New aphid found in faba beans

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Megoura cras­si­cau­da has been found in parts of north-east and cen­tral New South Wales (Syd­ney, Tam­worth, and Breeza). The species orig­i­nat­ed in north-east Asia, and is close­ly relat­ed to the vetch aphid (Megoura vici­ae), found in Europe, Ethiopia and North Amer­i­ca. Its host range is most­ly lim­it­ed to Vicia species — vetch­es, faba or broad beans, and may extend to Aus­tralian native vetch­es and vetch weeds.

At this point its dis­tri­b­u­tion in Aus­tralia is unknown. Since the orig­i­nal detec­tion in a Syd­ney back­yard in Octo­ber 2016, the only two addi­tion­al detec­tions have been in faba bean field tri­als at Breeza and DPI’s Tam­worth research sta­tion. Field reports from agron­o­mists and grow­ers will help deter­mine where they are present – so keep an eye out.

The dam­age poten­tial of this species, both in terms of direct feed­ing dam­age from the infes­ta­tions, and their poten­tial as vec­tors of virus­es is unclear. There is very lit­tle lit­er­a­ture from over­seas on this species as a pest of field crops.

Even though this pest has only recent­ly been record­ed in Aus­tralia, its host range, biol­o­gy, and the dis­tance between detec­tion loca­tions means erad­i­ca­tion is not like­ly to be tech­ni­cal­ly fea­si­ble.

Identifying M. crassicauda and distinguishing it from other pulse-infesting aphids

Adult M. cras­si­cau­da are large green aphids with red eyes and dark­ened areas on the head, tho­rax, legs, siphun­culi and cau­da. The species is larg­er than the oth­er com­mon aphid species with dark body parts found in faba bean, the cow­pea aphid (Aphis crac­civo­ra).

megoura-1

megouracolony1 megouracolony2

Close-up of adult M. crassicauda adult, and colonies on faba bean.
Images of Megoura in this article have been provided by NSW DPI.

Two oth­er species of aphid that com­mon­ly occur in puls­es are the cow­pea aphid and pea aphid. These can be eas­i­ly dis­tin­guished from M. cras­si­cau­da using the fol­low­ing fea­tures:

Species


M. cras­si­cau­da

megoura

Cow­pea aphid
(Aphis crac­civo­ra)

cowpeaaphid

Pea aphid
(Acyrthosiphon pisum)

peaaphid

Body colour

Bright green

Dark green to black;  nymphs green-grey

Green (can vary between brown–green–pinkish)

Eye colour

red

black

red

Appendages

Legs, cau­da and siphun­culi dark. Small, dark plates where siphun­culi join the body.

Legs white and black. Siphun­culi black.

Legs, cau­da and siphun­culi green-brown with black joints.  Siphun­culi and cau­da long.

Anten­na length

Longer than body

Short

Longer than body

cowpeaaphidcolony_DSCN2122 megouracolony3

Cowpea aphid (left) has been the predominant aphid species on faba beans in past seasons. A Megoura colony can be seen on the right. Both colonies pictured contains mainly nymphs.

Although the dam­age poten­tial of this species is unclear; in the event of heavy infes­ta­tion and lit­tle nat­ur­al ene­my activ­i­ty, it may be pru­dent to treat. There are no insec­ti­cides cur­rent­ly reg­is­tered for this pest, how­ev­er an appli­ca­tion for an Emer­gency per­mit for the use of pir­im­i­carb, chlor­pyri­fos and lamb­da cyhalothrin is cur­rent­ly being assessed. New South Wales DPI has used pir­im­i­carb to con­trol this and oth­er species of aphids in faba bean tri­als.

GRDC has request­ed that sus­pect­ed sight­ings of this aphid be report­ed. In the first instance, con­tact the NSW DPI or Qld DAF ento­mol­o­gists for con­fir­ma­tion of iden­ti­fi­ca­tion. They will inform the rel­e­vant Biose­cu­ri­ty enti­ty.

Further reading:

Hales, D et al (2017). First detec­tion of ‘Megoura cras­si­cau­da’ Maudvilko (Hemiptera: Aphi­di­dae) in Aus­tralia and a review of its biol­o­gy. Gen­er­al and Applied Ento­mol­o­gy 45:77–81.

F.C Tsaganou et al (2004). Effect of Aphis gossypii Glover, Bre­vi­co­ryne bras­si­cae (L.), and Megoura vici­ae Buck­ton (Hemiptera: Aphi­doidea) on the devel­op­ment of the preda­tor Har­mo­nia axyridis (Pal­las) (Coleoptera: Coc­cinel­l­i­dae). Bio­log­i­cal Con­trol 31(2):138–144