Illinoia spiraecola

Distinguished from other Illinoia species by the combination of: long slender cornicles with slight subapical swelling; 6-segmented antennae with terminal process longer than base of segment VI; green to yellow-green body color; and association with Spiraea hosts. Differs from Aphis spiraecola (also on Spiraea) by longer antennae, longer cornicles, and lack of abdominal dorsal dark markings. Alates have dark thorax contrasting with green abdomen.

Found on new growth and undersides of leaves of host plants; primarily associated with Spiraea species in natural and ornamental settings, and Citrus in agricultural contexts. Requires sheltered, humid microhabitats typical of aphid colonies on woody shrubs.

Native to North America; recorded from United States and Canada. Introduced and established in other regions including parts of Europe, Asia, and South America. Present in citrus-growing regions where it has been documented as an occasional pest.

Overwintering eggs hatch in spring; multiple parthenogenetic generations produced through summer; sexual forms and egg-laying females appear in autumn. Peak colony development occurs during late spring and early summer when new host growth is abundant.

Phloem-feeding specialist; primary hosts are Spiraea species (Rosaceae). Has been recorded on Citrus (Rutaceae) as a secondary host, particularly in Mediterranean and subtropical regions where it can cause economic damage to citrus nurseries and young trees.

• Spiraea - primary hostnative host; reproduction and colony establishment
• Citrus - secondary hostagricultural pest on young trees and nurseries

Holocyclic with sexual and parthenogenetic phases. Overwintering as eggs on Spiraea stems. Fundatrices hatch in spring and reproduce parthenogenetically, producing viviparous offspring. Multiple generations of apterous and alate parthenogenetic females through summer. Short-day photoperiod triggers production of sexual forms (males and oviparous females) in autumn; mating and egg deposition on Spiraea completes the cycle.

Forms dense colonies on new shoots and leaf undersides. Alates disperse to establish new colonies when host quality declines or crowding occurs. Exhibits typical aphid defensive behavior including cornicle secretion of alarm pheromone (E-β-farnesene) when disturbed. Tending by ants has been observed, though less frequently than for some other aphid species.

Herbivore that transfers nutrients from host phloem to higher trophic levels; serves as prey for generalist predators including lady beetles (Coccinellidae), lacewings (Chrysopidae), and parasitoid wasps (Braconidae: Aphidiinae). May contribute to local nitrogen cycling through honeydew production.

Minor to moderate economic pest: primary concern is damage to Spiraea in ornamental horticulture, and to young citrus trees in nurseries and new plantings. Feeding causes leaf curling, shoot distortion, and honeydew accumulation leading to sooty mold. Control rarely required in most situations; integrated pest management approaches effective when necessary.

• Aphis spiraecolaAlso occurs on Spiraea; differs by shorter antennae, shorter cornicles without subapical swelling, and presence of dark abdominal markings in some forms
• Illinoia pepperiCongeneric species on Vaccinium; differs by host association and slightly shorter cornicles
• Myzus persicaeGreen aphid on diverse hosts; differs by presence of frontal tubercles and shorter antennae relative to body

• aphid
• pest
• Spiraea
• Citrus
• ornamental pest
• agricultural pest
• Macrosiphini

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy