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POLYGONUM. Knotgrass. [Polygonaceae]
Six species of Polygonum are recorded as native to Britain - Equal-leaved Knotgrass (P. arenastrum), Knotgrass (P. aviculare), Northern Knotgrass (P. boreale), Sea Knotgrass (P. maritimum), Ray's Knotgrass (P. oxyspermum) and Cornfield Knotgrass (P. rurivagum). A further two species have been introduced - Lesser Red-knotgrass (P. arenarium) and Red-knotgrass (P. patulum). Sea Knotgrass (P. maritimum) is protected under Schedule 8 of the Wildlife and Countryside Act, 1981. Six dipterous miners, the anthomyiids Pegomya betae, Pegomya bicolor, Pegomya setaria and Pegomya solennis, the chironomid Cricotopus trifasciatus, and the ephydrid Hydrellia griseola, are recorded on Polygonum in Britain. The record of Pegomya betae requires confirmation.	Redleg - Polygonum persicaria
The agromyzids Liriomyza sativae and Liriomyza trifolii, polyphagous pest species of ornamental and vegetable crops occasionally intercepted at UK points of entry, are recorded on Polygonum. Elsewhere the agromyzids Liriomyza sativae and Liriomyza trifolii and the anthomyiids Pegomya bicolor, Pegomya setaria and Pegomya solennis are recorded mining Polygonum. One non-dipterous miner is recorded on Polygonum in Britain (see below).

Key for the identification of the known Diptera mines in Britain.

#>Details of mine unknown. Cricotopus trifasciatus (Meigen) [Chironomidae]. 1> Blotch mine. Mine of Pegomya setaria on Fallopia baldschuchianica. Image: Willem Ellis (Source: Nederlandse bladmineerders) Pegomya setaria (Meigen) [Anthomyiidae]. ->Leaf mine. 2. 2> Leaf mine. Linear mine, becoming a blotch. Two or more larvae feeding together. Frass in lines. Mine of Pegomyia solennis on Rumex obtusifolius. Image: Willem Ellis (Source: Nederlandse bladmineerders) Pegomya solennis (Meigen) [Anthomyiidae]. ->Leaf mine. Mine begins with a broad corridor, which is rather transparent, widening itself then becoming a dorsal or ventral, greenish blotch, which later, depending on the size of the leaf, can become, in places, full depth and transparent. Ample black frass scattered in the mine. Puparium Reddish brown, in the soil. The r ecord on Polygonum requires confirmation. Pegomya betae (Curtis) [Anthomyiidae]. ->Leaf mine. Large upper side blotch or blister mine, which can start with a short corridor. In small leaves the mine can be full depth in places. Often several larvae in a mine; frass irregularly scattered in large lumps. Pupation external. Pegomya bicolor (Wiedemann) [Anthomyiidae]. ->Irregularly formed mine, very shallow and as a result, whitish in colour. In broad leaved plants frequently star-shaped and sometimes a very shallow corridor. In grasses the mine frequently starts in the leaf sheath. The frass is finely grained, initially irregularly spread, later in clumps. The larva may mine more than one leaf. Pupation in separate mine (sometimes even on another plant) without frass. Puparium whitish to dark grey Mine of Hydrellia griseola on Glyceria fluitans. Image: Willem Ellis (Source: Nederlandse bladmineerders) Hydrellia griseola (Fallén) [Ephydridae].

Non-dipterous miners recorded on Polygonum in Britain Calybites phasianipennella (Hübner, 1813) Lepidoptera: Gracillariidae

Last updated 30-Jul-2008  Brian Pitkin

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