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Forest Invasive Species in Lao PDR

Thongphath Leuangkhamma and Vongdeuane Vongsiharath
Department of Forestry


The Lao People’s Democratic Republic (Lao PDR) is a land-locked country, located in the centre of the Indochina Peninsula, sharing borders with the People’s Republic of China in the north, the Socialist Republic of Viet Nam in the east, the Kingdom of Cambodia in the south, the Kingdom of Thailand in west and Myanmar in the northwest. The total land area of the country is 23.68 million hectares, of which about 70 percent of the total area is hilly and mountainous, mostly in the northern part of the country. The altitudes of the country vary from 300 metres to more than 2 500 metres.

The current population in Lao PDR is 5.2 million (2000 census), with an annual growth rate of 2.5 percent. Lao PDR is a multi-ethnic society. The major ethnic and linguistic groups have been broadly classified as Lao Lum (lowland Lao) 56 percent, Lao Theung (midland Lao) 34 percent and Lao Sung (upland Lao) 10 percent. More than 70 percent of the population lives in rural areas. The majority are subsistence farmers, whom are highly dependent on forest resources for their livelihoods. In terms of socio-economic development, Lao PDR is the least developed country in Southeast Asia, with an average income of US$380 per year/capita.

Forest situation

Lao PDR has a relatively large forest area per capita, compared with neighbouring countries. However, destruction and degradation of natural forests are clearly evident and are regarded as critical issues for the country. Degradation refers to a decline in the quality of forest in terms of species distribution, reduced biodiversity, loss of commercial value, and interference with habitats and food chains. Destruction refers to the complete removal of forests and transformation into other land use categories.

Statistics on destruction rates show that forest-covered areas in Lao PDR have been reduced from 16.5 million hectares (70 percent of total land area) in 1965, to about 14 million hectares (60 percent) in 1974 (Myers, 1980) and further down to 12 million hectares in 1981 (FAO, 1990). In 1989, the remaining forested land was approximately 11 million hectares (47 percent) (MAF, 1992).

Forest pests in Lao PDR

Teak (Tectona grandis L.) plantations are attacked by a number of insects. Two defoliators, Hyblaea puera (popularly known as teak defoliator) and Eutectona machaeralis (also known as teak skeletonizer), are the most important invasive species for teak in Lao PDR. Larvae of H. puera feed on the entire leaf - leaving only the major veins intact - thus qualifying for the name skeletonizer. Of the two species, H. puera is the more serious pest, because it feeds on young leaves during the early part of the growing season, whereas E. machaeralis feeds on old leaves not long before natural leaf fall. The outbreak season for H. puera occurs in early-May when teak develops new leaves. The warm temperatures enable the insect to complete its life cycle by late-July. The results of a study by Chansomphou (2000) indicated that H. puera preferred to attack young teak plantations. The population density of larvae was highest in the top stratum of the tree, although after feeding on leaves the larvae descend to the lower strata and ground for more feeding and pupation. Its life cycle is completed in approximately 15 to 20 days. Male moths live longer than female moths; the average lifespan of an adult male is 13.3 days, while that of a female is 8.8 days. The adult female usually dies after oviposition.

Defoliation does not kill teak trees, but it reduces tree growth. Study results show that natural defoliation by H. puera caused an average loss of 44 percent in potential volume increment in 4-9 year old teak plantations, while E. machaeralis had no significant impacts on growth. Although it has not yet been possible to quantify the effects in terms of volume loss over an entire rotation (60 years), there are indications that H. puera has a substantial impact on wood production.

Management efforts.

The first legislative efforts by the government concerning the protection of flora and fauna are stated in the Forestry Law (1996), Article 43 and 44 as follows:

Article 43: Plant and Wildlife Protection

Plant and wildlife species found in the forest, which are scarce, rare, endangered or have special value, must be protected in the same way as those found inside conservation forest. Forest management agencies, in coordination with local administrative authorities, are to issue specific regulations for this purpose. The export of these kinds of plant or animal species is forbidden, except with special permission from the Ministry of Agriculture and Forestry.

Article 44: The Prevention and Suppression of Disease and Insect Pests

Concerned forest management agencies are responsible to investigate the origins and spread of disease and insect pests and to organize and coordinate protection and control in forest areas for which they are responsible. Concerned agencies must also identify disease free seeds and/or seedlings, develop disease free and protection zones, and establish an organization for certifying the production, distribution and use of disease free plant varieties.

In order to prevent the spread of tree diseases and insect pests the import or movement of infected plants is prohibited. Following the issuance of the Forestry Law, the Ministry of Agriculture and Forestry issued several legal documents relating to monitoring and control of forest invasive species, e.g. Regulation on Long-Term Management of Tree Plantation (Article 8). Although laws and regulations on monitoring and control of removals (import and export) of flora and fauna are in place, actual implementation is still far from satisfactorily due to inadequate technical and financial support.

Institutional arrangements related to invasive species

The Science, Technology and Environment Agency (STEA) has two departments dealing with monitoring and control over the environment. The Department of Environment is responsible for field implementation of environmental impact assessments (EIA). The Environment Research Institute is involved in studies involving the environment. A major role of the STEA is to regulate imports and exports and to provide Certificates of Origin and to ensure that imported/exported species will not have any negative impact on the environment.

The Ministry of Agriculture and Forestry (MAF) is the designated forest management authority. There are several departments and institutions under this ministry:

As such, the main invasive species responsibility of MAF lies in monitoring and control of imports and exports and providing the necessary permission for importing and exporting. The Ministry of Finance (Customs Department) - in cooperation with the police - is the enforcement authority. The main responsibility of this authority is to control the import and export of species at international checkpoints.


The Government of Lao PDR is pursuing a policy on conservation and protection of existing natural forests, while stimulating the establishment of tree plantations in order to increase forest cover. The purpose of tree plantations has mainly been for commercial production. Although a number of native tree species have been planted, the introduction of exotic fast-growing tree species is now becoming more fashionable, especially in lowland areas with access roads. Despite the introduction of exotic tree species to Laos, very little research has been conducted on the impact of these introductions.

Defoliators are the main pest species attacking teak plantations throughout the country. Additional collaborative research on the management and control of these pests is needed, particularly with other countries in the region.

The Government of Laos is monitoring the import and export of flora and fauna. However, protection against invasive species is inadequate, due to scarcity of necessary inputs such as staff, funding, technology, information etc. Consequently, there is a need for cooperation with other neighbouring countries and international organizations.

Forest invasive species country paper - Nepal

Madhusudan Bista and Mahendra Prasad Chaudhary
Ministry of Forests and Soil Conservation Plant Quarantine Service


Nepal is a land-locked, mountainous country located along the southern slopes of the Himalayas between India and China. Situated at the junction of the Indomalayan and Palaearctic Biogeographic Realms, the land rises dramatically from altitudes of less than 100 metres in the tropical Terai in the south, to the highest point on the earth's surface (8 848 metres) on the edge of the Tibetan plateau, within a distance of less than 150 kilometre. It has an area of some 14.7 million hectares, of which the forest area covers 39.6 percent of the total area. The total population of the country is 23.2 million with an annual growth rate of 2.2 percent (2001 census). The economy is still largely rural and agrarian.

More than 70 percent of the people of Nepal are still largely dependent on forests for goods and services. Forest-trees form an integral part of rural livelihoods in Nepal. Forests dominate not only the landscape, but also the way people live. Forests provide 75 percent of total energy consumed in the country and more than 40 percent of livestock nutrition from fodder (MPFS 1988). Forests also play a dynamic role in the protection of fragile mountains and maintain complex and diverse ecosystems. (Thomson 1995).

Hill forest is the key resource in the Nepalese economy, providing fodder, timber and fuelwood. Its degradation has long been a concern. IDA's Forestry Sector Review of 1988 identified two major problems, which are still relevant today, a) rural energy crisis, and b) the environment deterioration caused by over-utilization of forests. The increasing population is exerting heavy pressure on the forest resources of Nepal, (Table 1). If this trend continues, then the forest condition of the country and species diversity will be badly affected. To counteract this trend, Nepal has established plantations of both exotic and indigenous species.

Table 1: Forest area decline and population growth in the last two decades




Forest area

43 percent

37.4 percent

29 percent


13.7 million

15 million

21.8 million

(Source: HMGN 1968, 1974, 1998,a and 1998,b)

Invasive species in Nepal

According to the IUCN definition, "Invasive species are alien species that threaten biological diversity". Invasive species include pests, insects and diseases. People are the main source for the introduction of alien species either by accident, deliberate action and/or imports. These species often have a high dispersal ability and adaptability, which enables them to rapidly acclimatize quickly to new habitats. Due to these abilities, invasive species compete with native species for resources such as nutrients, soil moisture, sunlight and space, often resulting in the loss of naturally occurring species.

His Majesty's Government of Nepal (HMGN) became a member of the International Protection Commission for Southeast Asia and the Pacific Region in 1956. In 1972, the Plant Protection Act was passed, which has been enforced throughout the country since 1974.

Probably the most widely distributed invasive species found in Nepal are Eupatorium adenophorum, E. odoratum and Lantana camara. This last species is easily dispersed by birds, which eat the fruit. A more comprehensive overview of invasive species in Nepal is provided in Table 2.

There are a number of other species noted for their invasive nature. Ageratum houstoniamum is an unwanted species growing as a weed, especially common on marginal agricultural land. Mikania micrantha is another weed with similar characteristics. Similarly, water plants like Eichornia and Nelumbius will cover ponds if not managed.

The systematic documentation of the flora of Nepal is a continuous process. Although thousands of plants have been collected and documented, a substantial number of plants have yet to be identified. It is quite possible that additional invasive species could be identified during this process.

Table 2: Ten most important invasive species in Nepal


Scientific Name

Local name



Eichornia crassipes


South America


Eupatorium adhenophorum




Eupatorium odoratum


Tropical America


Lantana camara

Masinu kanda

Central America


Mikania micrantha


Tropical America


Ipomea carnea


South America


Hyptis suaveolens


South America


Parthenium hysterophorus


Tropical America


Argemone mexicana


Tropical America


Ageratum conyzoides


South America

Additional threats could come from the various species introduced for Nepal’s plantation programme. The most import exotic plantation species include Pinus patula, Leucaena leucocephala and Eucalyptus camaldulensis. The ability of these species to thrive in Nepal, outside plantations, has not been well documented. Other indigenous species used in plantations have been Pinus roxburgii and Dalbergia sissoo. Infestation by the Leucaena psyllid (Heteropsylla cubana) and associated die-back in Leucaena leucocephala and Dalbergia sissoo presented one of the most serious threats to trees in Nepal during the late-1980s.

Documentation, control and other important activities

Many valuable plantation species have been introduced to Nepal. When plantations are established, records should be made of information such as the provenance derived from, when and where the plantation was established, and it should be mapped. This system would provide significant benefits in monitoring and reacting to invasive species infestations. To date, this documenting process has been very poor in the country, and it is therefore essential that a survey be conducted so that the introduction and the distribution of plantation species can be identified and mapped with full details.

Conclusions and recommendations

Nepal is in the early stages of developing a national strategy for the control and management of alien invasive species. The following issues have been identified as requiring additional work in the future:


DFRS (1999). Forest Resources of Nepal. Department of Forest Research and Survey, Forest Resources Information Systems Project, Babarmahal, Kathmandu, Nepal.

HMGN (1998). Statistical Pocket Book. Central Bureau of Statistics, National Planning Commission Secretariat, Kathmandu, Nepal

MPFS (1988). Master Plan for the Forestry Sector. Ministry of Forest and Soil Conservation of Nepal.

Thomson W. (1995). Using and Protecting Nepal's Forest Genetic Resources. In: Tree Breeding and Propagation News, Volume 4, No. 1.

A status report on some invasive forest species in Papua New Guinea

Robert Kiapranis and Patrick Nimiago
PNG Forest Research Institute, Papua New Guinea


Papua New Guinea, the eastern part of the island of New Guinea has a total land area of about 46.4 million hectares, including the islands of the Bismarck Archipelago and Eastern Milne Bay. Located just below the equator, it experiences a humid tropical regime with southeasterly winds in the middle of the year and the northwesterly following soon after. There is distinct wet and dry season associated with these two climatic regimes, although, variations in rainfall do occur, which are closely associated with the local topography. The country is very mountainous but also has vast areas of flat plains, large and long meandering river systems, numerous active volcanoes and about 70 percent of the land is covered with dense forest. The biological diversity is among the richest in the world.

For centuries, man has influenced and modified the vegetation through subsistence farming and hunting. Over the last 40 years, large areas of forests have been cleared by local inhabitants to cultivate food and cash crop plantations. In addition to human influences, natural phenomena such as cyclones, earthquakes, fires and volcanic eruptions have also affected large areas of forests, thus influencing their composition.

Invasive species are common in disturbed forests and modified habitats such as plantations, logged-over areas, shifting cultivation and sites affected by fires. Insects are the most devastating invasive group in both natural and planted forests and these are classified as minor or major pests according to the extent of damage caused to logs, lumber and living trees.

The full extent and status of invasive species affecting natural forests, farmlands, river systems and local plantations in PNG is unknown. This report covers observations and investigations done on selected invasive plant species and major pests and diseases of, particularly, commercial trees in plantations and natural forests of current economic importance.

Invasive plants

Most invasive species are opportunists, ecologically categorized as colonizer or pioneers with the ability to compete and establish successfully in various different environments. Natural and manmade disturbed sites provide opportunities for the increase of invasive species. In disturbed forests, where resources such as light are abundant, the germination of a large number of invasive species is triggered. Trees regenerating in open forest areas initially face severe competition from pioneer plant species. Many of these species are grasses, herbs and shrubs that sprout from dormant seeds.

The invasive plant species selected and presented here are species that appear to be widespread and dominant locally, thus suppressing the development of other local species. Many of the species covered are herbs, shrubs and grasses, the presence of which poses a threat to the regeneration of other plant species, particularly those of economic value. Henty and Pritchard (1988) published a weed species handbook that covers mainly ferns, herbs, shrubs, grasses and sedges that are widely distributed and invade open areas like roadsides, cultivated fields, gardens and pastures. Some of these species are referred to in this paper.

In regrowth forests and fallow gardening sites, Piper aduncum (Piperaceae) is a common shrubby weed. This weed is native to Central America and may have entered Papua New Guinea along with shipped logging equipment. It grows to about 7 metres in height and produces numerous small seeds. P. aduncum is now widespread and is persistent in many old garden sites where it effectively shuts out other vegetation. The other tree species that has established itself in many coastal provinces is Spathodea campanulata (Bignoniaceae). This species is native to Africa and it is referred to as "African tulip". It was introduced as ornamental tree because of its beautiful red flowers. It grows from seeds, cuttings and coppices very aggressively. Because of its regenerative ability, it easily replaces local species over time, wherever it grows. Many examples of such situations can be observed in coastal areas such as the Gazelle area in East New Britain Province and most areas around New Ireland Province.

The leading families with the most weed species are Asteraceae (27), Poaceae (14), Leguminosae (10), Amaranthaceae (9), Cyperaceae (6) and Lamiaceae (6). The common species are: Cyperus bifax, C. brevifolius, C. cyperoids, C. distans and C. rotundus (Cyperaceae); Euphorbia geniculata, E. heterophylla, E. hirta and E. thymifolia (Euphorbiaceae) and Polygonum barbatum, P. nepalense, P. orientale and P. strigosum (Polygonaceae).

Asteraceae are most abundant in open areas and are unwanted weeds in pastures and gardens. Species of this family that invade in plantations include, Eupatorium odoratum, a naturalized shrub, Wedelia biflora, a straggling shrub, and Youngia japonica, an introduced perennial herb.

Some grass species are weeds in many places, where they have rapidly colonized open areas - such as cleared sites, after burning. A common weedy grass in Papua New Guinea is Imperata cylindrica; an invader of disturbed areas, widely occurring in anthropogenic grasslands and abandoned shifting cultivation sites. Its presence in some plantations that are located in open valleys such as the Markham valley is a threat to cash crops and pastures. It has taken over large open areas in savannah grasslands in the Southern region and many dry areas of the Markham valley where regular burning has occurred. Imperata’s success is attributed to production of many small seeds with ability to withstand adverse conditions until germination, and their spread through rhizomes.

Some of the weedy species that have spread very rapidly over the last twenty years included three "nilgras" species: Mimosa invisa, M. pudica and M. pigra. These have localized in many areas, especially along roadsides, in pastures, and opened forest areas. In pastures, they prevent regeneration of palatable species thus limiting livestock grazing areas. The species Solanum erianthum, S. nodiflorum and S. torvum (Solanaceae) also occur in pastures and are regarded as harmful weeds to livestock on grazing lands, though not serious threats to other vegetation. Merremia peltata (Convolvulaceae) is a twining, creeping herb with round peltate leaves and a stout stem, often reaching 10-15 metres in height. This species is widespread and is an invader of forest clearings, often suppressing other important vegetation. Its presence and dominance can lead to poor representation of native species regenerating in an area.

Most control measures for individual weeds require chemical use that is not only expensive, but can be environmentally hazardous. However, weeding is still practiced in gardens, and slashing is carried out in plantations to reduce competitive vegetation - regardless of being labor-intensive and time-consuming efforts.

Major insect pests

Agrilus opulentus Kerr. (Coleoptera, Fam. Buprestidae)

Agrilus opulentus is an important pest affecting growth and survival of Eucalyptus deglupta and Syzygium spp. A. opulentus is widely distributed in the mainland of Papua New Guinea and the island of New Britain. The beetle naturally feeds on the cambium of many water gum trees. One of these water gum trees is Eucalyptus deglupta (Myrtaceae). The attack on E. deglupta is important for two reasons:

According to Mercer (1985), beetle eggs are deposited in crevices in the lower trunks. The hatched larvae bore into the inner bark and feed in a zigzag manner, disrupting translocation. Larvae bore lightly into the sapwood to pupate. Adult beetles emerge and fly to tree crowns, where they mate.

The attack appears to be confined to unhealthy trees under environmental stress with low sap content. Vigorous trees produce copious sap, which is sufficient to drown and kill the larvae. Vigorous infested trees will decline in growth, but initially stressed or suppressed trees gradually die after attack. Mercer (1985) reported that 23-25 percent of five-year old trees lost at least 1 centimetre of diameter at breast height in annual growth increment.

Lymantria ninayi B. Br. (Lepidoptera, Fam. Lymentriidae)

Pinus patula (Pinaceae), originally from Central America, has - despite poor soil conditions - been successfully planted in plantations in the highlands of PNG, where the climate is cooler. Early reports revealed that Lymantria ninayi, a species of moth, was present in various locations in the highlands and damage to P. patula trees was also reported by Gray and Wylie (1974). Serious defoliation occurred in the Lapegu Plantations in the Eastern Highlands Province between 1975 and 1978, over an area of 200 hectares. More than 25 percent mortality was recorded (Roberts, 1988). A recent outbreak of L. ninayi occurred in 1996, in Faiyantina, affecting 8-10 year old P. patula trees. However, a particular group of insect viruses, known as nuclear polyhedroses, was believed to be the main natural agent that brought about an evident crash in Lymantria ninayi populations. The control and management of L. ninayi is possible with chemical sprays and biological controls, but the chemicals are generally too expensive to obtain.

The females lay their eggs in patches on the bark of trees. After hatching, caterpillars feed on the foliage of the tree, the younger on new needle leaves and older caterpillars on mature leaves (Schneider, 1999).

The moth undergoes a three-stage life cycle. Adult females are flightless, but release pheromones to attract flying males for mating. After mating the female moves down the tree and lays eggs on the underside of branches. Within a period of nine to thirteen days, caterpillars emerge and move to feed on the needles, mostly at night (Mercer, 1985). The caterpillars develop and go into a pupa stage, among bundles of needles. Males emerge first, while females, who usually lack wings, emerge later. The life cycle is about four months, with three generations in a year. L. ninayi is spread when the small emerging caterpillar is blown away on strands of silk, while making their way to the tops of trees.

Lymantria ninayi alternatively feeds on local tree species such as Lithocarpus spp., Castanopsis spp., Casuarina papuana and Casuarina oligodon present in surrounding natural forests.

Coptotermes elisae Desneux (Isoptera, Fam. Rhinotermotidae)

Araucaria cunninghamii trees from Bulolo plantation have been attacked by Coptotermes elisae. This termite is becoming a major problem in second-rotation plantations. The mode of attack is usually via the roots. The termite tunnels through the stem, causing live trees to fall. Trees under stress and those with injuries sustained from thinning are easy targets. The termites are very active in wet periods, when the soil is waterlogged and allows for easy movement to construct galleries. Preventive measures include planting trees in moderately moist sites, and minimizing or avoiding thinning damage. Attempts have been made to locate and destroy queens, but failure to keep up with re-invasion has rendered this exercise impractical as a means of eradicating this pest.

Mastotermes darwiniensis Froggat (Isoptera, Fam. Mastotermitidae)

This species is a subterranean termite that was introduced to Lae, from Australia, among heavy fighting equipment and supplies, sometime during WWII. It has been observed killing live Araucaria hunsteinii, Ficus spp. Dracontamelon dao, and Mesua spp. within the vicinity of the Forest Research Institute (FRI). Termites enter from the base of trees and bore multiple tunnels, causing trees to defoliate and die. The same termite is now within the FRI building, causing extensive damage to wooden doors, bookshelves and other materials with cellulose makeup. There are no prescribed eradication measures in place and the institute is struggling with how to deal with this problem, apart from the costs of maintenance to the building. This termite is slowly but surely spreading to reach other parts of Lae.

Nasutitermes novaumherbridarum N. and K. Holmgren (Isoptera, Fam. Termitidae)

This termite is known to attack injured or stressed E. deglupta trees in plantations in Madang province. Trees with riddled wood take a comparatively short time to die. Most fall as a result of windthrow.

Vanapa obertthuri Pouillande (Coleoptera, Fam. Curculionidae)

This weevil species is a pest of A. cunninghamii plantations in the country. Eggs are deposited under loose bark or in tree wounds. The hatched larvae bore through the cambium causing live trees to die.

Main tree diseases

Phellinus noxius (Corner) G.H. Cunn

Phellinus noxius is a pathogen involved in heart rot disease of Araucaria cunninghamii and Eucalyptus deglupta. Trees of all ages are vulnerable to attacks from Phellinus noxius. A tree may appear healthy from outside appearance, but after felling the disease may be detected. In Araucaria cunninghamii plantations, the fungus is found in debris. Spores are transferred to standing trees through scratched bark and ripped roots. There is no control for the disease except to properly monitor thinning and pruning operations to minimize damage to trees. Eucalyptus deglupta in plantations and natural stands is also susceptible to a similar heart rot disease caused by P. noxius. The ability of this tree to self-prune by shedding branches makes it easy for fungi to enter through the rotten scars left by fallen branches and spread within the tree. Although P. noxius is suspected to be the pathogen responsible for heart rot in E. deglupta, other site factors have also been considered as potential causes, but not fully investigated. Mukiu (1992) suggested low content of polyphenols within the heartwood as a causal factor contributing to low resistance against pathogens. With E. deglupta, susceptibility to heart rot is assumed to be genetically inherited and the best approach to contain the problem is to selectively breed resistant trees.

Acacia mangium and Acacia auriculiformis are two robust species known to perform better than most tree species on impoverished sites. Both are used as reforestation trees in lowlands and coastal plains. Acacias are susceptible to root rot disease, where Phellinus and Ganoderma are believed to be involved in infection (Mukiu 1992). Infected and overlapping roots of adjacent trees spread this fungus and ultimately cause trees to fall.

Valsa sp. canker disease

Terminalia brassii occurs naturally on wet soil sites in Bougainville and the Solomon Islands. It has been introduced as a plantation tree to many coastal areas of PNG. The most important disease causing bark necrosis and dieback in T. brassii is a canker known as Valsa canker. The suspected pathogens are generally identified as being members of the Cryphonectria or Diaporthe genera, but these deaths may also result from infection by Valsa eugeniae from family Diaporthaceaceae (Mercer, 1987). Entry to the cambium is mainly through roots, split bark and hollows in trunks or branches. Symptoms of this disease are bark splits associated with copious black exudates. Incidences of canker disease associated with poor selection of sites were noticed in Gogol, Kerevat and Lae (Mercer, 1985). Trees under environmental stress or in water deficit areas allow the proliferation of this fungus; thus plantation sites must be carefully selected prior to planting as a control measure.

Phytopthora root disease

Pine trees from plantations often suffer from root rot caused by Phytopthora cryptpogea, and P. cinnamomi. Pine trees usually show early chlorosis followed by death. Pathogens are suspected to be present in the soil used at nurseries and are introduced to the field after planting. Fumigating or heating soil prior to tubing the seedlings can control this. Phytopthora cinnamomi is suspected of involvement in extensive die back of Nothofagus forests in Mt Giluwe, in Southern Highlands province.

Nothofagus occur in montane forests between 1000-3000 metres above sea level and around 750 metres in Kutubu and New Britain. At Mt. Giluwe, in the Southern Highlands, Nothofagus is dominant and forms pure stands, with two species, N. pullei and N. grandis being harvested commercially. Forests appear unhealthy when trees develop dead branches and upper crowns die while standing. Some reports suggest the presence of Phytopthora cinnamomi in the soil as partly responsible for the scenario (Ash 1988; Mukiu 1992). The exact cause remains unresolved with an assumption that multiple factors related to environmental conditions are responsible. Insects and pathogens, definitely contribute to this phenomenon.

Nectria haematococca

Anisoptera thurifera belongs to the Dipterocarpaceae family and is a major commercial tree, naturally occurring in some lowland forests. This species can also be regarded as an invader of logged sites where it surpasses other species as observed in Oomsis, Morobe province. It is a canopy tree, fast-growing and grows gregariously in good straight forms, which are ideal silvicultural characteristics. However A. thurifera stands in Oomsis, Morobe province have been invaded by fungus, Nectria haematococca, causing canker on trees. A survey by Nalish Sam, in 1995, indicated 63 percent of trees had canker (Nimiago and Nir, 1977). Although trees have no mortality problems at this stage, such a high incidence may have significant negative impacts on future crops.

Quarantine and phytosanitary regulations

The National Agriculture Quarantine Inspection Authority (NAQIA) of Papua New Guinea is the legal institution that administers, manages and monitors the country’s laws and regulations on quarantine and phytosanitary status of imported and exported goods. The most important pieces of enforceable legislation are the Plant Disease and Control Act 1953 and the National Agriculture Quarantine and Inspection Authority Act 1997.

NAQIA maintains an office at all major airports and seaports throughout the country. All importers of food products, agricultural products, supplies and equipment, biological products and equipment, and other general merchandise, are required to declare their goods to the authority for inspection. The authority also undertakes inspections of vessels (ships and aircrafts) on arrival at major ports in PNG and it also inspects all incoming parcels at major post offices. Any materials contaminated with a biological pest or disease are immediately isolated and destroyed. Other materials may be quarantined for a required period before they are released. The authority also maintains close contact with other quarantine services in neighbouring countries and takes necessary steps to prevent pests and diseases from other countries entering Papua New Guinea.

NAQIA also collaborates with the Australian Quarantine and Inspection Services (AQIS) on two regular surveys in PNG:

Legislation is mainly focused on restricting the deliberate introduction and spread of invasive species in the country. Laws may be less effective in situations where introduction and spread are accidental. This requires a more vigilant effort from monitoring programmes. Regular surveys and monitoring programmes are carried out for specific pests. For instance, the fruit fly problem in the East New Britain Province, the outbreak of Locusta migratoria in the Markham valley, the spread of Salvinia molesta along waterways within the Sepik river systems, and the spread of invasive weeds such as Mimosa pigra and Chromelena ordorata. Posters and information leaflets on these pests and invasive species are periodically produced and distributed for public awareness.

Key institutions involved in invasive species

NAQIA is the legal institution in Papua New Guinea required by law to execute the Plant Disease and Control Act and the National Agriculture and Quarantine Inspection Act. The National Agriculture Research Institute (NARI), the Department of Agriculture and Livestock (DAL) and the Papua New Guinea Forest Research Institute (PNGFRI) are other institutions that participate in assessment surveys, and wherever else their services are required.

Conclusions and recommendations

This report covers some of the common invasive forest species that are known in the forestry and agriculture sector. There are other invasive species considered to be weeds and insect pests that are not mentioned here. On the basis of this report, the following conclusions can be drawn:

The authors would like to make the following recommendations:


Ash J. 1988. Nothofagus (Fagaceae) forests on Mt Giluwe. New Zealand Journal of Botany, 26: 254-258.

Clunie N.M.U. 1978. The Vegetation. Pp. 1-11 in Handbook of the flora of Papua New Guinea (J.S. Womersley, ed.). Melbourne University Press, Melbourne, Australia.

Gray B. and Wylie F.R. 1974. Forest Tree and Timber Insect Pests in PNG. II. Pacific Insect, 16(1): 67-115.

Henty E.E. and Pritchard G.H. 1988. Weeds of New Guinea and their control 4th Edition. Botany Bulletin N0.7 Division Of Botany, Department of Forests, Papua New Guinea.

Johns R.J. 1986. The instability of the tropical ecosystems in New Guinea. Blumea 34: 341-371.

Mercer W.L.C. 1985. Pest and diseases in Papua New Guinea forest plantations. Seminar Proceedings. Future of Forestry in Papua New Guinea, PNG University of Technology.

Mercer W.L.C. 1987. The influence of site quality on the incidence of Valsa species canker on Terminalia brassii in Papua New Guinea forest plantations. Seminar Proceedings. Proceedings of 11th International Congress of Plant Protection. Manila. Philippines

Mukiu J. 1992. Some tree diseases in Papua New Guinea. The Mycologist, 6(4): 203-204.

Nimiago P. and Nir E. 1977. A silviculture demonstration trial undertaken in logged-over forest at Oomsis, Morobe Province. Silviculture Techniques: Series Report N0: 1. Papua New Guinea Forest Research Institute, Lae 39 pp.

Schneider F.M. 1999. Entomology: A text book for students, agriculturalist and foresters in Papua New Guinea. Training Manual No. 19. Bulolo University College, Papua New Guinea. 312 pp.

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