Pest Management in Commercial Forestry

Presented by

Madhushi Weerasinghe

Forest Pest can be defined as “any insect, disease or closely related organism which is harmful, injurious, or destructive to forest or timber”. All parts of a tree roots, stems, foliage, shoots and terminal leaders 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, vertebrates, and nematodes.

There are several common pests that can be commonly seen in commercial forestry. In Tectona grandis the most common insects cause severe damage plantations are Leaf Skeletonizer (Eutectona machaeralis) and Defoliator (Hyblaea puera). In Swietenia macrophylla the most common pest is Mahogany Shoot Borer (Hypsipyla grandella). Moreover, there are insect pests in Eucalyptus grandis, such as Eucalyptus gall wasp (Ophelimus maskelli). Also some pathogens such as Leaf Spot Fungi (Cryptosporiopis eucalypti),Cylindrocladium Leaf Spot Blight-Fungi (Cylindrocladium reteaudii), Botryoshharia Canker (Botryosphaeria spp.) and Bacterial Wilt (Ralstonia solanacerum) are common. In Aquilaria malaccensis, Leaf spot Disease caused by Corynespora cassicola is common. Considering Sandalwood (Santalum album L.) there are some nursery diseases such as Damping off and Pre-emergence wilt.Also forest plantations can be damaged by Elephants and small mammals.

Managing tree pests effectively should be based on thorough consideration of ecological and economic factors. The pest, its biology, and the type of damage are some of the factors that determine which control strategies and methods should be used. Pest management decisions represent a compromise between the value of the product, the extent of the pest damage, the relative effectiveness and cost of the control measures, and the impact on the environment.

Here the concept of Integrated Pest Management (IPM) is mainly used. That relies on an understanding of the ecology of the pest, draws on this knowledge non-chemical approaches that will make the environment less suited to the development of the pest population. Integrated Pest Management practice may involve in the control program, the judicious and sensitive use of pesticides where necessary. There are five major steps in IPM. Monitoring is the first step. Monitoring forests and newly established plantations will help detect problems early, while there is still time to take action. Identification of pests and the diagnosis of pest damage is the second step of IPM. Threshold level is point at which the pest or its damage becomes unacceptable. The threshold level may be related to the beauty, health, or economic value of the tree crop and that comes as the third step of IPM. Selection of management strategy is fourth step and under this there are several management strategies such as, do nothing, cultural management, mechanical management, biological management and chemical management. Evaluation is the final step of IPM. It is very important to determine how effective the management and control tactics are. This information will determine whether any follow-up treatment is needed and will improve management strategies for next year.

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.

Maho Plantations: Establishment of a Mahogany Plantation

Abstract of the presentation of

Shernima Rodrigo

Swietenia macrophylla, which belongs to Meliaceae family, is one of the most valuable and quality furniture timbers in the world timber market, for its decorative and attractive timber with good technical characteristics. Mahogany has a long history in Sri Lanka, and this tree is maintained mainly in the intermediate zone and low country wet zone in Sri Lanka.

By realising the timber value of Mahogany, Maho Plantations Ltd. has also started creating mahogany plantations in Sri Lanka. The company head office is at Narahenpita. The mahogany plantations are mainly concentrated in Kurunegala area. The company provides variety of investment benefits to their investors.

Maho Plantations Ltd. has a competent team of consultants who has experience and knowledge in the field of plantation management and they take care of the mahogany plantations. This company does not only plant mahogany trees on the land acquired, but also has taken steps to intercrop banana as a value addition to the existing mahogany lands. This practice enables the company to provide returns ranging from short-term to long-term, and everything in between. Plus, as a result of unparalleled planning and forest management practices, the harvest yields consistently forecast returns that are above the industry average.

The company is looking forward to expand the land area and the variety of species used, to identify new business opportunities, such as Carbon fixation value of the plantation and achieving ISO 14001 and ISO 9001 standards.

Young mahogany plantation in Rathnapura, Sri Lanka

Establishment of hypothetical forest Plantation Company for (Swietenia macropylla) AirForest Plantation Limited

Abstract of the presentation of

Sampath Bandara

S. macrophylla is one of the most valuable furniture timbers in the world due to the decorative and attractive timber with good technical characteristics. In agro forestry systems it is used for shade and fuel wood. In 1840, Mahogany was first planted in Jaffna as an avenue tree. According to the 2010 data of   FAO there were 5505 ha of Mahogany cover in SL, mainly in the intermediate zone and low country wet zone of Sri Lanka.

AirForest Plantation Limited was established in 1998, and the head office located in No-6, Glenaber Pl, Colombo 03. This company provides numerous benefits to the investors such as Deed of the land, money back guarantee, right of transfer, providing maturity value of the plantation and free maintains facilities with online monitoring facility.

Though AirForest entered into forestry and agricultural plantation industry only 15 years ago (1998), the management of AirForest has decades of experience and knowledge in the field of plantation management. Currently, the company is managing plantations at Kurunegala, Monaragala, Galle, Udawalawa, Badulla, Kegalle and Beragala. (over 250 ha, island wide). AirForest is one of the forestry management companies which use Drip Irrigation System. This ensures a higher and rapid growth and a maximum harvest as each and every tree gets sufficient nutrition by drippers.

AirForest Plantations ensures continuous monitoring and improvements by forestry consultants and experts in the industry and over 15,000 delighted clients in Sri Lanka. It provides harvest-purchase back guarantee, with many additional offers with exclusive premier membership benefits

This value addition is also a very important aspect in the plantation sector because it is eventually a business, and the increasing of profit becomes underlying target. The value addition to a plantation can be done in several aspects. It can be either by increasing the quantity of the timber produced from the plantation or by improving the quality of the mahogany produced and also especially by increasing the utility of the plantation land. Company exporting the Mahogany fruit (Sky Fruit) as a byproduct obtains from the plantation.

There are some difficulties of the Mahogany plantation sector; lack of suitable lands for establishment of plantations, shoot borer attacks, problems related to site quality, competition, problems of the labors, problems related to accessibility, lack of previous informations, political influences. 

Currently company is planning to expand the land area of the plantations and the plantation species verities. And Carbon fixing value is identified as a new business opportunity.

Mahogany sapling in a plantation of Sri Lanka

Establishment of relationships of growth at 7-year old mahogany trees with selected site factors

Establishment of relationships of growth at 7-year old mahogany trees with selected site factors in low country wet zone, using GIS as a tool

Himesha Randeni and Upul Subasinghe

Paper presented for the 14th International Forestry and Environment Symposium 2009

Mahogany (Swietenia macrophylla) is an exotic tree, which is heavily adapted to the climatic conditions of wet and intermediate zones of Sri Lanka. Although the state sector manages mahogany with longer rotations, private sector expects to achieve the maximum timber yield within a shorter period. Due to the land scarcity, many of these mahogany plantations have been established in barren and rubber uprooted lands which were heavily degraded. Therefore the soil conditions and site factors directly affect the growth of the mahogany within short rotations.

The present study was carried out in a 7 years old mahogany monoculture plantation established in Gomaragala, in low country wet zone of Sri Lanka to find out the effect of soil and site factors to the mahogany tree growth. Extent of this forest is 20.7 ha and it is managed by a private plantation company. This forest has been divided into 2 lots for the purpose of administration and further divided into 240 plots of 20 perch each.

In order to identify the relationships, tree dbh and height were used as growth parameters. Slope, bedrock establishment and terrain were selected as selected site factors. The growth parameters (i.e.dbh and height) were measured for all the trees in plantation (one measurement from each plot). Slope and terrain as geographical parameters were measured of all 240 plots in the entire plantation.

Since the regression based methods were not adequate for both qualitative as well as quantitative parameter analysis, GIS based analysis was decided to use for the present study, using ArcView 3.3. In order to create digital maps, the survey plan of the selected forest was digitized and georeferanced using 10 ground control points collected by a GPS data receptor. Then the georeferanced base map was digitized to demarcate all the plots and other land marks. After that different maps were prepared in vector form separately for each parameter. However, for the analysis, all these vector layers were converted to raster layers. Raster layers were then reclassified and overlaid two or three layers at a time with the growth parameters to identify the effects. Then map analysis was completed to make decisions regarding tree growth in different site factors.

Results revealed that there are significant relationships between tree growth and the selected site parameters. However, the best conditions for the mahogany tree growth in the particular area are the slope between 11⁰-24⁰, and shallow bedrock prevalence and stony terrain.

Change of crown diameter with dbh of mahogany

Change of crown diameter with dbh of Swietenia macrophylla (mahogany)

even-aged monocultures

Shanika Lakmali and Upul Subasinghe

Paper presented for the 14th International Forestry and Environment Symposium 2009

Mahogany is one of the renowned timber species for its beautifully grained, hard and red-brown wood. It is an introduced timber species, dominated in Sri Lankan forest plantations with fast growth rates and higher timber value. Mahogany plantations are widely established in the intermediate zone and low country wet zone in Sri Lanka. Recently, private sector has started to establish of mahogany monocultures with shorter rotations to gain high income.

Due to the lack of research studies on mahogany, the objective of the present study was to establish an empirical model to predict crown diameter accurately using dbh. For this purpose, data were collected from 16 mahogany monocultures in Kalutara, Ratnapura and Matale districts. In order to represent the whole plantation, sixty trees were selected from good, moderate and poor areas from each plantation.

In order to build a reliable model, theoretical basic structures were developed assuming the crown diameter is a function of tree dbh. This basic structure was fitted to the data as linear, exponential, and logistic form separately for different growth types. In addition to the untransformed variables, transformations were also made whenever possible. Suitable candidate models were preliminary selected by R2 and residual distributions. After further analysis, it was proven that the best results were given by the logistic model structure for good, moderate and poor site types (R2 = 92.0%, 71.4%, 65.9% respectively). In order to eliminate the difficulty of using separate models for different growth types, the possibility of using a common model for all growth types were tested. For this reason, one way ANOVA was used for residuals of different growth types generated after fitting respective models. Results indicated that it was possible to use a common model and therefore the logistic form was re-fitted to pooled data.

The final model was “crown diameter = 0.645 + 2.682 / (1+exp (-0.356 (dbh –7.749)))” and it had a R2 of 60.9%.

Establishment of relationships of growth with site factors and some selected soil parameters of a selected 7 years old mahogany plantation in Eheliyag

Establishment of relationships of growth with site factors and some selected soil parameters of a selected 7 years old mahogany plantation in Eheliyagoda DS, using GIS as a tool

B.Sc. Dissertation

Himesha Randeni and Upul Subasinghe

Mahogany (Swietenia macrophylla) is an exotic tree, which is heavily adapted to the climatic conditions of wet and intermediate zones of Sri Lanka. Although the state sector manages mahogany with longer rotations, private sector expects to achieve the maximum timber yield within a shorter period. Due to the land scarcity, many of these mahogany plantations have been established in barren and rubber uprooted lands which were heavily degraded. Therefore the soil conditions and site factors directly affect the growth of the mahogany within short rotations.

The present study was carried out in a 7 years old mahogany monoculture plantation established in Gomaragala, in low country wet zone of Sri Lanka to find out the effect of soil and site factors to the mahogany tree growth. Extent of this forest is 20.7 ha and it is managed by a private plantation company. This forest has been divided into 2 lots for the purpose of administration. However, for the sales purposes it has been divided into 240 plots.

In order to identify the relationships, tree dbh and tree height as growth parameters; slope and terrain were selected as geographical factors as well as soil texture, soil organic carbon level and soil pH levels were selected as soil parameters. The growth parameters (i.e.dbh and height) were measured of all the trees in plantation. Slope and terrain as geographical parameters were measured of all 240 plots in the entire plantation. Soil parameters namely soil pH, soil organic carbon and soil texture were measured for systematically selected 50 plots out of 240 plots to represent the entire plantation. There are some qualitative parameters namely tree growth, terrain, presence of bedrock, included into the present study. These were usually assessed to give a single value for each plot.

Since the regression based methods was not adequate for both qualitative as well as quantitative parameter analysis, GIS based analysis was decided to use for the present study, because it serves as an analytical and decision supporting tool. ArcView 3.3 was used for this purpose. In order to create digital maps, the survey plan of the selected forest was digitized and georeferanced by main 10 ground control points collected by a GPS data receptor. Then the georeferanced base map was digitized to demarcate all the plots and other land marks. After that different maps were prepared in vector form separately for each parameter. However, for the analysis, all these vector layers were converted to raster layers. Raster layers were then reclassified and overlaid two or three layers at a time with the growth parameters to identify the effects. Then map analysis was completed to make decisions regarding tree growth in different site factors and soil conditions with similar other environmental conditions. Since the soil pH, soil organic carbon level and soil texture were measured in selected 50 plots out of 240 plots, the raster layers were interpolated for entire area.

Results of the present study revealed that there are significant relationships between tree growth with the selected parameters. However, the best conditions for the mahogany tree growth in the particular area are the slope between 11⁰-24⁰, soil pH level bellow 4.0, soil organic carbon range between 9.0%-14.0%, soil with sand between 50%-70%, shallow bedrock prevalence and stony terrain.

Changes of branch and crown characteristics with stem parameters and age of Swietenia macrophylla even-aged monocultures

Changes of branch and crown characteristics with stem parameters and age of Swietenia macrophylla (mahogany) even-aged monocultures

B.Sc. Dissertation

Shyanika Lakmali and Upul Subasinghe

Growth predictions in the plantation forestry play a vital role in order to maximize the future gains specially in the field of economy. Plantations of mahogany monocultures in private sector directly focus in the timber production and thereby the financial gain. Tree growth is accompanied with the photosynthesis process and it increases the stem parameters of the trees. Therefore there is a close relationship between crown development and tree growth. In addition to that, crown growth causes a competition after the canopy closure in the forest plantations.

The main objective of the present study was to establish a series of empirical models for predicting the relationships between stem, crown and branch parameters. In addition to that an attempt was taken to predict the above parameters with age. It was expected to use those relationships to prepare a pruning schedule for mahogany monoculture plantations in Sri Lanka.

In order to achieve the objectives, data were collected from 16 mahogany monocultures in Kalutara, Ratnapura and Matale districts. In order to represent the whole plantation, due to growth differences, sixty trees were selected from each of plantation as twenty trees from each good, moderate, and poor growing areas. The measurements were taken including dbh, total tree height, crown diameter, height to the first branch, height to the second branch, branch lengths and base diameters up to two branches.

Regression analysis was employed to build the suitable relationships between related variables. Both linear and non-linear regression equations were tested for each relationship using MINITAB and GENSTAT statistical software. In order to obtain the best equations, both qualitative (R² ) and quantitative (residual distribution and fitted line plots) were used. Initially, the data were grouped as good, moderate and poor growth types. Then different theoretical model structures (linear with untransformed and transformed variables, exponential and logistic) were separately fitted to those data. After that the best model was selected for each relationship for each growth type. At this point, it was a must to select the similar model structure (with different regression parameter sets) for each relationship in each growth type.

According to the results, crown and branch variables were highly correlated with the stem variables such as dbh and total height. Therefore the predictions of the crown and branch growth could be expressed by using dbh and total height. It was not possible to build linear relationships and

In order to predict the required variable, 12 non-linear models were constructed. Then the possibility of using a common model for all growth types was tested for each variable with pooled data. However, only three models out of 12 models proved the possibility of using as common models for all growth types. The rest of models were therefore decided to use as growth specific ones.

Finally using those models, a pruning schedule was prepared for different growth types of mahogany monocultures in Sri Lanka.

Challenges faced in establishing khaya plantations in Sri Lanka

Challenges faced by the Forest Department in establishing khaya plantations in Sri Lanka

Abstract of a seminar presentation

Benica Jayasekara

Khaya senegalensis is the scientific name for khaya, which belongs to the Family Meliaceae. It is commonly known as African mahogany or dry zone mahogany. It’s a fast growing tree species in dry conditions and grows up to 20-30m in height. Timber of khaya is hard, dense and reddish brown in colour.

Khaya is one of the major timber species used by the Forest Department in reforestation programs in dry and intermediate zones of Sri Lanka. It was introduced from Africa during 1960’s. However, most of the khaya plantations of Sri Lanka are less than 10 years old.

The reasons for the use of Khaya by the Forest Department is the high demand for timber, fast growth rates in dry and intermediate zones, tolerance to poor site quality and resistance to heavy weed competition, harsh conditions and diseases and pests (except borer). Moreover the rural community prefers khaya over teak because khaya is morphologically more similar to the native species in Sri Lanka. In addition to those, wild elephants do not damage khaya trees.

According to the Forest Department, khaya was selected as the best tree species for the dry zone. There are however, a few challenges faced by the Forest Department in establishment of khaya plantations. Expensive seeds, low seed viability, fertilization, weeding, multiple shoots, porcupine damage, black twig borer attack, red stem borer attack and the forest fires as examples.

Forest Department had taken remedial actions for these challenges and still they are doing further studies to improve the khaya plantations. Still the khaya plantations in Sri Lanka are less than 10 years and therefore the Forest Department might face more problems with the time, because the rotation age of khaya is 30 years and still the yield tables for this species has not been prepared.