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Geoica setulosaHairy-tailed pistachio-grass root aphidOn this page: Identification & Distribution Biology & Ecology Other aphids on the same host Damage & ControlIdentification & Distribution:Adult Geoica setulosa apterae on their secondary host (grass roots) are light yellowish brown, off-white or pale greenish-grey (see first picture below). The primary rhinaria are transversely elongated; slit-like, or of irregular shape with narrow diverticula. Geoica setulosa dorsal body hairs are pointed, spatulate or fan-shaped.Adult Geoica setulosa have the anal plate enlarged and extended or displaced dorsally, surrounded on three sides by the U-shaped abdominal tergite 8 so as to form a trophobiotic organ to retain honeydew for collection by ants. The anal plate has long and usually pointed hairs arranged in two longitudinal rows (see second picture above), as well as finer, shorter hairs grouped near their anus (cf. Geoica utricularia, which has only scattered, shortish hairs on the anal plate, and not arranged in two rows). The body length of the adult Geoica setulosa aptera is 1.6-2.6 mm. The body length of alatae on the secondary host is 1.8-2.3 mm. The clarified slide mounts below are of adult viviparous female Geoica setulosa : wingless, and winged.
Micrograph of clarified mounted aptera and alate, courtesy Favret, C. & G.L. Miller, AphID. Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO. On the primary host, (Pistacia khinjuk) in Iran, Geoica setulosa forms galls at the bases of leaflets. These galls open in late August-October. Emigrant alatae found colonies on roots of grasses (e.g. Agrostis, Briza, Festuca, Holcus), attended by ants. Where the primary host Pistacia khinjuk does not occur (most of the aphid's range), the hairy-tailed pistachio-grass root aphid spends its entire life cycle on grass roots reproducing parthenogenetically, often overwintering in the nests of Lasius flavus. Geoica setulosa is found over much of Europe, and has been introduced to USA. Biology & Ecology:Geoica setulosa is not uncommon on grass roots in southern Britain, often in the company of other species also living on grass roots - such as various Anoecia species and Tetraneura ulmi. Ivens (2012) showed that frequency of alate production was very low in some other subterranean ant tended species including the closely related Geoica utricularia,. In Poland Depa & Wegierek, 2011 only found Geoica utricularia, and Geoica setulosa) in the nests of Lasius flavus in moist meadow. Zwo1fer (1958) also found that Geoica setulosa was closely associated with ants, although in breeding experiments the aphids were able to survive without ants. Primary hostsGeoica setulosa is only found on 1 Pistacia species (Pistacia khinjuk) which grows in Iran. Blackman & Eastop list 11 species of aphid as feeding on of Pistacia khinjuk worldwide and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 4 as occurring in Britain (Show British list).
Secondary hostsBlackman & Eastop list 66 species of aphid as feeding on grass roots (Poaceae) worldwide (Show world list). Paul (1977) found at least 16 aphid species recorded on grass roots in Britain: (Show British list).
Damage and controlGeoica aphids feeding on grass roots can be a major problem on golf courses because the Lasius ants that tend the aphids tend to construct nest mounds on the greens (Maier & Potter, 2005).
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