Unaspis citri

(Comstock, 1883)

Citrus Snow Scale, Orange Chionaspi, Orange Snow Scale, White Louse Scale, White Snow Scale

is an insect (Hemiptera: Diaspididae) that infests citrus crops worldwide. The forms dense colonies on bark, fruit, and leaves, causing direct damage through sap feeding and indirect harm by promoting growth. It is economically significant in citrus-producing regions, particularly Florida, where management requires integrated approaches combining monitoring, , and targeted chemical applications.

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Pronunciation

How to pronounce Unaspis citri: //juːˈnæspɪs ˈsɪtraɪ//

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

Identification

is distinguished from other citrus by its narrow, snow-white, elongate test that resembles a or small white line. It differs from Lepidosaphes ulmi (oystershell scale) by preference and test shape—U. citri tests are more uniformly linear and strictly associated with citrus. It differs from (Lepidosaphes beckii) by coloration (white vs. purple-brown) and from Florida red scale (Chrysomphalus aonidum) by test and lack of reddish coloration. Microscopic examination of the ( body segment) reveals diagnostic sclerotized plates and gland spines for definitive identification.

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Habitat

Citrus groves and orchards; residential citrus plantings. Colonizes all above-ground plant parts including bark of trunk and branches, leaves, and fruit. Thrives in humid subtropical climates typical of major citrus production regions.

Distribution

in citrus-growing regions worldwide. Documented across North, Central, and South America (including United States, Mexico, Brazil, Argentina); Caribbean islands; Europe (Azores, Spain, Italy, Greece); Africa (West Africa, South Africa, Mauritius, Madagascar); Asia (China, Japan, Southeast Asia, Indonesia, Philippines); Australasia (Australia, New Zealand, Papua New Guinea); and Pacific Islands (Fiji, Samoa, Tonga, New Caledonia).

Diet

Phloem sap feeder; inserts stylets into vascular tissue of citrus plants to extract nutrients.

Host Associations

Citrus - primary All commercial citrus cultivars including oranges, lemons, mandarins, grapefruit, and limes

Life Cycle

Females develop through , (first-instar nymph), and stages beneath the protective test. Males complete egg, two nymphal instars, and pupal stages before emerging as winged . is sexual; males locate sessile females for mating. Multiple overlapping occur annually in favorable climates.

Behavior

First-instar are the only mobile stage, dispersing to find suitable feeding sites before secreting their permanent tests. are (females) or short-lived and non-feeding (males). Colonies form dense on preferred bark surfaces, with older developing characteristic snowy white appearance on trunks and branches.

Ecological Role

Primary consumer; phloem feeder that converts plant sap to . Honeydew supports growth of fungi (Capnodium spp.), which reduces and fruit marketability. Serves as prey for natural enemies including and predatory beetles.

Human Relevance

Major economic pest of citrus causing direct yield loss through tree debilitation, premature fruit drop, and reduced fruit quality. renders fruit unmarketable for fresh consumption. Control costs and production losses are substantial in Florida and other citrus regions. Subject to regulations and programs. using has been implemented in some regions.

Similar Taxa

Lepidosaphes ulmiPreviously misidentified as U. citri in the Philippines; differs in broader range (rosaceous and other woody plants) and test
Lepidosaphes beckii on citrus; distinguished by dark purple-brown test coloration and different pygidial
Unaspis lansivoraRecently described from Lansium domesticum in Philippines; previously misidentified as U. citri; differs in plant and subtle morphological characters

More Details

Management

combines monitoring of , conservation of natural enemies (including Aphytis spp. and Encarsia spp., and predatory beetles), and selective applications timed to vulnerable crawler stages. Heavy may require or insecticide treatments.