Biology and Life Cycle

Tarnished plant bugs (Lygus lineolaris in the eastern US and L. hesperus in the western US), also known as lygus bugs or TPB, are becoming an important pest of strawberries in North Carolina. They used to be an occasional pest of strawberries, showing up in summer, close to the end of the strawberry season. However, TPB infestations have been reported yearly in NC strawberry fields in recent years. During warm late winters and early springs, TPB can show up as early as the 1st week of April in fields in the coastal or piedmont areas of North Carolina. In the mid-Atlantic and southeastern United States, TPB typically completes two to three generations per year.

TPB overwinters exclusively as adults, sheltering in leaf litter, dead weeds, brushy field margins, grassy areas, and woodlot edges. Adults are oval, flattened, approximately 6 mm (¼ inch) long, and mottled brown, green, and reddish-bronze. The most diagnostic feature is a pale yellow triangle in the center of the V-shaped area on the back of the head. Adults have long legs and piercing-sucking mouthparts. They are fast-moving and can fly readily when disturbed. In North Carolina, overwintered adults become active in early-to-mid spring once temperatures consistently exceed 46°F, feeding on buds and flowers of early-blooming wild hosts such as dandelion, chickweed, mustards, and other early annuals. In the spring, females begin laying eggs in the tissue of suitable host plants once daytime temperatures average 60–68°F or higher. Eggs are cylindrical, slightly curved, approximately 1 mm long, and are inserted into plant tissue, making them virtually undetectable during routine scouting. Eggs hatch in approximately 7–10 days under warm conditions. Immature TPB called nymphs pass through five instars and are active during bloom and fruit development, making this the most vulnerable window for crop damage. Very young tarnished plant bugs (first and second nymphal instars) look similar to green aphids, but move more rapidly and lack cornicles (the pair of tube-like structures aphids have on their abdomens). Older nymphs (third, fourth, and fifth instars) develop increasingly dark wing pads. Older nymphs have five distinct black spots on the abdomen: four arranged between the wing buds and one near the middle.

Older tarnished plant bug nymphs have five black dots on their backs and mottled brown wing pads.

Hannah Burrack

Photo of adult tarnished plant bug on strawberry.

The adult tarnished plant bug has two pair of wings. The outer wings are mottled brown with a yellow V-shaped marking between them and yellow triangular blotches on their tips.

Hannah Burrack

open strawberry flower with an insect tarnish plant bug adul feeding on it

Adult TPB on strawberry flower.

Lorena Lopez

Damage

Both adults and nymphs feed with piercing-sucking mouthparts, injecting salivary enzymes that cause localized cell death and disrupt normal tissue development. However, nymphs are generally considered the more economically important stage in strawberry because they are present in greater numbers during bloom and early fruit set and because the earliest nymphal feeding (at petal fall or earlier) causes the most severe fruit malformation. TPB can feed on all parts of the developing fruit. TPB feeding on developing achenes (seeds) on the fruit surface disrupts localized fruit growth underneath the damaged achenes. The result is "cat-faced" or "button berry" malformation: fruit that is small, knobby, unevenly developed, or misshapen. Severely damaged fruit may have a hard, seedy tip with a shrunken or absent flesh portion beneath it.

Other factors, such as poor pollination, can cause misshapen fruit as well, so the presence of misshapen fruit does not always indicate a problem with tarnished plant bugs. Poor pollination is often very common in the first picking of spring-fruiting strawberries in the southeast, when the weather is often less suitable for bee activity. Misshapen fruit due to poor pollination can readily be distinguished from that damaged by tarnished plant bugs by examining the seeds. Seeds on fruit deformed due to poor pollination will vary in size, while those on fruit damaged by TPB will be uniform in size.

Because NC strawberry growers depend on high-quality fresh-market fruit, even low levels of cat-facing can cause significant economic loss, justifying the conservative thresholds described below.

Fruit damaged by tarnished plant bug feeding.

Hannah Burrack

Misshapen strawberry fruit due to poor pollination (top). Note variable seed sizes compared to a normal strawberry (bottom).

Hannah Burrack

strawberry fruit deformed and not yet ripe, held by a hand showing deformation caused by TPB pest

Strawberry showing deformation caused by TPB with same size of seeds.

Lorena Lopez

Sampling and Thresholds

The easiest way to sample for tarnished plant bugs is by using a beat sheet. A beat sheet can consist of a white tray, a white piece of paper on a large clipboard, or white fabric drawn over a 12” embroidery hoop. To sample, walk a W- or Z-shaped pattern through the field, sampling one plant every 20 feet and a minimum of 30 plants (one fruit/flower cluster per plant). Hold the beat sheet below each cluster, and strike or shake it against the sheet with the other hand. Quickly count all nymphs (small, fast-moving, pale green to greenish-yellow insects) falling onto the sheet. Most insecticides are more effective against nymphs than against adult TPB because nymphs are a vulnerable stage, whereas adults are strong fliers. Therefore, the threshold is based mostly on nymph counts.

In high-risk locations with a history of annual TPB infestations, sampling should be standard practice from white bud through early fruit set. Scout weekly or twice a week if possible. The threshold for TPB in strawberries when sampling using a beat sheet is 4.5 nymphs per 30 clusters (0.15 nymphs per cluster).

Be sure to correctly identify tarnished plant bugs and avoid confusing them with beneficial big-eyed bugs. As their name suggests, big-eyed bugs have much larger eyes than tarnished plant bugs. Other pests like false chinch bugs can be mistaken for TPB; thus, it's important to correctly identify pests. BugGuide has a helpful identification guide for Lygus lineolaris (the east-coast species that feeds on strawberries).

Management

Cultural

Avoid locating strawberry fields immediately adjacent to alfalfa fields, large weedy areas, small-grain fields, or disturbed vegetation or other major TPB source habitats. Even modest spatial separation (300–600 ft) can reduce colonization pressure. Similarly, avoid planting near host crops, including alfalfa, clover, canola, and other TPB-preferred hosts, as this significantly increases the risk of colonization, particularly when those crops are cut or have matured. Control flowering broadleaf weeds in and around the planting, especially dandelion, chickweed, mustard family plants, and clover. Do not mow or till weedy field margins adjacent to strawberries during bloom, as this flushes adults directly into the crop. Time weed management at least 3-4 weeks before or after the bloom period.

Trap cropping uses highly attractive plant species to draw TPB away from the main crop, concentrating insects in a smaller area where they can be managed more efficiently. Research identifies several effective trap crop plants:

Buckwheat (Fagopyrum esculentum): Highly attractive to adults because flowers are a preferred feeding site. Can accumulate significantly more adults than adjacent strawberry plants. Flowering period can be synchronized with TPB activity.
White mustard (Sinapis alba): Attractive to TPB; flowers provide feeding sites. Can be sown alongside buckwheat for an extended trap crop window.
Alfalfa (Medicago sativa): Well-documented trap crop in California organic strawberry systems. Alfalfa strips paired with vacuuming reduced western TPB populations by 70–90% in that context. Alfalfa also supports natural enemies.
Canola/rapeseed (Brassica napus): Highly attractive flowering canola can draw adults, though production logistics in NC may limit practical use.

Research involving trap cropping and TPB has demonstrated important constraints, including when insecticides were applied only to the buckwheat or mustard trap crop, TPB populations on adjacent strawberry plants were not significantly reduced. This may be because bugs moved away from treated trap crop plants before they died, or because untreated adults continued to migrate from other areas. Trap crops did concentrate more bugs than strawberries, but the insecticide-on-trap-crop strategy alone was insufficient to protect the main crop. For NC growers, trap crops should be considered a supplementary component of an IPM program, not a replacement for scouting and threshold-based treatment decisions.

Conventional Insecticides

Insecticide applications are currently the primary tool for managing TPB populations that exceed thresholds in strawberry. Effective insecticide management requires attention to: product efficacy and selectivity, preharvest interval (PHI), pollinator safety, and spider mite management.

TPB populations in eastern North America have developed documented resistance to pyrethroids (IRAC 3A) and organophosphates (IRAC 1B). Pyrethroids can provide rapid TPB knockdown but are broad-spectrum insecticides that disrupt natural enemies of spider mites (Tetranychus urticae) and other beneficial arthropods. Overuse of pyrethroids is strongly associated with spider mite outbreaks, which can cause significant yield loss. Pyrethroids also have relatively short residual activity (approximately 7–10 days) in strawberry. Resistance to pyrethroids has been documented in TPB populations across eastern North America. For these reasons, pyrethroids should be used sparingly and not as a default first choice.

North Carolina strawberry growers often rely on managed honey bee hives or native pollinators during bloom. Many insecticides, including pyrethroids, are toxic to bees. Apply insecticides as late in the day as possible, when bee activity is minimal, to avoid harming bees foraging on open flowers during the day. Products rated as lowest risk to pollinators include flonicamid and novaluron. Ensure thorough coverage of flower clusters and young fruit, where nymphs are feeding. Poor coverage of the plant interior reduces efficacy significantly.

Refer to the North Carolina Agricultural Chemicals Manual and the Southern Region Small Fruit Consortium Strawberry IPM Guide for materials recommended against TPB in North Carolina and more details about their management.

Organic

Cultural methods are the only effective organically acceptable control methods at this time. Entomopathogenic fungi, such as Metarhizium robertsii isolates, have reported greenhouse mortality of TPB nymphs comparable to flonicamid in one controlled study. Beauveria bassiana is also active against Lygus. Field efficacy under NC conditions has not been fully validated, and fungal entomopathogens typically require high humidity and appropriate timing to achieve maximum efficacy. They are promising tools for future integration into IPM programs, but should currently be viewed as supplementary rather than primary options.

Biological Control

Biological control of TPB is currently supportive rather than standalone. Several natural enemies attack TPB, but their populations in strawberry fields are typically insufficient to keep TPB populations below economic thresholds on their own, especially during bloom. The most practical biological control strategy for NC growers is conservation, avoiding broad-spectrum applications that disrupt resident natural enemies.

TPB is an omnivore, meaning it can consume both plant material and small arthropods. This omnivorous diet means it can persist in a field even when prey-based natural enemies are abundant, making classical and augmentative biocontrol strategies less straightforward than for purely phytophagous pests.

insect feeding in another insect in a plant leaf

Big-eyed bug insect predator can be differentiated from TPB due to their big eyes and wing coloration pattern

Russ Ottens, University of Georgia, Bugwood.org

Summary Considerations for TPB in Strawberries

Before Bloom	Scout fields and field borders beginning at white bud stage. Note proximity to known host plants (alfalfa, clover, weedy areas, small grains). Apply border management if appropriate. Ensure spray equipment is calibrated and selective insecticide options are on hand.
During Bloom	Scout weekly or twice weekly using the beat sheet method. Walk a W -or Z-pattern, sample ≥30 blossom clusters, compare infested clusters to the sequential sampling table. If nymphs reach 0.15/cluster, apply selective insecticides, preferably not a pyrethroid. Avoid spraying during peak bee activity.
After Bloom	Continue monitoring weekly through early fruit set. Populations can reinvade rapidly. If a second application is needed, rotate to a different IRAC group. Reassess mite populations if broad-spectrum products were used.
All Season	Never base treatment on fruit deformity or spray prophylactically without a threshold. Document applications by IRAC group for resistance management. Check field edges and areas nearest to adjacent host habitats first.