Insects in the family of Pseudococcidae are named as mealybugs because powdery secretions covering their bodies. They are small, soft-bodied insects that feed on plant sap by sucking. Adult females and immature stages (nymphs) are wingless; adult males are winged, but very short lived compared to females. The immature stages and adult females are important pests worldwide. (Miller et al., 2002; Williams and Granara de Willink, 1992; McKenzie, 1967). Their feeding may cause leaf yellowing, defoliation, reduced plant growth, and death of severe case. They also damage plants indirectly by vectoring of plant diseases. In addition, they produce abundant honeydew which contributes to the development of sooty molds that, in turn, decrease photosynthesis by plants. Beside direct and indirect damage to plants, mealybugs are also a quarantine concern (Miller et al., 2002). About 1, 989 species of mealybug reported worldwide, 345 are known to distribute in Southeast Asia, but only 22 species previously recorded in Cambodia and 12 in Laos (ScaleNet, 2014; CABI, 2015; Williams, 2004). Analysis of host plant information in the catalogue of Ben-Dov (1994), show that mealybugs occur on about 250 families of host plant, such as the families Asteraceae, Rubiaceae, Euphorbiaceae, Myrtaceae, Labiatae, Moraceae and Cyperaceae. Many of those are ornamental plants which are predominantly infested by various mealybugs.

Material and Methods

Survey and collection

The survey was conducted in early 2015 at National Parks and gardens in two countries. In Cambodia the survey was conducted in two provinces (Stung Treng and Siem Reap) and in Laos in three provinces (Vientiane Capital, Vientiane and Champassak) (Fig. 1). A detection survey method was adopted following McMaugh (2005). Adult mealybug females were collected from plants into small tubes containing 70% alcohol. These specimens were transferred to the laboratory for slide mounting.

Slide mounting

Slides specimens were prepared following Malipatil et al. (2013) and Williams and Watson (1988):

Maceration: Specimens were placed in 10% KOH and heated at 80°C for 10 minutes to clear body contents.

Staining: Specimens were left in a stain made up of 3 drops of acid fuchsin, 3 drops of acid alcohol and 6 drops of 95% ethanol for at least 30 minutes.

Dehydration: Mealybug specimens were transferred from stain to 95% ethanol for 10 minutes then moved to 100% ethanol. Specimens were moved to clove oil for an hour, and then mounted in Canada balsam. Slides were dry in an incubator at 40°C for two weeks.

Identification

Slide-mounted specimens were identified using the southern Asian key in Williams (2004).

Results

During this study we collected a total of thirteen species of mealybugs in Cambodia and Laos. Among these, eight species have not been reported previously from these countries. Twenty two species have been recorded previously from Cambodia (Table 1) and three are newly recorded in this study (Table 3; Figs. 2, 4, 9). The three newly recorded species are: (1) Dysmicoccus neobrevipes (Beardsley, 1959), (2) Phenacoccus solani (Ferris, 1918) and (3) Rastrococcus iceryoides (Green, 1908).

Only twelve species are recorded from Laos in the literature reviewed (Table 2). Six species are newly recorded in this study (Table 3; Figs. 2, 3, 5-8). These six species comprise: (1) D. neobrevipes (Beardsley, 1959), (2) Paracoccus invectus (Williams, 2004), (3) Phenacoccus solenopsis (Tinsley, 1898), (4) Planococcus litchi (Cox, 1989), (5) Planococcus minor (Maskell, 1897) and (6) Pseudococcus jackbeardsleyi (Gimpel & Miller, 1996). Important characters to identify these genera and species are described and illustrated below (Figs. 10-29).

Dysmicoccus neobrevipes (Beardsley) (Figs. 2, 22)

D. neobrevipes was collected from Jastropha integerrima in Strung Teng province, Cambodia, and from Ixora spp. in Vientiane Capital and Agave sp. in Vientiane province, Laos.

Descriptive notes: Body of adult female oval; cerarii numbering 17 pairs, anal lobe cerarii each bearing 2 conical setae; many cerarii each with 4-7 conical setae; discoidal pores conspicuous each larger than a trilocular pore, present medially on dorsum and few on ventral abdominal segments; 3 discoidal pores present adjacent to each eye. Oral collar tubular ducts present on venter abdomenal. Antennae with 8 segments, legs well developed; translucent pores absent from hind coxae, present on hind femora and tibiae. Multilocular disc pores present on venter around vulva, and abdominal segment VI. Anal ring normally developed, bearing 6 setae.

Paracoccus invectus (Williams) (Figs. 3, 23)

P. invectus was collected on Plumeria rubra in Champasak province, on Carica papaya in Vientiane Capital, Laos.

Descriptive notes: Body of adult female oval, cerarii numbering 14 pairs, anterior cerarial almost on abdominal segments, each contains 2 smaller conical setae. Antennae with 8 segments, legs well developed. Translucent pores present on hind coxae and hind femora. Anal lobes moderately developed, anal ring normally bearing 6 setae. Dorsal ?surface with short slender setae, trilocular pores present, oral rim tubular ducts with rim only slightly wider than a ventral multilocular disc pore, present singly behind each frontal cerarius, and near some thoracic cerarial, about 28 present. Ventral surface with normal flagellate setae present, multilocular disc pores distributed in single row across posterior of abdominal segments IV-VII, present also posterior to vulva and laterally to margins, a few located on abdominal segment III and on lateral margins of abdominal segment II. Trilocular pores present, oral rim ducts absent, oral collar tubular ducts of 2 sizes present.

Phenacoccus solani (Ferris) (Figs. 4, 24)

Ph. solani was collected on Chromolaena odorata in Strung Teng province, Cambodia.

Descriptive notes: Body of adult female broadly oval, cerarii numbering 18 pairs, and each cerarii containing 2 setae. Antennae with 9 segments, legs well developed, translucent pores present on posterior surface of hind tibia, denticle on claw. Circulus oval and sclerotized, anal lobe well developed, with 6 setae. Dorsal surface with short lanceolate setae, trilocular pores fairly numerous, 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 nearly margin on abdomen segment V, trilocular pores present but less numerous than on dorsal surface, quinquelocular pores absent, oral collar ducts present.

Phenacoccus solenopsis (Tinsley) (Figs. 5, 25)

Ph. solenopsis was collected on Ageratum sp. in Vientiane Capital, Laos.

Descriptive notes: Body of adult female oval, cerarii numbering 18 pairs, each bearing 2 setae. Circulus present, oval, occasionally slightly constricted laterally. Antennae with 9 segments, legs well developed, translucent pores present on hind femur and tibia; denticle on claw, anal ring with 6 setae. Multilocular disc pores present on ventral surface of abdominal segments VI-VII, a few near margin on abdomen segment V, a few near margin on abdomen segment V-II. Quinquelocular pores absent, oral collar tubular ducts present both dorsal and ventral.

Planococcus litchi (Cox) (Figs. 6, 26)

Pl. litchi was collected on Psidium guajava in Vientiane province, Laos.

Descriptive notes: Body of adult female broadly oval; cerarii numbering 18 pairs, except for 2 cerarii on thorax, each with 3 setae. Dorsal setae similar to cerarian setae about same size, mostly with flagellate tips, each with 2-4 trilocular pores associated with setae collar. Antennae with 8 segments; legs well developed. Anal ring well developed with 6 setae, anal lobe bar present. Oral collar tubular ducts present, of 2 sizes. Multilocular disc pore present in medial areas of abdominal segments III-IV, several of abdominal segments V-VII and a few on thorax and head.

Planococcus minor (Maskell) (Figs. 7, 27)

Pl. minor was collected on Plumeria rubra in Vientiane province; on Croton sp., Heliconia sp., and Tabernaemontana sp in Vientiane Capital, Laos.

Descriptive notes: Body of adult female oval; cerarii numbering 18 pairs, preocular pair (C₃) with 3 setae; antennae with 8 segments; legs well developed, translucent pores present on surfaces of hind coxa and tibia. Anal ring well developed with 6 setae, anal lobe bar present. Dorsal setae short and blunt, trilocular pores and discoidal pores present, oral collar tubular ducts present on dorsum and abdominal. Multilocular disc pore present around vulva, double rows of abdominal segments V-VII, and in smaller marginal group on abdominal segments IV-VI, a few occurring on medial areas of thorax.

Pseudococcus jackbeardsleyi (Gimpel & Miller) (Figs. 8, 28)

Ps. jackbeardsleyi was collected on Plumeria rubra, in Champasak province; from Crotron sp., and Psidium guajava in Vientiane Capital, Laos.

Descriptive notes: Body of adult female broadly oval, cerarii numbering 17 pairs. Anal lobe cerarii each containing 2 setae, head cerarii each bearing 3-5 conical setae, each cerarii with 4-5 auxiliary setae. Antennae with 8 segments, legs well develope d, translucent pores fairly numerous on hind femur and tibia. Each eye with an adjacent sclerotized rims, and containing 5 discoidal pores. Dorsal setae with all flagellate setae, oral rim tubular ducts present singly behind each frontal cerarius, others present submarginally and submedially on thorax, usually submedially on abdomen and a few at midline of abdomen, totalling 18 oral rim tubular ducts on abdomen. Ventral oral rim tubular ducts present, 4 on each side of thorax and anterior abdomen. Oral collar tubular ducts present on mesothorax, opposite each anterior spiracle; Multilocular pores present on ventral at abdominal segments VI-VI.

Rastrococcus iceryoides (Green) (Figs. 9, 29)

R. iceryoides was collected on Phyllanthus acidus in Strung Teng province, Cambodia.

Descriptive notes: Body of adult female broadly oval, 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, distorted trilocular pores extending from each cerarius to submargin. Antenae each with 9 segments, legs well developed, translucent pores on hind tibia and tarsus, claw with denticle, circulus almost transversely rectangular rounded, 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; quinquelocular pores distributed over medial and submedial area on venter; oral collar tubular ducts of 3 types as illustrated.

Discussion

Eight species of mealybugs found from this study are common in Southeast Asia. D. neobrevipes is considered to be a pest of pineapple fruit and there are many other economic records. It was first recorded from the Philippines in 1915 on Musa sp. In Southeast Asia and was also reported in 1983 on pineapple. P. invectus was first recorded in Thailand in 1979 on the leaf of an orchid. Ph. solani is a pest of potatoes, previously known from nearby Thailand and Vietnam. Ph. solenopsis is a pest of cotton, previously known from Thailand. Pl. litchi is most commonly found on lychees, having been recorded in 1989 from the Philippines, Singapore and Thailand. Pl. minor is a pest of cotton and cocoa, and is known to be widespread in Southeast Asia. Ps. jackbeardsleyi is a polyphagous species which attacks bananas, tomatoes, potatoes, peppers and Hibiscus throughout Southeast Asia. R. iceryoides is a pest of coffee and mangoes, previously known from Brunei Darussalam, Malaysia, Singapore and Thailand.

pAbout 345 species of mealybug species are known to occur in Southeast Asia, including 22 species from Cambodia and 12 species from Laos. As a result of the present survey, the number of species recorded in Cambodia and Laos increased to 25 and 18 species, respectively. All species recorded from Cambodia and Laos are listed in Table 4, with their distribution in other Southeast Asian countries. Neighboring countries to Laos Cambodia, Thailand and Vietnam have reported 55 species and 40 species respectively (ScaleNet, 2014; CABI, 2015; EPPO, 2014; Williams (2004)`). This study will continue and it is expected that more new records for Cambodia and Laos will be obtained, especially near to their borders with neighboring countries. Because of the similarity of host plant flora of mealybug throughout Southeast Asia, it is likely to be reflected in the mealybug fauna.

Conclusion

This field survey was conducted in Cambodia and Laos and focused on important pests of ornamental plants and other plants grown nearby. The survey was undertaken during the dry season in January 2015. These preliminary investigations have detected no fewer than seven 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 will be that pest lists for Cambodia and Laos will become more credible. This will guide more rational phytosanitary practices at national borders.