Table 1 indicates that out of the 29 nurseries surveyed from 15 locations in three states, 15 nurseries had either Alternanthera brasiliana (L.) Kuntze (red Alternanthera) or/and Alternanthera ficoidea (L.) Sm. (green Alternanthera) plants for sale.
Table 1
Collection localities of Alternanthera spp. and the mealybug, H. pungens
| S. No. | Survey locality | Presence or absence of plant for sale (P – Present, A – Absent) | Presence of mealybug (Y-Yes, N-No, NA-Not applicable) |
| Alternanthera brasiliana (L.) Kuntze (red Alternanthera) | Alternanthera ficoidea (L.) Sm. (green Alternanthera) |
| 1 | Judicial layout, Yelhanka, Bengaluru |
| Nursery 1 | P | P | Y |
| 2 | Dairy Farm, Hebbal, Bengaluru |
| Nursery 2 | A | A | NA |
| Nursery 3 | A | A | NA |
| 3 | Amruthnagar, Bengaluru |
| Nursery 4 | A | A | NA |
| 4 | Coffee Board Layout, Bengaluru |
| Nursery 5 | A | A | NA |
| 5 | Yelhanka |
| Nursery 6 | P | P | N |
| 6 | Kodigehalli, Bengaluru |
| Nursery 7 | A | A | NA |
| Nursery 8 | A | A | NA |
| 7 | Dasarahalli, Bengaluru |
| Nursery 9 | P | P | Y |
| 8 | Jakkur, Bengaluru |
| Nursery 10 | P | A | N |
| Nursery 11 | | | |
| 9 | Gandhi Krishi Vigyan Kendra Campus, Bengaluru |
| Nursery 12 | A | A | NA |
| Nursery 13 | A | A | NA |
| 10 | Vijayapura, Devenahalli, Bengaluru Rural |
| Nursery 14 | A | A | NA |
| Nursery 15 | P | P | Y |
| Nursery 16 | A | A | NA |
| Nursery 17 | A | P | N |
| 11 | Avalagurki, Isha Foundation Road, Chikkaballapur |
| Nursery 18 | P | P | Y |
| 12 | Horamavu Agara, Bengaluru |
| Nursery 19 | A | A | NA |
| Nursery 20 | P | A | Y |
| Nursery 21 | P | A | Y |
| 13 | Attibele, Anekal, Bengaluru |
| Nursery 22 | P | P | Y |
| Nursery 23 | P | P | Y |
| 14 | Agalakottai, Denkanikotta, Krishnagiri, Tamil Nadu |
| Nursery 24 | P | P | N |
| Nursery 25 | P | P | Y |
| Nursery 26 | P | P | N |
| Nursery 27 | A | A | NA |
| 15 | Rajendranagar, PJTSAU Horticulture Telangana, Hyderabad, Garden |
| | Nursery 28 | P | P | N |
| | Nursery 29 | A | A | NA |
Of these 15 nurseries with Allternanthera, 60 percent of the nurseries showed the presence of mealybug infestation, but at only two nurseries (Vijayapura, Devanahalli and Avalagurki, Chikkaballapura), four plants bore heavy infestation and these plants were segregated by the nursery owners and kept away from the main area, where other plants were maintained for commercial purposes. These heavily infested plants yielded all the predators and males of the mealybug. Nursery holders, during the interview, mentioned that they have been supplying Alternanthera for many years, however, the mealybug problem was recent, and they were reluctant to reveal the source from where they get the plants. Nursery owners also mentioned taking up need-based blanket sprays of safer chemicals and isolating infested plants while monitoring, but these sprays failed to contain the mealybug problem. Despite the presence of Alternanthera plants in the nursery at Telangana, we could not find the mealybug infestation, however, the mealybug was recorded in nearby locations on Portulaca sp. (Portulacaceae). Alternanthera spp. are generally not used as an individual ornamental potted plant but are used for landscaping and vertical gardening and hence these plants were found only in large commercial wholesale nurseries which cater the needs of landscapers.
Examination of the material in live and mounted conditions led to the identification of the species as Hypogeococcus pungens Granara de Willink. This is the first report of the genus Hypogeococcus Rau from India. Among Asian countries, it is known to occur only in China, which was reported indirectly through interception in the Netherlands (Jansen & Alferink, 2023).
Field characters (Fig. 1): The infestation of the mealybug can be detected as a clump of cotton wool gathered on the axillary areas of the plants. The female body oval to round, broad anteriorly, and tapering posteriorly. The body colour varies from pink to yellowish orange, lightly dusted with mealy wax, with yellowish transparent appendages. Lateral wax filaments absent but the female removed from the ovisac retains tufts of wax filaments of ovisac on posterior end of the body. Ovisac dorsal, covers the female completely. The wax threads of ovisac are tenacious and long threads can be drawn if the ovisac is grasped and pulled with the fingers or pin. Eggs could not be seen, perhaps ovoviviparous. First instars deep pink, can be observed walking on the threads of ovisac.
Diagnostic characters of mounted female (modified from Williams1973) (Fig. 2): Body of adult female rotund, elongate oval (Fig. 2a); posterior end of body rounded; anal lobes poorly developed (Fig. 2b). Antennae 7-segmented (Fig. 2c). Legs rather small; hind trochanter + femur and hind tibia + tarsus almost equal in length (Fig. 2d). Translucent pores well defined on the dorsal (Fig. 2e) and ventral sides (Fig. 2f) of coxa, on the outer half, and in two small groups on the outer distal edge of tibia (Fig. 2g). Claw without a denticle; claw and tarsal digitule clavate (Fig. 2h). Second and hind legs with stout spine-like setae (Fig. 2i). Ostioles represented by poorly developed posterior pair only, upper and lower lips without trilocular pores and setae (Fig. 2j). Anal ring wide with three rows of pores and six setae (Fig. 2k). Circuli numbering three (Fig. 2l), situated between fourth and fifth segments and on the intersegmental folds of the two preceding segments; well developed, the two anterior circuli oval and the posteriormost usually notched on posterior margin (Fig. 2m). Ultimate cerarii with concentrations of 4–7 wide lanceolate spine-like setae of different sizes (Fig. 2n); penultimate cerarii similar (Fig. 2o). Similar dorsal setae present in transverse rows on the last five segments of abdomen (Fig. 2p). On the fourth and anterior segments there are normal short slender setae of various sizes which are not numerous. Multilocular disc pores in transverse rows (Fig. 2q) at the anterior and posterior edges of segments in single rows except on the sixth and posterior segments where they are in double rows. Multilocular pores with 10 loculi (Fig. 2r). Oral collar tubular ducts of two sizes mainly across the middle of segments between the rows of multilocular disc pores (Fig. 2t). A small type numerous on the abdomen but anteriorly they become fewer and are replaced by the larger type (Fig. 2u). Trilocular pores absent.
Ventral surface with anal lobe setae longer than anal ring setae. Other setae slender and pointed, tending to be slightly stouter on the abdomen (Fig. 2u) than the slender setae on dorsum. Multilocular disc pores in transverse rows on the abdomen in single or double rows at the anterior and posterior edges of segments, scattered on the thorax and head. There are noticeable groups around spiracles (Fig. 2v). Oral collar tubular ducts, similar to those on dorsum, in transverse rows on the abdomen and in no definite arrangement on thorax and head.
Three species of Alternanthera viz., A. pungens (Granara de Willink, 1981), Alternanthera sp. (Germain & Grassart, 2005) and A. paronychioides (Triapitsyn et al., 2014) have been reported earlier as host plants of H. pungens, we report A. brasiliana and A. ficoidea, as new host plants for this mealybug through this study. In addition to these, one more host Protulaca sp. (Portulacaceae) was recorded as host in Telangana state. Surprisingly, no honeydew deposition or tending ants could be observed at the surveyed locations. Apart from Cactaceae, the species has been reported on the host plants belonging to Amaranthaceae, Apocynaceae, Malvaceae, and Portulacaceae. Earlier studies have indicated that the mealybug infesting non-Cactaceae hosts cannot infest Cactaceae hosts. However, other host plants of this species such as Hibiscus rosa-sinensis, Portulaca oleracea, and Gomphrena globosa are very common either in nurseries or in urban landscapes and could represent a risk factor for rapid spread and invasion of this mealybug species.
Predators viz., Scymnus (Pullus) syoitii Sasaji (Fig. 1g & 1h), Brumoides suturalis (Fabricius) (Fig. 1i & 1j) (Coleoptera: Coccinellidae), and an unidentified midge (Diptera: Cecidomyiidae) were reported during the present study. These were found only at two locations surveyed. Brumoides suturalis is a common predator of several soft-bodied insects in India and S. syoitii was reported earlier in Bengaluru, Karnataka in 1993 as a predator of Planococcus citri (Risso) (Poorani et al., 2024). Of these predators, S. syoitti was the most predominant with more than 175 grub and 96 adults emerging from four heavily infested plants. We could get only two adults each of B. suturalis and unidentified midge. No predators or parasitoids of this mealybug species are on record from any part of the world.
The deposited sequence results matched with Hypogeococcus pungens in the NCBI database for both COX 1 and 28S D2-D3 set of sequences with 97 and 99% similarity, respectively. Four sequences for each gene COX 1 (PQ203598-PQ203601) and 28S D2-D3 (PQ206262-PQ206265) were submitted to the NCBI and allotted with accession numbers.
Our local investigation could not precisely determine the pathway of introduction of this species. However, we are convinced this was possible through infested ornamental plants introduced for commercial purposes since the mealybug was discovered in the commercial nurseries. There are several online retail shopping platforms through which imported red Alternanthera can be bought directly without any interventions from regulatory agencies. International Plant Protection Convention (IPPC, 2012) has rightly pointed out that in the current globalized world, the Internet has become a convenient means of product promotion, marketing, and distribution for a range of products for which phytosanitary measures should be applied or should be scrutinized using pest risk analysis. E-commerce is becoming increasingly common and presents another pathway by which many small consignments of plants and plant products move across international borders into countries and across continents.
The United States Department of Agriculture considers H. pungens to be a species of quarantine significance (Miller et al., 2014) and was intercepted 8 times at U. S. ports-of-entry between 1995 and 2012, with specimens originating from Hawaii, Monaco, Puerto Rico, and The U. S. Virgin Islands. Hence, it is important to make great efforts to prevent the spread of this exotic insect throughout the Indian subcontinent. There is therefore a clear need for early and correct detection of the species in newly infested localities, particularly nurseries where plats are sold, and offices, commercial complexes and luxury apartments where landscapes and vertical gardens are common. The colour photographs of the different life stages provided here will help nursery owners and agricultural officers to detect new infestations of this species. Similarly, the slide-mounted characters will help researchers and students to separate this species from other common species of mealybugs, leading to development of accurate strategies for its containment. The present article also emphasizes possibilities for rearing natural enemies in the laboratory in the event of an outbreak of this species. As the mealybug remains hidden throughout its life under the heavy mealy mass (owing to dorsal ovisac) pesticides are less likely to be effective. On the other hand, due to lack of presence of ants (due to lack of honeydew deposition) biological control agents are more likely to be successful.