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Aphidinae : Macrosiphini : Megoura crassicauda
 

 

Megoura crassicauda

Japanese vetch aphid, Bean aphid

On this page: Identification & Distribution Other aphids on the same host Damage & Control

Identification & Distribution

Adult apterae of Megoura crassicauda are green with black head, prothorax, antennae, siphunculi and cauda, dusky mesothorax, and variably pigmented tibiae. The antennae are 0.9-1.1 times the body length, with a terminal process about 4 times as long as the base of antennal segment VI. The species is very similar to the European Megoura viciae, differing only with respect to the number of secondary rhinaria on the antennae. Antennal segment III has 21-50 secondary rhinaria in a row extending over 0.75-0.90 of the segment (cf. Megoura viciae, which has segment III with 5-26, usually 10-18, rhinaria, not in a row, on basal 0.75 of segment). The rostrum reaches to just past the middle coxae. The apical rostral segment (RIV+V) is 0.63-0.87 times the second hind tarsal segment (HTII). The abdomen has antesiphuncular and small postsiphuncular sclerites, and short cross bands on tergites VII & VIII. The siphunculi are cigar shaped, about 0.16 times body length, and the same length as the cauda. The body length of adult Megoura crassicauda apterae is 3.0-3.7 mm.

Note: Mordvilko (1919) originally described this species as Megoura viciae subsp. crassicauda. Miyazaki (1971) used Megoura japonica for the same species, a name still used in some of the literature about Megoura crassicauda.

First picture above copyright Department of Primary Industries, New South Wales, Australia;
second picture copyright Thomas Mesaglio under a under a creative common licence.

The alate Megoura crassicauda has the head and thorax black, the abdomen green with black marginal, ante- and post-siphuncular sclerites, and cross bands on tergites VII and VIII. The antennae are slightly longer than the body. Antennal segment IV has more than 17 rhinaria (cf. Megoura viciae alate, which has 0-7 secondary rhinaria on segment IV).

Megoura crassicauda is monoecious on the stems and growing points of beans (Vicia spp.) and vetches (Lathyrus spp.). It has also been recorded from garden pea (Pisum sativum) and Amphicarpaea edgeworthii. The species is thought to normally be holocyclic, although anholocyclic populations are present in warmer areas. It is found in east Asia including east Siberia, China, Taiwan, Japan and Korea. It has recently been introduced to New South Wales in Australia.

 

Other aphids on the same host

Megoura crassicauda has been recorded on 3 vetch species (Lathyrus davidii, Lathyrus japonicus, Lathyrus palustris).

Megoura crassicauda has been recorded on 13 bean species (Vicia amoena, Vicia amurensis, Vicia angustifolia, Vicia cracca, Vicia faba, Vicia flava, Vicia japonica, Vicia megalotropis, Vicia pseudo-orobus, Vicia sativa, Vicia sepium, Vicia unijuga, Vicia venosa).

Megoura crassicauda has also been been recorded on Pisum sativum and Amphicarpaea bracteata ssp. edgeworthii (=Amphicarpaea edgeworthii =Amphicarpaea trisperma, Chinese hog-peanut, which has also been recorded hosting the soybean aphid, Aphis glycines).

 

Damage and control

Megoura crassicauda is a serious pest in broad beans (Vicia faba) and other leguminous crops in much of Asia. Hales et al (2017) reported its first detection in Australia, on faba bean crops in 2017. High population densities covering the entire stems and basal shoots of infested plants were reported. Hand-spraying with petroleum oil and subsequently imidacloprid (a neonicotinoid) were ineffective in controlling the aphid infestations, and the plant shoots and pods turned black and died. The yield of mature bean pods was almost zero. Natural enemies had no noticeable effect on the number of aphids, possibly because Megoura crassicauda may be toxic to coccinellid larvae. Infestations have since been effectively controlled with pirimicarb (a selective carbamate insecticide), using two sprays per season at least 14 days apart (Duric, 2021). Surprisingly, and in contrast to the earlier observations, Kasai (2016) found that infestation with Megoura crassicauda did not reduce bean production in narrow-leaved vetch (Vicia sativa).

Acknowledgements

We are grateful to Thomas Mesaglio for making his image of Megoura crassicauda available for use under a creative commons licence.

We have used the account given by Miyazaki (1971) (as Megoura japonica) together with information from Hales et al. (2017) and Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections as the source for the (summarized) taxonomic information we have presented. Any errors in 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

  • Duric, Z. (2021). Keep an eye out for faba bean aphid, particularly during spring. The Beatsheet Nov 15 2021. Queensland Government Full text

  • Hales, D.F. et al. (2017). First detection of Megoura crassicauda Mordvilko (Hemiptera: Aphididae) in Australia and a review of its biology. General and Applied Entomology: The Journal of the Entomological Society of New South Wales 45, 77-81. Full text

  • Kasai, A. (2016). Vetch aphid, Megoura crassicauda (Hemiptera:Aphididae), parasitism does not reduce the bean production of narrow-leaved vetch, Vicia sativa subsp. nigra (Fabaceae). Ecological Research 31, 189194. Abstract

  • Miyazaki, M. (1971). A revision of the tribe Macrosiphini of Japan (Homoptera: Aphididae, Aphidinae). Insecta Matsumurana 34(1), 1-247 (p. 49.) Full text

  • Mordvilko, A.K. (1919). Insectes Hemipteres (Insecta Hemiptera). I. Aphidoidea. Faune de la Russie et des pays limitrophes fondee principalement sur les collectionnes du Musee Zoologique de l'Acadamie Imperiale des Sciences de Petrograd. Livraison 2, 237-508 (pp. 301, 327)