Aleurodicus cocois (coconut whitefly)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Hosts/Species Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Natural enemies
- Notes on Natural Enemies
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Aleurodicus cocois Curtis, 1846
Preferred Common Name
- coconut whitefly
Other Scientific Names
- Aleurodicus anonae Morgan, 1892
- Aleyrodes cocois Curtis, 1846
International Common Names
- English: coconut mealywing
- Spanish: mosca blanca del cocotero
- Portuguese: aleurodideo do cajueiro; mosca branca do cajueiro
Local Common Names
- : aleurodideo do cajueiro
- Brazil: cashew whitefly; mosca brancha do cajueiro
- ALEDCO (Aleurodicus cocois)
- Aleurodicus cocois anacardi
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Arthropoda
- Subphylum: Uniramia
- Class: Insecta
- Order: Hemiptera
- Suborder: Sternorrhyncha
- Unknown: Aleyrodoidea
- Family: Aleyrodidae
- Genus: Aleurodicus
- Species: Aleurodicus cocois
Notes on Taxonomy and NomenclatureTop of page A. cocois was originally described from Barbados as Aleyrodes cocois by Curtis (1846). Douglas (in Morgan, 1892) erected the genus Aleurodicus for A. anonae (since recognised as a junior synonym of A. cocois). A. cocois is therefore the type species of Aleurodicus (Martin, 1997). The genus currently consists of 18 recognised species, 15 of them native to the Neotropical region. In the neotropics, a group of 10 closely related Aleurodicus species (including A. cocois) all feed on a similar range of host-plants; several of these species can damage palms and other hosts. Martin and Watson (1998) provide a key for their identification. Further research may reveal additional, undescribed species belonging to this group.
Mound and Halsey (1978) listed A. iridescens as a synonym of A. cocois, but Martin and Watson (1998) showed that A. iridescens is a junior synonym of A. pulvinatus, also a pest of coconut in the Caribbean. This recent taxonomic change renders older literature records of the distribution and host range of A. cocois somewhat uncertain because they may refer to one or other species, or both.
Serious damage of cashew nut trees in north-eastern Brazil has been caused by an insect morphologically indistinguishable from A. cocois, but which apparently will not feed on coconut. Carvalho et al. (1976) proposed that this population is a separate race, A. cocois anacardi. This datasheet, based on literature and slide-mounted insect material, does not distinguish between races of A. cocois.
Several species of Aleurodicus in different parts of the world are found on coconut and may be referred to by the common name `coconut whitefly' (A. cocois, A. pulvinatus and A. dispersus in the neotropics; A. destructor and A. dispersus in Australasia and southern Asia). Computer searches should be done using the relevant species name, or information on the wrong species could be retrieved.
DescriptionTop of page The following is true of all species belonging to the genus Aleurodicus.
Eggs, each about 0.25 mm long, are laid perpendicular to the lower leaf surface, each on a very short pedicel. They are pale initially and turn dark grey as they mature. They are laid in a spiral pattern (about 2 cm or more across) amongst patches of white wax deposited by the female. The eggs hatch into tiny crawlers that tend to settle and feed within, or close to, the oviposition spiral of white wax patches; after this, the insect is sessile until the winged adult emerges.
There are four immature stages, each successively larger than the last, with the fourth instar/pupal stage measuring up to 0.95-1.4 mm long and 0.75-1.05 mm wide; males are smaller than females. In the second to fourth instars, legs are reduced to non-functional stubs. Shortly after moulting, each immature stage develops a coating of mealy white wax, thicker in some areas than others; with the passage of time, a marginal fringe of thick, white, flocculent wax is produced to form a striking feature, forming thick, sculpted patterns around, and (in the case of A. cocois) sometimes over, the late pupal stage. Paired dorsal submarginal compound pores each secrete a filament of glassy wax that projects from the insect and periodically breaks off and falls to litter the immediate area with glistening rods. If several immature individuals are close together, the colony may become quite thickly coated with a mass of flocculant white wax and glassy wax filaments.
The adult emerges from the pupa as a yellow-orange insect, about 2- 2.5 mm long, with black eyes and 2 pairs of pale, translucent wings that are folded into a triangular profile with the wings held at a shallow angle to the horizontal, like some moths. The hind wings are only slightly shorter than the forewings. The insect remains sitting on the leaf near the oviposition spiral for 1-2 days while it develops a powdery wax coating. Wax pores on either side of the abdomen produce powdery white wax that is used to coat the body with a mealy layer and to turn the wings white. In A. cocois (also in A. dispersus and A. destructor, which do not belong to the A. cocois species group but do occur on palms) the wings are entirely white; in A. pulvinatus and several other species in the A. cocois species group, part of each forewing has a faint patch of grey pigment. Like most species in subfamily Aleurodicinae, the males have a very large pair of claspers at the posterior end.
DistributionTop of page The recent separation of Aleurodicus iridescens from A. cocois (Martin and Watson, 1998) renders older literature records of the distribution of A. cocois somewhat uncertain. The records listed that are supported by authenticated specimens in the Natural History Museum (London, UK; NHM in list) are regarded as definitely referring to A. cocois, while records based solely on earlier literature could refer to A. (iridescens) pulvinatus, A. cocois or other closely related, misidentified species.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
Risk of IntroductionTop of page A. cocois, and closely related species such as A. pulvinatus, have demonstrated serious pest potential on coconut, cashew and other tree crops in situations where their natural enemies are lacking, either due to introduction without them, or to elimination by excessive pesticide use. The major outbreak of A. cocois on coconut palms in Barbados in the 1830s was probably caused by accidental introduction of A. cocois on palms imported from other islands for re-planting after a major hurricane in 1831 (Curtis, 1846). Living plants/leaves of known host-plants, imported from areas infested by A. cocois, present the greatest risk to non-infested countries. Fruit are not a major risk, as the whiteflies feed on the leaves.
HabitatTop of page Members of the A. cocois species group form colonies on the lower leaf surfaces of their host plants.
Hosts/Species AffectedTop of page The recent separation of Aleurodicus iridescens from A. cocois (Martin and Watson, 1998) renders older literature records of the host range of A. cocois somewhat uncertain, as they may refer to A. (iridescens) pulvinatus or A. cocois, or both species. The list of host-plants given here is based on authentic specimens of A. cocois in the Natural History Museum (London, UK) collection. Literature published before 1998 may refer to A. pulvinatus or A. cocois or both species together, which is probably why the host range may appear larger: for example, Mound and Halsey (1978) list hosts from 14 plant families including guava (Psidium guajava) and seagrape (Coccoloba uvifera), which are common hosts for A. (iridescens) pulvinatus.
IIBC (1997) mentions that, of the A. cocois species group collected in Trinidad, A. cocois was the commonest on coconut, while A. pulvinatus was found on seagrape, coconut and guava, and A. maritimus was the commonest species on guava and pigeonpea. It is possible to culture A. cocois on young coconut plants in the laboratory.
Growth StagesTop of page Flowering stage, Fruiting stage, Vegetative growing stage
SymptomsTop of page Direct feeding on phloem sap by heavy infestations of Aleurodicus species, including A. cocois, may cause wilting due to loss of fluid and nutrients; leaf undersides become covered with white woolly wax, which may impede gas exchange and photosynthesis. The honeydew excreted by the insects drops onto leaf surfaces below the infestation and often forms a medium for sooty mould growth, screening more light and air from the leaves and further reducing photosynthetic productivity. Amenity trees become coated with an unsightly layer of black mould and the lower leaves die and fall, leaving a sparse crown/canopy. Ultimately the tree may die, leaving only the naked bole/branches.
Heavy infestations of coconut palms cause the oldest fronds to die and fall successively; flowers also die and fall off, and nuts fail to develop; eventually only the crown is left, and this dies and falls off, leaving the bole standing (Curtis, 1846; illustration in Martin and Watson, 1998). On cashew, the pest feeds in colonies on the lower leaf surfaces (Coodenardoria de Sanidade Vegetal, 1976) and can kill trees (Dunham and Andrade, 1971).
List of Symptoms/SignsTop of page
|Leaves / external feeding|
|Leaves / honeydew or sooty mould|
Biology and EcologyTop of page Distribution of A. cocois is mainly achieved by the winged adults, which fly about actively especially when disturbed; wind probably assists their dispersal over longer distances. The first-instar (crawler) stage usually moves only a few millimetres from the egg before settling to feed, so immature stages are often found in small colonies. Crawlers may be carried longer distances if picked up by the wind or passing animals. Subsequent immature stages are incapable of locomotion. Longer distances may be traversed if man transports plant material infested by eggs and immature stages.
Reproduction is usually sexual in whiteflies, although parthenogenesis may occur in some species. Gondim and Sales (1983) record a sex ratio of 1 male: 2 females in A. cocois in laboratory studies. Like other species of Aleurodicus, the female of A. cocois walks in a tight spiral on the leaf underside, laying eggs and depositing patches of white wax as she goes, forming an oviposition spiral of small white patches, about 2 cm across. This often remains visible even after the immatures have emerged and are developing.
Once the crawler settles at a feeding site, development continues; there are four immature instars altogether, all of which feed and produce honeydew. The last immature stage ceases to feed after a while and goes on to metamorphose into the adult; hence this stage is termed a pupa, or 'pseudopupa' (since technically a true pupa never feeds). The adult emerges from a T-shaped split in the dorsum of the pupa. In the laboratory at 20-25°C and about 88% RH, with a photoperiod of around 12 hours, Gondim and Sales (1983) recorded the average duration of the four instars of A. cocois anacardi as 6.17, 7.5, 5.5 and 8.5 days respectively; and the adults lived 16.14 +/- 1.99 days. They found there was a pre-oviposition period of ca 3.4 days.
In Ceara State, Brazil, Melo and Calvacante (1979) noticed that infestations of A. cocois are heaviest in areas near the coast where humidity was high, and decreased steadily as the relative humidity decreased.
Populations of whiteflies are often reduced by strong wind and heavy rain; however, the waxy colonies of Aleurodicus species, situated on the protected leaf undersides, are less badly affected than most.
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Encarsiella noyesi||Parasite||Adults/Nymphs||Barbados; Brazil; St Vincent and the Grenadines||Arecaceae; cashews; Cocos nucifera|
Notes on Natural EnemiesTop of page IIBC (1998) identified two species of Encarsiella as the most promising candidates for classical biological control of Aleurodicus pulvinatus; these species also attack A. cocois. E. noyesi has been responsible for successfully controlling A. cocois when introduced to Barbados (Simmonds, 1958; Cock, 1985; IIBC, 1997).
The records for Clitostethus dispar may be misidentifications for Nephaspis spp. (N. amnicola and N. cocois).
Simmonds (1958) mentions that scymnine predators of A. cocois, found in Trinidad, were also introduced to Barbados. Arruda (1976) recorded that Nephaspis cocois was the most effective natural enemy attacking A. cocois in Pernambuco State, Brazil.
According to Carvalho et al. (1972), the parasitic fungus Cladosporium herbarum [Mycosphaerella tassiana] attacks and kills all stages of A. cocois in Brazil (Pernambuco), but attempts to apply it as a control agent to other infested cashew trees were unsuccessful. They concluded that the fungus is uncommon and attacks the mealybug only when conditions are favourable.
ImpactTop of page When A. cocois was accidentally introduced to Barbados without its natural enemies in the 1830s, it was reported to have attacked virtually every palm tree on the island, halting coconut production, and there were fears that all the coconut palms would die (Curtis, 1846). Dash (1922) recorded A. cocois as the most important pest of coconut in Guadeloupe. A. cocois anacardi was reported seriously damaging and sometimes killing cashew trees in northeastern Brazil (Arruda, 1970; Dunham and Andrade, 1971) in areas where A. cocois is only a minor pest of coconut (Carvalho et al., 1971). Silva (1977) reported heavy attacks on pepper in Para, Brazil, and that rubber was also infested. The closely related species, A. pulvinatus, was observed causing extensive damage and coconut palm deaths in St Kitts and Nevis in 1994 (Martin and Watson, 1998) and has caused serious damage to coconuts in Antigua.
DiagnosisTop of page A. cocois and A. pulvinatus can only be identified authoritatively by examination of slide-mounted pupae under a compound light microscope and use of the taxonomic key in Martin and Watson (1998). In the slide-mounted pupa, the presence of 5 pairs of large, submarginal compound pores, each with a central, protruding rod, two pairs of smaller compound pores situated on either side of the vasiform orifice, and a long lingula extending well beyond the vasiform orifice, characterize species of the A. cocois group. Martin (1987) describes a method for preparation of slide mounts.
Detection and InspectionTop of page Examine living palms and woody shrubs/trees; check leaf undersides for tight oviposition spirals about 2 cm across of small wax patches; clusters of immature stages coated in white woolly wax, surrounding leaf surfaces sometimes coated with a waxy bloom and glittering with short, broken rods of glassy wax; and leaf upper surfaces coated with sooty mould or sticky honeydew. If white adults are present they often sit on the leaf undersides near colonies and may need to be disturbed before they fly actively. The honeydew produced may attract attendant ants.
Good light conditions are essential for examination; in poor light, a powerful flashlight is helpful. One of the commonest, favoured hosts of A. cocois is coconut palm; this is a good host to monitor for early detection of the arrival of either A. cocois or A. pulvinatus. A. destructor also favours coconut palm, and A. dispersus will also feed on it.
Similarities to Other Species/ConditionsTop of page In the neotropics, the A. cocois species group (about 10 closely related species including A. cocois) all feed on a similar range of host-plants; several of these species can damage palms and other hosts. Immature stages of the different members of the A. cocois species group differ subtly in wax secretion patterns of the immatures in life, and in the number and distribution of compound and other types of wax-producing pores. Detailed examination of slide-mounted pupae is necessary for authoritative identification to species, because some other species of aleurodicine whiteflies resemble A. cocois in live appearance and damage caused, for example, A. pulvinatus, A. dispersus, A. destructor and Lecanoideus floccissimus. Martin and Watson (1998) provide a key for their identification.
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Various members of the A. cocois species group are not present on all the Caribbean islands, and several occurrences have demonstrated their pest potential on coconut palms (Curtis, 1846; Dash, 1922; Martin and Watson, 1998). As such, planting material of palms and guava originating in the neotropics should be checked to ensure they are free of Aleurodicus infestation before they are allowed into any country where members of the A. cocois species group are not already present.
Introduction of Encarsiella noyesi and scymnine predators from Trinidad to Barbados achieved successful control of A. cocois (Simmonds, 1958; IIBC, 1997). Similar introductions were made into Brazil in 1962, but the results are unknown (Cock, 1985).
Natural enemies must be important in controlling populations of A. cocois on cashew in Algoas, Sergipe and Bahia states in Brazil, since outbreaks of this pest have been attributed to a disruption of biological control (Dunham and Andrade, 1971).
The effectiveness of pesticide sprays against Aleurodicus species tends to be reduced because of their habit of living under leaves, and the water-repellent waxy covering that develops over colonies. Any pesticide used against them should be carefully selected to avoid injury to the natural enemies, since they are likely to be important in helping to keep populations at low levels in the long term. Outbreaks of A. cocois on cashew in Algoas, Sergipe and Bahia states in Brazil have been attributed to a disruption of biological control (Dunham and Andrade, 1971), possibly due to the use of pesticides.
Sales et al. (1983) reported excellent control of A. cocois in laboratory tests of 24 organosynthetic insecticides in Brazil (Ceara) using malathion and fenithion. Branco-Filho et al. (1988) tested five insecticides against A. cocois on cashew trees in the field in Piaui, Brazil, and found that diazinon and mineral oil gave only 68% control. However, no mention is made of the impact these pesticides had on the natural enemy populations.
ReferencesTop of page
Arruda EC de, 1976. Nephaspis cocois (Coleoptera Coccinellidae), a new predator of the cashew whitefly, found in Pernambuco. Anais da Universidade Federal Rural de Pernambuco, Ciencias Biologicas, 3(1):39-43.
Branco Filho ATC; Lima FN; Medeiros Moura MM; Ribeiro VQ, 1988. Efficiency of insecticides for the control of the white fly (Aleurodicus cocois) (Curtis, 1846) of the cashew tree. Brasil Florestal, 15(63):49-52.
Carvalho MB de; Aquino M de LN; Oliveira MHCCde, 1972. Considerations on the biological control of Aleurodicus cocois (Curtis, 1846) (Homoptera, Aleyrodidae), cashew whitefly. Anais do Instituto de Ciencias Biologicas, 2(2):25-30.
Carvalho MB de; Freitas A de O; Arruda GP de, 1971. Some observations on Aleurodicus cocois (Curtis, 1846) (Homoptera, Aleyrodidae), the cashew 'white fly' in the State of Pernambuco. Boletim Technico do Instituto de Pesquisas Agronomicas, Recife, 1971, 18.
Coordenadoria de Sanidade Vegetal; Governo do Estado do Ceara, 1976. The cultivation of cashew. A cultura do Cajueiro. Fortaleza, Brazil: Coordenardoria de Sanidade Vegetal, Secretaria de Agricultura e Abastecimento, Governo do Estado do Ceara.
Curtis J, 1846. Entomology: Aleyrodes cocois (the cocoa-nut Aleyrodes). Gardeners Chronicle, 1846:284-285.
Dash JS, 1922. Troisiéme rapport de la Station Agronomique del la Guadeloupe, juillet 1920 á juin 1921. Point-á-Pitre, Gaudeloupe: Station Agronomique del la Guadeloupe, 7-17. [from Review of Applied Entomology. Series A Agricultural, 1922, 10:329].
Dunham O; Andrade SN de, 1971. The occurrence of the white fly Aleurodicus cocois as a pest of cashew, Anacardium occidentale, in the State of Bahia. Boletim do Instituto Biologico da Bahia, 10(1):32-36.
Martin JH, 1997. The type species of Aleurodicus Douglas, a whitefly genus of economic importance (Homoptera: Aleyrodidae). Memoirs of the Museum of Victoria, 56(1):125-128.
Morgan ACF, 1892. A new genus and species of Aleurodidae. Entomologist's Monthly Magazine, 28:29-33.
Núñez del Prado E; Iannacone J; Gómez H, 2008. Effect of two entomopathogenic fungi in controlling Aleurodicus cocois (Curtis, 1846) (Hemiptera: Aleyrodidae). Chilean Journal of Agricultural Research, 68(1):21-30. http://www.inia.cl/at/agritec.htm
Silva QMp; Cavalcante RD, 1977. The occurrence of the whitefly (Aleurodicus cocois Curtis) (Hom. Aleyrodidae) as a pest of cashew (Anacardium occidentale L.) in the State of Ceara. Fitossanidade, 2(1):13-14.
Simmonds FJ, 1958. Recent work on biological control in the British West Indies. 10th International Congress of Entomology Proceedings 4:476.
Distribution MapsTop of page
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