Phenacoccus manihoti (cassava mealybug)

Identity

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Preferred Scientific Name

Phenacoccus manihoti Matile-Ferrero, 1977

Preferred Common Name

cassava mealybug

International Common Names

Spanish: chinche harinosa de la yuca
French: cochenille farineuse du manioc
Portuguese: cochonilha da mandioca

Local Common Names

Germany: Maniok-Schmierlaus

EPPO code

PHENMA (Phenacoccus manihoti)

Summary of Invasiveness

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Cassava mealybug spread across the width of Africa in a period of 16 years. Its accidental introduction damaged a staple crop that is particularly important in times of drought, during a time of drought, leading to famine (Herren and Neuenschwander, 1991).

Taxonomic Tree

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Domain: Eukaryota
Kingdom: Metazoa
Phylum: Arthropoda
Subphylum: Uniramia
Class: Insecta
Order: Hemiptera
Suborder: Sternorrhyncha
Unknown: Coccoidea
Family: Pseudococcidae
Genus: Phenacoccus
Species: Phenacoccus manihoti

Notes on Taxonomy and Nomenclature

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The cassava mealybug was first reported in 1973 from the Kinshasa (Congo Democratic Republic [Zaire]) and Brazzaville (Republic of Congo) areas of Africa (Hahn and Williams, 1973; Sylvestre, 1973). The hitherto unknown insect was subsequently described and named in 1977 as Phenacoccus manihoti (Matile-Ferrero, 1977), originating from the neotropics. In the neotropics, the insect was first discovered in Paraguay in 1981 by A.C. Bellotti of CIAT. P. manihoti had earlier been confused with another mealybug species found on cassava in Guyana and northern Brazil. Whilst exploration for the natural enemies of P. manihoti continued, this other mealybug was identified as P. herreni (Cox and Williams, 1981). The taxonomic clarification greatly enhanced successful introductions and establishment of specific natural enemies of P. manihoti in an Africa-wide classical biological control programme.

Description

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Eggs

Eggs are oblong, golden yellow and enclosed in woolly ovisacs located at the posterior end of the adult females. Length and breadth measurements are 0.30-0.75 mm and 0.15-0.30 mm, respectively (Matile-Ferrero, 1978; Nwanze, 1978).

Larva

Antennae are 6-segmented in first instars and 9-segmented in subsequent instars. Body length and breadth measurements are, respectively, 0.40-0.75 mm and 0.20-0.30 mm for first instars/crawlers; 1.00-1.10 mm and 0.50-0.65 mm for second instars; 1.10-1.50 mm and 0.50-0.60 mm for third instars; and 1.10-2.6 mm and 0.50-1.40 mm for fourth instars/newly emerged adults (Matile-Ferrero, 1978; Nwanze, 1978).

Adult

Adult females of the cassava mealybug are ovoid, rose-pink and dusted with white, powdery wax; the eyes are relatively prominent, legs are well developed and of equal size (Matile-Ferrero, 1978). The mealybug's body segmentation is apparent. Body segments bear very short lateral and caudal white wax filaments in the form of swellings that produce a toothed appearance to the body outline.

- antennae often 9-segmented, occasionally with 7 or 8 segments
- denticle usually present on claw - body generally with 18 pairs of cerarii
- quinquelocular pores usually present on venter - dorsal and cerarian setae lanceolate
- cerarii usually each with 2 lanceolate setae and no auxillary setae, except on anal lobes

All of the microscopic features listed above as typical for genus Phenacoccus are present in P. manihoti. Other important characters of P. manihoti are:

- underside of head with 32-68 quinquelocular pores immediately anterior to the clypeolabral shield
- circulus 'ox-yoke' shaped
- no translucent pores on hind tibiae

The above characters will facilitate recognition of many Phenacoccus species, especially the economically important ones. The lanceolate setae are especially distinctive for this genus. Regional keys to mealybug faunas, such as the one provided by Williams and Granara de Willink (1992), should, however, be used to support an identification of Phenacoccus, as some species have only a few of the morphological features which are typically found in this genus. A useful key to identify P. manihoti may be found in Williams and Granara de Willink (1992).

Distribution

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P. manihoti is indigenous to South America, where it is found in Argentina, Bolivia, Brazil, Colombia, Guyana and Paraguay. It was accidentally introduced from South America to the Congo Republic in 1973 (Herren and Neuenschwander, 1991). It has spread in Africa to practically all countries where cassava is grown, in a broad belt from West through to East Africa and down to the eastern edge of South Africa. A distribution map is provided by CIE (1993).

Distribution Table

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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.

Last updated: 12 May 2022

Continent/Country/Region	Distribution	Origin	First Reported	Invasive	Reference	Notes
Africa
Angola	Present	Introduced	1975	Invasive	Zeddies et al. (2001) EPPO (2022)
Benin	Present	Introduced	1979	Invasive	Akinlosotu and Leuschner (1981) Zeddies et al. (2001) EPPO (2022)
Burundi	Absent, Unconfirmed presence record(s)		1987		Herren and Neuenschwander (1991) EPPO (2022) CABI (Undated)
Cameroon	Present, Localized	Introduced	1985	Invasive	Herren and Neuenschwander (1991) Zeddies et al. (2001) CABI (Undated)
Central African Republic	Present	Introduced	1984	Invasive	Herren and Neuenschwander (1991) Zeddies et al. (2001) EPPO (2022) CABI (Undated)
Congo, Democratic Republic of the	Present	Introduced	1973	Invasive	Hahn and Williams (1973) Matile-Ferrero (1978) Nwanze et al. (1979) Hennessey and Muaka (1987) EPPO (2022) CABI (Undated)
Congo, Republic of the	Present	Introduced	1973	Invasive	Zeddies et al. (2001) EPPO (2022)
Côte d'Ivoire	Present	Introduced	1985	Invasive	Zeddies et al. (2001) EPPO (2022) CABI (Undated)
Equatorial Guinea	Present, Localized	Introduced	1989	Invasive	Zeddies et al. (2001) EPPO (2022) CABI (Undated)
Gabon	Present	Introduced	1976	Invasive	Boussienguet (1986) Zeddies et al. (2001) EPPO (2022)
Gambia	Present	Introduced	1976	Invasive	Herren and Neuenschwander (1991) Neuenschwander (2003) EPPO (2022)
Ghana	Present	Introduced	1982	Invasive	Korang-Amoakoh et al. (1987) Zeddies et al. (2001) EPPO (2022)
Guinea	Present	Introduced	1986	Invasive	Zeddies et al. (2001) EPPO (2022) CABI (Undated)
Guinea-Bissau	Present	Introduced	1982	Invasive	Zeddies et al. (2001) EPPO (2022)
Kenya	Present	Introduced	1989	Invasive	Herren and Neuenschwander (1991) Neuenschwander (2003) IPPC-Secretariat (2005) EPPO (2022)
Liberia	Present	Introduced	1990	Invasive	Zeddies et al. (2001) EPPO (2022) CABI (Undated)
Madagascar	Present, Localized	Introduced		Invasive	CABI (Undated a)
Malawi	Present	Introduced	1985	Invasive	Herren and Neuenschwander (1991) Neuenschwander (2003) EPPO (2022) CABI (Undated)
Mali	Present				EPPO (2022) Muniappan et al. (2012)
Mozambique	Present	Introduced	1986	Invasive	Herren and Neuenschwander (1991) EPPO (2022) CABI (Undated)
Niger	Present	Introduced	1986	Invasive	Zeddies et al. (2001)
Nigeria	Present	Introduced	1979	Invasive	Zeddies et al. (2001) EPPO (2022) CABI (Undated)
Rwanda	Present	Introduced	1984	Invasive	Birandano (1986) Herren and Neuenschwander (1991) EPPO (2022) CABI (Undated)
Senegal	Present	Introduced	1976	Invasive	Herren and Neuenschwander (1991) Neuenschwander (2003) EPPO (2022)
Sierra Leone	Present	Introduced	1982	Invasive	James (1987) James and Fofanah (1992) Zeddies et al. (2001) EPPO (2022)
South Africa	Present, Localized	Introduced		Invasive	Herren and Neuenschwander (1991) CABI (Undated)
Sudan	Present	Introduced		Invasive	Neuenschwander (2003) EPPO (2022) CABI (Undated)
Tanzania	Present	Introduced	1987	Invasive	Herren and Neuenschwander (1991) EPPO (2022) CABI (Undated)
-Zanzibar Island	Present, Localized	Introduced		Invasive	CABI (Undated)
Togo	Present	Introduced	1980	Invasive	Zeddies et al. (2001) EPPO (2022) CABI (Undated)
Uganda	Present	Introduced	1992		Zeddies et al. (2001) EPPO (2022) CABI (Undated)
Zambia	Present	Introduced	1984	Invasive	Chakupurakal et al. (1994) Zeddies et al. (2001) EPPO (2022) CABI (Undated)
Zimbabwe	Present	Introduced		Invasive	Giga (1994) EPPO (2022) CABI (Undated)
Asia
Cambodia	Present	Introduced	2010	Invasive	Parsa et al. (2012) EPPO (2022)
China	Present	Introduced	2014		Seebens et al. (2017)
India	Present				Sunil Joshi et al. (2020) EPPO (2022)	via PestLens newsletter
Indonesia	Present, Localized				EPPO (2022)
-Java	Present				EPPO (2022)
Laos	Present				EPPO (2022)
Malaysia	Present				Dewi Sartiami et al. (2015) EPPO (2022)
-Peninsular Malaysia	Present				EPPO (2022)
Thailand	Present	Introduced	2008	Invasive	Parsa et al. (2012) EPPO (2022)
Vietnam	Present	Introduced	2012	Invasive	Parsa et al. (2012) EPPO (2022)
South America
Argentina	Present	Native			Santis (1963) EPPO (2022)
Bolivia	Present	Native			UK, CAB International (1984) Löhr and Varela (1987) EPPO (2022)
Brazil	Present, Localized				EPPO (2022)
-Amazonas	Present	Native			UK, CAB International (1984) Foldi (1988) EPPO (2022)
-Mato Grosso do Sul	Present	Native			UK, CAB International (1984) EPPO (2022)
-Para	Present	Native			Matile-Ferrero (1977) EPPO (2022)
-Parana	Present	Native			Löhr and Varela (1987)
-Rio Grande do Sul	Present	Native			Foldi (1988)
Colombia	Present	Native			CABI (Undated a)
French Guiana	Present				EPPO (2022)
Guyana	Present				EPPO (2022)
Paraguay	Present	Native			Löhr and Varela (1987) EPPO (2022) CABI (Undated)

Risk of Introduction

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P. manihoti poses a threat to other cassava-growing regions of the world, such as Indonesia.

Accidental introduction to new territories is possible through the movement of infested living cassava material for propogative purposes through shipping or air transport/mail.

It may be advisable for plant quarantine services to regulate trade in fresh planting material of cassava from Africa and tropical South American countries to other tropical countries. Trade may still be possible through a system of inspection of source areas and pre-export certification of shipments being free of infection. Planting material should be inspected in the growing season previous to shipment and be found free of infestation. A phytosanitary certificate should guarantee absence of the pest from consignments of planting material.

Habitat

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In Africa, P. manihoti survives and occurs on cassava in all agroecosystems where it has spread.

Hosts/Species Affected

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The cassava mealybug strongly prefers cassava and other Manihot species; the other host crops and wild hosts are only marginally infested. Talinum triangulare, Croton and Poinsettia species are particularly suitable for laboratory rearing and experiments.

Records from other plants are apparently accidental (Herren and Neuenschwander, 1991). Although it has been collected on plants in various families, such as citrus and tomato, there is no evidence that it can survive for more than one generation on plants other than Manihot and perhaps certain other Euphorbiaceae (Williams and Granara de Willink, 1992).

Host Plants and Other Plants Affected

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Plant name	Family	Context	References
Alternanthera sessilis (sessile joyweed)	Amaranthaceae	Other
Blumea lacera	Asteraceae	Other
Boerhavia diffusa (red spiderling)	Nyctaginaceae	Wild host
Capsicum spp.	Solanaceae	Other
Citrus	Rutaceae	Other
Cyperus (flatsedge)	Cyperaceae	Wild host
Euphorbia pulcherrima (poinsettia)	Euphorbiaceae	Wild host
Glycine max (soyabean)	Fabaceae	Other
Ipomoea batatas (sweet potato)	Convolvulaceae	Other
Manihot esculenta (cassava)	Euphorbiaceae	Main	Chakupurakal et al. (1994); Muniappan et al. (2012); Dewi et al. (2015)
Manihot glaziovii (ceara rubber)	Euphorbiaceae	Wild host
Sida acuta (sida)	Malvaceae	Wild host
Solanum (nightshade)	Solanaceae	Other
Solanum lycopersicum (tomato)	Solanaceae	Other
Synedrella nodiflora (synedrella)	Asteraceae	Other

Growth Stages

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Flowering stage, Fruiting stage, Seedling stage, Vegetative growing stage

Symptoms

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In cassava and on Manihot glaziovii, the pest causes stunting, leaf distortion and loss, dieback and weakening of stems used for crop propagation. The insect does not cause any significant damage to its other known host crops/plants which may only serve as a temporary support for 'drifting' populations of the insect that fall on them.

List of Symptoms/Signs

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Sign	Life Stages	Type
Growing point / dieback
Growing point / distortion
Leaves / abnormal colours
Leaves / abnormal forms
Leaves / abnormal leaf fall
Leaves / honeydew or sooty mould
Leaves / leaves rolled or folded
Leaves / wilting
Leaves / yellowed or dead
Roots / reduced root system
Stems / dieback
Stems / distortion
Stems / stunting or rosetting
Stems / witches broom
Whole plant / dwarfing
Whole plant / plant dead; dieback
Whole plant / seedling blight

Biology and Ecology

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Herren and Neuenschwander (1991) reviewed the biology of cassava mealybug. The life cycle has been studied in the Congo by Fabres (1980) and by Fabres and Boussiengue (1981). Mealybug populations begin to build up in February, and there are nine generations. The largest generation is that during the dry season. Population numbers drop at the onset of the rainy season, when many mealybugs are washed off the plant. Within cassava fields, this mealybug occurs in a markedly aggregated distribution pattern, which differs between seasons.

P. manihoti reproduces by parthenogenetic oviparity. The life cycle consists of an egg and four instar stages with the fourth being the adult mealybug. Various laboratory experimental results (Nwanze et al., 1979; Iheagwam, 1981; Lema and Herren, 1985; Le Rü and Fabres, 1987; Schulthess et al., 1987) summarize that the insect has a lower thermal threshold of 14.7°C, an optimal temperature of about 28°C, no development above 35°C and a net reproductive rate of about 500 eggs in an average life span of 20 days. Egg incubation lasts approximately 8 days and the insect usually dies 1-3 days after it ceases egg production (Nwanze, 1978). The average development period of egg to adult lasts for about 33 days. The most favoured sites for oviposition are terminal shoot tips, lower leaf surfaces and leaf petioles. The eggs hatch into crawlers (= first instars) and the insect moults thrice in its development to a fourth instar (= adult mealybug). Except for crawlers, all instars prefer the lower surfaces of fully expanded leaves (Nwanze, 1978) from where they move sluggishly to the stems and shoot tips. At low population densities, therefore, the insect is most abundant in the shoot tips (Schulthess et al., 1987; Neuenschwander and Hammond, 1988).

The stunted, distorted cassava tips which result from feeding offer a protective environment for the mealybugs which feed on the sap (Calatayud and Le Rü, 1997). Crawlers move actively within the plant, usually to upper leaf surfaces from where they easily get blown away by wind. Movement in air currents and transportation of infested stem planting material by man are the main methods by which the insect is dispersed over long distances.

Ants attending mealybugs for their honeydew are known to defend the pests from natural enemies that would otherwise attack them. They have been observed interfering with biological control of cassava mealybug in Ghana (Cudjoe et al., 1993).

Natural enemies

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Natural enemy	Type	Life stages	Biological control in	Biological control on
Allobaccha eclara	Predator	Adults; Arthropods\|Nymphs
Anagyrus nyombae	Parasite
Anagyrus pseudococci	Parasite		Gambia; Nigeria; Senegal	cassava
Anagyrus pullus	Parasite
Blaptostethus pallescens	Predator	Adults; Arthropods\|Nymphs	Rwanda	cassava
Brumoides foudrasii	Predator	Adults; Arthropods\|Nymphs	Gambia; Nigeria	cassava
Cacoxenus oligodous	Predator
Cardiastethus exiguus	Predator	Adults; Arthropods\|Nymphs	Nigeria; Rwanda; Zaire	cassava
Ceratochrysa antica	Predator	Adults; Arthropods\|Nymphs	Nigeria	cassava
Cheilomenes lunata	Predator	Adults; Arthropods\|Nymphs	Zaire	cassava
Cheilomenes propinqua	Predator	Adults; Arthropods\|Nymphs	Nigeria; Zaire	cassava
Cheilomenes propinqua vicina	Predator	Adults; Arthropods\|Nymphs	Guinea Bissau	cassava
Cheilomenes sulphurea	Predator	Adults; Arthropods\|Nymphs	Nigeria; Rwanda; Zaire	cassava
Chilocorus angolensis	Predator	Adults; Arthropods\|Nymphs	Zaire	cassava
Choristoneura freemani	Predator	Adults; Arthropods\|Nymphs	Nigeria; Zaire	cassava
Clitostethus neuenschwanderi	Predator	Adults; Arthropods\|Nymphs	Congo; Zaire	cassava
Coccodiplosis citri	Predator	Adults; Arthropods\|Nymphs
Cryptoblabes gnidiella	Predator	Adults; Arthropods\|Nymphs	Nigeria	cassava
Declivitata uncifera	Predator	Adults; Arthropods\|Nymphs	Zaire	cassava
Dicrodiplosis manihoti	Predator	Adults; Arthropods\|Nymphs	Gambia; Ghana; Guinea Bissau; Nigeria; Zaire	cassava
Diomus hennesseyi	Predator	Adults; Arthropods\|Nymphs
Diomus neuenschwanderi	Predator	Adults; Arthropods\|Nymphs	Burundi; Central African Republic; Cote d'Ivoire; Gambia; Ghana; Guinea; Guinea-Bissau; Malawi; Mozambique; Nigeria; Rwanda; Senegal; Sierra Leone; Togo; Zaire; Zambia	cassava
Domomyza perspicax	Predator
Epidinocarsis diversicornis	Parasite		Africa	cassava
Epidinocarsis lopezi	Parasite	Adults; Arthropods\|Nymphs
Exochomus flavipes	Predator	Adults; Arthropods\|Nymphs	Gambia; Ghana; Guinea Bissau; Nigeria; Senegal; Togo; Zaire	cassava
Exochomus flaviventris	Predator	Adults; Arthropods\|Nymphs	Congo
Exochomus promtus	Predator	Adults; Arthropods\|Nymphs	Ghana; Nigeria; Rwanda; Zaire	cassava
Exochomus troberti	Predator	Adults; Arthropods\|Nymphs
Exochomus ventralis	Predator	Adults; Arthropods\|Nymphs	Zaire	cassava
Geocoris amabilis	Predator	Adults; Arthropods\|Nymphs	Nigeria; Senegal	cassava
Hyperaspis aestimabilis	Predator	Adults; Arthropods\|Nymphs	Zaire; Zambia	cassava
Hyperaspis delicatula	Predator	Adults; Arthropods\|Nymphs
Hyperaspis jucunda	Predator	Adults; Arthropods\|Nymphs	Malawi
Hyperaspis notata	Predator	Adults; Arthropods\|Nymphs	Africa; Burundi; Central African Republic; Ghana; Guinea; Malawi; Mozambique; Sierra Leone; Zaire; Zambia	cassava
Hyperaspis pumila	Predator	Adults; Arthropods\|Nymphs	Gambia; Guinea Bissau; Nigeria; Senegal; Togo	cassava
Hyperaspis raynevali	Predator	Adults; Arthropods\|Nymphs	Congo
Hyperaspis raynevali	Predator	Adults; Arthropods\|Nymphs	Congo	cassava
Hyperaspis senegalensis	Predator	Adults; Arthropods\|Nymphs	Congo; Gambia; Nigeria; Zaire	cassava
Hyperaspis senegalensis hottentotta	Predator	Adults; Arthropods\|Nymphs
Hyperaspis vinciquerrae	Predator	Adults; Arthropods\|Nymphs
Isora circularis			Zaire	cassava
Mallada boninensis	Predator	Adults; Arthropods\|Nymphs
Melanostoma annulipes	Predator	Adults; Arthropods\|Nymphs	Zaire	cassava
Micraspis striata	Predator	Adults; Arthropods\|Nymphs	Zaire	cassava
Neozygites fumosa	Pathogen	Adults; Arthropods\|Nymphs	Congo	cassava
Nephus flavomaculatus	Predator	Adults; Arthropods\|Nymphs	Guinea Bissau; Nigeria; Zaire	cassava
Nephus phenacoccophagus	Predator	Adults; Arthropods\|Nymphs	Gabon; Nigeria; Rwanda; Senegal; Zaire	cassava
Nephus reunioni	Predator	Adults; Arthropods\|Nymphs	Zaire	cassava
Nephus vetustus	Predator	Adults; Arthropods\|Nymphs
Orius albidipennis	Predator	Adults; Arthropods\|Nymphs	Nigeria	cassava
Parapyrus manihoti	Parasite
Platynaspis capicola	Predator	Adults; Arthropods\|Nymphs	Zaire	cassava
Platynaspis vittigera	Predator	Adults; Arthropods\|Nymphs	Zaire	cassava
Ptyonocera atrifusella			Nigeria	cassava
Pyroderces hemizopha	Predator		Nigeria; Senegal; Togo; Zaire	cassava
Rodolia occidentalis	Predator	Adults; Arthropods\|Nymphs	Ghana; Nigeria	cassava
Scymnus kibonotensis	Predator	Adults; Arthropods\|Nymphs	Gambia; Nigeria; Rwanda; Zaire	cassava
Scymnus levaillanti	Predator	Adults; Arthropods\|Nymphs	Nigeria; Zaire	cassava
Scymnus quadrivittatus	Predator	Adults; Arthropods\|Nymphs	Nigeria	cassava
Scymnus scapuliferus	Predator	Adults; Arthropods\|Nymphs	Nigeria	cassava
Scymnus viduus	Predator	Adults; Arthropods\|Nymphs	Zaire	cassava
Spalgis lemolea	Predator	Adults; Arthropods\|Nymphs	Ghana; Guinea Bissau; Nigeria; Rwanda; Zaire	cassava
Sympherobius maculipennis	Predator	Adults; Arthropods\|Nymphs
Xylocoris afer	Predator	Adults; Arthropods\|Nymphs	Nigeria	cassava

Notes on Natural Enemies

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In Africa, P. manihoti is attacked by the usual guild of polyphagous or oligophagous predators and parasitoids of mealybugs in Africa (Bartlett, 1978; Moore, 1988; Ben-Dov and German, 2003), which switched over to it as a new food source, and by indigenous entomopathogenic fungi, for example, Neozygites fumosa, which causes epizootics in the pest populations under warm and very humid conditions (Le Rü et al., 1985; Le Rü, 1986).

Prior to the introduction of Apoanagyrus lopezi (Hymenoptera: Encyrtidae) in Africa, lists of natural enemies of the pest were compiled for Congo (Matile-Ferrero, 1977; Fabres and Matile-Ferrero, 1980), Congo Democratic Republic (Nsiama Shè et al., 1984), Nigeria (Akinlosotu and Leuschner, 1981; Iheagwam., 1981) and Gabon (Boussienguet, 1986). Following the establishment of A. lopezi, the cassava mealybug food web was investigated over the whole continent and found to comprise about 130 species (Neuenschwander et al., 1987; Nsiama Shè, 1987; Biassangama et al., 1989). Many of the associated fauna are opportunistic and do not reproduce on the cassava mealybug; some are attracted more to the bunchy tops with the rich organic material from living and dead cassava mealybugs. Only about 20 species are common and seem to have some impact (Neuenschwander et al., 1987).

Wherever A. lopezi was established, it became the most important parasitoid and abundant natural enemy (Neuenschwander and Hammond, 1988; Hammond and Neuenschwander, 1990). Indigenous polyphagous hyperparasitoids adopt A. lopezi as an alternate host. The common hyperparasitoids in West Africa are Prochiloneurus insolitus and Chartocerus hyalipennis (Neuenschwander et al., 1987; Goergen and Neuenschwander, 1990; 1992; 1994). In Central Africa the hyperparasitoid P. aegyptiacus is usually most common (Fabres and Matile-Ferrero, 1980; Boussienguet, 1986; Neuenschwander et al., 1987; Biassangama et al., 1989). The most important predators are coccinellids, e.g., Hyperaspis spp., Exochomus sp., and Diomus sp., which usually occur at high densities of cassava mealybug (Fabres and Kiyindou, 1985; Boussienguet, 1986; Neuenschwander et al., 1987; Neuenschwander and Hammond, 1988; Stäubli Dreyer et al., 1997a,b). Results from olfactometer studies indicate that exotic and indigenous species of Diomus react more strongly to cassava mealybug, honeydew and exuviae than do indigenous Exochomus spp. (van den Meiracker et al., 1988).

Ants attending mealybugs for their honeydew are known to defend the pests from natural enemies that would otherwise attack them. They have been observed interfering with biological control of cassava mealybug in Ghana (Cudjoe et al., 1993).

Means of Movement and Dispersal

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Natural dispersal

The dispersal stage of mealybugs is the first-instar crawler stage; these are often dispersed passively in the wind.

Vector transmission

Crawlers may also be carried passively by passing animals and people that brush past the host plant.

Agricultural practices

Harvesting infested plant material aids dispersal by scattering the crawlers into the air, where the wind may carry them away. Prunings of infested plants, and the clothing, tools and vehicles of agricultural workers can become contaminated with the crawlers and so aid in their dispersal.

Plant Trade

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Plant parts liable to carry the pest in trade/transport	Pest stages	Borne internally	Borne externally	Visibility of pest or symptoms
Bark	arthropods/larvae		Yes	Pest or symptoms not visible to the naked eye but usually visible under light microscope
Flowers/Inflorescences/Cones/Calyx	arthropods/adults; arthropods/eggs; arthropods/larvae; arthropods/nymphs	Yes	Yes	Pest or symptoms usually visible to the naked eye
Fruits (inc. pods)	arthropods/adults; arthropods/eggs; arthropods/larvae; arthropods/nymphs		Yes	Pest or symptoms usually visible to the naked eye
Growing medium accompanying plants	arthropods/larvae		Yes	Pest or symptoms not visible to the naked eye but usually visible under light microscope
Leaves	arthropods/adults; arthropods/eggs; arthropods/larvae; arthropods/nymphs		Yes	Pest or symptoms usually visible to the naked eye
Roots	arthropods/larvae		Yes	Pest or symptoms not visible to the naked eye but usually visible under light microscope
Seedlings/Micropropagated plants	arthropods/adults; arthropods/eggs; arthropods/larvae; arthropods/nymphs		Yes	Pest or symptoms not visible to the naked eye but usually visible under light microscope
Stems (above ground)/Shoots/Trunks/Branches	arthropods/adults; arthropods/eggs; arthropods/larvae; arthropods/nymphs		Yes	Pest or symptoms usually visible to the naked eye

Plant parts not known to carry the pest in trade/transport
Bulbs/Tubers/Corms/Rhizomes
True seeds (inc. grain)
Wood

Wood Packaging

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Wood Packaging not known to carry the pest in trade/transport
Loose wood packing material
Non-wood
Processed or treated wood
Solid wood packing material with bark
Solid wood packing material without bark

Impact Summary

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Category	Impact
Animal/plant collections	None
Animal/plant products	Negative
Biodiversity (generally)	None
Crop production	Negative
Environment (generally)	None
Fisheries / aquaculture	None
Forestry production	None
Human health	Negative
Livestock production	None
Native fauna	None
Native flora	None
Rare/protected species	None
Tourism	None
Trade/international relations	Negative
Transport/travel	None

Impact

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In 1973, P. manihoti was reported as an introduced arthropod species on cassava in Congo (Sylvestre, 1973; Matile-Ferrero, 1978) and Congo Democratic Republic (Hahn and Williams, 1973). Within a few years after these first reports, the insect became the major cassava pest and spread rapidly through most of the African cassava belt. By the end of 1986, for example, it had reached about 25 countries and covered 70% of the African cassava belt (Neuenschwander and Herren, 1988). In most countries the mealybug caused severe damage by stunting the growth points of cassava plants, sometimes totally defoliating the plants. Storage root yield losses of 84% have been reported (Nwanze, 1982). The pest-induced defoliation reduces availability of healthy leaves which are consumed as leafy vegetables in most of West and Central Africa. After the pest cripples plant growth, weed and erosion problems sometimes lead to total destruction of the crops. Additionally, pest-infested plants produce poor quality stem cuttings for use as planting material. The insect is more abundant and its damage severity is greater in the dry than in the wet season.

Examples of monetary values of damage are given by Norgaard (1988) and Neuenschwander (1990).

Zeddies et al. (2001) analysed the cost benefits of the biological control programme against cassava mealybug in Africa over a period of 40 years. Losses of cassava yield in the year of introduction were estimated at 80%; within 5 years, more tolerant varieties of cassava were cultivated and indigenous predators adapted to a new diet, so reducing annual losses to 20% (in rain forest) to 40% (in highlands and savanna).

Social Impact

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The accidental introduction of P. manihoti to Africa damaged a staple crop that is particularly important in times of drought, during a time of drought, leading to famine (Herren and Neuenschwander, 1991).

Detection and Inspection

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Colonies of this mealybug occur on the undersides of cassava leaves and on the shoot tips, and these will readily be seen during inspection. Minute crawlers, which may be present on plants before colonies are established, will only be detected by careful examination with the aid of a strong light and magnification. The plant tips are favoured feeding sites.

Similarities to Other Species/Conditions

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P. manihoti is similar to P. madeirensis which also occurs on cassava. In P. madeirensis the body colour is greenish white and the ovisacs are much denser than those of P. manihoti. The presence of males in P. madeirensis is another distinguishing feature.

A very similar species, Phenacoccus herreni, is also common on cassava, but is yellow, produces males as well as females, and only occurs in South and Central America (Cox and Williams, 1981). Authoritative identification is difficult and should be done by an expert, using slide-mounted specimens. P. herreni may be identified using the key provided by Cox and Williams (1981) and Williams and Granara de Willink (1992).

Prevention and Control

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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.

Biological Control

On the basis of the exotic origin and rapid spread of the cassava mealybug in Africa, classical biological control has been the main and most appropriate approach to the pest problem. Among several natural enemies introduced to combat the pest (Herren and Lema, 1982; Lema and Herren, 1985; Herren et al., 1987a; Neuenschwander and Zweigert, 1994), the solitary endophagous parasitoid Apoanagyrus lopezi, specific to P. manihoti, has been the most successful. Herren and Neuenschwander (1991) reviewed the biological control campaign against cassava mealybug in Africa. A. lopezi, collected from South America (Löhr and Varela, 1987; Löhr et al., 1988; Löhr et al., 1989; Löhr et al., 1990), has been the main natural enemy reared (Haug et al., 1987; Haug and Mégevand, 1989; Neuenschwander et al., 1989a, 1989b) and released across the cassava belt in Africa (Herren and Lema, 1982; Lema and Herren, 1985; Bird, 1987; Herren et al., 1987a,b). It was introduced to Nigeria in 1981 and is now established in at least 26 African countries (Ganga, 1984; Herren et al., 1987b; Korang-Amoakoh et al., 1987; Biassangama et al., 1988; Neuenschwander and Herren, 1988; Neuenschwander et al., 1989a, 1989b; Boussienguet et al., 1991; Hennessey et al., 1990; Herren and Neuenschwander, 1991; Neuenschwander and Zweigert, 1994). The biological and ecological impact of A. lopezi has been assessed in several laboratory and field experiments. In some studies, the results indicate a successful role of A. lopezi (Neuenschwander et al., 1986; Neuenschwander and Sullivan, 1987; Sullivan and Neuenschwander, 1988; Goergen and Neuenschwander, 1990; 1992; 1994; Cudjoe et al., 1992; 1993), whereas others are critical of reported success by A. lopezi (Fabres, 1981; Odebiyi and Bokonon-Ganta, 1986; Fabres et al., 1989; Iziquel and Le Rü, 1989; 1992; Le Rü et al., 1990; Souissi and Le Rü, 1997; 1998). Large-scale and sustained field studies have, however, recorded excellent biological control of the pest by A. lopezi (Neuenschwander and Madojemu, 1986; Hammond et al., 1987; Gutierrez et al., 1988a,b; Neuenschwander and Hammond, 1988; Neuenschwander and Gutierrez, 1989; Neuenschwander et al., 1989a, 1989b; van Alphen et al., 1989; Hammond and Neuenschwander, 1990; Neuenschwander et al., 1990; Gutierrez et al., 1993; Chakupurakal et al., 1994; Neuenschwander and Ajuonu, 1995; Neuenschwander, 1996). Ants attending mealybugs for their honeydew are known to defend the pests from natural enemies that would otherwise attack them. They have been observed interfering with biological control of cassava mealybug in Ghana (Cudjoe et al., 1993). It may be advisable to discourage ants in cassava fields if this becomes a problem. The economic impact of biological control of the cassava mealybug, mainly by A. lopezi, has been judged to be excellent (Norgaard, 1988a, b; Zeddies et al., 2001). Nominal costs of the biological control programme 1979-2013 were estimated at US$ 34.2 million, with the peak annual cost of the programme coming to US$ 5.2 million in 1985. The benefit to cost ratio of biological control by Apoanagyrus (Epidinocarsis) lopezi was calculated as at least 199:1. Where the soil is very infertile, however, biological control has been shown to be unsatisfactory, unless it can be complemented by cultural practices such as soil improvement (Neuenschwander et al., 1990; Le Rü et al., 1991; Schulthess et al., 1997) and host-plant resistance (Le Rü and Tertuliano, 1993; Tertuliano et al., 1993; Souissi and Le Rü, 1998). Biological control (particularly using the parasitoid Apoanagyrus lopezi) and the use of resistant varieties to control the pest are briefly described by Calatayud and Le Rü (1997). The coccinellid Hyperaspis notata is associated with the mealybugs P. manihoti and P. herreni on cassava in southern Brazil and the highlands of Colombia. It was brought to Africa to help control the accidentally introduced P. manihoti (Staubli-Dreyer et al., 1997). The parasitoids A. diversicornis, Allotropa sp., and the neuropteran predator Sympherobius maculipennis apparently failed to establish following their releases in Africa (Neuenschwander and Zweigert, 1994).

Organic Chemical Control

Immersion of cassava cuttings in manipueira (a liquid extract from cassava roots) for 60 minutes was found to significantly reduce infestation (Razafindrakoto et al., 1999). Mourier (1997) found that cassava leaves treated with a 1% neem kernel water extract (NKWE) were less attractive to first-instar cassava mealybug than untreated leaves, and those that started feeding died in the second instar. Three NKWE treatments at weekly intervals protected cassava against established early instar nymphs; however, some phytotoxicity was observed.

Host-Plant Resistence

Cassava contains two significant compounds whose levels increase in response to mealybug infestation. Cyanide content acts as a phagostimulant for the mealybug, whereas rutin has an antibiotic effect on the pest. It was found that the use of mulch and manure increased cassava resistance against mealybug infestation (Tertuliano et al., 1999). The use of resistant varieties to control the pest are briefly described by Calatayud and Le Rü (1997).

Cultural Control

Use of manure or other fertilizers can result in a reduction in the mealybug population because improved nutrition results in the production of larger parasitoid wasps with higher fertility levels (Schulthess et al., 1997). Mulch and fertilizer use also enhances the antibiotic properties of cassava against mealybug infestation (Tertuliano et al., 1999).

References

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Neuenschwander P, Schulthess F, Madojemu E, 1986. Experimental evaluation of the efficacy of Epidinocarsis lopezi, a parasitoid introduced into Africa against the cassava mealybug Phenacoccus manihoti. Entomologia Experimentalis et Applicata, 42(2):133-138

Neuenschwander P, Sullivan D, 1987. Interactions between the endophagous parasitoid Epidinocarsis lopezi and its host, Phenacoccus manihoti. Insect Science and its Application, 8(4-6):857-859

Norgaard RB, 1988. Economics of the cassava mealybug (Phpnacoccus manihoti; Hom.: Pseudococcidae) biological control program in Africa. Entomophaga, 33(1):3-6

Norgaard RB, 1988. The biological control of cassava mealybug in Africa. American Journal of Agricultural Economics, 70(2):366-371

Nsiama ShF HD, 1987. ProgrFs enrégistré en matiFre de lutte biologique contre la cochenille farinuese du manioc au Zaire, Séminaire sur les maladies et les ravageurs des principales cultures vivriFres d'Afrique centrale, Bujumbura. Wageningen, Netherlands; Bruxelles: CTA; AGCD, 256-265

Nwanze KF, 1978. Biology of the cassava mealybug, Phenacoccus manihoti Mat.-Ferr. in the Republic of Zaire. In: Nwanze KF, Leuschner K, ed. Proceedings of the International Workshop on the cassava mealybug Phenacoccus manihoti Mat.-Ferr. (Pseudococcidae) held at INERA-M'vuazi, Bas-Zaire, Zaire, June 26-29, 1977. International Institute of Tropical Agriculture. Ibadania Niger, 20-28

Nwanze KF, 1982. Relationships between cassava root yields and crop infestations by the mealybug, Phenacoccus manihoti. Tropical Pest Management, 28(1):27-32

Nwanze KF, Leuschner K, Ezumah HC, 1979. The cassava mealybug, Phenacoccus sp. in the Republic of Zaire. PANS, 25(2):125-130

Odebiyi JA, Bokonon-Ganta AH, 1986. Biology of Epidinocarsis (=Apoanagyrus) lopezi (Hymenoptera: Encyrtidae) an exotic parasite of cassava mealybug, Phenacoccus manihoti (Homoptera: Pseudococcidae) in Nigeria. Entomophaga, 31(3):251-260

Parsa S, Kondo T, Winotai A, 2012. The Cassava Mealybug (Phenacoccus manihoti) in Asia: First Records, Potential Distribution, and an Identification Key. PLoS ONE, 7(10):e47675

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Ru B le, Fabres G, 1987. Influence of temperature and relative humidity on the capacity for increase and population dynamics of the cassava mealybug, Phenacoccus manihoti (Hom., Pseudococcidae), in the Congo. Acta Oecologica, Oecologia Applicata, 8(2):165-174

Ru B le, Iziquel Y, Biassangama A, Kiyindou A, 1991. Variation in abundance and regulatory factors of the cassava mealybug Phenacoccus manihoti (Hom.: Pseudococcidae) five years after the introduction of the Neotropical parasitoid Epidinocarsis lopezi (Hym.: Encyrtidae) into the Congo in 1982. Entomophaga, 36(4):499-501

Ru Ble, 1986. Epizootiology of the fungus Neozygites fumosa (Zygomycetes, Entomophthorales) in a population of cassava mealybug, Phenacoccus manihoti (Hom.: Pseudococcidae). Entomophaga, 31(1):79-89

Ru BLe, Silvie P, Papierok B, 1985. The entomophthoraceous fungus, Neozygites fumosa parasitizing the cassava mealybug, Phenacoccus manihoti (Hom.: Pseudococcidae), in the People's Republic of the Congo. Entomophaga, 30(1):23-29

Rü B le, Iziquel Y, Biassangama A, Kiyindou A, 1990. Comparaison des effectifs de la cocchenille du manioc Phenacoccus manihoti avant et aprFs introduction d'Epidinocarsis lopezi Encyrtidae Americain, au Congo en 1982. In: Ru B le, Iziquel Y, Kiyindou A, Biassangama A, Fabres G, Nenon JP, eds. La Cochenille du manioc et sa Bioenose au Congo: 1985-1987. Paris, France: ORSTOM, 1-18

Santis L de, 1963. Encirtidos de la Republica Argentina (Hymenoptera: Chalcidoidea). Anales de la Comision de Investigacion Cientifica Provincia de Buenos Aires Gobernacion. La Plata, 4:9-422

Schulthess F, Baumgartner JU, Herren HR, 1987. Factors influencing the life table statistics of the cassava mealybug Phenacoccus manihoti. Insect Science and its Application, 8(4-6):851-856

Schulthess F, Neuenschwander P, Gounou S, 1997. Multi-trophic interactions in cassava, Manihot esculenta, cropping systems in the subhumid tropics of West Africa. Agriculture, Ecosystems & Environment, 66(3):211-222; 24 ref

She HDN, Odebiyi JA, Herren HR, 1984. The biology of Hyperaspis jucunda (Col.: Coccinellidae) an exotic predator of the cassava mealybug Phenacoccus manihoti (Hom. Pseudococcidae) in southern Nigeria. Entomophaga, 29(1):87-93

Souissi R, Rn Ble, 1997. Comparative life table statistics of Apoanagyrus lopezi reared on the cassava mealybug Phenacoccus manihoti fed on four host plants. Entomologia Experimentalis et Applicata, 85(2):113-119; 35 ref

Souissi R, Rn Ble, 1998. Influence of the host plant of the cassava mealybug Phenacoccus manihoti (Hemiptera: Pseudococcidae) on biological characteristics of its parasitoid Apoanagyrus lopezi (Hymenoptera: Encyrtidae). Bulletin of Entomological Research, 88(1):75-82; 45 ref

StSubli Dreyer B, BaumgSrtner J, Neuenschwander P, Dorn S, 1997. The functional responses of two Hyperaspis notata strains to their prey, the cassava mealybug Phenacoccus manihoti. Bulletin de la Société Entomologique Suisse, 70:21-28

StSubli Dreyer B, Neuenschwander P, BaumgSrtner J, Dorn S, 1997. Trophic influences on survival, development and reproduction of Hyperaspis notata (Col., Coccinellidae). Journal of Applied Entomology, 121(5):249-256; 21 ref

Sullivan DJ, Neuenschwander P, 1988. Melanization of eggs and larvae of the parasitoid, Epidinocarsis lopezi (De Santis) (Hymenoptera: Encyrtidae), by the cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Homoptera: Pseudococcidae). Canadian Entomologist, 120(1):63-71

Sunil Joshi, Pai, S. G., Deepthy, K. B., Ballal, C. R., Watson, G. W., 2020. The cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Coccomorpha: Pseudococcidae) arrives in India. Zootaxa, 4772(1), 191-194. doi: 10.11646/zootaxa.4772.1.8

Sylvestre P, 1973. Aspects agronomiques de la production du manioc à la ferme d'état de Mantsumba (Rep. Pop. Congo). I. R. A. T., Paris, mission report

Tertuliano M, Calatayud PA, Rü BP le, 1999. Seasonal changes of secondary compounds in the phloem sap of cassava in relation to fertilization and to infestation by the cassava mealybug. Insect Science and its Application, 19(1):91-98

Tertuliano M, Dossou-Gbete S, Le Ru B, 1993. Antixenotic and antibiotic components of resistance to the cassava mealybug Phenacoccus manihoti (Homoptera: pseudococcidae) in various host-plants. Insect Science and its Application, 14(5):657-665

Tsacas L, Chassagnard MT, 1999. The Afrotropical species of the subgenus Gitonides Knab of the genus Cacoxenus Loew, with larvae predatory on mealybugs (Diptera: Drosophilidae). Annales de la Socie^acute~te^acute~ Entomologique de France, 35(1):91-121; 22 ref

Williams DJ, Granara de Willink MC, 1992. Mealybugs of Central and South America. Wallingford, UK: CAB International

Zeddies J, Schaab RP, Neuenschwander P, Herren HR, 2001. Economics of biological control of cassava mealybug in Africa. Agricultural Economics, 24(2):209-219; 36 ref

Distribution References

Akinlosotu T A, Leuschner K, 1981. Outbreak of two new cassava pests (Mononychellus tanajoa and Phenacoccus manihoti) in southwestern Nigeria. Tropical Pest Management. 27 (2), 247-250.

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Boussienguet J, 1986. The natural enemy complex of cassava mealybug, Phenacoccus manihoti (Hom. Coccoidea Pseudococcidae) in Gabon. I.- Faunistic inventory and trophic relationships. (Le complexe entomophage de la cochenille du manioc, Phenacoccus manihoti (Hom. Coccoidea Pseudococcidae) au Gabon. I.- Inventaire faunistique et relations trophiques.). Annales de la Société Entomologique de France. 22 (1), 35-44.

CABI, Undated. Compendium record. Wallingford, UK: CABI

CABI, Undated a. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

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IPPC-Secretariat, 2005. Identification of risks and management of invasive alien species using the IPPC framework. Proceedings of the workshop on invasive alien species and the International Plant Protection Convention, 22-26 September 2003. In: Identification of risks and management of invasive alien species using the IPPC framework. Proceedings of the workshop on invasive alien species and the International Plant Protection Convention, 22-26 September 2003 [Identification of risks and management of invasive alien species using the IPPC framework. Proceedings of the workshop on invasive alien species and the International Plant Protection Convention, 22-26 September 2003.], Rome & Braunschweig, Italy & Germany: FAO. xii + 301 pp.

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Nwanze K F, Leuschner K, Ezumah H C, 1979. The cassava mealybug, Phenacoccus sp. in the Republic of Zaire. PANS. 25 (2), 125-130.

Parsa S, Kondo T, Winotai A, 2012. The cassava mealybug (Phenacoccus manihoti) in Asia: first records, potential distribution, and an identification key. PLoS ONE. 7 (10), e47675. DOI:10.1371/journal.pone.0047675

Santis L de, 1963. (Encirtidos de la Republica Argentina (Hymenoptera: Chalcidoidea)). In: Anales de la Comision de Investigacion Cientifica Provincia de Buenos Aires Gobernacion, 4 La Plata, 9-422.

Seebens H, Blackburn T M, Dyer E E, Genovesi P, Hulme P E, Jeschke J M, Pagad S, Pyšek P, Winter M, Arianoutsou M, Bacher S, Blasius B, Brundu G, Capinha C, Celesti-Grapow L, Dawson W, Dullinger S, Fuentes N, Jäger H, Kartesz J, Kenis M, Kreft H, Kühn I, Lenzner B, Liebhold A, Mosena A (et al), 2017. No saturation in the accumulation of alien species worldwide. Nature Communications. 8 (2), 14435. http://www.nature.com/articles/ncomms14435

Sunil Joshi, Pai S G, Deepthy K B, Ballal C R, Watson G W, 2020. The cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Coccomorpha: Pseudococcidae) arrives in India. Zootaxa. 4772 (1), 191-194. DOI:10.11646/zootaxa.4772.1.8

UK, CAB International, 1984. Phenacoccus manihoti. [Distribution map]. In: Distribution Maps of Plant Pests, Wallingford, UK: CAB International. Map 466. DOI:10.1079/DMPP20056600466

Zeddies J, Schaab R P, Neuenschwander P, Herren H R, 2001. Economics of biological control of cassava mealybug in Africa. Agricultural Economics. 24 (2), 209-219. DOI:10.1111/j.1574-0862.2001.tb00024.x

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Phenacoccus manihoti (cassava mealybug)

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