Insect Management in Commercial Forestry

Presented by

Pabasara Gunawardane

All parts of a tree are vulnerable to attack by pests. Pest damage can range from slight damage that has no effect on the value of the harvested product, to severe damage that stunts or kills the trees or reduces their market value. Tree pests include insects and mites, diseases, weeds, vertebrates, and nematodes. 

Insects belong to the kingdom Animalia and in the phylum Arthropoda. Insects are categorised under the class Insecta. More than one million different species of insects have been identified. Some insects of orders such as Coleoptera, Lepidoptera, Hymenoptera, Hemiptera, Isoptera and Orthoptera are considered as pests in plantation forestry. Tectona grandis, Eucalyptus sp. Swietenia macrophylla, Santalum album and Aquilaria sp. are some of the major plantation species in Sri Lanka and the world

When consider about the insects, at least 174 species of insects have been recorded from the living teak tree. Most of these insects are not economically significant in their attacks. Teak defoliator (Hyblaea puera) causes severe defoliation and, hence, reduce growth rate of the tree. The larva of leaf skeletonizer (Eutectona machaeralis) feeds on the green leaf tissue between the network of veins, leaving the skeleton of veins intact. The most important stem borer in young teak plantations is Zeuzera coffeae. Another stem borer is Xyleutes ceramicus and it is found in older Teak plantations.

More than 920 species of insects are associated in Eucalypts. The most common pest problem of exotic eucalypts is mortality of saplings caused by root-feeding termites. Eucalyptus Gall Wasp has been reported in Sri Lanka in 2010 and it was successfully controlled by natural enemies of the pest insect.

Mahogany shoot borer (Hypsipyla robusta) outbreak is the most severe pest attack found in Mahogany. It is suggested that the relatively low level of attack in Sri Lanka may be due to good overhead shade where the trees have been planted.

Zeuzera coffease (red borer) Indarbela quardinotata (bark-feeding caterpillar) and Aristobia octofasiculata (heartwood borer) are some of the pests causing considerable damage to living Sandalwood trees. In agar plantation no such serious pests and diseases have been observed. A leaf-eating caterpillar (Heortia vitessoides) is considered to be the most destructive pest causing damage by complete defoliation of agar plantations. When compare with the other countries of the region the status of the pest outbreaks in forest plantations are lower in Sri Lanka.

In earlier attempts to control pest the commonly used method was to kill all the pests and with time plantation managers realized that pests need to be controlled only if they cause economic damages. The pest management concept is used to indicate management of the pest population to limit it to a tolerable level. With the advancement of knowledge and the science the concept of integrated pest management (IPM) has been introduced in order to manage the insects and pests in commercial plantations.

Lack of sufficient scientific research, inapplicability of sophisticated pest management methods used in developed countries and having the low attention on the pest management in forest plantation species by the government are major challenges in insect management in Sri Lankan forestry context.

Species Selection in Commercial Forestry

Presented by

Tharani Dilshara

Selection of species is important in starting a plantation project because the species selected decides the affected silvicultural practice and the management and utilisation of crops.

Selection of a tree crop for planting depends on the purpose, the species potentially available for planting, site qualities, silvicultural and economic factors. Before considering the site characteristics and demands, it is essential to have clear understanding of the objectives of raising the particular plantations and those factors will narrow the choice of a species. Species selection in commercial forestry is mainly determined, however, by the demand and establishment costs.

As a rule, where a native species meets the need there is no reason to choose an alternative because of the conservation purposes more prefer the native species. However, the majority of successful plantation in the tropics consist exotic species.

Species and provenance trials have to be carried out before establishment of plantations using new species. Site qualities play a major role in the interactions between genotype and environment. Site quality factors such as climate, soil, physiographic and biotic factors affect the growth at different manner even for the same species. Another major determinant of species selection is the specific silvicultural requirement of the tree species. Having matched species to the site, a further vital decision is selection of the most suitable provenance.

In Sri Lanka the main plantation species are Teak, Eucalyptus (Eucalyptus grandis) and Mahogany. Most of the fuel wood, miscellaneous hardwood and teak plantations are located in the dry zone, Eucalypts and Pine plantations are mostly in the up country wet zone and Mahogany plantations are situated in intermediate and wet zone.

Establishment and management plan of Eucalyptus grandis plantation by Greenhill (Pvt) Ltd

Abstract of the presentation of

Savindi Caldera

Eucalyptus spp were introduced to Sri Lanka in the latter part of 18th century by planters who had links with Australia. After 1953, Forest Department established Eucalyptus grandis in the hill country Sri Lanka, especially in degraded lands for the rehabilitation. These were to obtain sawn timber, transmission poles, railway sleepers and fuel wood.

As there is a population increase and growing demand for timber in Sri Lanka, Eucalyptus grandis plantations had a positive aspect due to fast growth and adoptability to harsh conditions. It meets requirements of people, industries and paved the way to reduce pressure on natural forests. But criticism was voiced in environmental degradation with allegations of adverse effects on soil, hydrology and habitat. However, most of these criticisms have now been addressed by value additions to those plantations as well as to the end-products. Greenhill Company has five main steps in their business model such as aacquiring and subdividing land, establishment, plantation management, and harvest and distributes returns.

The plantation is based in Nuwara Eliya with an extent of 50 ha and it was selected based on the unique climatic and soil conditions which are conducive for the growth of Eucalyptus grandis. Planting objective is to obtain sawn timber mainly to cater the local market with construction timber. In order to supply the perfect fit for each individual’s investment needs short-term cash crops such as beans chilies, green gram or other cash crops such as cotton are being intercropped.

Our business practices are certified by the International Organization for Standardization, achieving ISO 14001 for environmental management and the plantation is well managed as certified by FSC Certification. Value addition can be done through good silvicultural practices, planting superior clones of hybrids and genetically modified high yielding; disease-free, non-splitting trees obtained via vegetative propagations which would improve timber quality and quantity within the plantation. Practicing agroforestry and promoting related industries such as beekeeping, extraction of Eucalyptus oils would generate additional income to the company. At the same time it maximises the land use of the area. Adding organic fertilisers, managing plantations for longer rotational periods, fire management and trench management are some of the eco-friendly management practices that add values to the plantations.  Timber seasoning, pre-treatments, designs used in furniture manufacturing and forest certifications will add value to the end product.

An investment plan was given while assuring absolute ownership of a land with Eucalyptus grandis trees to the clients, ensuring continuous monitoring and improvements by Forestry Consultants. Short term returns will be gained through the intercrops, the thinned material sold as fuel wood and essential oil production which will be outsourced to Bio Extractors’ Pvt Ltd. 

Young plantation of E. grandis

Value addition to Eucalypt plantations

Abstract of a Seminar presentation

Ama Wickramarachchi

Eucalyptus is a native tree to Australia which is now widespread across the world because of its fast growing rates and adoptability to wide range of geographical area from lower altitudes to higher altitudes. There are about 700 Eucalyptus species recorded in the world. It was introduced to Sri Lanka in late 1800s as a fuel wood to the upcountry households and tea industry and later different species were introduced to dry, wet and intermediate zones of the country.

Eucalyptus plantations receive criticisms due to its effect on soil fertility and hydrology. However, most of these criticisms have now been addressed by value additions to those plantations as well as to the end-products through sustainable management which optimizes economic, environmental and social benefits of the plantations.

Good silvicultural practices, planting superior clones of hybrids and genetically modified high yielding, disease-free, non-splitting trees obtained via vegetative propagations and field trials and mixed plantations would improve timber quality and quantity within the plantation. Practicing agroforestry and promoting related industries such as beekeeping, extraction of Eucalyptus oils and Eucalyptus dyes would generate additional income to the rural communities. At the same time it maximises the landuse of the area. Adding organic fertilisers, managing plantations for longer rotational periods, fire management and trench management are some of the eco-friendly management practices that add values to the plantations.

Timber seasoning, pre-treatments, designs used in furniture manufacturing and forest certifications will add value to the end product.

When comes to local context, it is very limited that Sri Lanka follows any value additions at the plantation level. Therefore agroforestry, promoting related industries, advanced silvicultural techniques, research and development and obtaining forest certification can be recommended to follow in order to add value to the plantation.

At the end-product level, Sri Lanka has to practice more advanced pre-treatment methods and designs in furniture manufacturing have to be improved in accordance with the current trends. Forest certification to the end-product would surely add a more value at the market level, specially in international markets. Moreover, it is becoming a must to compete in most of the export markets. Therefore Sri Lankan manufactures need to concern at least in obtaining this certifications to the eucalypt plantations and its products.

Challenges faced in establishing eucalypt plantations in Sri Lanka

Challenges faced by the Forest Department in establishing eucalypt plantations in the up country of Sri Lanka

Abstract of a seminar presentation

Jithya Wijesinghe

Eucalyptus was introduced to Sri Lanka in the latter part of 18th century as an exotic species to be raised as a forest plantation species. These were originally raised in the upcountry to produce fuel wood for households and tea industry. But later most of these species were found very promising for railway sleepers and industrial timber. Therefore at present Eucalyptus are planted to meet the requirements of sawn timber, railway sleepers, transmission poles, fuel wood, extraction of essential oils and paper pulp.

Eucalyptus is also planted as windbreaks and shelter belts in certain locations particularly in the upcountry. Beekeeping is another common practice in some areas where eucalypt plantations are raised.

Afforestation of the patana grasslands in the upcountry began in 1930's with planting of E. grandis, E. microcorys and E. robusta in compact blocks on the crests of ridges and hill tops as windbreaks in upcountry.

Environmental issues, social issues, economic issues, accessibility issues, harvesting issues, management issues, unforeseen catastrophes and others are some challenges faced by the forest department establishingEucalyptus plantations in upcountry.

With the sloppy areas, soil erosion was a major challenge that faced by the Forest Department. Furthermore high cost for road constructions, labour cost, encroachment of local people, limited land areas in upcountry, lack of water, high intensity for fire hazards, need of additional effort for soil conservation practices, contours makings are some of challenges faced by the FD.

In order to overcome these challenges establishment of more fire lines, use of soil conservation practices, use of wood aids to protect saplings from wind, enhanced management practices that are used by the FD.

Make harvesting operations well controlled and road guidelines specially in slopes >60⁰, to reduce the wind damage to new plantations, proper grading of seedlings, establishment of water supply programs for field nurseries, enhance the involvement of the local communities to reduce the encroachments are some practices that can be used for further improvement of the establishment of the Eucalyptus plantations in upcountry.

Construction of a stem volume prediction model for E. grandis

Construction of a stem volume prediction model for mature Eucalyptus grandis plantation in Pidurutalagala of Nuwara Eliya, Sri Lanka
by
Kandiah Selvarathnam and Upul Subasinghe

Timber volume is the most crucial variable in commercial forest plantations. Therefore a precise volume prediction model was constructed for the mature Eucalyptus grandis plantation located in the Pidurutalagala mountain of Nuwara Eliya District, Sri Lanka.

0.02 ha circular samples were used for the data collection. Breast height diameter (dbh) and total height (h) were measured as the preliminary measurements. Then the stems of the standing trees in the sample plots were divided into sections and section lengths, end-diameters and mid-diameters were measured in order to use the Newton's formular for the stem volume estimations. Altogether 14 samples were used for the data collection.

A basic relationship was then developed by assuming the stem volume (v) can be predicted as a function of h, basal area (g) which is calculated using dbh and site quality as given below.

v = f (g, h, site quality)

In order to represent the site quality, top height and top height / age functions were used. Regression analysis (linear) was used to quantify the relationships. In order to obtain the best models, the variables in the above equation were transformed into different forms that can biologically be accepted. R2 and standard residual distrinbution were used to evaluate the model quality. After a careful study, two models were selected to predict the stem volume of E. grandis trees in the selected plantation.