Metcalfa pruinosa

(Say, 1830)

Citrus Flatid Planthopper

Metcalfa pruinosa is a planthopper native to North America that has become a significant pest across Europe, Asia, and other regions. measure 5.5–8 mm in length and are covered in a distinctive bluish-white waxy coating. The produces one per year, with in bark crevices. It feeds gregariously on plant sap, excreting honeydew that promotes growth and causes direct damage to crops and ornamentals. First described by Thomas Say in 1830, it has spread to over 20 countries and is known to attack more than 300 plant species.

Metcalfa pruinosa by (c) Katja Schulz, some rights reserved (CC BY). Used under a CC-BY license.

Metcalfa pruinosa by (c) Sandra H Statner, some rights reserved (CC BY), uploaded by Sandra H Statner. Used under a CC-BY license.

Kifejlett lepkekabocák by Keszeics. Used under a CC0 license.

Pronunciation

How to pronounce Metcalfa pruinosa: /mɛtˈkælfə pruˈɪnoʊsə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from other flatid planthoppers by the combination of: vertical tent-like wing posture at rest; bluish-white waxy coating on and nymphs; yellow ; trapezoidal forewings with characteristic whitish spots and veined costal ; and presence of two lateral spines on hind tibiae. The gregarious feeding habit and frosty appearance are field diagnostic. In Europe and Asia, it can be separated from native flatids by its North American origin and association with disturbed . Similar in the Petrusa (e.g., P. epilepsis in the Caribbean) differ in wing venation details and geographic range.

Images

Appearance

are 5.5–8 mm long and 2–3 mm wide at the widest point, with a flattened, oval body shape. The body is covered in a conspicuous bluish-white epicuticular wax that gives a frosted or appearance; color varies from whitish to brown or gray depending on wax . Large are yellow. Forewings are trapezoidal, held vertically tent-like over the body at rest, with a veined costal and several characteristic whitish spots. Hind tibiae bear two lateral spines in addition to spines. Nymphs reach approximately 3.2 mm, varying from whitish to light green with prominent tufts of white wax on the .

Habitat

Occurs in diverse environments including urban green spaces, orchards, vineyards, hedgerows, railway corridors, forests, and agricultural landscapes. In invaded regions, thrives in neglected hedgerows, abandoned gardens, and orchards that serve as . Shows particular affinity for roadside vegetation, with 46.7% of Korean found in roadside . plant availability is the primary habitat determinant; established populations require woody plants for oviposition and .

Distribution

Native to North America (), with established throughout the eastern and central United States and southeastern Canada. Introduced and in Europe (first recorded Italy 1979, now present in Austria, France, Spain, Italy, Hungary, Romania, Slovenia, Poland, Switzerland, Ukraine, and others), South Korea (since 2008), and parts of the . In Ukraine, present in Kyiv since 2016 with disjunct distribution pattern; climatic modeling indicates potential for establishment across the entire country. Spreads rapidly along transportation corridors.

Seasonality

with one per year. present primarily in summer and fall (July–October in temperate regions), with peak activity in late summer. Mating occurs at night in fall. are laid in bark crevices of plants in autumn, until spring hatch. In Korea, 50% egg hatch predicted at 360.50 from January 1, with first instar nymphs falling from trees approximately one week later (452.23 DD). Nymphal development occurs spring through summer.

Diet

Phloem-feeding sap-sucker using . Highly , feeding on over 300 plant across more than 60 . Preferred include maples (Acer), dogwoods (Cornus), hawthorns (Crataegus), willows (Salix), elms (Ulmus), privet (Ligustrum), black locust (Robinia), elder (Sambucus), grape (Vitis), citrus (Citrus), apricot and peach (Prunus), blackberry and raspberry (Rubus), hop (Humulus lupulus), and walnut (Juglans regia). Feeds gregariously, with large on favored host plants.

Host Associations

Acer - preferred maples
Cornus - dogwoods
Crataegus - hawthorns
Salix - willows
Ulmus - elms
Ligustrum - privet
Robinia - black locust
Sambucus - elder
Vitis - preferred grapevine
Citrus - citrus trees
Prunus - apricot, peach, plum
Rubus - blackberry, raspberry
Humulus lupulus - preferred common hop
Juglans regia - preferred common walnut

Life Cycle

Hemimetabolous with . are laid in autumn (approximately 100 per female) in bark crevices and cracks of plant branches. Eggs overwinter, hatching in spring when accumulated reach threshold (10.1°C lower development threshold). First instar nymphs initially remain on natal trees, then fall to ground and disperse to other host plants. Nymphs pass through five instars, developing through spring and summer. emerge in mid-summer, feed gregariously, and mate in fall. No adult .

Behavior

Gregarious at all life stages, forming dense on plants. and nymphs feed in groups, producing copious honeydew . Adults are relatively sedentary and can be approached closely; they exhibit limited when disturbed. Nymphs are negatively geotactic, crawling upward when placed on vertical surfaces. First instar nymphs disperse by falling from trees and crawling, with potential for wind-assisted movement. Adults mate at night. The spreads actively along transportation corridors, with vehicles implicated in long-distance .

Ecological Role

Phytophagous pest causing direct damage through sap feeding and indirect damage via honeydew production. Honeydew supports growth of fungi (primarily Cladosporium ), reducing and plant vigor. Serves as prey/ for introduced agents, particularly the dryinid Neodryinus typhlocybae in Europe. are parasitized by native European egg including Oligosita collina group (Trichogrammatidae), with parasitization rates exceeding 40% reported in Italy. Honeydew attracts bees and other insects, though this is an incidental interaction rather than a functional mutualism.

Human Relevance

Significant agricultural and horticultural pest in invaded regions. Causes economic damage to grapevines, stone fruits, citrus, hops, berries, and ornamental plants. Direct feeding reduces plant vigor and crop yields; honeydew and reduce fruit quality and marketability. In Korea, classified as highly harmful . Management relies on applications, with efficacy varying by compound and plant. using Neodryinus typhlocybae has been implemented in Italy, Slovenia, and proposed for Ukraine. Monitoring using white sticky traps has been tested. Listed as regulated non- pest in some jurisdictions; recommended for inclusion in Ukrainian pest lists.

Similar Taxa

Petrusa epilepsisSimilar frosty appearance and tent-like wing posture in Flatidae, but differs in geographic range (Caribbean/West Indies), specific associations (seagrape, coffee, black mangrove), and detailed wing venation patterns.
Ormenis marginataHistorical misidentification in Puerto Rico; now synonymized with Petrusa epilepsis. Distinguished by reticulate versus parallel cross- in forewing costal margin.
Native European FlatidaeGenerally lack the dense bluish-white waxy coating, have different wing venation, and are not associated with the same disturbed types or gregarious feeding .

More Details

Biological Control

The North American dryinid Neodryinus typhlocybae has been introduced to Europe as a agent. In Italy and Slovenia, it has established and reduced planthopper . in the Oligosita collina group (Trichogrammatidae) have been found parasitizing M. pruinosa eggs in Italy at rates exceeding 40%, representing a newly discovered native natural enemy association.

Invasion Dynamics

Spread in Europe began from Italy in 1979; by 2024 established in most of southern, central, and eastern Europe. In Ukraine, first detected 2016 in Kyiv, with modeling indicating potential for nationwide establishment. Spread is facilitated by transportation networks, with roadside serving as primary corridors. The exhibits disjunct distribution patterns in newly invaded areas.

Degree-Day Models

Developmental models based on Korean predict 50% hatch at 360.50 DD (base 10.1°C, starting January 1) and 50% first instar falling at 452.23 DD, indicating approximately 92 DD (about one week) residence on natal trees before . These models inform timing of control interventions.