Knotweed Leaf Beetle

Animal / parasitoid
larva of Bracon fuscipennis is parasitoid of larva of Gastrophysa polygoni

Foodplant / open feeder
larva of Gastrophysa polygoni grazes on live, riddled with holes leaf of Polygonum
Remarks: season: late 5-late 9

Foodplant / open feeder
adult of Gastrophysa polygoni grazes on live, riddled with holes leaf of Rumex
Remarks: season: 8-9

Foodplant / open feeder
adult of Gastrophysa polygoni grazes on live, riddled with holes leaf of Polygonum aviculare agg.
Remarks: season: 8-9
Other: major host/prey

Foodplant / open feeder
adult of Gastrophysa polygoni grazes on live, riddled with holes leaf of Fagopyrum
Remarks: season: 8-9

Foodplant / open feeder
adult of Gastrophysa polygoni grazes on live, riddled with holes leaf of Fallopia baldschuanica
Remarks: season: 8-9

Foodplant / open feeder
adult of Gastrophysa polygoni grazes on live, riddled with holes leaf of Persicaria maculosa
Remarks: season: 8-9

Animal / parasitoid
larva of Meigenia mutabilis is parasitoid of larva of Gastrophysa polygoni

Animal / parasite
colony of Nosema gastroideae parasitises adult of Gastrophysa polygoni

In Great Britain and/or Ireland:
Animal / predator
Saprinus virescens is predator of adult of Gastrophysa polygoni

Due to their being an invasive species from Europe (Lesage and Majka 2009) and their widespread distribution, conservation efforts do not seem warranted.

April to October (Blatchley 1910), varying somewhat by region.

Throughout Europe, western and central Asia, the United States, and Canada (Borowiec 2011, Islami and Nikbakhtzadeh 2009, and Lesage and Majk 2009). The Strickland collection includes specimens collected in the southern half of Alberta and Ontario.

Have fewer tiny depressions spread over the head and thorax compared to the elytra which are very punctate. They are 4-5 mm in length and are oblong oval in shape. Antennal bases, thoraces and legs red/orange (Blatchley 1910). Elytra and head are black, with a metallic blue or green sheen (Lesage and Majka 2009).

Accoding to Blatchley (1910) the habitat of this species is "... in yards and along pathways” and in cereal fields (Lesage and Majka 2009).

They may pupate in the soil, similar to G.cyanea . They may be multivoltine, similar to G. viridula.

Will eat cultivated buckwheat (Lesage and Majka 2009). They have been considered as a potential form of control for Rumex spp. (Piesk et al. 2011, Lesage and Majk 2009), Polygonum spp.(Blatchley 1910, Lesage and Majka 2009) and Fallopia spp. (Lesage and Majka 2009).

Gastrophysa polygoni is a species of leaf beetle in the subfamily Chrysomelinae. It was described by Carl Linnaeus in 1758. The species can be up to 5mm long and is green-blue in colour. The thorax is orange and the wing cases are a metallic green, and the beetle can be seen in spring and summer.