In life, scale cover of adult female subcircular, convex, white, with yellow exuviae at the margin. Scale cover of male not documented, but probably smaller than that of female, elongate, parallel-sided, white and tricarinate with yellow terminal exuviae. Exposed body of gravid adult female 1.8 mm long and 0.9 mm wide at the anterior end, deep pink due to eggs within; after egg-laying, the female shrinks and loses her pink coloration. Adult male apterous, deep pink, smaller than adult female; without mouthparts; walks sluggishly. Eggs each 250-280 µm long and 110 µm wide, amber-yellow and covered with white, powdery wax (Williams, 1970).
Slide-mounted adult female with swollen, more or less rounded cephalothorax; gland spines and macroducts absent from thorax and head AUTEGS.jpg . Pygidium with median lobes zygotic, without any setae or gland spines between their bases; abdominal segment VI bearing 5-9 submedian macroducts on each side; pore prominences between pygidial lobes short AUTEGP.jpg . Feeds only on grasses.
Aulacaspis tegalensis has a restricted host range on grasses (plant family Gramineae). It only multiplies intensively on cultivated sugarcane (Saccharum officinale) or wild sugarcane (S. spontaneum). It has been reported on the grass Erianthus arundinaceus in Java, but the distinction between this species and Saccharum is doubtful (Williams, 1970). Aulacaspis tegalensis has been reported on Sorghum halepense in Tanzania, but is not generally found on cereals near sugarcane fields.
Affected plant stages: vegetative growing, flowering and fruiting stages
Affected plant parts: stems (under the leaf sheaths, near the nodes) and sometimes leaves
Biology and ecology
The biology and ecology of A. tegalensis on sugarcane were described in East Africa (Greathead, 1975) and Mauritius (Williams, 1970). Eggs were not usually laid unless mating had occurred. Each female laid an average of 700-800 eggs over 10 weeks in summer (14 in winter); the life cycle took 21-25 days in mid-summer and about 49 days in winter (Williams, 1970). The egg stage lasted 10-11 days and development from oviposition to the mature adult female took about 40 days at 30°C (Raich and Waiyaki, 1973).
Aulacaspis tegalensis is essentially a stem-feeder. It is often found on leaves, but this is usually a secondary infestation or caused by crowding on the stem nodes (Williams, 1970). In early stem growth, the leaf sheaths are tight against the stem, which prevents scale insects reaching the stem surface. Later in growth, the leaf sheaths loosen, favouring the scale insects by providing cover. Large injurious populations are, therefore, only possible when the stems are well developed. Crawlers prefer to aggregate in the nodal regions. Raich and Waiyaki, 1973, found that infestation on planted sugarcane was greatest at the second and eighth nodes. When the insects are abundant, their massed bodies form crusts on sugarcane stems.
The first instar crawlers are responsible for dispersal but are unable to migrate far; they may wander for up to 48 hours before settling at a feeding site, usually on the shoot on which they hatched, or an adjacent shoot (Williams, 1970). However, eggs and crawlers are easily dislodged and may then be carried to new locations. Eggs have been transported by ants, birds and coccinellids, but wind also disperses the eggs and crawlers. However, the main form of dispersal is through agricultural practices (Waiyaki, 1979). Infestation can be carried over from one crop to the next on ratoons (pieces of cane left in the field after harvest) or on planting material (Fewkes, 1972). Crawlers first emerge from under the female scale in the morning and move upwards towards the light, where they can be dispersed by wind from the leaf tips (Greathead, 1972). At night, the crawlers move downwards and settle beneath the leaf sheaths.
The survival of A. tegalensis is affected by the weather. The behaviour of crawlers is affected by temperature, humidity and sunshine; dry, bright conditions favour the aerial dispersal of crawlers and lead to an increase in the population (Greathead, 1972).
In feeding, the stylets of A. tegalensis (which are about 2.4 mm long) pass between the cells and penetrate only the pith (storage) cells of sugarcane. No indication of necrosis or toxaemia results from feeeding (Williams, 1970). The symptoms of A. tegalensis damage are chlorotic spots and necrotic lesions on the leaves, caused by the toxicity of the saliva injected into the host-plant's tissues during feeding.
Heavy infestation by A. tegalensis can cause severe damage to sugarcane, resulting in loss of yield (Williams et al., 1969). The economic impact of A. tegalensis includes a reduction in the total yield, a decrease in the sucrose content and a reduction in the purity of the sugar; also the cost of replanting damaged fields. 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 (Van Deventer, 1911).
Aulacaspis tegalensis was first recorded damaging sugarcane in Mauritius in 1899, but attacks became more extensive in the late 20th century, probably because of changes in agriculturalmethods, and it continues to be a severe but localised pest there ([l][m]Literature[/m][r]Ganeshan, 2000[/r]Ganeshan, 2000). Damaging attacks in East Africa were reported from the 1960s. An outbreak in northern Tanzania in 1969 resulted in a loss of yield of almost 20% (Waiyaki, 1979). Greathead, 1975, reported peak losses of 25% due to A. tegalensis; Bjorking et al., 1977, estimated crop losses of 10-15% due to A. tegalensis and two other major sugarcane pests in Tanzania. Williams et al., 1969, described yield losses in sugarcane in Mauritius and elsewhere. Williams and Watson, 1993, mentioned that A. tegalensis is an important pest of sugarcane in southern Asia, and the species continues to be a pest of some consequence in the above countries (Williams and Greathead, 1990). Williams and Watson, 1988, described A. tegalensis as a potential pest of sugarcane throughout the tropical Pacific area.
Detection and inspection methods
Sugarcane stems should be inspected by pulling leaf sheaths away from the stems. Infestations are usually found under the protection of the loose leaf sheaths. Look for subcircular, convex, white scale covers, each with yellow exuviae at the margin.
There is a risk of introduction of A. tegalensis to more tropical countries if infested planting material of sugarcane is imported.
Natural enemies of A. tegalensis include hymenopterous parasites, predatory Coleoptera (Coccinellidae and Nitidulidae) and a range of general predators. Between them they can suppress A. tegalensis populations to low levels (Williams and Greathead, 1973). A number of natural enemies of A. tegalensis are listed in Rosen, 1990. Adelencyrtus miyarai is the main parasitoid of Aulacaspis tegalensis in Mauritius, where it is the only parasite that can effectively suppress scale insect populations (Williams, 1970).
Greathead and Pope, 1977, discussed the coccinellids in East Africa; Chilocorus schioedtii was considered to be an effective predator of A. tegalensis only in tropical areas with a dry season, while C. distigma and C. nigrita were important predators under a wider range of conditions. In Mauritius coccinellid beetles, Rhyzobius lophanthae and Cybocephalus mollis, are the most important predators (Williams, 1970), but their impact may not be as great as first thought (Facknath, 1989).
- Adelencyrtus miyarai in Mauritius, Réunion, Madagascar, Tanzania, Thailand, India
- Adelencyrtus moderatus attacking: larvae, adults, in Tanzania, Mauritius, Reunion, Madagascar, Singapore, Thailand, Indonesia (Java), Malaysia (Sabah)
- Aphytis lignanensis, in Mauritius
- Aphytis mytilaspidis, attacking: larvae, nymphs, adults, in Indonesia (Java), Singapore, introduced to Mauritius
- Arrhenophagus chionaspidis, in Tanzania
- Coccobius distigma, in Thailand
- Coccobius flavidus, attacking: larvae, adults, in Indonesia (Java), Singapore, Malaysia (Sabah)
- Coccobius schioedti, in Thailand
- Coccobius seminotus, attacking: larvae, nymphs, adults, in Uganda, Kenya, Tanzania, Thailand, Mauritius (introduced)
- Coccobius subflavus, attacking: larvae, nymphs, adults, in Uganda, Kenya, Tanzania
- Metaphycus sp., attacking: larvae, adults, in Tanzania
- Chilocorus distigma, attacking: eggs, larvae, nymphs, pupae, adults, in Tanzania, Kenya
- Chilocorus melanophthalmus, attacking: eggs, larvae, nymphs, pupae, adults, in Indonesia (Java), introduced: Kenya, Tanzania
- Chilocorus nigrita, attacking: eggs, larvae, nymphs, pupae, adults, in Sri Lanka, India, Thailand, Mauritius, introduced: Kenya, Tanzania, Réunion, Madagascar
- Chilocorus politus, attacking: eggs, larvae, nymphs, pupae, adults, in Indonesia (Java), introduced: Réunion, Mauritius
- Chilocorus schioedtii, attacking: eggs, larvae, nymphs, pupae, adults, in East Africa, Ghana
- Cybocephalus mollis, attacking: eggs, larvae, nymphs, pupae, adults, in Mauritius, Réunion
- Podothrips semiflavus, in Uganda
- Rhyzobius lophanthae, attacking: eggs, larvae, nymphs, pupae, adults, in Australia (Queensland), Mauritius, Réunion, India, introduced: Tanzania
- Sticholotis madagassa, attacking: eggs, larvae, nymphs, pupae, adults, in Réunion, Mauritus, India
A pathogenic fungus that grew over and choked the scale insect colonies was observed in Mauritius (Williams, 1970).
See Aulacaspis tegalensis distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species. Williams and Watson, 1993 provide a key to species of Aulacaspis species that feed on sugarcane.
Aulacaspis takarai Takagi AULTAKL3.jpg is similar to A. tegalensis; however, it has well-developed pore prominences between the pygidial lobes, each prominence being about half as long as a lobe, whereas in A. tegalensis the pore prominences are barely perceptible (Williams and Watson, 1993) AUTEGP.jpg. Aulacapis takarai is known from Japan and Ryukyu Is on Saccharum officinarum and bamboo (Gramineae) (Kawai, 1980; Williams and Watson, 1993). The scales colonise the stem and inner surface of the leaf sheaths, forming heavy incrustations. AULTAKL2.jpg , AULTAKL1.jpg
Aulacaspis tegalensis is a tropical species indigenous to the islands of South-East Asia and West Malaysia, and was first described from Indonesia (Java). It has been introduced to the Mascarene Islands (Mauritius and Reunion) and East Africa. The species is not known from Europe, or from the Western Hemisphere.
Uttar Pradesh: The Natural History Museum collection, London, UK
Irian Jaya: present, no further details (Williams and Watson, 1993)
Java: present, no further details (Williams and Williams, 1988; Williams and Greathead, 1990)
West Malaysia: present, no further details (Williams and Williams, 1988; Williams and Greathead, 1990)
Sabah: present, no further details (Williams and Williams, 1988; Williams and Greathead, 1990)
Philippines: present, no further details (Williams and Williams, 1988; Williams and Greathead, 1990)
Singapore: present, no further details (Williams and Greathead, 1990)
Southern Asia: present, no further details (Williams and Watson, 1988)
Thailand: present, no further details (APPPC, 1987; Williams and Williams, 1988; Waterhouse, 1993)
Taiwan: present, no further details (Williams and Greathead, 1990; Tao, 1999)
Kenya: present, no further details (Williams and Williams, 1988; Williams and Greathead, 1990)
Madagascar: present, no further details (Williams and Williams, 1988; Williams and Greathead, 1990)
Mauritius: present, no further details (Williams and Williams, 1988; Williams and Greathead, 1990)
Réunion: present, no further details (Williams and Williams, 1988; Williams and Greathead, 1990)
Seychelles: present, no further details (CIE, 1964a)
Tanzania: present, no further details (Williams and Williams, 1988; Williams and Greathead, 1990)
Uganda: present, no further details (Rogers et al., 1972; Williams and Greathead, 1990)
Papua New Guinea: present (Williams and Watson, 1988)
Yap Is: present (Beardsley, 1966)