killed or blasted
- Bronzed or discoloured cauliflower heads
- Dimpled, scabbed apples and fruit buds dropping
- Crumbly, deformed raspberries
Lifecycle & degree days
It spends the winter as an adult and becomes active as the leaves open in spring. Females lay eggs in the stems and leaf ribs of weeds and crops, and the first nymphs are on strawberry flowers in May in New England. There are two or possibly three generations a year there, and the University of Kentucky reports several. A nymph takes from 12.5 days at 93 °F to 40 days at 53 °F to become an adult. Adults move in large numbers when their weed or alfalfa hosts dry out, are mown or are harvested, and UMass warns that mowing near a crop at the wrong moment drives them into it.
- Generations / yr
- 2–3 (New England); several (Kentucky)
- Nymph development
- 12.5 days at 93 °F to 40 days at 53 °F
- Eggs
- 1–3 a day; 30–120 per female
- Overwinters
- Adults
J
F
M
A
M
J
J
A
S
O
N
D
Host crops
StrawberrySnap, dry & lima beansLettuce, celery & greensCauliflower & broccoliPotatoAsparagusApplePeachCut flowers
Penn State records it on 385 plant species, 130 of them economically important. UMass notes that more than half of the cultivated crops in the US are hosts. Weeds matter as much as crops, because that is where the population builds. UMass lists wild carrot, pigweed, lambsquarters, mustards, shepherd's purse, goldenrod and mullein, and alfalfa is a favourite. Where a garden sits next to weedy ground or hay, expect more of them.
Monitoring & action thresholds
Action threshold
4 of 30 flower clusters with nymphs
This is the UMass strawberry threshold. Shake 30 flower clusters over a white surface, spread across the planting. If four or more have any nymphs at all, a spray is recommended. It is a commercial figure. UMass notes there are no thresholds for most vegetable crops.
In strawberries, sample at bloom by tapping flower clusters over a white plate or card: 30 clusters, taken in small groups across the bed. White sticky cards set just above the canopy show when adults become active in spring and give a rough idea of numbers, but they are not a threshold on their own. The bugs are mobile and hide, so looking for them on the plants is unreliable. In California, UC IPM also watches weeds around the field from February for the first nymphs.
Beneficial
Biological control
No purchased beneficial is recommended against it. The parasitic wasp Peristenus digoneutis was released against it in New Jersey alfalfa and has spread through the Northeast. UMass reports it can cause up to 50% mortality, but not enough to prevent damage in key crops. Lady beetles, spined soldier bugs and insidious flower bugs eat the nymphs. In California, UC IPM names big-eyed bugs, damsel bugs, minute pirate bugs and spiders as predators of lygus nymphs. It adds that the naturally occurring parasitic wasp Anaphes iole is present but cannot give acceptable control, because the damage threshold is so low.
Cultural controls
Weeds are the source, and managing them at the right moment is fundamental to control. UC IPM and UMass agree on the principle, and UMass warns about the timing.
- Keep weeds down around beds and field edges, especially before the weeds flower
- Remove or mow weed hosts while the bugs are still nymphs, and avoid mowing beside the crop when it is most vulnerable, such as at strawberry bloom
- Mow or dig in legume cover crops before they flower
- Expect a surge of adults when nearby alfalfa is cut or weeds dry out or are mown, and check the crop then
- Trap plants in flower beside the crop can draw adults to lay, but only if the nymphs on them are destroyed before they mature
Chemical, last resort
Never spray during bloom. Registered insecticides hit nymphs better than adultsCheck any product before it goes on. Open the compatibility matrix →
Rating: the effect on this pest's natural enemies if a spray hits them or they feed on treated plants. REI is the re-entry interval on farm and greenhouse labels; home labels usually give none, so follow the label.
Sources
UMass Extension Vegetable, Tarnished Plant Bug (R. Hazzard & S. Schloemann, 2019)
Penn State Extension, Tarnished Plant Bug (updated 2026)
UC IPM Pest Management Guidelines: Strawberry — Lygus Bug
University of Kentucky ENTFACT-419, Plant Bugs and Lacebugs
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →