(Green, 1903)
Diagnosis
In the original description, Green, 1903, described the scale cover of the adult female as irregularly circular, 2.5 mm in diameter, slightly convex, smoky brown or greyish-black, with large, shining black exuviae that are usually concealed beneath secretion; ventral scale stout, entire and whitish. He remarked that the scales are often so closely crowded as to be difficult to distingish their individual shapes. Scale cover of male similar to that of female but much smaller (1.0 mm long) and more oval.
Body of slide-mounted adult female pyriform, membranous, with front of head not protruberant MELGLS.jpg . Pygidium broad (subtended by an angle greater than 90°) with quite long macroducts; about five dorsal submedian macroducts present on each side of segment VI; fringed plates present, perivulvar pores present; three pairs of rounded lobes present, fourth lobes small and pointed MELGLP.jpg . Paraphyses present; a few short, irregularly spaced paraphyses present lateral to fourth lobes MELGLP2.jpg .
Host range
Melanaspis glomerata has been recorded from hosts belonging to the plant family Graminae, genus Saccharum (Borchsenius, 1966), especially S. officinarum. Its original host was probably S. spontaneum in northern India (Rao, 1970).
Affected plant stages: vegetative growing, flowering and fruiting stages
Affected plant parts: moderately hard internodes and leaf midribs
Biology and ecology
In Uttar Pradesh, India, the life-history of M. glomerata was studied under glass by Shukla and Tripathi, 1983. There were six generations a year. The second, third and fourth generations were completed in 40, 38 and 43 days, respectively, at average minimum temperatures of 23.3-24.8° C, average maximum temperatures of 33.4-35.1° C, average minimum relative humidities of 61.9-64.5% and average maximum relative humidities of 87.2-90.5%. The fifth and sixth generations lasted 121 and 79 days respectively, at average minimum and maximum temperatures and relative humidities that were much lower than those for the previous three generations. Rainfall had no direct effect on generation time. On average, each female produced 110 -390 crawlers.
In a laboratory study in India by Tripathi and Tewary, 1984, eight generations on sugarcane were observed in 388 days. The duration of the life cycle of females was 32-87 days, whereas that of males was 11-52 days. Between 98 and 239 crawlers were produced per female. Both developmental period and fecundity appeared to be influenced by environmental factors such as temperature and nutritional value of the cane. The ratio of females to males was 3:1.
From the literature it seems that M. glomerata thrives best between 24 and 34 °C and at high relative humidities; the traditional method of irrigation by flooding fields strongly favours survival of the pest. Rao et al., 1991, found that a long dry period immediately after the rains favoured a rapid build-up of M. glomerata populations. Wind is an important aid to the dispersal of the scale (Tripathi et al., 1985).
Studies have shown that, in feeding, the stylets pass between the cells and penetrate only the pith (storage) cells of sugarcane.
Symptoms
No indication of necrosis or toxaemia results from feeding (Agarwal et al., 1959; Agarwal, 1960). The only obvious symptom is the presence of approximately circular, smoky brown or greyish-black scale covers on stems and leaf midribs.
Economic impact
Melanaspis glomerata was described in 1903, but only assumed economic importance in India after 1942 (Williams and Greathead, 1990). Serious losses and even complete failure of the crop have been reported with increasing frequency (Rao and Sankaran, 1969; Tewari and Tripathi, 1979; Misra and Pawar, 1981; Rao, 1981). Infestation may affect both cane weight and cane quality (Agarwal, 1960; Sathiamoorthy and Muthukrishnan, 1978; Williams and Greathead, 1990), causing low dry matter and sucrose contents. In Andhra Pradesh, India, heavy infestation of canes by M. glomerata reduced cane weight, juice brix, sucrose content of the juice and purity by up to 51.6, 27.7, 39.0 and 13.4% respectively (Goel and Raghunath, 1983). Low sucrose content makes sucrose extraction more difficult and therefore more costly. There is no decrease in the quantity of juice produced unless rotting sets in; a persistent heavy infestation can lead to decay and death of canes (Williams and Greathead, 1990). Loss of cane quality (size and weight) can also result from prolonged infestation by M. glomerata (Agarwal, 1960; Sathiamoorthy and Muthukrishnan, 1978). The extensive literature indicates that this insect continues to be a major pest of sugarcane in India.
Detection and inspection methods
Examine internodes and leaf midribs for irregularly circular, slightly convex, smoky brown or greyish-black scale covers, with large, shining black exuviae that are usually concealed beneath secretion. The scales may be so closely crowded as to be difficult to distingish their individual shapes.
Phytosanitary risk
Melanaspis glomerata has the potential to increase its geographical range (within and beyond India) and importance yet further.
Natural enemies
Parasitoids:
- Adelencyrtus bifasciata, in India
- Adelencyrtus femoralis, in India
- Adelencyrtus mayurai, attacking females only, in India
- Adelencyrtus sp. nr odonaspidis, in India
- Astymachus japonicus, in India
- Botryoideclava bharatiya, in India
- Cheiloneurus sp., in India
- Coccobius sp., in India
- Microterys sp., in India
- Neastymachus delhiensis, in India
- Tetrastichus sp., in India
- Rhopus nigroclavatus, in India
Predators:
- Brumoides suturalis, in India
- Chilocorus cacti, in West Indies, introduced to: India
- Chilocorus nigrita, in India
- Pharoscymnus horni, in India
- Podothrips lucasseni, in India
- Rhyzobius lophanthae, in Mauritius, Australia, introduced to: India
- Sticholotis cribellata, in India
- Sticholotis madagassa, in Réunion, introduced to: India
- Sticholotis quadrisignata, introduced to: India
- Saniosulus nudus, in India
Distribution
See Melanaspis glomerata distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species.
Melanaspis bromiliae (Leonardi) (brown pineapple scale) MELBRS.jpg could be misidentified in the key as M. glomerata, but differs in its host preference and in having a fairly acute and triangular pygidium with up to 35 macroducts on one side MELBRP.jpg. In contrast, M. glomerata has a somewhat rounded pygidium with a lateral swelling on each side of segment V and with more than 50 macroducts on one side. Melanaspis bromiliae is known from Cameroon, Côte d'Ivoire, Guinea, South Africa, Seychelles, Togo, Portugal including the Azores, Belgium (under glass), Hungary, Italy (under glass), Netherlands, Spain (Canary Is), Taiwan, Japan, USA (Florida, and under glass in Pennsylvania), Brazil, Bahamas, Bermuda, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, Guatemala, Haiti, Honduras, Jamaica, Martinique, Mexico, Panama, Puerto Rico, USA (District of Colombia, Florida, Hawaii), India, Federated Malay States, Philippines, Singapore, South Mariana Is (Guam), Palau Is, Yap Is, and Pohnpei on pineapple fruit (Ananas spp.) (on which it is a pest), and leaves of dryland taro (Colocasia esculenta), Cocos nucifera, and species of Neoglaziovia and Pandanus and other hosts (Beardsley, 1966; Kawai, 1980; Nakahara, 1982; Deitz and Davidson, 1986; Longo et al., 1995; Miller, 1996; Gill, 1997; Danzig and Pellizzari, 1998; Tao, 1999; Heu, 2002). Colonies MELBRL1.jpg , MELBRIL1.jpg
Melanaspis inopinata (Leonardi) could be misidentified as M. glomerata, but differs in host preference and in lacking any submedian macroducts on abdominal segment VI, more or less level with the anus MELINP.jpg. In contrast, M. glomerata has about 5 submedian macroducts in this position on either side of the anus. Melanaspis inopinata is known from Cyprus, Greece, Italy, Sicily, Malta, former USSR (Transcaucasus: Armenia), Israel, Lebanon, Iran, Iraq, Israel, Syria, Turkey, Pakistan and Egypt on trunks, branches and stems of (mostly rosaceous) species of Arbutus, Celtis, Cercis, Crataegus, Fraxinus, Juglans regia, Malus, Pistacia vera, Prunus, Pyrus, Rhamnus and Sophora (Balachowsky, 1951; Konstantinova, 1976; Longo et al., 1995; Danzig and Pellizzari, 1998; Abivardi, 2001; The Natural History Museum collection, London, UK). This viviparous species had one generation per year on Pistacia in Greece and overwintered as unfertilized adults; each female produced 63-95 eggs (Katsoyannos and Stathas, 1997); it rarely occurs on fruits. Balachowsky, 1951, describes the species as damaging and Danzig and Pellizzari, 1998 describe it as a dangerous pest. It is a minor pest of Pistacia in Syria, encrusting the foliage (Hill, 1983).
Melanaspis tenebricosa (Comstock) (gloomy scale) MELTENS.jpg could be misidentified as M. glomerata, but differs in host preference and in lacking any submedian macroducts on abdominal segment VI, more or less level with the anus. In contrast, M. glomerata has about 5 submedian macroducts in this position on either side of the anus. Melanaspis tenebricosa is a polyphagous species known from USA (Alabama, Arkansas, District of Colombia, Delaware, Florida, Georgia, Illinois, Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, North Carolina, New Jersey, New York, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia and West Virginia), Mexico and Panama on the bark of twigs and branches of a wide variety of hosts including species of Acacia, Acer spp., Carya, Catalpa, Celtis, Cornus, Fraxinus, Gardenia, Gleditsia, Juglans regia, Liriodendron, Maclura, Malus pumila, Morus, Nerium, Pithocellobium, Platanus, Prunus persica, Ribes, Salix, Sapindus, Thevetia, Ulmus and Vitis (Nakahara, 1982; Deitz and Davidson, 1986; Miller, 1996). Melanaspis tenebricosa is often damaging to Acer species in the USA; heavy infestations kill the terminal growth and large branches, leading to the growth of suckers from the base of the tree; it may even kill whole shade trees (Deitz and Davidson, 1986). In North Carolina and Maryland this species has one generation per year, and overwinters as fertilized females; the adult female lays 5-7 eggs per day, and her exposed body is pink to purplish (Stoetzel, 1975; Deitz and Davidson, 1986). Scale cover of adult female circular, very convex, brown to grey with black subcentral exuviae; scale cover of male similar to that of female but smaller and more elongate, with black subterminal exuviae (Davidson and Miller, 1990). MELTENL5.jpg
MELTENL4.jpg
MELTENL1.jpg
MELTENL2.jpg
MELTENL3.jpg
MELTEDAM.jpg
In M. inopinata, the paraphyses in the interlobular spaces are all approximately the same length as the paraphyses arising from the corners of the lobes (Balachowsky, 1951) MELINP.jpg. In contrast, in M. tenebricosa the paraphyses in the interlobular spaces are all different in length to the adjacent paraphyses arising from the corners of the lobes - either obviously shorter (in the inner two interlobular spaces) or longer (in the third interlobular space) MELTENP.jpg (Ferris, 1941).
Comments
Melanaspis glomerata is probably native to North India (Rao, 1970). It has not been recorded from outside the Indian subcontinent.
Asia
Bangladesh: present, no further details (FAO, 1976)
India
Andra Pradesh: present, no further details (Rao, 1981)
Assam: The Natural History Museum collection, London, UK
Bihar: present, no further details (Tewari and Tripathi, 1979)
Delhi: present, no further details (Kumar et al., 1972)
Gujarat: present, no further details (Tewari and Tripathi, 1979)
Haryana: present, no further details (Chillar et al., 1993)
Karnataka: present, no further details (Tewari and Tripathi, 1979)
Madhya Pradesh: present, no further details (Tewari and Tripathi, 1979)
Maharashtra: present, no further details (Tewari and Tripathi, 1979)
Nagaland: The Natural History Museum collection, London, UK
Orissa: present, no further details (Tewari and Tripathi, 1979)
Tamil Nadu: present, no further details (Tewari and Tripathi, 1979)
Uttar Pradesh: present, no further details (Misra and Pawar, 1981)
West Bengal: present, no further details (Ansari et al., 1987)
Pakistan: The Natural History Museum collection, London, UK