Glyptotermes dilatatus (live-wood tea termite (Sri Lanka))
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Plant Trade
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Glyptotermes dilatatus Bugnion & Popoff
Preferred Common Name
- live-wood tea termite (Sri Lanka)
Other Scientific Names
- Calotermes dilatatus Bugnion & Popoff
- Kalotermes dilatatus
International Common Names
- English: dry-wood, termite, tea (Sri Lanka)
- GLYMDI (Glyptotermes dilatatus)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Arthropoda
- Subphylum: Uniramia
- Class: Insecta
- Order: Isoptera
- Family: Kalotermitidae
- Genus: Glyptotermes
- Species: Glyptotermes dilatatus
Notes on Taxonomy and NomenclatureTop of page Glyptotermes dilatatus was first described (as Calotermes dilatatus) by Bugnion and Popoff (1910) from material collected in Sri Lanka.
DescriptionTop of page A colony of G. dilatatus has different castes; these are described below (after Pinto (1941):
These are the winged reproductive adults or alates found in new colonies. The males and females are usually called true 'kings' and 'queens' and form the royal pair. They have a dark, chitinous body with well developed eyes and reproductive organs.
These include two distinct forms: brachypterous and apterous. The brachypterous form, together with the apterous reproductive forms, are often called neotenics, supplementary, substitute or complementary kings and queens. These brachypterous reproductives have short wing pads of varying size. They are brown and their eyes and reproductive organs are less developed than in the macropterous forms (reproductive adults). The apterous form is also brown but lacks wing pads and eyes; egg laying is similar to the brachypterous forms.
This is a highly specialized, distinct, sterile caste, about 6.3 mm long with non-functional reproductive organs. They are wingless and the eyes are vestigial or absent. The morphological description of the species G. dilatatus is based on the head capsule of the soldier caste (Ranaweera, 1962; Cranham, 1966). The head is large and prominent, slightly raised between the antennae to form two points. Mandibles are brownish black. Left mandible is unevenly toothed and the right mandible with one tooth not more than half way from the tip and serrated below. Pronotum is as broad as the head, more or less rectangular. Antennae with 11 to 12 segments. The main function of soldiers is to defend the colony against invasion by enemies.
Immature forms (nymphs)
All other forms arise from the nymphs and so they do not constitute a separate caste although functionally they represent the worker caste. The name 'pseudogate' was given to the working nymph of Kalotermitidae by Weesner (1960). Development from nymph to winged adult (alates) may be arrested temporarily or permanently at any stage to meet the needs of the community.
DistributionTop of page G. dilatatus has only been reported from Sri Lanka. Although there are reports of termite infestation in tea areas in India (Borthakur, 1984; Das and Kakoty 1991), Kenya and Indonesia, there are no studies on G. dilatatus in these areas and the species attacking tea has not yet been identified. Recent information suggests that the termite infestation in Indonesia is very similar to that in Sri Lanka.
Although recognized early on as a pest of tea, G. dilatatus only surfaced as a serious pest of tea in low altitude tea areas of Sri Lanka (below 300 m) in the late 1960s. Until then, it was an occasional, innocuous pest encountered only in a few older tea bushes that were replaced at consecutive prunings (Jepson, 1941). Since the mid-1960s, it has spread rapidly in newly replanted clonal tea fields, resulting in massive losses of tea bushes and a consequent decline in yield (Danthanarayana and Fernando, 1970a; Sivapalan et al., 1977).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
Hosts/Species AffectedTop of page Artocarpus integrifolia is the endemic host and supports low populations of G. dilatatus in natural forests. Soft-wooded clonal tea selections allow the build up of populations and are therefore the preferred hosts. Introduced shade trees Albizia sp., Erythrina lithosperma and Grevellia robusta serve only as marginal reservoir hosts. No economic damage has been reported for the other plants listed, these are only associated with G. dilatatus.
G. dilatatus mostly attacks unhealthy tea bushes, those affected with dieback, wood rot or recovering from pruning, and are thus considered secondary pests which accelerate the death of debilitated bushes (Cranham, 1966; Sivapalan and Seneratne, 1977; Sivapalan et al., 1977).
Host Plants and Other Plants AffectedTop of page
|Camellia sinensis (tea)||Theaceae||Main|
|Coffea canephora (robusta coffee)||Rubiaceae||Habitat/association|
|Erythrina subumbrans (December tree)||Fabaceae||Other|
|Grevillea robusta (silky oak)||Proteaceae||Other|
|Hevea brasiliensis (rubber)||Euphorbiaceae||Habitat/association|
|Moringa oleifera (horse radish tree)||Moringaceae||Habitat/association|
|Syzygium aromaticum (clove)||Myrtaceae||Habitat/association|
|Theobroma cacao (cocoa)||Sterculiaceae||Habitat/association|
Growth StagesTop of page Flowering stage, Fruiting stage, Post-harvest, Seedling stage, Vegetative growing stage
SymptomsTop of page G. dilatatus is often detected during pruning as the pruning cuts reveal the tell-tale galleries. Attack is initiated by swarmers, which descend on wood-rotted snags, i.e. pruned cut ends affected by dieback and wood rot. The developing colony forms a network of galleries within the heart wood of branches and progresses over time towards the main trunk and collar. In longitudinal section they produce a 'honeycombed' appearance in the wood. There are no other visible symptoms at this initial stage. Damage to non conducting tissue does not cause any visible debilitation and attack rarely extends to the roots.
The network of galleries spreads rapidly as the colony size increases and the galleries extend into the conducting tissues. This causes water stress during dry weather and results in early wilting of affected branches, which may die in continuous dry weather. Dead branches are readily noticed in the field (Vitarana, 1986).
In the advanced stages of attack, the bark has a pitted appearance. When the galleries reach the sap wood and damage the bark tissues, the wounds callous giving rise to the characteristic pitted appearance often seen at the base of mature branches and the collar of affected tea bushes.
Attack by G. dilatatus is distributed randomly throughout the field and is not confined to groups or patches of bushes (Ranaweera, 1962).
List of Symptoms/SignsTop of page
|Leaves / wilting|
|Stems / internal feeding|
|Stems / rot|
|Whole plant / internal feeding|
|Whole plant / plant dead; dieback|
Biology and EcologyTop of page The biology of G. dilatatus has been studied intermittently since its first description (Jepson, 1926; Pinto, 1941; Ranaweera, 1962; Sivapalan and Seneratne, 1977).
The colony is initiated by a winged pair. Male and female reproductives are present in equal numbers in a colony. The swarming winged adult termites locate appropriate entry points on branch tips pre-disposed to dieback and wood rot by pruning. More than one pair of colony founders explore these entry points. Having located the weak points, the swarmers mate after de-alation and begin burrowing an initial gallery cell to deposit the eggs, which the parents will look after until the larvae develop. More than one independent colony may exist in a tea bush. The hatched nymphs transform into different forms (castes) including soldiers and supplementary reproductives (neotenic nymphs), the rest remain as immature nymphs performing the duties of 'workers'. These insects have complete control over their development. Field and laboratory observations indicate that external factors such as overcrowding, shortage of food and other unfavourable conditions determine the development of fully grown larvae to the winged adult stage. Observations in tea fields indicate the presence of incipient colonies only at the interface of rotted tissues and healthy wood. Only eggs, de-alated imagos and undifferentiated larvae are encountered at this initial stage. With further progress into apparently healthy wood, more active pseudogates (worker nymphs) are observed along with few soldiers. Soldiers appear only when the galleries have progressed further into sound wood. Soldiers account for about 4% of the total colony (Sivapalan and Seneratne, 1977).
Supplementary reproductives are very rare, less than 0.5% of the total colony. The nymphs gather food and expand the nest by constructing galleries. The food of the live-wood termites is almost exclusively the heart wood. In the advanced stages of attack, the sap wood and bark are also eaten causing branches to die. Longitudinal galleries are constructed within the heart wood, forming a network of communication tunnels. Attack rarely extends into the roots (Pinto, 1941; Sivapalan and Senaratne, 1977; Sivapalan et al., 1977).
With further construction of the gallery network, a few of the young nymphs become reproductives (neotenic nymphs) and commence egg laying. Among the neotenic nymphs are both brachypterous forms, with only partially developed short wing pads, and apterous nymphs. Brachypterous nymphs and alates are seldom encountered in colonies in the branches. Limited space and crowded conditions promote the production of brachypterous nymphs. The population thus expands rapidly through these neotenic reproductive forms. Colonies of G. dilaltatus seldom exceed 3000 individuals. Within a relatively short period (1-2 years), the entire bush can become excavated by galleries and once these reach the base of the trunk (collar), tunneling ceases as excavation into the roots is avoided. At this late stage, when overcrowding occurs and there is a shortage of food, a large proportion of the nymphs metamorphose into mature, swarming, winged adults (alates). Swarming takes place when there is high atmospheric humidity, usually in the early hours of the morning. Swarmers are not encountered in newly attacked fields and are only found in fields that have suffered prolonged termite damage. Very wet weather discourages swarming activity. Although swarming (nuptual flight) appears to be staggered throughout the year, there is an increase in the frequency and number of swarms before the monsoon period. In addition to weather factors, the number of swarmers per swarm is determined by the availability of tea plants in an advanced state of attack (Sivapalan and Seneratne, 1977).
Notes on Natural EnemiesTop of page There are no records of any known natural enemies of G. dilatatus other than predatory insects, amphibious birds and insectivorous bats, which attack the swarmers. Laboratory reared Heterorhabditis spp. when introduced artificially into infested galleries within tea stems killed a colony of G. dilatatus and bred in the cadavers (Danthanarayana and Vitarana, 1987).
Means of Movement and DispersalTop of page When atmospheric humidity increases during favourable weather conditions, the wing pads of the brachypterous nymphs extend and they metamorphose into winged adults. During the prevailing high humidity, the winged adults swarm, mainly at dawn. The survival of these swarmers is poor as many are destroyed by predators (insects, birds and bats). The swarmers are specifically attracted to wood-rotted branch ends (wood-rotted pruned stumps of tea bushes). Volatile and non-volatile compounds in the rotted stumps are known to attract the swarmers (Samarasinghe et al., 1999). The swarmers that descend on the rotted stumps attract the opposite sex and a pair of these alates shed their wings and establish a new colony by burrowing into the rotted stump forming the initial 'gallery cell'. The winged pair (the 'royal pair') de-alate, mate and begin egg laying. The hatching nymphs extend out of the cell by burrowing galleries into the heart wood of the living branch.
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Stems (above ground)/Shoots/Trunks/Branches||adults; eggs; nymphs; pupae||Yes||Pest or symptoms usually visible to the naked eye|
ImpactTop of page G. dilatatus became a serious pest of tea in low altitude tea plantations in Sri Lanka in the late 1960s, especially in the more recently replanted high-yielding clonal tea fields. With progressive infestation of tea bushes, the crop loss was enormous. Rapid escalation in the loss of productivity up to >50-60% resulted in the total collapse of affected tea bushes and huge capital losses. A modest estimate of the damage caused during the 1970s and early 1980s is the total collapse of about 50,000 ha of replanted tea fields. The cost of replanting at that time (1970s) was estimated at Sri Lankan Rupees 200,000/ha (equivalent to US$ 11,500/ha).
Detection and InspectionTop of page Termite infested bushes can be identified by inspecting debilitated tea bushes and examining them for gallery formation. The intensity of attack is estimated by inspecting tea fields at pruning and carrying out detailed dissections of plants taken from randomly selected sections of the field. Examination of shade trees for termite colonies is confined to dissection of rotting stumps of branches in situ (Sivapalan et al., 1977). The species of live-wood termite attacking the bush can then be identified by examining the shape of the head and jaws of the soldier caste.
Similarities to Other Species/ConditionsTop of page There are three species of live-wood termites which attack tea plants in Sri Lanka: G. dilatatus, Postelectrotermis militaris and Neotermis greeni. P. militaris is found at higher altitudes than G. dilatatus and N. greeni, which are often found concurrently at lower altitudes. G. dilatatus is widely distributed but N. greeni only attacks isolated bushes.
Both G. dilatatus and N. greeni enter the host through weak points in aerial parts of the host (trunk or branch) unlike P. militaris which enters through the roots.
The galleries of G. dilatatus and N. greeni are smaller and narrower than those formed by P. militaris. Furthermore, the galleries of G. dilatatus are much less regular in size and pattern than the regular networks of N. greeni and P. militaris. G. dilatatus completely hollows out the heart wood. The galleries of both G. dilatatus and N. greeni do not extend below the soil level (Ranaweera, 1962; Cranham, 1966).
Prevention and ControlTop of page Chemical Control
Early attempts at chemical control by injecting insecticidal emulsions into exposed galleries were not only laborious but futile (Danthanarayana and Fernando, 1970b).
The use of laboratory cultures of entomopathogenic nematodes (Heterorhabditis spp.) against G. dilatatus proved promising (Danthanarayana and Vitarana, 1987) but there is no possibility that these nematodes will seek out infested galleries and this is therefore not a practical means of control.
The incidence of G. dilatatus is low in fields interplanted with the shade tree Gliricidia sepium, which acts as a diversionary host by diverting the swarming alates to their own wood-rotted stumps. Once within the wood-rotted stumps, the swarmers commence egg laying, but the hatching nymphs are killed by chemical substances in the rotted stumps. The planting of shade trees is encouraged in fields prone to termite damage and branches are freely lopped offering several access points for swarmers. Care is taken to not clean the rotted ends so that they attract the swarmers (Sivapalan et al., 1977).
In locations where colonies are confined to branches of the host, the affected portions can be removed and burned (Cranham, 1966).
In areas where the termites have damaged the bushes beyond recovery, the bushes are uprooted and burned and the resulting area replanted with termite-resistant varieties.
The most promising approach against G. dilatatus is the selection of tea clones that offer natural resistance to attack. In general, high-yielding tea clones with soft-wooded, sappy frames suffer extensive dieback following pruning, are very sensitive to wood rot and therefore susceptible to termite attack (Sivapalan et al., 1980). On the other hand, the modest-yielding, hard-wooded tea clones suffer minimal dieback following pruning and are least sensitive to wood rot. The hard-wooded clones display significant resistance to termite attack. It is therefore recommended that modest-yielding, termite resistant clones be planted in termite prone areas.
In Sri Lanka, an integrated management strategy is currently recommended to minimize termite attack. This strategy involves the use of modest-yielding, hard-wooded clonal selections in place of soft-wooded, high-yielding clones; balanced fertilizer mixtures with enhanced potash and a N/K ratio of 1:1 or 2:3 in place of mixtures with a high proportion of N; compulsory cleaning of all dead-wood and snags following pruning, 18-20 inches above ground level, and treating larger prune cuts with an anti-fungal wound-dressing; and extensive interplanting of the green manure crop G. sepium to serve as a diversionary host.
ReferencesTop of page
Bugnion E; Popoff N, 1910. Les Calotermes de Ceylon. Memoires de la Societe Zoologique de France, 23:124.
Cranham JE, 1966. Termites. In: Monograph on Tea Production in Ceylon - No. 6. Insect and mite pests of tea in Ceylon and their control. Tea Research Institute of Ceylon, 75-85.
Jepson FP, 1926. Some preliminary notes on tea termites. Tropical Agriculturist, 67:67-79.
Pinto MPD, 1941. Some observations on the biology of the Ceylonese Calotermitidae. Indian Journal of Entomology, 8:73-105.
Ranaweera DJW, 1962. Termites on Ceylon tea estates. Tea Quarterly, 33:88-103.
Samarasinghe SM; Ahangama D; Kumar V; Vitarana SI, 1999. Volatile and non volatile compounds of the host plant affecting behaviour of the low country live wood termite (Glyptotermes dilatatus Bugnion and Popoff) of tea. Tropical Agricultural Research, 11:380-392; 11 ref.
Sivapalan P; Delucchi V, 1974. Integrated approach in tea pest control in Sri Lanka. Proceedings of the FAO Conference on Ecology in relation to Plant Pest Control, Rome, Italy, 11-15 December, 1972. Rome, Italy: Food and Agriculture Organization, 183-196.
Sivaplan P; Karunaratie AAC; Jayatilleke DGS, 1980. Clonal susceptibility and the influence of shade trees on the incidence of Glyptotermes dilatatus (Bugnion & Popoff) (Isoptera: Kalotermitidae) in tea. Bulletin of Entomological Research, 70(1):145-149
Vitarana SI, 1986. Tea Termites. In: Sivapalan P, Kulasegaram S, Kathiravetpillai A, eds. Handbook on Tea. Sri Lanka: Tea Research Institute of Sri Lanka, 143-153.
Weesner FM, 1960. Evolution and biology of the termites. Annual Review of Entomology, 5:153-170.
Distribution MapsTop of page
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