Chaetosiphon tetrarhodum

Identification & Distribution:

Chaetosiphon tetrarhodum adult apterae (see first picture below) are pale green to yellow-green or occasionally reddish. The head is rather smooth with few if any spicules. The antennae are short, only 0.6-0.8 times the body length. The dorsal cuticle is densely covered with flat warts giving it a wrinkled appearance. Each abdominal segment bear 5 pairs of capitate hairs. Their siphunculi are 1.1 to 2.5 times longer than the cauda. The body length of Chaetosiphon tetrarhodum is 0.7-2.1 mm, with the smallest individuals in mid-summer.

Micrographs of clarified mounts by permission of Roger Blackman, copyright AWP all rights reserved.

Chaetosiphon tetrarhodum is found on various species of roses especially the Japanese rose (Rosa rugosa). In spring they can be found on the shoot tips, young leaves and developing flower. Later in the year they can be found singly or in small groups on the undersides of mature leaves. Sexual forms occur in autumn. The distribution of Chaetosiphon tetrarhodum is worldwide.

Biology & Ecology:

Life cycle

Several workers have monitored the seasonal changes in the species composition and abundance of aphids on roses. For example in Lublin, Poland Jaskiewicz (2003) describes the species composition and number of aphids on rose bushes in urban conditions over three years. Their numbers varied over time with peak numbers in June. Chaetosiphon tetrarhodum comprised 0.8-15.3% of the total number of aphids on roses.

In a similar study, Kmiec (2007) sampled four varieties of rose on 28 occasions over 3 years, and calculated a constancy index for each of seven species of aphids as the percentage of occasions when the species was present. For Rosa rugosa Chaetosiphon tetrarhodum was present in about 70% of samples, higher than any other species for this type of rose.

In Britain we have found some evidence of parthenogenetic overwintering. For example the images above and below below reveal thriving populations of Chaetosiphon tetrarhodum on rugose roses in the East Sussex village of Alfriston in mid-March in both 2017 and 2018.

This would seem to be too early in the year for these aphids to be fundatrices. They would have to have hatched from the eggs in January, which seems improbable.

Natural enemies

Barjadze et al. (2010) reported the aphid parasitoid Aphidius eglanteriae attacking Chaetosiphon tetrarhodum, with a parasitism rate of 0-4%. Tomanovic et al. (2009) records Ephedrus laevicolis as a parasitoid of this species.

We have yet to identify the species responsible for parasitizing Chaetosiphon shown in the picture above.

Other aphids on same host:

Blackman & Eastop list 21 species of aphid as feeding on Japanese rose (Rosa rugosa) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 14 as occurring in Britain (Show British list).

Damage and control

Jaskiewicz (2006) looked at the effect of feeding of Chaetosiphon tetrarhodum and the larger Macrosiphum rosae on the flowering of roses. Both species when found in large numbers (see picture below) caused deformation of the leaf blades, shortening of shoots and petioles and flower deformation.

Chaetosiphon tetrarhodum is one of the main pest aphids of the Damask Rose (Rosa damascena) in Turkey. The plant is weakened by heavy infestations and great quantities of honeydew are deposited on the leaves. It is currently controlled solely by chemical means. Barjadze et al. (2010) suggested that mass rearing and release of Aphidius eglanteriae should be considered.

Acknowledgements We wish to thank the staff of Plumpton College for their kind assistance and permission to sample. Our particular thanks to Roger Blackman for images of his clarified slide mounts. Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made 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 Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). 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 Barjadze, S. et al. (2010). New evidence of parasitoids of pest aphids on roses and grapevine in Turkey (Hem., Aphididae; Hym., Braconidae, Aphidiinae). Journal of Entomological and Acaralogical Research Ser. II,42(3), 143-145. Full text Jaskiewicz, B. (2003). The species composition and number of aphids on the shrubs Pinus mugo Turra and Rosa sp. in urban conditions. Electronic Journal of Polish Agricultural Universities, Horticulture 6(2). Full text Jaskiewicz, B. (2006). The effect of feeding of Macrosiphum rosae (L.) and Chaetosiphon tetrarhodum (Walk.) on the flowering of roses. Acta Agrobotanica 59(1), 515-520. Full text Kmiec, K. (2007). Constancy of occurrence of aphid community (Hemiptera, Aphididae) on roses in the urban conditions of Lublin. Annales Universitatis Marie Curie-Sklodowska Lublin - Polonia. 17(1), 53-59. Full text Tomanovic, Z. (2009). Ephedrus Haliday (Hymenoptera: Braconidae: Aphidiinae) in Serbia and Montenegro: Tritrophic associations and key. Acta entomologica serbica 14(1): 39-53. Full text