Pseudococcidae or mealybugs are small, soft-bodied insects, usually covered by white powdery wax. Adult females and immature stages (nymphs) are wingless; adult males are winged, and very short lived compared to females. The immature stages and adult females are important pests worldwide. They are direct pests feeding by sucking from almost all part of plants, from roots to fruit. Mealybugs also damage plants indirectly by vectoring plant diseases. Because of direct and indirect damage to plants, they are of considerable quarantine concern (Miller et al., 2002; Williams and Granara de Willink, 1992). About 353 species in 61 genera are known to be distributed in Southeast Asia, but only 25 species have previously been recorded from Cambodia and only 18 in Laos (ScaleNet, 2015; CABI, 2015; Williams, 2004; Soysouvanh et al., 2015). Mealybugs are common on many plants; see the first report. This report is the second part, following the first one (Soysouvanh et al., 2015), of the study for documenting more comprehensively the mealybug fauna of Cambodia and Laos, and identifying species which threaten agricultural production or pose quarantine risks.

Materials and Methods

Survey and collection

The survey was conducted in June - July 2015 in two countries at National Parks and gardens in Cambodia and Laos. In Cambodia, the survey was conducted in two provinces (Stung Treng and Siem Reap) and in Laos, in three provinces (Vientiane Capital, Vientiane province, Bolikhamsay province and Champassak province). A detection survey method was adopted following McMaugh (2005). Adult mealybug females were collected from plants into small tubes containing 75% alcohol. These specimens were transferred to the entomology laboratory in Sunchon National University for slide mounting.

Slide mounting and identification

See the first report of this study (Soysouvanh et al., 2015).

Results

During this study, we collected a total of 14 species of mealybugs in Cambodia and Laos. Among these, six species have not been reported previously from these countries. Two species are newly recorded in Cambodia and five are newly recorded in Laos: Coccidohystrix insolita (Green, 1908) in Cambodia; Antonina graminis (Maskell, 1897) in both countries; and Nipaecoccus viridis (Newstead, 1894), Paracoccus marginatusWilliams & Granara de Willink, 1992, Phenacoccus solani (Ferris, 1918) and Rastrococcus iceryoides (Green, 1908) in Laos (Table 1).

Antonina graminis (Maskell, 1897) (Figs 1, 4)

A. graminis was collected on Panicum sp. (Poaceae) in Strung Teng province, Cambodia and on Centotheca lappacea (Poaceae) in Vientiane Capital, Laos.

Descriptive notes: Living on node and crown of grasses, dark brown and covered with thick white wax. Adult female on microscope slide almost quadrate, 2 mm long and 1.7 mm wide, cerarii absent. Posterior segments sclerotized, and abdominal segment VII and VIII heavily sclerotized. Antennae each about 40 μm long, with 2 segments, leg absent. Anal ring about 110 μm wide, ostiole absent, vulva directed ventrally, circulus 179 μm wide with strong setae. Multilocular disc pores present around opening of anal tube, present on both ventral and dorsum, present numerous on ventral and of 2 types, diameter of each about 7-10 μm. Oral collar tubular duct of two sizes, large type 16 μm long and 5 μm wide, narrow types about 12 μm long and 3 μm wide. Large types forming dorsal and ventral on base of sclerotized abdomen segment VII to VIII and margin of segment VI. Narrow types were abundant anterior to large type. Large and narrow types were present on both surfaces.

Coccidohystrix insolita (Green, 1908) (Figs 5, 8)

C. insolita was collected on Achyranthes aspera (Amaranthaceae) in Strung Teng province, Cambodia.

Descriptive notes: Living on the leaves and young stems of herbaceous host plant. In field light green in colour, covered with white long hairs around body. Adult female on microscope slide oval body about 1.9 mm long, 1.2 mm wide. Antenna with 9 segments, 584 μm long; posterior ostioles present, anterior ostioles absent, circulus absent also. Cerarii on margins numbering 17 pairs, almost cerarius consisting of 8-13 large conical setae situated on a sclerotized prominence, C₁-C₂ smaller than other with 2-5 conical setae, C₉ largest with 15 conical setae, each about 9-13 μm. Legs well developed, each claw with a denticle, anal lobes well developed, each with a sclerotized ventral bar. Quinquelocular pores numerous on venter, each about 5 μm diameter. Multilocular disc pores numerous on venters of abdominal segments III-IX, a few also present on the venter of segments I and II and on the dorsum of segment VII, each of them about 7 μm diameter. Ventral oral collar ducts present three sized, about 12 μm, 9 μm and 5 μm long respectively on submargins of abdominal segments V-VIII, oral rim ducts absent from ventral surface entirely and dorsum.

Nipaecoccus viridis (Newstead, 1894) (Figs 9, 12)

N. viridis was collected on Citrus aurantifolia (Rutaceae) in Champasak province, Laos.

Descriptive notes: Living on the leaves, young stems and shoot tips of host plant, body dark brown and covered by white wax. Adult female on microscope slide broadly oval, with 1.8 mm long and 1.2 mm wide. Antennae 247 μm long, each with 7 segments, legs well developed. Cerarii numbering 17 pairs, each about 22 μm long. Dorsum surface with lanceolate setae, each similar in size to cerarian setae. Multilocula disc pore absent from dorsum, ventral multilocular pores present, each about 7.5 μm. Oral collar tubular ducts of two sizes, larger size about 8 μm long, both sizes were present ventrally and on dorsum.

Paracoccus marginatusWilliams & Granara de Willink, 1992 (Figs 13, 16)

P. marginatus was collected on Manihot esculenta (Euphorb iaceae) in Vientiane Capital, Laos.

Descriptive notes: Body light green in colour, covered in powdery and white wax, without any longitudinal depressions. Short waxy filaments develop around body margin including short caudal filaments. On slide, adult female elongate oval, about 2.4 mm long and 1.4 mm wide, antennae 396 μm long with eight segments. Up to 18 pairs of cerarii on body margins, auxiliary setae present in the anal lobe cerarii only, ventral anal lobe bars present, 35 μm long. Legs well developed, translucent pores present on hind legs, ostioles moderately developed. Dorsal oral-rim ducts present on margin only, ventral oral-rim tubular ducts present on thorax, each about 12 μm long, oral collar tubular ducts present on ventral surface, about 7.5 μm long. Ventral multilocular pores present, double, low on abdominal segments V-VII and single, low on abdominal segment IV.

Phenacoccus solani (Ferris, 1918) (Figs 17, 20)

Ph. solani was collected on Justicia fragilis (Acanthaceae) in Vientiane province, Laos.

Descriptive notes: Body light green in colour, found on young leave and shoot tip, adult female on microscope slide elongate, 2.3 mm long and 1.3 mm wide, cerarii numbering 18 pairs, and each cerarii containing 2 setae without auxiliary setae. Antennae 582 μm long with 9 segments, legs well developed, translucent pores present on posterior surface of hind tibia, enticle present on claw. Circulus oval and sclerotized, anal lobe well developed, with 6 setae, each about 190 μm long. Dorsal surface with short lanceolate setae, each about 15 μm long. Trilocular pores fairly numerous on dorsum but less numerous on ventral surface, discoidal pores each narrower than a trilocular pore. Ventral surface with normal flagellate setae, multilocular disc pores present at abdominal segments VI-VIII and a few near margin on abdomen segment V, quinquelocular pores absent, oral collar ducts present, each about 12 μm long.

Rastrococcus iceryoides (Green, 1908) (Figs 21-24)

R. iceryoides was collected on Mangifera indica (Anacardiaceae) in Vientiane Capital, Laos.

Descriptive notes: Found on leaves and stem of host body covered by thick white wax, adult female on microscope slide broadly oval, 2.6 mm long and 1.8 wide. Cerarii numbering 17 pairs, each situated on a large area, abdominal cerarii each bearing 22-25 truncate-conical setae, cerarii on head and thorax containing more numerous setae, accompanied by large about 15-22 μm long, distorted trilocular pores extending from each cerarius to submargin. Antenae 793 μm long, each with 9 segments, legs well developed, translucent pores on hind tibia and tarsus, claw with denticle. Dorsum surface with cone setae, each about 17 μm long; circulus almost transversely rectangular rounded, 475 μm wide, located with borders of abdominal segment III. Anal lobe poorly developed, ostioles well developed represented on both anterior and posterior. Ventral multilocular pores present in double to triple rows across medial area of abdominal segments and around margins as far forwards as area between antennal bases, diameter about 12 μm. Quinquelocular pores distributed over medial and submedial area on venter, diameter about 6 μm; 4 sizes of oral collar tubular ducts, largest size about 25 μm long.

Discussion

Six species of mealybugs found for the first time in this study are common in Southeast Asia. A. graminis, were collected from the node of Pannicum sp. and the crown of Centotheca lappacea, both species of grasses belonging to the family Poaceae. Poaceae is the main host of A. graminis according to several studies; severe damage by it has been reported, mainly on grass (Chada & Wood, 1960), Chloris gayana (Ghani, 1981), and occasionally it is a pest of sugarcane (Pruthi & Rao, 1942). About 150 species of Poaceae have been recorded as hosts of A. graminis, distributed across 95 countries worldwide (ScaleNet, 2015). Some studies shows that it was also found on Cyperaceae (Cyperus rotundus, Fimbristylis cymosa) (Mamet, 1949; Reyne, 1964), Euphorbiaceae (Croton), and Orchidaceae (Disa tenuifolia) (Hendricks & Kosztarab, 1999). C. lappacea is a new host species A. graminis.

In this study, C. insolita were found on Achyranthes aspera. This species has already been recorded on the same host by Ali (1970), Avasthi & Shafee (1987), Ben-Dov (1994), Lit (1997) and Varshney (1992). C. insolita occurrs on about 19 families and 45 genera of host plants, including about 20 species of Solanac eae. C. insolita is reported as a main pest on Solanum sp., and is distributed across 20 countries in Asia and South Africa (ScaleNet, 2015).

N. viridis was found on Citrus aurantiifolia (key limes). This mealybug is widespread throughout the tropics and subtropics, attacking numerous plant species and often causing considerable damage (Clausen, 1978; Sharaf & Meyerdirk, 1987). C. aurantiifolia was also reported as a host by Williams and Watson (1988). This mealybug species occurs on plants of about 44 families and 111 genera, distributed in 61 countries worldwide (ScaleNet, 2015).

P. marginatus was found on M. esculenta. It also occurred on papaya, infesting the veins of older leaves, which turn yellow, dry up and shed prematurely, and all parts of young leaves and fruits. Tender leaves of papaya also become crinkled and curly; flowers and young fruit drop and shoots become bunchy. Papaya trees die within a few months of becoming infested (Miller et al., 2002). Infestation of frangipani, Plumeria causes the leaves to curl and new leaves fail to expand fully (Muniappan et al., 2009). P. marginatus occurs on plants belonging to about 48 families and 133 genera, distributed in 33 countries worldwide (ScaleNet, 2015).

Ph. solani which was found during this study on J. fragilis (Acanthaceae) was previously reported by Ben-Dov (2012) from only one host Dicliptera sp. This study records J. fragilis as a host for the first time. This mealybug is a pest of potatoes (Flanders, 1944) and was previously known from nearby Thailand and Vietnam (Williams, 2004). Globally, it has been reported from about 29 families and 64 genera of host plants, distributed in 30 counties worldwide (ScaleNet, 2015).

R. iceryoides was found frommango, M. indica. It has been recorded as a pest of coffee and mangoes, and was known from Brunei Darussalam, Malaysia, Singapore and Thailand. R. iceryoides has been reported from about 30 families and 65 genera of host plants, distributed in 14 countries from Asia and Africa (ScaleNet, 2015).

As a result of the present survey, the number of species of Pseudococcidae recorded in Cambodia and Laos has increased to 27 and 23 species, respectively. All species recorded from Cambodia and Laos are listed in Table 2.

Conclusion

This survey is the second study of Pseudococcidae in Cambodia and Laos. The survey was undertaken during the wet season in June to July 2015. The survey has shown that mealybugs are important pests of ornamental plants, fruit trees and other plants in these countries. These investigations have detected six species in these countries for the first time. Further collections from a wider range of hosts and during different seasons will no doubt further expand our understanding of the mealybug faunas of these countries. An important outcome of mealybug pest lists for Cambodia and Laos will become more credible. This will also guide more rational phytosanitary practices at national borders.