Planococcus kenyae
(coffee mealybug)

Pictures

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Identity

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Preferred Scientific Name

• Planococcus kenyae (Le Pelley)

Preferred Common Name

• coffee mealybug

Other Scientific Names

• Planococcus subukiaensis De Lotto, 1954
• Pseudococcus kenyae Le Pelley, 1935
• Pseudococcus kenyaensis Betrem, 1936

International Common Names

• English: coffee, mealybug, common; common coffee mealybug; Kenya mealybug

Local Common Names

• Germany: Schmierlaus, Afrikanische Kaffee-

EPPO code

• PLANKE (Planococcus kenyae)

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: Planococcus
•                                         Species: Planococcus kenyae

Notes on Taxonomy and Nomenclature

Top of page Planococcus kenyae was first described in 1935 from coffee in Kenya (Le Pelley, 1935, 1943) as Pseudococcus kenyae. Before then, the species had been misidentified as Planococcus citri (Risso) in East Africa for several years (Wilkinson, 1925) and then for many years as Planococcus lilacinus (Kirkpatrick, 1927; James, 1933). The only synonyms are Pseudococcus kenyaensis (Betrem, 1936) and Planococcus subukiaensis (De Lotto, 1954). Ezzat and McConnell (1956) placed it in the genus Planococcus.

Description

Top of page Detailed description of the morphology of P. kenyae is available in Le Pelley (1935 and 1968), Williams (1958), De Lotto (1964), Cox and Freeston (1985) and Cox (1989). The body of the adult female is oval, somewhat flattened and measures about 2.5 mm long and 1.5 mm wide. It is yellow but this is obscured by a white waxy secretion that is less dense in a central longitudinal line (dorsal median line) and in the inter-segmental lines. Along the edge of the body are white wax filaments that are short at the head end and increase in length to about 0.5 mm at the apex of the abdomen (Le Pelley, 1968). Like other Planococcus species, the adult female has eight-segmented antennae. The legs are inconspicuous under the body. Nymphs are similar to adults but wax secretion is slight. The eggs are yellow, oval and are not contained in an ovisac.

The male is a delicate two-winged fly measuring about 1 mm long. It is slightly covered with powdery wax, with long ten-segmented antennae and the end of the abdomen bears two long setae covered with wax.

Microscope slide-mounted adult female specimens are oval to rotund, 1.4-2.7 mm long and 0.8-2.0 mm wide (Cox, 1989). Margin of the body with 18 pairs of cerarii, all with a moderately stout conical setae. Legs elongate, hind trochanter + femur 225-340 µm long, ratio of hind tibia + tarsus to hind trachanter + femur is 0.97:1.11. Translucent pores present on hind coxae and tibiae. Inner edges of ostioles moderately sclerotized. Circulus quadrate and of moderate size, width 50-160 µm. Cisinal setae usually noticeably longer than anal ring setae. Anal lobe cerarii each situated on a large, pronounced sclerotized area that is apparent only in well-stained specimens.

Venter

Multilocular disc pores are usually confined to median areas of venter where they occur around vulva and in single rows across posterior borders of median areas of abdominal segments IV-VII. A few pores are sometimes present on anterior borders of median areas of abdominal segment VI and/or of median areas of abdominal segments V-VII. Trilocular pores (tp) are moderately numerous and are evenly distributed. Oral collar tubular ducts (octd) are of two sizes; smaller ducts occur sparsely in rows across the median areas of abdominal segments VI or VII. Larger ducts are present in rows across median areas of all abdominal segments, usually sparsely scattered over the median areas of the thorax, and often present singly or in small marginal groups around the entire venter. A single duct is often located adjacent to postocular cerarius. Simple disc pores (sdp) about the same size as the trilocular pores are sparsely but evenly distributed.

Dorsum

Multilocular disc pores (mdp) and tubular ducts absent. Trilocular pores as described for venter. Simple pores are of two sizes: the smaller size pores are smaller than the trilocular pores and are sparsely scattered over the entire dorsum. The larger size pores, about twice the size of the trilocular pores, occur in groups on the mid-line of abdominal segments I-V. Setae on dorsum are flagellate and moderately short and stout, length of longest seta on abdominal segments V or VI usually measures 15-26 µm, rarely up to 40 µm (Cox, 1989).

Distribution

Top of page P. kenyae occurs only in the Afrotropical Region where it is known to be of limited distribution. It occurs in parts of Uganda and a small adjoining lake shore area of Tanzania and in an area of Kenya roughly from Nairobi to Meru (Le Pelley, 1968). It has also been recorded in Sudan, Ghana, Nigeria, Congo Democratic Republic, Togo, Zimbabwe, Burundi and Rwanda (Mayné and Ghesquiére, 1934; Cox, 1989; EPPO, 2003). P. kenyae is believed to be indigenous in Uganda, where it maintains a complex of primary and secondary parasites. On the other hand, it is clearly an introduced species in Kenya in view of its mode of spread and the fact that it is almost without endemic parasites there. It was first recorded in Kenya in 1923 (Le Pelley, 1968).

The presence of P. kenyae was not detected in West Africa until about 1952 when Donald (1955) found it infesting cocoa in Western Nigeria and later also in Ghana (Entwistle, 1972) and Sierra Leone (EPPO, 2003). In Nigeria, it is reported to be co-dominant with P. njalensis each being only about half as common as P. citri. Le Pelley (1968) cautions that its presence on cocoa in Nigeria is doubtful but the Natural History Museum (NHM), London, UK, has a few specimens collected in Nigeria in 1943 and also some for Malawi collected in 1987. In Ghana, very few specimens have been recorded (Donald, 1955); the NHM collection has specimens collected from Ghana in 1938 and 1952. It was not recorded in recent works by Bigger (1981), Campbell (1983) and Padi (1990). Thus, its presence in Ghana in recent times is doubtful but it is possible that it may have been mistaken for P. citri in these latter studies.

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.

Habitat

Top of page Planococcus kenyae occurs mainly on leaves, stems and on fruits but has also been recorded on roots of Coccinia sp. and Phaseolus sp (De Lotto, 1964). On coffee, it occurs on the upper leaf surface, around clusters of berries and on flower buds (MH Mugo, Coffee Research Foundation, Kenya, personal communication). On cocoa, it occurs mainly on fan tissue in the tree canopy (Entwistle, 1972).

Hosts/Species Affected

Top of page P. kenyae has been recorded from a large range of host plants from at least nine plant families many of which are suitable for the production of heavy populations (Le Pelley, 1968; Ben-Dov, 1994). Lists of host plants may be found in De Lotto (1964) and Cox (1989).

The primary hosts are Coffea species, Passiflora sp. (grenadilla), Cajanus cajan (pigeon pea), Dioscorea species (yams), Saccharum officinarum (sugarcane), Ipomoea batatas (sweet potato), Citrus sp. and Theobroma cacao (cocoa).

In Kenya, the species has been recorded on the aerial parts of Gossypium sp. (cotton), Ficus verrucocarpa, Jacaranda mimosaefolia, Bauhinia purpurea, Beta vulgaris, Lolium perenne, Sonchus oleraceus, Carissa edulis, Cassia didymobotrya, Annona squamosa, Pueraria thumbergiana, Solanum seaforthianum, Hedysarium coronarium and on roots of Coccina sp. and Phaseolus sp. (Le Pelley, 1968). P. kenyae is also reported as being among the important insect species occurring on Passiflora edulis (passion fruit) in Kenya (Odienki, 1975).

In Uganda, P. kenyae has been recorded on Tristania conferta, Coffea arabica, Coffea canephora, Coffea eugenoides, Annona cherimola, Gardenia sp., Gliricidia sp., Cadiaeum variegatum, Erythrina abyssinica., Psidium guajava, Solanum sp., Ricinus communis, and Theobroma cacao (De Lotto, 1964). The species has also been recorded as sporadic on cocoa and a variety of other crops in the Congo Republic (Mayné, 1917, cited in Entwistle, 1972). Other hosts include Lannaea discola (Anacardaceae), Costus sp. (Costaceae), Croton sp. (Euphorbiaceae), Inga sp. (Leguminoceae), Loranthus sp. (Loranthaceae), Hibiscus gossypinus (Malvaceae), Barteria fistulosa (Pasifloraceae), Cuviera angloensis and Leptactinia sp. (Rubiaceae) (Cox, 1989).

In West Africa, P. kenyae has been recorded on cacao mainly in Nigeria, Ghana and Sierra Leone (Entwistle, 1972).

Host Plants and Other Plants Affected

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Growth Stages

Top of page Flowering stage, Fruiting stage, Seedling stage, Vegetative growing stage

Symptoms

Top of page Symptoms for the presence of P. kenyae include wilting and shedding of leaves, dead branches, honeydew and sooty mould on leaves, and external feeding on fruits/pods. On coffee in Kenya, symptoms described include white masses of mealybugs between clusters of berries, on flower buds or apical shoots (i.e. external feeding), and spots of transparent honeydew and black sooty mould on the upper leaf surface (Anon., 1989).

List of Symptoms/Signs

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Species Vectored

Top of page Cacao swollen shoot virus (cacao swollen shoot)

Biology and Ecology

Top of page Kirkpatrick (1927) studied the life history and feeding habits of P. kenyae in the laboratory. The adult female lays between 50 and 200 eggs that are not enclosed in an ovisac. The eggs hatch in 2-3 days. The first instars crawl a short distance, usually upwards away from the eggs, until they find a suitable place to feed. The first- and second-instar stages last 6-10 days and 10-14 days, respectively. At this stage, both sexes are indistinguishable.

At the end of the second-instar stage, the young males move downwards to form rough cocoons of waxy threads, cast their skin to become a quiescent prepupa with wing buds, and again to a pupa with more developed wing buds. From formation of cocoon to emergence of winged male is about 10 to 14 days. The male completes its development in about 33 days under laboratory conditions.

The second-instar female moults to the last immature instar, similar to the second but larger and with more waxy secretion. At this stage, the insects move about freely. In the laboratory the female completed its development in about 36 days.

Little is known about the function of the male, which appears in considerable numbers, usually in colder weather in about August, and is apparently absent at other times (Le Pelley, 1968; Entwistle, 1972). Thus parthenogenetic reproduction has been assumed, but whether or not it occurs has yet to be confirmed.

According to Kirkpatrick (1927), the flower buds and young fruits of coffee are of the highest nutritive value, followed by young leaves and green stem, older fruits up to 5 months from setting, mature fruits, leaves and stems in decreasing order of nutritive value. Only when there is an abundance of flower buds, flowers and young fruits will a sudden and devastating outbreak of P. kenyae occur.

In Kenya, P. kenyae is reported to be attended mainly by the ant Pheidole punctulata. Association of the mealybug and ant is a highly developed mutualism, with both insects increasing markedly in numbers when they are together. Mealybug colonies flourish and spread when the sticky honeydew produced is removed and the cast skins and dead mealybugs are cleaned up by the ants. In the absence of ants, P. kenyae breeds more slowly and numerous predators bring the species under control (Le Pelley, 1968).

In Nigeria, P. kenyae appears to be co-dominant on cocoa with Planococcoides njalensis, each species being half as common as P. citri (Entwistle, 1972). Data collected by Donald (1955) suggest that its distribution on the tree may be more like that of P. njalensis, with the bulk of individuals in the canopy and on fan tissue.

Natural enemies

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Notes on Natural Enemies

Top of page Natural enemies have been recorded only in Uganda, where the species is believed to have originated, and in Kenya (Le Pelley, 1959, 1968). Primary parasitoids recorded include some ten or more species of Encyrtidae, including several species of Anagyrus, and species of Pauridia, Leptomastix, Pseudaphycus, Gyranusoidea and Hungariella (Le Pelley, 1968; Prinsloo, 1983). Anagyrus sp. near kivuensis may be one of the most important species in Uganda, since it proved to result in the most effective control when introduced to Kenya. External parasitoids include a Cecidomyiid, Schizobremia coffeae (Barnes, 1935, 1939), a Chamaemyiid, Leucopis africana, and a few other dipterans, none of which appears to have any great influence on the mealybug populations.

The predators in Uganda are not well known because the generally low populations of mealybugs do not favour them. Thus, far fewer Coccinellids have been recorded in Uganda than in Kenya. The coccinellids that have been recorded in Uganda and not in Kenya are three species of Hyperaspis. One important predator in Uganda is the larva of a Lycaenid butterfly, Spalgis lemolea, which is common and voracious, destroying large numbers of the mealybug. Common to both Uganda and Kenya are species of Scymnus and Platynaspis.

In Kenya, the position in respect of natural enemies is quite different. With the rare exception of three rare Encyrtid parasitoids, Anagyrus aurantifrons, Gyranusoidea citrina and Leptomastix jeanneli bred from P. kenyae, these being parasitoids of other mealybugs, no internal parasitoids were recorded for the species from its first appearance in 1923 until introductions were made from Uganda. The three parasitoids had no controlling effect on P. kenyae. The list of predators, on the other hand, has been impressive. Over 20 species of Coccinellids have been recorded, among which the most important are Chilocorus angolensis, two species of Hyperaspis, and several species of Scymnus. Given time, and with the trees freed of ants, they were capable of reducing and finally almost clearing up heavy attacks. Also present were at least three species of Syrphid flies, several predacious Mirid species, a Lycaenid, a Noctuid, several Chrysopid species and at least one Hemerobiid that contributed to the destruction of the mealybugs.

Means of Movement and Dispersal

Top of page Information on the mode of dispersal for P. kenyae is lacking. Nevertheless, since the three nymphal instar stages are the most active stages, it can be assumed that dispersal between and within trees takes place at these stages. There is also the likelihood that the mealybugs are carried from place to place over short distances by the attendant ants, particularly when conditions are unfavourable, as described for other cocoa mealybugs (Entwistle, 1972). Movement of infested plant materials from place to place can also be an indirect mode of dispersal.

Natural dispersal (non-biotic)

Although information on aerial dispersal is lacking, it is possible that aerial dispersal of the early instars over long distances takes place as reported for the cocoa mealybugs, Planococcoides njalensis and P. citri (Strickland, 1950; Entwistle, 1972).

Vector transmission

P. kenyae is a vector of various cocoa virus isolates including the cocoa swollen shoot virus disease. The virus is transmitted as the vector feeds from tree to tree. Alternative hosts of the virus, from which it can be transmitted onto cocoa, are mainly in the families Sterculiaceae, Bombacaceae and Malvaceae (Posnette et al., 1950, Legg and Agbodjan, 1969, Owusu and Lovi, 1970), but of these, only Gossypium hirsutum is likely to be a host plant of P. kenyae, since Le Pelley (1968) lists Gossypium species as hosts.

Plant Trade

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Plant parts not known to carry the pest in trade/transport
True seeds (inc. grain)

Impact

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In Uganda, P. kenyae has never been a pest of economic importance, since populations are kept low by the numerous indigenous parasioids present (Le Pelley and Melville, 1939). Following its introduction into Kenya in 1923, P. kenyae became a pest of economic importance in an area roughly from Nairobi to Meru, East of the Rift Valley, between 1923 and 1939 (Le Pelley, 1968). Severe attack in 1923-1930 resulted in defoliation, dead branch tips and crop losses of up to 10% (Le Pelley, 1968). Heavily attacked leaves become covered with sooty mould, wilt and drop. Kirkpatrick (1927) established a loss of £100,000 in the first six months of 1927, attributed to crop loss and cost of control measures. On 20 plantations, £58,000 was spent from 1930 to 1939 on control measures alone. Following the introduction of parasitoids from Uganda in 1938 the species became and has remained a minor pest, causing slight damage in sporadically severe attacks (Anon., 1961, 1989). Only 2-2.5% crop losses were reported in 1967 in limited areas. Young coffee trees have on occasion suffered a setback due to P. kenyae attack and the attack often seems to be associated with anti-parasite factors such as dust or the too frequent use of insecticides (Le Pelley, 1968).

Several African food plants have also suffered economic damage from P. kenyae in the past. Attacked crops became black and ruined. For example, Le Pelley (1968) reports that cultivation of yams in certain African areas ceased following the severe and persistent mealybug attacks. Also severe damage was done to pigeon pea and other food crops with severe losses to thousands of African farmers.

P. kenyae is known to be a vector of several isolates of cocoa swollen shoot disease in West Africa (Entwistle 1972; Dufuor, 1991).
 

Detection and Inspection

Top of page On coffee, look for white masses of mealybugs between clusters of berries, flower buds or apical shoots and spots of transparent honeydew and dark sooty mould on the upper leaf surfaces. Cocoa shoots, leaves, flowers and pods and yam tubers and roots of Coccinia sp. and Phaseolus sp. should also be inspected for the presence of mealybugs.

Similarities to Other Species/Conditions

Top of page The female P. kenyae is superficially very similar to other Planococcus species, particularly Planococcus citri and Planococcus lilacinus (James, 1933). It, nevertheless, differs externally from P. citri by having a more prominent dorsal median stripe and shorter legs. It also differs from the latter by the fact that it lays naked eggs, not enclosed in an ovisac, but this character is useful only in ovipositing females.

A slide-mounted female P. kenyae differs from P. citri by its well-sclerotised prominent anal lobes, relatively few marginal tubular ducts, cisanal setae that are longer than the anal ring setae, and multilocular disc pores largely restricted to the posterior borders of the median areas of the abdominal segments. It, however, shares the last two characters, i.e. long cisanal setae and multilocular disc pores absent from the margin of the venter, with P. lilacinus but lacks the stout legs and the very long dorsal setae of the latter (Cox, 1989).

In a study on morphological variation in cocoa mealybugs, field-collected P. citri and P. kenyae were distinctly separated by Discriminant Function Analysis (DFA) but not by Principal Component Analysis (PCA) of measured characters (Padi, 1997). P. kenyae had relatively shorter hind tibia, smaller spiracles and longer eighth antennal segment. Gel electrophoresis also clearly separated the two species at two (Esterase 1 and Esterase 2) of the six esterase loci identified (Padi, 1994).

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

Various introductions of parasitoids to control P. kenyae have been listed by Le Pelley (1959). Abasa (1975) also reviewed the use of natural enemies to control P. kenyae and other coffee pests in Kenya between 1911 and 1970. The successive misidentifications of P. kenyae on coffee in Kenya, as P. citri and P. lilacinus, led to searches for natural enemies in the wrong geographical areas (Rosen, 1978). Thus, introductions of parasites of P. citri and large numbers of parasites and predators of P. lilacinus from the Far East all failed to provide control, since the parasitoids tend to be host specific. Later, introductions of parasites of P. kenyae from Uganda proved successful. Of the five parasitoids introduced to Kenya (Anagyrus nr kivuensis, Anagyrus beneficians, Pauridia peregrina, Leptomastix bifasciatus and Pseudaphycus sp.) Anagyrus nr kivuensis, proved to be outstanding, based on the fact that it was hardy, vigorous, adaptable, mates readily and is an excellent searcher. It is capable of maintaining itself on very low and scattered mealybug population, and showed itself capable of controlling infestations even with ants around i.e. without the need to control ants by stem banding with insecticides. Anagyrus beneficians was also quite successful as a control agent, particularly in areas where the mealybug was widespread on indigenous shrubs and herbs and where cultivation was scattered among this vegetation. The other three species all passed several generations in the field, probably established but are not of much importance. Following these introductions, P. kenyae on coffee in Kenya fell from a major pest status and was classified as a minor pest in 1963 (Le Pelley, 1968) and has remained so to date (MH Mugo, Coffee Research Foundation, Kenya; personal communication). Since then, P. kenyae has been hard to find on coffee in most parts of Kenya and it has not been necessary to make further introductions of natural enemies. In 1945, an unidentified hyperparasitoid which had transferred from another host to Anagyrus nr kivuensis appeared able to prevent the parasite from effecting control on coffee when mealybugs occurred on young vigorously growing suckers coming from near the base of the tree. This new development was kept under control by prompt stripping of unwanted suckers and since 1967, only the odd estate has an occasional attack by this hyperparasitoid. The coccinellid predator, Cryptolaemus montrouzieri, was introduced into Kenya from South Africa in 1924 and 1929-30 for the control of P. kenyae on coffee but was preyed upon by attendant ants and was believed to have disappeared. The beetle was, however, found in 1971 some 50 km away from the release site, preying upon Dactylopius indicus, which had itself been introduced from South Africa to control prickly pear (Opuntia) but had not been successful (Greathead, 1972).

Cultural/Integrated Control

Buam (1972) discussed the prospects for the integrated control of P. kenyae and other coffee insect pests. Anon (1990) also presented recommendations for an integrated management strategy for the control of P. kenyae and other coffee pests. The method involved the use of insecticides and poison baits for ant control to encourage predators and parasitoids that would otherwise be killed by the ants. Cultural control of P. kenyae since its introduction from Uganda has entirely consisted of measures to break the association of mealybug and the ant Pheidole punctulata. In the early days, direct spraying and use of poison bait were not effective against the ant. Later, effective control was achieved by banding the tree trunk with some repellent or sticky substance to prevent access of the ant to the mealybug. Under these conditions, the mealybug bred more slowly and the numerous predators present brought the mealybug under control. After the introduction of parasites from Uganda, banding was almost entirely dispensed with but has come back in use in special cases, with the availability of effective chemicals for stem banding. This together with the introduced parasites, has resulted in a form of integrated control that has virtually eliminated P. kenyae as a threat on coffee in Kenya (Le Pelley, 1968). For stem banding to be effective, unwanted suckers and branches touching the ground are removed; also unwanted suckers should be promptly removed. Where the coffee plant is small for stem banding, the tree collar and the mulch around it are sprayed with the chemical.

Chemical Control

Among the earliest chemicals used to control P. kenyae were primitive soap and oil mixtures and methylated spirit used to paint mealybug colonies but these proved ineffective. Then followed the use of poison baits and several chemicals aimed at controlling the attendant ants. These included treating the soil with naphthalene, aradichlorobenzene and other fumigants, using boiling water on ant nests or blow lamps, digging for queens but these were all abandoned. Later castor oil placed on paper bands or paper cones around the trunk gave some weeks of protection but this was superseded by high-boiling point tar obtained by distilling creosote or anthracene oil, a substance which became known as kresotow. It was used on a cloth band over greaseproof paper or painted onto a paper cone (James, 1930) since it was injurious to the bark if applied directly. This method was expensive to apply and was later replaced by banding greases of the tanglefoot type that could be applied directly on the bark with no ill effects. This was integrated with the removal of lower primaries to prevent them touching the ground to form bridges for the ants. Although this method enabled some coffee to be picked on even heavily mealybug-infested plantations, it was only partially effective and was tedious and expensive. After the establishment of introduced parasites, banding was dispensed with. As a direct spray for badly affected trees or on sucker growth, diazinon was recommended, using 60% miscible liquid at a quarter of a pint in 40 gallons (Anon., 1961). Dimefox, a systemic insecticide, was also tried with some success but has not been adopted in practice (Bond, 1953). Chemicals presently being used in Kenya against attendant ants include supracide, chlorpyrifos and rhodocide, in each case adding 15 g Methylene blue. These are applied as a 15 cm-wide stem band on the tree trunk by painting or spraying, followed by the removal of drooping primaries which would otherwise serve as bridges for the ants. Amdro (Hydramethylnon) applied on the soil around the base of coffee trees is also effective against the ants (Anon., 1989).

References

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Distribution Maps

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