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Aphis citricidus (=Toxoptera citricida)

Brown citrus aphid

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

Identification & Distribution

Adult apterae of Aphis citricidus (previously Toxoptera citricida) are shiny, very dark brown to black, with dark siphunculi and cauda (see first picture below) (cf. Aphis spiraecola, which are yellow or green). The antennae of adult wingless forms and larger nymphs are not striped, but are dark on about the distal half of its length (cf. Aphis aurantii, which has black-and-white banded antennae; and cf. Aphis craccivora, which has the antenna dark on only the distal 0.3 of its length). The terminal process is 4.0-4.5 times as long as the base of antennal segment VI. The longest hairs on antennal segment III are 1.5-2.0 times the basal diameter of that segment (cf. Aphis aurantii, which has the longest hairs on that segment 0.5-1.0 times the basal diameter). The siphunculi are about 1.5 times as long as the cauda. The body length of adult Aphis citricidus apterae is 1.5-2.4 mm.

First image above by permission, copyright Sunil Joshi & Poorani, J. Aphids of Karnataka. (accessed 12/8/20).
Second image above copyright Centre for Invasive Species Research under a creative commons licence.

Alatae of Aphis citricidus (see second picture below) have a shiny black abdomen. Antennal segment III is dark (cf. Aphis aurantii, which has antennal segment III mainly pale). The forewing has a pale pterostigma and a twice-branched medial vein (cf. Aphis aurantii, which has a very dark pterostigma, and usually a once-branched media).

Images of clarified mounts, above, copyright Brendan Wray under a Creative Commons License.

Immature Aphis citricidus are a distinctive orange-brown (see two pictures below of colonies of the brown citrus aphid).

First image above, copyright Marco Gaiani under a Creative Commons License.
Second image above, copyright Marina VM under a Creative Commons licence.

Aphis citricidus is mainly found on young growth of plants in the Rutaceae, although occasionally large colonies of aphids develop on young growth of other trees and shrubs. The main host is undoubtedly Citrus spp, where it rolls the leaves and stunts shoots sometimes causing significant damage. However, most damage results from transmission of the tristeza virus. Aphid colonies are ant-attended. When disturbed, the aphids may make stridulatory movements with their hind legs, but the sound produced is not audible. The species is anholocyclic in most parts of the world - but Komazaki (1988) recorded a sexual phase on Citrus unshiu in Japan, suggesting that is where the species originated. The brown citrus aphid is found in southern Africa, southern Asia, Australia, New Zealand, Pacific islands and subtropical and warm temperate parts of South America. More recently it has spread to important citrus-growing areas in Central America, the Caribbean and southern USA, as well as to Madeira, Portugal and north-western Spain. It has not so far reached the Mediterranean region nor the Middle East.

 

Other aphids on the same host

  • Aphis citricidus occurs on at least 8 species of citrus fruits (Citrus aurantiifolia, Citrus aurantium, Citrus glauca, Citrus limon, Citrus maxima, Citrus media, Citrus reticulata, Citrus sinensis).

    Blackman & Eastop list 16 species of aphid as feeding on Citrus species worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 11 as occurring in Britain (Show British list).

  • Aphis citricidus occurs on 2 species of tea (Camellia japonica, Camellia sinensis).

    Blackman & Eastop list 5 species of aphid as feeding on tea (Camellia sinensis) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 2 as occurring in Britain (Show British list).

  • Aphis citricidus occurs on 1 species of mango (Mangifera indica).

    Blackman & Eastop list 14 species of aphid as feeding on mango (Mangifera indica) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 9 as occurring in Britain (Show British list).

 

Damage and control

High populations of Aphis citricidus during bloom periods can cause direct feeding damage to citrus. But the major damage to citrus associated with infestations of Aphis citricidus is caused by transmission of Citrus tristeza virus (CTV or Tristeza virus). CTV is a closterovirus which causes possibly the most serious virus disease of citrus world-wide. More specifically it causes multiple disease syndromes, the most important of which are quick decline of trees on sour orange rootstock and stem-pitting in susceptible scions irrespective of rootstock. CTV transmission is thought to best fit the semi-persistent mode of transmission in which the virus is acquired and transmitted by aphids with feeding times ranging from several minutes to several hours, but usually not by brief probing. A number of studies have shown that Aphis citricidus is a relatively efficient vector of CTV when compared with other aphids that feed on citrus.

Historically, introduction of the brown citrus aphid has resulted in the rapid spread of CTV throughout entire citrus growing regions. The best examples of this are the virtual destruction of the citrus industry in Brazil and Argentina in the 1930s and 1940s (Knorr & DuCharme, 1951) and in Colombia, Venezuela and Peru during the 1970's (Lee et al., 1992). The brown citrus aphid was first detected in Florida in 1995, probably as a result of introduction on infested plant material rather than natural spread from the Caribbean. By the end of 1997, the entire Florida citrus production area had been colonized.

Halbert & Brown (1996, 1998) give an account of the introduction of Aphis citricidus into mainland USA, and also describe the different components for integrated pest management to achieve a measure of control over CTV. Components include cultural control (transition from sour orange rootstock to less susceptible rootstocks, protection of propagation sources, inoculum suppression), biological control, chemical control for protecting nursery stock and cross protection (deliberate infection with mild strain of CTV to suppress severe strains). A recent update is given in Batuman et al. (1995, 2020).

Acknowledgements

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 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

  • Batuman, O. et al. (1995, revised 2020). 2020-2021 Florida citrus production guide: Tristeza decline. PP-181. Plant Pathology Department, University of Florida IFAS Extension. Google

  • Halbert, S.E. & Brown, L.G. (1996, revised 1998). Toxoptera citricida (Kirkaldy), Brown Citrus Aphid - Identification, biology & management strategies. Entomology Circular No. 374. Fla. Dept. Agric. & Consumer Services, Division of Plant Industry. Full text

  • Knorr, L.C. & DuCharme, E.P. (1951). This is tristeza - Ravager of Argentina's citrus industry. Citrus Mag. 13, 17-19.

  • Komazaki, S. (1988). Growth and reproduction in the first two and summer generations of two citrus aphids, Aphis citricola van der Goot and Toxoptera citricidus (Kirkaldy) (Homoptera: Aphididae), under different thermal conditions. Applied Entomology and Zoology 23(3), 220-227. Full text

  • Lee, R. F. et al. (1992). Presence of Toxoptera citricidus in Central America: a threat to citrus in Florida and the United States. Citrus Ind. 73, 13-24.