Darna trima (nettle caterpillar)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Hosts/Species Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Natural enemies
- Notes on Natural Enemies
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Darna trima (Moore)
Preferred Common Name
- nettle caterpillar
Other Scientific Names
- Darna trima ajavana Holloway
- Orthocraspeda trima Moore
Local Common Names
- Indonesia: ulat api; ulat gatal
- Malaysia: ulat beluncas
- DARNTR (Darna trima)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Arthropoda
- Subphylum: Uniramia
- Class: Insecta
- Order: Lepidoptera
- Family: Limacodidae
- Genus: Darna
- Species: Darna trima
Notes on Taxonomy and NomenclatureTop of page D. trima was first described by Horsfield and Moore in 1859 under the genus Orthocraspeda. Holloway (1986) recognized two subspecies: D. t. trima which occurs in Java, and D. t. ajavana in Sumatra, Java, Borneo, Singapore and Peninsular Malaysia. Externally, the two subspecies are identical and can only be differentiated on the basis of genitalia characteristics.
DescriptionTop of page The description below applies to the subspecies D. t. ajavana unless otherwise mentioned. This has been described by Horsfield and Moore (1859), Piepers and Snellen (1900), Kalshoven and van der Laan (1981), Holloway (1986) and Holloway et al. (1987). The general description of the Limacodidae given by Godfray et al. (1987) is a useful supplement.
Eggs are flat, scale-like, translucent and ovoid; dimensions range from 0.7 x 0.5 mm (Desmier de Chenon, 1982) to 1.5 x 1.0 mm (Tiong and Munroe, 1977).
Newly hatched larvae are 1.3 x 0.5 mm in size and are cream-coloured with distinct lateral setae (Tiong and Munroe, 1977). Description of mature larvae collected from oil palm in Peninsular Malaysia: size 15 x 5 mm; first thoracic segment dark brown, rest of body dark with a conspicuous yellow lateral marking (Holloway et al., 1987). Like other nettle caterpillars, the larva of D. t. ajavana bears rows of scoli (protuberances on which are arranged the stinging spines) on its body.
Pupation takes place within cocoons which are globular or slightly ovoid, brown and 6 mm in diameter (Tiong and Munroe, 1977).
The following description of the adults is from Holloway et al. (1987). Males 8-9 mm, females 9-12 mm. Wings are brownish-grey, traversed by series of straight, darker lines, with much fainter lines in between; in females the postmedial band between the medial and submarginal lines tends to be paler than the rest. In the male genitalia the gnathus is bifid; sections are adjacent in the typical trima from Java, separated in ajavana from the rest of the geographical range; the uncus is more deeply divided in trima; the costal process of the valve is double, the more distal portion is longer and larger, particularly in ajavana where it is more sharply angled downward. In the female genitalia the bursa copulatrix is immaculate in trima, and that in ajavana has numerous fine spines (scobinate) with a signum (spiny process) set laterally on a slight infold; the transverse pair of flanges associated with the ostium is narrow in trima, 2-3 times as broad in ajavana.
DistributionTop of page D. trima has a limited regional distribution being found in Indonesia, Malaysia and Singapore only. Records of the occurrence of D. trima in China and Thailand probably refer to other Darna species, most likely D. furva (see Holloway et al., 1987).
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.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|-Java||Present||Kalshoven and van, 1981; Waterhouse, 1993|
|-Kalimantan||Widespread||Kalshoven and van, 1981|
|-Sumatra||Present||Kalshoven and van, 1981; Waterhouse, 1993|
|-Peninsular Malaysia||Widespread||Yunus, 1966; Wood, 1968; Arulandi, 1971|
Hosts/Species AffectedTop of page D. trima has a very wide host range covering many plant families.
Growth StagesTop of page Flowering stage, Fruiting stage, Seedling stage, Vegetative growing stage
SymptomsTop of page In oil palm the lacerations caused by the early instar D. trima larvae will soon become necrotic; portions of some of these patches may eventually drop off leaving elongated holes surrounded by brown tissue. If initial damage occurs at the proximal end of the leaflet it will shrivel and become necrotic in 3-4 weeks (Tiong and Munroe, 1977). The feeding habit of later instars results in leaflets stripped to their midribs. In severe infestations entire fronds become necrotic and many of the leaflets have only their midribs with bits of lamina attached. In cocoa, repeated attacks result in dieback of lateral branches and excessive production of lateral buds (Entwistle, 1972).
List of Symptoms/SignsTop of page
|Leaves / abnormal leaf fall|
|Leaves / external feeding|
|Leaves / necrotic areas|
Biology and EcologyTop of page The life cycle of D. trima has been reported by several authors and is summarized in a table by Holloway et al. (1987). As an example, the life cycle reported by Tiong and Munroe (1977) is as follows: eggs 2-3 days, larvae 30-33 days, pupae 12-14 days and adults 7-10 days.
On oil palm, eggs are laid singly or in groups of up to four (Holloway et al., 1987) and are glued to the abaxial surface of the leaflets (Tiong and Munroe, 1977). The first-instar larva feeds on the abaxial leaf epidermis and mesophyll layer resulting in small (1.5-2.0 x 2.0-3.0 mm) lacerated patches but the adaxial epidermis is left intact (Tiong and Munroe, 1977). The second and later instars are able to consume the whole thickness of the leaflet but not the midrib. The mature larva pupates within a cocoon on the lower part of the frond near the base of the leaflets, in the leaf axils, amongst the epiphytes commonly found on the trunk, or among the debris at the base of the palm (Holloway et al., 1987). The adult emerges through a circular opening in the cocoon.
Outbreaks of limacodids have been observed to occur suddenly (Wood, 1982). An infestation of D. trima seems to start as a big pocket (Syed and Shah, 1977). Attacks may occur at particular times of the year, e.g. at the beginning of the year in Peninsular Malaysia. They are known to recur in the same locality year after year.
Rainfall is believed to play an important role in the population dynamics of many tropical insects. Increases in the populations of insect pests of oil palm are often associated with periods of low rainfall. Rainfall may help to regulate oil palm pests by making conditions conducive for the promotion of certain pathogens, e.g. non-occluded virus in D. trima (Syed and Shah, 1977).
Parasitoids and predators are an important mortality factor in the dynamics of limacodid populations and certain plantation practices can decimate these natural enemies. The detrimental effects of insecticides, particularly the non-selective ones, are well known (Syed and Shah, 1977; Wood, 1987). Less well known are the indirect effects of indiscriminate weed control or loss of ground cover due to fire; certain types of flowering weeds are necessary for maintaining the natural enemy fauna (Syed and Shah, 1977).
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
|Apanteles aluella||Parasite||Larvae||Indonesia; Sumatra||oil palms|
|small RNA viruses||Pathogen||Larvae|
Notes on Natural EnemiesTop of page Of the various species of parasitoids of D. trima found in Sumatra, Trichogrammatoidea thoseae has been singled out as being of major importance because it accounts for a high proportion of egg mortality (Desmier de Chenon et al., 1990). However, its short life cycle of 12-15 days requires that alternative hosts are available so that it may persist in sufficiently high numbers.
Other potentially effective candidates for use in biological control of limacodids are members of the tribe Euplectrini, family Eulophidae (Desmier de Chenon et al., 1990). Among the species in the tribe is Platyplectrus orthocraspedae. The larvae of this predator are ectoparasitoids of the early instars of Limacodidae and the adults prey on later instars.
Asopin bugs belonging to the genera Eocanthecona and Cantheconidea are regarded as good candidates for biological control of leaf-eating caterpillars of oil palm (Desmier de Chenon et al., 1990). These predators lay their eggs on the oil palm, and nymphs and adults live on young and mature palms (even the tall ones). They feed on a wide range of prey, including all the lepidopteran families with the exception of bagworms. Their fecundity is high and their life cycle is short at 2 months.
Ants (species unspecified) have been observed to account for considerable mortality in the host prepupae present on the ground (Young, 1971).
Viruses can give rise to epizootics which may quickly terminate outbreaks (Wood, 1968; Syed, 1971; Holloway et al., 1987). A review of virus diseases of Limacodidae is given by Entwistle (1987). Viruses identified from D. trima collected from oil palm in Sarawak were a granulosis virus and a mixture of small non-occluded RNA viruses (Tinsley, cited by Tiong and Munroe, 1977) the latter almost certainly including a member of the Nudaurelia b group (Entwistle, 1987). Three types of viral particles were identified from infected caterpillars of D. trima collected in Indonesia. They were Nudaurelia b viruses, Picornaviruses and Baculoviruses (Desmier de Chenon et al., 1987).
ImpactTop of page Although limacodids are largely polyphagous, most reported outbreaks occur on palms, in particular oil palm and to a lesser extent coconut (Wood, 1987) and sago palms (Kimura, 1979). Outbreaks of limacodids on oil palm in Malaysia were mainly reported in the mid-1960s and mid- 1970s. Wood (1976) observed that limacoids were scarce in Peninsular Malaysia, more common in Sabah and common in some estates in Sarawak. From a survey of oil palm estates in Malaysia conducted in 1990, Norman and Basri (1992) concluded that limacodids were less important in the 1980s; an average of only five outbreaks per year were recorded during the 10-year period covered by the survey.
Of the various species of limacodids known to infest oil palm, D. trima is the commonest found in outbreaks (Holloway et al., 1987). Young plantings are more severely attacked, but mature palms are also defoliated. In one outbreak it was reported that as many as 2000 larvae per frond were found and the leaf area of some palms was reduced up to 60% (Young, 1971). It has been estimated that a single larva consumes 20 cm² of leaf tissue over its entire life (Kimura, 1974).
Defoliation of oil palm by leaf-eating caterpillars can have a drastic effect on yield. In a trial in which palms were artificially defoliated, there was a 43% drop in yield a year after 50% defoliation of the upper part of the crown, followed by a 17% drop in the year after that (Wood et al., 1973a). The main effect was expressed 4-6 months after defoliation and complete recovery took some years (Wood, 1982). Even limited damage can lead to some crop loss and remedial action is beneficial, provided that measures taken are well-timed and selective in action (Wood, 1987). In immature palms the effect of artificial defoliation was less marked.
Outbreaks of D. trima have been reported on cocoa in Java, Indonesia and West Malaysia (Entwistle, 1972).
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Integrated Pest Management
Pardede (1992) found that an IPM approach integrating the application of Bacillus thuringiensis, conservation of the natural enemy population (in particular Cantheconidea javana) and collection and destruction of cocoons and adults of D. trima, can rapidly bring an outbreak under control.
Many cultural practices are modified towards enhancing the effectiveness of indigenous natural enemies (see Biological Control).
Tiong and Munroe (1977) studied the effects of spraying a virus suspension on an outbreak of D. trima in Sarawak. Dead larvae were macerated and strained to produce an inoculum containing a mixture of granulosis virus and small RNA viruses. The suspension was more effective when applied with mistblowers than with knapsack sprayers: more than 77% of the larvae died within 4 days, with almost complete mortality by the 12th day. The cost of using the virus was about 40% of that using chemical treatment; virus suspension appeared to provide a more durable control.
Another approach for utilizing viruses to control leaf-eating caterpillars infesting oil palm in North Sumatra was described by Sipayung et al. (1990). For general field treatment at least 300 g diseased caterpillars are required per hectare. During a pest outbreak a mixture of a sublethal dose of a pyrethroid insecticide (less than 10% of the normal dosage) and the virus is recommended; the pyrethroid increases the susceptibility of the caterpillars to the virus, resulting in faster infection and higher mortality.
Various workers have suggested the conservation or establishment of suitable plants to enhance the numbers and reproductive potential of parasitoids and predators. Syed and Shah (1977) believe that extensive destruction of weeds, either deliberately or inadvertently, is a major indirect cause of pest outbreaks in oil palm in Sabah. They recorded several beneficials visiting the weeds Euphorbia geniculata, E. prunifolium, Ageratum conyzoides and A. mexicanum. They argued for the maintenance of certain weeds, especially the flowering ones, to help support the natural enemy fauna. Desmier de Chenon et al. (1990) has made several recommendations in the same vein; less competitive non-crop plants, such as members of the Euphorbiaceae, should be grown in the borders of plantation blocks to provide sources of food for the parasitoids. In Sumatra larvae of the sawfly Neostromboceros luchti is an important source of food for predators like Eocanthecona furcellata and some reduviids. These sawfly larvae are frequently found feeding on the fern Diplazium asperum which is common in oil palm plantations, and the conservation of this plant should provide an alternative source of food for the predators to tide them over periods when leaf-eating caterpillars of oil palm are scarce. The tachinid Chaetexorista javana with its high fecundity, good searching ability and wide host range can be a very useful parasitoid. However, the adults like to feed on flowers in sunny situations and this feeding is necessary to enable their eggs to mature. The lack of suitable flowering plants in sunny locations should be rectified in oil palm plantations. Pardede (1992) recommends the planting of Pueraria javanica [P. phaseoloides] in young oil palm plantings. In addition to its other beneficial effects, this leguminous cover crop acts as a host for caterpillars of Lamprosema [Omoides] diemenalis, which in turn, is an alternative prey for Cantheconidea javana, an important predator of D. trima.
Improper use of insecticides has been repeatedly blamed for causing outbreaks through their effect on the natural enemy fauna (Wood, 1971; Syed and Shah, 1977). Rational use of insecticides is achievable through: (1) early detection of infection so that control can be effected when the pest population is still restricted to small areas; (2) monitoring the pest population to time insecticide application when the stage most vulnerable to insecticides predominates; (3) permitting and encouraging the operation of natural mortality factors whenever possible. A decision to implement chemical control should preferably be based on some threshold level (see Field Monitoring/Economic Threshold Levels). Chemical control should be applied when most of the eggs have hatched and while the larvae are in the early stages of development (Wood, 1987). The area sprayed should include the lightly infested field margins.
A wide range of insecticides are effective against limacodids and a comprehensive list is given by Wood (1987). Insecticides chosen should have a selective action so that effective control is achieved with minimal effect on the natural enemies. Selectivity can be achieved through specificity, residual action, and route of uptake. Examples of insecticides that achieve selectivity through specificity and that are known to be effective against limacodids are those based on Bacillus thuringiensis and insect growth regulators. Organophosphates such as trichlorfon and quinalphos have a certain degree of selectivity because of their relatively short residual effect. Regarding route of uptake, systemic insecticides are suitable for the purpose of achieving selectivity in oil palm. As well as its selectivity, trunk injection has a number of advantages (Khoo et al., 1983). Ground spraying using trichlorfon is popular (Wood, 1987; Norman and Basri, 1992) although there are suitable alternatives such as leptophos, quinalphos and aminocarb (Wood et al., 1977). Aerial application, often of trichlorfon, has been used on a number of occasions to control outbreaks of leaf-eating caterpillars in oil palm. In general, aerial application is not a popular option in Malaysia (Norman and Basri, 1992). The pros and cons of this method of application have been discussed by Wood and Nesbit (1969) and Wood et al. (1973b).
Field Monitoring/Economic Threshold Levels
Various systems of field monitoring are practised (Wood, 1976). Wood (1987) recommends a two-stage system. In the 'alert' stage, field workers keep a look-out for frond damage, and if it is detected the area is examined to determine if the damage is caused by an active population of the pest. If so, the 'enumeration' stage proceeds to estimate the number of caterpillars on sampled fronds.
As a example of a system of field monitoring in practice, Hoong and Hoh (1992) carried out 'detection' followed by 'census'. Detection entails monthly monitoring of palms along harvesting paths for presence of pests; in addition workers in the field are encouraged to report the occurrence of pests. Soon after a pest is detected a census is carried out to determine the pest species, its abundance and distribution. Usually, one palm in every ten within a row and one row in every ten is selected; one frond is sampled from each of the upper, middle and lower levels of the canopy. Wood (1987) discussed the practical difficulties of deciding on threshold levels. Nevertheless, levels of 10-12 larvae per frond are set for the larger species and 30-80 larvae for the smaller species. For D. trima, the 'critical pest hazard level' has been arbitrarily set at 10 larvae per frond (Hoong and Hoh, 1992). If this level is exceeded a detailed assessment is immediately carried out to determine the predominant stage and health of the pest so that control can be timed for best results. Control measures are implemented when the number of healthy larvae exceeds the critical level.
ReferencesTop of page
APPPC, 1987. Insect pests of economic significance affecting major crops of the countries in Asia and the Pacific region. Technical Document No. 135. Bangkok, Thailand: Regional Office for Asia and the Pacific region (RAPA).
Arulandi K, 1971. Observations on and control of leaf-eating caterpillars in oil palm. In: Wastie RL, Wood BJ, eds. Crop Protection in Malaysia. Kuala Lumpur, Malaysia: Incorporated Society of Planters, 116-122.
IPPC, 2006. IPP Report No. NL-1/4. Rome, Italy: FAO.
Piepers MC; Snellen PCT, 1900. Enumération des LepidoptFres HeterocFres receuillis à Java. Tijdschrift voor Entomologie, 43:12-106.
Syed RA; Shah S, 1977. Some important aspects of insect pest management in oil palm estates in Sabah, Malaysia. In: Earp DA, Newall W, eds. International Developments in Oil Palm. Kuala Lumpur, Malaysia: Incorporated Society of Planters, 577-590.
Waterhouse DF, 1993. The Major Arthropod Pests and Weeds of Agriculture in Southeast Asia. ACIAR Monograph No. 21. Canberra, Australia: Australian Centre for International Agricultural Research, 141 pp.
Wood BJ, 1968. Pests of Oil Palms in Malaysia and Their Control. Kuala Lumpur, Malaysia: Incorporated Society of Planters.
Wood BJ, 1982. The present status of pests on oil palm estates in South-east Asia. In: Pushparajah E, Chew Poh Soon, ed. The oil palm in the eighties. A report of the Proceedings of the International Conference on Oil Palm in Agriculture in the Eighties held in Kuala Lumpur from 17-20 June 1981. Volume II. Incorporated Society of Planters Kuala Lumpur, West Malaysia, 499-518
Yunus A, 1966. Pests of oil palm. In: The Oil Palm in Malaya. Kuala Lumpur, Malaysia: Ministry of Agriculture and Cooperatives, 87-95.
Distribution MapsTop of page
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