Carolinaia rhois (sumac-grass aphid) identification, images, ecology, control

Adult apterae of Carolinaia rhois (see first two pictures below) on the primary host (Rhus) are reddish-brown, light orange or greenish yellow. Their antennal tubercles are weakly developed. The antennal terminal process is over twice as long as the base of antennal segment VI. Antennal segment III usually has less than 10 secondary rhinaria, with none on segment IV. The siphunculi are mainly black, apart from their bases, and are asymmetrically swollen on the inner edge. The cauda is pale, nearly parallel-sided with a slight neck and 5 hairs. The body length of adult Carolinaia rhois apterae is 1.9-2.3 mm. The apterae on secondary hosts (grasses) are somewhat smaller, light brown to greenish yellow with black siphunculi.

Note: Hottes & Frison (1931) describe the ovipara of the species under the name Rhopalosiphum rhois; the species is also covered under this name in Palmer (1931).

Carolinaia rhois (sumac-grass aphid) adult aptera on Rhus typhina (sumac vinaigrier, staghorn sumac) at Stationnement des lacs, Parc national du Mont-Saint-Bruno, Montreal, Quebec, Canada on 26/07/10; Claude Pilon

Alatae (see first picture below) have a brown or greenish yellow abdomen with dusky dorsal markings. They have rather few secondary rhinaria (2-8) on antennal segment III. Immature Carolinaia rhois (see second picture below) also vary in colour from reddish-brown or light orange to green.

Carolinaia rhois (sumac-grass aphid) alate on Rhus typhina (sumac vinaigrier, staghorn sumac) at Bois-de-l'Heritage, Park-Nature de la Pointe-aux-Praries, Montreal, Quebec, Canada on 17/08/09; Claude Pilon

The clarified slide mounts below are of adult viviparous female Carolinaia rhois : wingless, and winged.

Clarified slide mount of Carolinaia rhois (sumac-grass aphid) aptera; HM Queen,Canada

First image above copyright (2010) Her Majesty the Queen in Right of Canada, Agriculture & Agri-Food Canada.
Second image above copyright CBG Photography Group under a Creative Commons License.

In spring colonies of Carolinaia rhois occur on undersides of leaves of smooth sumac (Rhus glabra) and staghorn sumac (Rhus typhina). Hottes & Frison (1931) note that "this large brown aphid is often very conspicuous because of its superabundance on the undersides of the leaves of sumach". After several parthenogenetic generations on sumac, Carolinaia rhois then host alternates to the flowerheads of cereals and grasses (Poaceae) such as oats (Avena sativa), barley (Hordeum vulgare), wheat (Triticum aestivum), cocksfoot (Dactylis glomerata) and timothy grass (Phleum pratense). The sumac-grass aphid is widely distributed in North America, but has not been found elsewhere.

Other aphids on the same host

Primary hosts

Carolinaia rhois is the only species of aphid recorded from Rhus trilobata (= three-leaf sumac, skunkbush), but has been recorded from 2 other sumac species (Rhus glabra, Rhus typhina).

Blackman & Eastop list 3 species of aphid as feeding on smooth sumac (Rhus glabra) and staghorn sumac (Rhus typhina = Rhus canadensis) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 1 as occurring in Britain (Show British list).

Secondary hosts

Carolinaia rhois has been recorded on 1 species of the Hordeum genus (Hordeum vulgare).
Blackman & Eastop list 47 species of aphid as feeding on barley (Hordeum vulgare) worldwide, and provide formal identification keys (Show World list). Of those species, Baker (2015) lists 26 as occurring in Britain (Show British list).
Carolinaia rhois has been recorded on 1 species of the Triticum genus (Triticum aestivum).
Blackman & Eastop list 60 species of aphid as feeding on 'common wheat' (Triticum aestivum) worldwide, and provide formal identification keys (Show World list). Of those species, Baker (2015) lists 30 as occurring in Britain (Show British list).
Carolinaia rhois has been recorded on 1 species of the Phleum genus (Phleum pratense).
Blackman & Eastop list 32 species of aphid as feeding on timothy grass (Phleum pratense) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 20 as occurring in Britain (Show British list).

Acknowledgements

We are especially grateful to Claude Pilon for pictures of Carolinaia rhois.
We have made provisional identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Palmer (1952) and Hottes & Frison (1960) as well as Blackman & Eastop (1994) and Blackman & Eastop (2006). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References

Hottes, F.C. & Frison, T.H. (1931). The Plant Lice, or Aphidae, of Illinois. Illinois Natural History Survey Bulletin 19(3), 123-447. Full text
Palmer, M.A. (1952). Aphids of the Rocky Mountain Region: including primarily Colorado and Utah, but also bordering area composed of southern Wyoming, southeastern Idaho and northern New Mexico. Thomas Say Foundation, Denver. Full text

Carolinaia rhois (= Glabromyzus rhois)

Sumac-grass aphid, Monell's sumach aphid

Identification & Distribution

Other aphids on the same host

Primary hosts

Secondary hosts

Acknowledgements

Useful weblinks

References