Phenacoccus manihoti (cassava mealybug)
Index
- Pictures
- Identity
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Description
- Distribution
- Distribution Table
- Risk of Introduction
- Habitat
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- Symptoms
- List of Symptoms/Signs
- Biology and Ecology
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Plant Trade
- Wood Packaging
- Impact Summary
- Impact
- Social Impact
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- References
- Distribution Maps
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Top of pageIdentity
Top of pagePreferred 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
Top of page 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
Top of page- 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
Top of page 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
Top of pageEggs
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
Top of page 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
Top of pageThe 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 Introduction
Top of page 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
Top of page In Africa, P. manihoti survives and occurs on cassava in all agroecosystems where it has spread.Hosts/Species Affected
Top of page 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
Top of pagePlant name | Family | Context |
---|---|---|
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 |
Manihot glaziovii (ceara rubber) | Euphorbiaceae | Wild host |
Sida acuta (sida) | Malvaceae | Wild host |
Solanum (nightshade) | Solanaceae | Other |
Solanum lycopersicum (tomato) | Solanaceae | Other |
Growth Stages
Top of page Flowering stage, Fruiting stage, Seedling stage, Vegetative growing stageSymptoms
Top of page 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
Top of pageSign | 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
Top of page 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
Top of pageNatural enemy | Type | Life stages | Specificity | References | Biological control in | Biological control on |
---|---|---|---|---|---|---|
Allobaccha eclara | Predator | Adults/Nymphs | ||||
Anagyrus nyombae | Parasite | |||||
Anagyrus pseudococci | Parasite | Gambia; Nigeria; Senegal | cassava | |||
Anagyrus pullus | Parasite | |||||
Blaptostethus pallescens | Predator | Adults/Nymphs | Rwanda | cassava | ||
Brumoides foudrasii | Predator | Adults/Nymphs | Gambia; Nigeria | cassava | ||
Cacoxenus oligodous | Predator | |||||
Cardiastethus exiguus | Predator | Adults/Nymphs | Nigeria; Rwanda; Zaire | cassava | ||
Ceratochrysa antica | Predator | Adults/Nymphs | Nigeria | cassava | ||
Cheilomenes lunata | Predator | Adults/Nymphs | Zaire | cassava | ||
Cheilomenes propinqua | Predator | Adults/Nymphs | Nigeria; Zaire | cassava | ||
Cheilomenes propinqua vicina | Predator | Adults/Nymphs | Guinea Bissau | cassava | ||
Cheilomenes sulphurea | Predator | Adults/Nymphs | Nigeria; Rwanda; Zaire | cassava | ||
Chilocorus angolensis | Predator | Adults/Nymphs | Zaire | cassava | ||
Choristoneura freemani | Predator | Adults/Nymphs | Nigeria; Zaire | cassava | ||
Clitostethus neuenschwanderi | Predator | Adults/Nymphs | Congo; Zaire | cassava | ||
Coccodiplosis citri | Predator | Adults/Nymphs | ||||
Cryptoblabes gnidiella | Predator | Adults/Nymphs | Nigeria | cassava | ||
Declivitata uncifera | Predator | Adults/Nymphs | Zaire | cassava | ||
Dicrodiplosis manihoti | Predator | Adults/Nymphs | Gambia; Ghana; Guinea Bissau; Nigeria; Zaire | cassava | ||
Diomus hennesseyi | Predator | Adults/Nymphs | ||||
Diomus neuenschwanderi | Predator | Adults/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/Nymphs | ||||
Exochomus flavipes | Predator | Adults/Nymphs | Gambia; Ghana; Guinea Bissau; Nigeria; Senegal; Togo; Zaire | cassava | ||
Exochomus flaviventris | Predator | Adults/Nymphs | Congo | |||
Exochomus promtus | Predator | Adults/Nymphs | Ghana; Nigeria; Rwanda; Zaire | cassava | ||
Exochomus troberti | Predator | Adults/Nymphs | ||||
Exochomus ventralis | Predator | Adults/Nymphs | Zaire | cassava | ||
Geocoris amabilis | Predator | Adults/Nymphs | Nigeria; Senegal | cassava | ||
Hyperaspis aestimabilis | Predator | Adults/Nymphs | Zaire; Zambia | cassava | ||
Hyperaspis delicatula | Predator | Adults/Nymphs | ||||
Hyperaspis jucunda | Predator | Adults/Nymphs | Malawi | |||
Hyperaspis notata | Predator | Adults/Nymphs | Africa; Burundi; Central African Republic; Ghana; Guinea; Malawi; Mozambique; Sierra Leone; Zaire; Zambia | cassava | ||
Hyperaspis pumila | Predator | Adults/Nymphs | Gambia; Guinea Bissau; Nigeria; Senegal; Togo | cassava | ||
Hyperaspis raynevali | Predator | Adults/Nymphs | Congo | |||
Hyperaspis raynevali | Predator | Adults/Nymphs | Congo | cassava | ||
Hyperaspis senegalensis | Predator | Adults/Nymphs | Congo; Gambia; Nigeria; Zaire | cassava | ||
Hyperaspis senegalensis hottentotta | Predator | Adults/Nymphs | ||||
Hyperaspis vinciquerrae | Predator | Adults/Nymphs | ||||
Isora circularis | Zaire | cassava | ||||
Mallada boninensis | Predator | Adults/Nymphs | ||||
Melanostoma annulipes | Predator | Adults/Nymphs | Zaire | cassava | ||
Micraspis striata | Predator | Adults/Nymphs | Zaire | cassava | ||
Neozygites fumosa | Pathogen | Adults/Nymphs | Congo | cassava | ||
Nephus flavomaculatus | Predator | Adults/Nymphs | Guinea Bissau; Nigeria; Zaire | cassava | ||
Nephus phenacoccophagus | Predator | Adults/Nymphs | Gabon; Nigeria; Rwanda; Senegal; Zaire | cassava | ||
Nephus reunioni | Predator | Adults/Nymphs | Zaire | cassava | ||
Nephus vetustus | Predator | Adults/Nymphs | ||||
Orius albidipennis | Predator | Adults/Nymphs | Nigeria | cassava | ||
Parapyrus manihoti | Parasite | |||||
Platynaspis capicola | Predator | Adults/Nymphs | Zaire | cassava | ||
Platynaspis vittigera | Predator | Adults/Nymphs | Zaire | cassava | ||
Ptyonocera atrifusella | Nigeria | cassava | ||||
Pyroderces hemizopha | Predator | Nigeria; Senegal; Togo; Zaire | cassava | |||
Rodolia occidentalis | Predator | Adults/Nymphs | Ghana; Nigeria | cassava | ||
Scymnus kibonotensis | Predator | Adults/Nymphs | Gambia; Nigeria; Rwanda; Zaire | cassava | ||
Scymnus levaillanti | Predator | Adults/Nymphs | Nigeria; Zaire | cassava | ||
Scymnus quadrivittatus | Predator | Adults/Nymphs | Nigeria | cassava | ||
Scymnus scapuliferus | Predator | Adults/Nymphs | Nigeria | cassava | ||
Scymnus viduus | Predator | Adults/Nymphs | Zaire | cassava | ||
Spalgis lemolea | Predator | Adults/Nymphs | Ghana; Guinea Bissau; Nigeria; Rwanda; Zaire | cassava | ||
Sympherobius maculipennis | Predator | Adults/Nymphs | ||||
Xylocoris afer | Predator | Adults/Nymphs | Nigeria | cassava |
Notes on Natural Enemies
Top of page 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
Top of page Natural dispersalThe 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
Top of pagePlant parts liable to carry the pest in trade/transport | Pest stages | Borne internally | Borne externally | Visibility of pest or symptoms |
---|---|---|---|---|
Bark | larvae | Yes | Pest or symptoms not visible to the naked eye but usually visible under light microscope | |
Flowers/Inflorescences/Cones/Calyx | adults; eggs; larvae; nymphs | Yes | Yes | Pest or symptoms usually visible to the naked eye |
Fruits (inc. pods) | adults; eggs; larvae; nymphs | Yes | Pest or symptoms usually visible to the naked eye | |
Growing medium accompanying plants | larvae | Yes | Pest or symptoms not visible to the naked eye but usually visible under light microscope | |
Leaves | adults; eggs; larvae; nymphs | Yes | Pest or symptoms usually visible to the naked eye | |
Roots | larvae | Yes | Pest or symptoms not visible to the naked eye but usually visible under light microscope | |
Seedlings/Micropropagated plants | adults; eggs; larvae; nymphs | Yes | Pest or symptoms not visible to the naked eye but usually visible under light microscope | |
Stems (above ground)/Shoots/Trunks/Branches | adults; eggs; larvae; 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
Top of pageWood 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
Top of pageCategory | 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
Top of page 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
Top of page 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
Top of page 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
Top of page 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
Top of pageBiological 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
Top of pageAlphen JJM van; Neuenschwander P; Dijken MJ van; Hammond WNO; Herren HR, 1989. Insect invasions: the case of the cassava mealybug [Phenacoccus manihoti] and its natural enemies evaluated. Entomologist, 108(1-2):38-55
Bartlett BR, 1978. Pseudococcidae. In: Clausen CP, ed. Introduced Parasites and Predators of Arthropod Pests and Weeds: a World Review. Agriculture Handbook No. 480, 137-170.
Ben-Dov Y; German V, 2003. ScaleNet, Maconellicoccus hirsutus. 27 November 2003. http://www.sel.barc.usda.gov/catalogs/pseudoco/Phenacoccusmanihoti.htm.
Birandano B, 1986. Une nouveau ravageur du manioc au Rwanda: la cochenille farineuse (Phenacoccus manihoti) et la lutte biologique contre les ravageurs de cette culture. Bulletin Agricole du Rwanda, Juillet 1986.
Bird TJ, 1987. Fighting African cassava pests from the air. Aerogram, 4:6-7.
Calatayud PA; Le Rü B, 1997. La lutte contre la cochenille du manioc en Afrique. Cahiers de la Recherche Developpement No. 43, 59-66.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Fabres G, 1980. Bioécologie de la cochenille du manioc (Phenacoccus manihoti Hom. Pseudococcidae) et de ses populations en République Populaire de Congo. 2. Variations saisonniFres d'abondance. Brazzaville, ORSTOM, 5 pp.
Ganga T, 1984. Possibilités de régulations de la cochenille du manioc Phenacoccus manihoti Mat-Ferr. (Hom. Pseudococcidae) par un entomophage exotique Epidinocarsis lopezi De Santis (Hym. Encyrtidae) en Republique Populaire du Congo. ORSTOM. June 1994.
Goergen G; Neuenschwander P, 1990. Biology of Prochiloneurus insolitus (Alam) (Hymenoptera, Encyrtidae), a hyperparasitoid on melaybugs (Homoptera, Pseudococcidae): immature morphology, host acceptance and host range in West Africa. Bulletin de la Société Entomologique Suisse, 63:317-336.
Hahn SK; Williams RJ, 1973. Investigations on cassava in the Republic of Zaire. Report to the Minister of Agriculture of the Ibaban, Republic of Zaire: IITA Mimeograph.
Haug T; Mégevand B, 1989. Development of technologies in support of contemporary biological control. In: Yaninek JS, Herren HR, eds. Biological Control: A Sustainable Solution to Crop Pest problems in Africa. Ibadan, Nigeria: IITA, 141-46.
Herren HR; Lema KM, 1982. CMB - first successful releases. Commonwealth Agricultural Bureaux, Biocontrol News and Information, 3:185.
Löhr B; Varela AM, 1987. The cassava mealybug, Phenacoccus manihoti Mat.-Ferr., in Paraguay: further information on occurrence and population dynamics of the pest and its natural enemies. In: Herren HR, Hennessey RD, Bitterli R, eds. Proceedings of an International Workshop on Biological Control and Host Plant Resistance to Control the Cassava Mealybug and Green Spider Mites in Africa, Ibadan, Nigeria, 6-10 December 1982. Ibadan, Nigeria: IITA, 57-69.
Neuenschwander P; Gutierrez AP, 1989. Evaluating the impact of biological control. In: Yaninek JS, Herren HR, eds. Biological Control: A Sustainable Solution to Crop Pest Problems in Africa. Ibadan, Nigeria: IITA, 147-155.
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.
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.
Razafindrakoto C; Ponte JJ da; Andrade NC de; Silveira Filho J; Pimentel Gomes F, 1999. [Manipueira and heat treatment for the treatment of cassava cuttings attacked by scale insects.] Manipueira e termoterapia no tratamento de estacas de mandioca atacadas por cochonilhas. Revista de Agricultura Piracicaba, 74(2): 127-136.
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.
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.
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.
Distribution Maps
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