Olax zeylanica: An environmentally safe bio-pesticide for the control of the Maize weevil Sitophilus zeamais Mots. (Curculionidae)

M.T.H.P. Perera and M.M.S.C. Karunaratne
Department of Zoology, University of Sri Jayewardenepura, Sri Lanka

Leaf powders of seven commonly found plant species, Ocimum graticimum, Morinda citrifolia, Aegle marmelos , Annona squamosa, Annona reticulata, Olax zeylanica and Ricinus communis were screened for their insecticidal activity under laboratory conditions (30±1 ºC and 84 – 86% RH) against the maize weevil, Sitophilus zeamais. The powders at the rate of 15g/50g of maize grains were tested separately and the mortality of adult weevils was recorded after 24 hours. The results of this bioassay revealed that O. zeylanica was most active towards S. zeamais eliciting a hundred percent mortality of the weevils. However, the mortality values for the other six plant powders were significantly very low with 20% for Ocimum graticimum, 16.6% for Morinda citrifolia and Aegle marmelos, and 6% for Ricinus communis, A.squamosa and A. reticulata. Leaf powder of O. zeylanica, then, was tested at five dose rates (1.0, 2.5, 5.0, 7.5, 10.0g) against the weevils.

Mortality of adult weevils was recorded after 6, 12 and 24 hours of treatment and LD50 and LD99 values were given at the respective time intervals. It was observed, in this experiment, that the mortality of weevils increased with the increase of the dose as well as the exposure time.  Also, weevil mortality was found to be 100% at the dose rate of 10g just after 12h of treatment. Results from this study indicated that leaf powder for O. zeylanica was extremely toxic to S. zeamaize weevils with LD50 values of O. zeylanica were 5.84, 2.47 and 1.84g at 6, 12 and 24 hours of exposure respectively. In a similar vein, LD99 values of 38.55, 8.33 and 6.51g were observed for the same exposure times. The present study revealed that Olax zeylanica could be highly promising as a bio-pesticide which can compete effectively with the hazardous synthetic insecticides in the management of maize weevil infestations in storage.

Response of low frequency harvesting systems under drier climatic conditions

K.V.V.S. Kudaligama1, V.H.L. Rodrigo1, K.M.E.P. Fernando2 and P.A.J. Yapa
1Department of Biochemistry and Physiology, Rubber Research Institute of Sri Lanka
 2Department of Botany, University of Sri Jayewardenepura, Sri Lanka

The rubber plantations in Sri Lanka lie mostly in the Wet zone (WZ) of the country and in certain regions in the Intermediate zone (IZ). In the IZ rubber plantations are condensed in IL1a agro ecological region. In today context escalating cost of production and inadequate supply of skilled harvesters are among the major issues of natural rubber industry. Low frequency harvesting (LFH) systems, of which trees are tapped in a lesser frequency than once in two days, are considered to be one of the solutions to overcome these issues. In LFH, the trees are generally stimulated to obtain yields comparable that of traditional d2 (i.e., tapping a tree once in two days) frequency. Obviously, the stimulation protocol depends mostly on the clone and harvesting frequency. With the higher level of climatic variability resulted from the climate change, prolong droughts are expected adding another factor to be considered in designing the stimulation protocol of LFH systems.

Almost all regions of the island have a potential threat of drought and such possibilities in the IZ are relatively high compared to the wetter parts of the island. Therefore, the present study was aimed atinvestigating the variability in yield in LFH systems, viz. harvesting trees once in three (d3), four (d4) and six (d6) days in drier climates. 

As expected, yield per tree per tapping increased with the decrease in harvesting frequency in both climatic zones. Percentage dry rubber content in latex increased with the decrease in the harvesting frequency. Volume of latex per harvest increased with the reduction of the harvesting frequency. The flow rates of LFH systems in IZ were not up to the expected level resulting insufficient latex volumes.  As a result, ultimate yields given by d4 & d6 systems were less than that of d2 only in IZ. This could be attributed to the lack of soil moisture in IZ to replenish the water taken out from the tree with latex. Therefore, stimulation protocols are to be designed to obtain higher yields in IZ during its wet periods.

Effect of different fertilizers on the growth of coconut seedlings, availability of some nutrients and soil microbial activities

S.R.M.R. Attanayake1, C.M. Nanayakkara2 and N.A. Tennakoon3
1Agriculture Biotechnology Centre, University of Peradeniya, Sri Lanka
2Department of Plant Sciences, University of Colombo, Sri Lanka
3Soils and Plant Nutrient Division, Coconut Research Institute, Lunuwila, Sri Lanka

The present fertilizer application is manly based on chemical fertilizers which are costly and exerts negative impacts on soil health. Therefore a study was planned to find out the effect of different fertilizers on the growth of coconut seedlings, availability of some nutrients and soil microbial activities with the aim of developing a fertilizer mixture that supports the plant growth with simultaneous improvement of soil health.

Eight months old coconut seedlings of CRIC 65 cultivar was planted in large plastic pots (45 cm x 55 cm) and kept inside the green house at Coconut Research Institute, Lunuwila, Sri Lanka. Each pot was filled with Madampe series soils of Latosols which belongs to the land suitability class S1 of coconut growing soils. Six treatments were selected with three replicates 1 kg of Dolomite was added to all as the basal dressing. The treatments were: control (T1), inorganic fertilizer mixture (T2), BioGold® (T3), cattle manure (T4), Kochchikade biofertilizer (T5) and compost (T6). The growth performances of seedlings were measured by taking seedling girth, seedling height, number of leaves per seedling and total leaf area.

The measurements were recorded before and eight weeks after application of treatments. For the soil chemical analysis, soils were tested weekly for pH, EC (Electrical Conductivity) and macro and micro nutrients K, P and Mg. The microbial activities were also investigated weekly by measuring microbial biomass carbon and CO2 evolution.

The experiment design was a Complete Randomized with three replicates. The data were analyzed by analysis of variance (ANOVA) and significant means were compared by Least Significant Design (LSD) using the MINITAB statistical package. At the end of the research period no significant difference (P>0.05) was observed in growth parameters in any of the treatments. Similarly, none of the treatments were able to make a significant effect on soil pH (P=0.499) and EC (P= 0.100) throughout the research period. The significantly the highest available phosphorous (P) level was observed in inorganic fertilizer treatment and BioGold®, cattle manure, Kochchikade biofertilizer and compost also shown significant effects. A significantly high K level in soil after a six months period was shown by all the treatments except inorganic fertilizer treatment. Cattle manure contributed a significantly high level of Mg to the soil. By considering this result, it is possible to recommend cattle manure as a good fertilizer to increase the Mg level in a particular soil. A high acceleration of microbial activity was observed in BioGold® and the compost treatments. Cattle manure and Kochchikade biofertilizer had a similar effect with inorganic fertilizer showing the lowest activity. This implies that organic fertilizers are more environmental friendly compared to inorganic fertilizers. Although inorganic fertilizers are more fast and effective on increasing the available P in soil, in comparison to the organic and biofertilizers, they showed a negative impact on soil health. However, the contribution of inorganic fertilizer for K increment was not considerable. Therefore, it is important to consider all these facts before selecting a fertilizer to obtain the maximum benefit from coconut lands. Further, on recommending environmental friendly cost effective fertilizers, it is possible to recommend organic fertilizers as the environmental friendly and cost effective compared to the inorganic fertilizers.

Stimulant levels to be used with two Low Intensity Harvesting (LIH) systems of Rubber under wet and intermediate zones of Sri Lanka

W.R.A.C. Prasanna1, V.H.L. Rodrigo2, D.C. Abeysinghe 1 and K.V.V.S. Kudaligama2
1Department of Plantation Management, Wayamba University, Sri Lanka
2Biochemistry and Physiology Department, Rubber Research Institute of Sri Lanka, Agalawatta, Sri Lanka

Harvesting latex from rubber trees (Hevea brasiliensis) is rather labour consuming and hence is the most costly operation contributing to 1/3 of the cost of production in rubber plantations. Further, it requires high level of skill which plays a part in the shortage of latex harvesters. Harvesting of latex is undertaken through the systematic wounding in the bark of the trunk. In Sri Lanka, two harvesting systems are widely used in base panel tapping, i.e., a half of trunk circumference tapped once in two (S/2 d2) and three (S/2 d3) days.

With the reduction of harvesting frequency, labour use in harvesting hence the cost decreases. However, yield stimulants (viz. Ethephon) are to be applied to increase the  yield on harvesting days as a compromise for the yield reduction due to less number of harvesting days in low frequency harvesting (LFH). In order to address labour issues, a system of harvesting the tree once in four days (S/2 d4) has recently been introduced and a weekly harvesting system (S/2 d7) is presently under investigation. In S/2 d4 and S/2 d7, the required doze of Ehephon has exactly not known and that would vary with the climatic condition. Therefore, the present study was aimed to identify the suitable concentrations of Ehephone required for S/2 d4 and S/2 d7 systems under two climatic regions, wet and intermediate zones of Sri Lanka.

Ethephon was applied in four concentrations (i.e. 2%, 3%, 4% and 5%) in the genotype RRIC 121 planted in both climatic zones. Yield performance in each system was evaluated against that of the traditional harvesting systems of S/2 d2 of which no stimulation was done. In the Intermediate zone, the S/2 d4 and S/2 d7 systems showed a yield increase of 7 and 14 grams per harvest per 1% increase in Ethephon concentration, respectively.  In the Wet zone, respective increases were recorded as 4 and 7 grams. The S/2 d4 system required ca. 3.7% and 3.3% concentrations of Ethephon in the Intermediate and Wet zones, respectively, to achieve the yields given by S/2 d2 system. In S/2 d7, Ethephon concentration of 5% was sufficient for both zones. The study also revealed that the range tested in Ethphone concentrations had no adverse effect on tree health as indicated by the percentage dry rubber content in latex. However, long-term studies at commercial scale together with financial analyses are required before coming to firm conclusions.

 

Livestock farmers strategic response to climate change: Exploring the case of dairy cattle farms in the intermediate zone of Sri Lanka

R.T.D. Yasarathne, J.M.M. Udugama and U.K. Jayasinghe-Mudalige
Department of Agribusiness Management, Wayamba University of Sri Lanka

This study was aimed to examine the adaptation measures used by cattle farmers in the Panduwasnuwara Divisional Secretariat of the Kurunegala District, which holds the largest livestock population in the Low Country Intermediate Zone in Sri Lanka, in response to climate change, especially the fluctuations in the level of temperature in this region with an increasing trend over time. A structured questionnaire-based personal interview was conducted during May to June in 2010 with 60 small to medium-scale cattle farmers selected randomly using the information obtained from the Department of Agrarian Services.

The data were fitted into a Probit Model to estimate the likelihood of these farmers engaged in various adaptation measures followed by specification of a Multinomial Logit Model to identify the factors affecting the choice of adoption of these practices. The results show that farmers adopt various measures to overcome the negative effects of climate change, and the changing levels of the temperature in particular, including: alteration of feed and the feeding patterns, alternative housing practices, and selection of tolerant cattle breeds, etc. It further reveals that the overall income of the farming household, the number of cattle in the farm, the net earnings per cattle, age and the level of education of the farmer had a significant impact on climate change adaptation. The outcome of analysis implies that rural poor livestock farming communities exploit the existing traditional resource base characterized by land and labor to overcome the negative effects of climate change and further research is warranted to explore the applicability of which for continuity of the enterprise in the long run.

 

Key words: adaptation, climate change, dry zone agriculture, livestock farming

Effects of dried curry leaves and tea leaves on oxidative rancidity of rice bran

P.H.G.J. De Silva and N.S.B.M. Atapattu
Department of Animal Science, University of Ruhuna, Sri Lanka

Control of the rancidity of rice bran (RB) is difficult due to the oxidative rancidity that persists even after inhibiting lipolytic rancidity by heating. Anti-oxidants are widely used to control the oxidative rancidity. Leaves of some plants such as curry leaves (Murrya koenigi) and tea (Camellie sinensis) are reported to contain high levels of natural anti-oxidants (NAO). The objective of this study was to test whether curry leaves and tea leaves could be used to control the oxidative rancidity of RB. A 2 x 3 factorial experiment was conducted. Heat stabilized and nonheat stabilized RB were stored without NAO or with 4% dried curry leaves (CL) or tea leaves powder (TL).

Each of the six treatment combinations had four replicates. Peroxidase values (PV) of the samples were determined weekly for 8 weeks.  Heating alone reduced the PV only by 43%. The initial PV (Meq/kg) of nonheat stabilized RB stored without NAO increased linearly (PV = 0.756 + 1.48 x days; R2= 0.99) from 2.5 to 85 over the eight weeks of storage.  The PV of the heat stabilized  RB stored without NAO also increased linearly (PV = -1.00 + 0.820 x days,R2=0.97) from 2.3 to 48 over the eight weeks of storage. Throughout the eight weeks of storage period, the PV of heat stabilized RB were significantly lower than those of non-heat-stabilized rice bran. Storage of non-heat stabilized RB with CL and TL significantly reduced the PV compared to same type of rice bran stored without CL or TL.

Similarly, PV of heat-stabilized RB stored with CL and TL were significantly lower than those of heat-stabilized rice bran stored without CL or TL.  Though there was no significant difference, CL was more effective compared to TL. Use of both CL and TL was more effective when used with heat-stabilized RB than with non-heat stabilized RB. When CL was mixed with non-heat stabilized RB, the PV at 56th day of storage reduced by 45% (from 85-46).  Meanwhile, when heat stabilized RB was mixed with CL, the PV at 56th day of storage reduced by 72% (from 48-13). It was concluded that dried powders curry leaves and tea leaves reduced the oxidative rancidity of rice bran on storage.

Use of bio- fungicides for controlling powdery mildew disease of Rambutan

P.W. Alahakoon, N.H. Jayawardene, K.C. Madushani and  R.K. Nilmini
Fruit Crop Research and Development Center, Department of Agriculture, Horana, Sri Lanka

Powdery mildew of Rambutan (Nephelium lappaceum) incited by the fungus Oidium nephelii attack young leaves, flowers and immature fruits which become discolored and dry off causing fruit quality deterioration and heavy fruit losses. Oidium nephelii is controlled by application of fungicides. According to the Department of Agriculture recommendations, spraying of wettable sulphur, Chlorothalonil or Thiophanate methyl were recommended to control the disease.

Although the chemical application is the most common conventional means to control fungal diseases in crops, it is also a well known fact, that chemical control creates a lot of problems in humans and other organisms as well as it degrades the environment. Therefore new environment safe technologies should be introduced to replace the existing harmful ones. Use of biofungicides like plant extracts to control plant diseases are one of them.

An experiment was conducted at Fruit Crop Research and Development Center, Horana, to study the efficacy of herbal extracts compared with the Department of Agriculture recommended fungicides to control powdery mildew disease of Rambutan. The treatments consisted of six herbal extracts (Neem oil, Citronella oil, Cinnamon leaf extract, Clove leaf extract, Neem seed extract, Vinegar) and two recommended fungicides: Thiovit (wettable sulphur) and Daconil (chlorothalonil). Rambutan needs a critical dry period for flowering and to fruit set. Severity and spread of powdery mildew basically depends on the environment. The change in the weather pattern was to blame for the inability in the control of powdery mildew. In the past years, flowering and fruit set occurred during heavy rain conditions. Therefore selection of herbal extracts was done during heavy rain and in dry weather condition.

The results obtained from the experiment revealed that under the dry weather condition, the maximum number of healthy fruit set at harvest was given by the Citronella oil and Neem oil. The Clove leaf extract and Cinnamon leaf extract significantly controlled the powdery mildew disease and increased the healthy fruit production than that of the recommended fungicides. Neem seed extract and Vinegar controlled the disease similar to the Department recommended fungicides. In contrast to the data obtained under dry weather condition, in the heavy rain conditions, only the Citronella oil and Neem oil moderately increased the healthy fruit set at harvest while other plant extracts and all Department recommended fungicides failed to control the powdery mildew disease. Since in the dry weather condition, (normally flowering and fruit set season) plant extracts Neem oil, Citronella oil, Clove leaf extract, Cinnamon leaf extract controlled the disease than that of recommended fungicides, they can be used as the bio-fungicides. Bio- fungicides are eco friendly and are not known to cause pollution to climate or soil. Therefore it needs to be applied to reduce the degradation of environment, increased crop yield and better food safety.

Carbon sequestration potential of replanted Rhizophora mucronata in Puttlam Lagoon, Kalpitiya, Sri Lanka

U.Y.I.L. Dharmasoma1, D.M.S.H.K. Ranasinghe1 and S. Wahala2
1
Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka
2
Department of Tourism Management, Sabaragamuwa University, Sri Lanka

The potential of trees to act as carbon sinks is very important as global warming, which occurs due to increasing levels of carbon dioxide is risen over decades. Mangroves as any other tree are capable of removing carbon from atmosphere through the carbon stored in their biomass. The present study was carried in the mangrove replanted sites with 6 months, 5 and 10 years old Rhizophora mucronata in the Kalpitiya Peninsula in the Puttlam Lagoon in North West of Sri Lanka. Objectives of the present study were to assess the carbon sequestration potential of replanted R. mucronata at different ages in Puttlam Lagoon and to estimate biomass partitioning in R.mucronata in selected sites.

Transects were demarcated in each sampling site traversing from the Lagoon to inland to cover the entire width of the plantation. The width of transects were 5m and they were laid at 15m intervals within the plantation. Each transact was divided in to 5m x 5m sample plots at 5m intervals. A representative tree was selected from each diameter class in each study site for destructive sampling. The above ground parts of uprooted trees were separated in to plant components.

The belowground roots in 1m×1m area around each uprooted tree were collected by digging soil up to 30 cm depth. Fresh weight of each component was measured in the field and representative sub samples were taken to the laboratory, oven dried to constant weight at 1050C in order to calculate wet-dry weight ratio.

According to the results, average total carbon content that could be lodged in 6 months, 5 and 10 years old R. mucronata stands having survival rates of 60.67%, 83.46%, 77.33% are 0.08 t C ha-1, 1.39 t C ha-1 and 66.30 t C ha-1, respectively. Average total CO2 that could be stored as carbon without being emitted to the atmosphere in 6 months, 5 and 10 years old R. mucronata are 0.28 t C ha-1, 5.13 t C ha-1 and 243.33 t C ha-1, respectively. Carbon sequestration rate of 6 months, 5 and 10 years old R. mucronata are 0.1564 t C ha-1 yr-1, 0.3134 t C ha-1 yr-1.and 6.6302 t C ha-1 yr-1, respectively. The percentage of biomass in propagule, stem, leaves and roots of 6 months old R.mucronata are 72.95%, 9.41%, 9.64% and 8.00%, respectively. In 5 years old replanted R.mucronata the proportion of biomass in stem, leaves, branches, stilt roots and roots are 23.75%, 17.36%, 9.31%, 38.76% and 10.91%, respectively. The percentage carbon partitioning in trees are similar to percentage biomass partitioning. Root: shoot ratio of 6 months, 5 and 10 years old R.mucronata is varied with the age and the values are 1:11.5, 1:8 and 1:4.7, respectively.

Climate change mitigation: Sri Lanka’s perspective

D.M.S.H.K. Ranasinghe
Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka

Climate Change with the associated increase in global temperature and sea level rise has become the most important global concern in the present day. A land mark event in this regard is the signing of the Climate Change Convention in 1992 in Rio, Brazil which provided targets for especially developed countries to reduce their Green House Gas (GHG) emissions by 5% of the 1990 levels by 2012.  Mitigation of global warming involves taking actions to reduce greenhouse gas emissions and to enhance sinks aimed at reducing the extent of global warming It has been found that almost 5400 million tons (Mt) of CO2 equivalents are emitted annually from various sources linked to human activities. Sri Lanka’s CO2 emission from fossil fuel combustion estimated at 2007 had been about 12,400 Gg CO2 which is only 0.04% of the global emission of 29,300 MtCO2 . The corresponding per capita CO2 emission was 648 kg in 2007 and although this is still much less than the global values, Sri Lanka has taken many policy measures that would result in mitigating GHG emissions.

In keeping with the global concern on sustainable development, the Government of Sri Lanka has taken many policy and program initiatives towards sustainable development which in turn helps to mitigate the adverse impacts of climate change.

Some of them are National Environmental Action Plan (1998-2001), establishment of National Council for Sustainable Development under the chairmanship of the President of Sri Lanka and the Haritha Lanka Action Plan having targets up to 2013.

Mitigatory measures have been taken in all the sectors including energy (power, transport, industry and household and commercial), land use, land use change and forestry, waste etc. The Energy Policy and Strategies (2006) of the country emphasizes the need to resort to sustainable energy and has a target of having  10% of the energy from renewable sources (Non-Conventional Renewable Sources) by 2015, a target which can be achieved if all the pending initiatives towards this is made operational. Further, the Government is constantly questing for clean energy. Some of the other initiatives to reduce the carbon footprint in the service sector are Leadership in Energy and Environmental Design” (LEED), ‘Greening Sri Lankan Hotels Programme’, setting up of the Sri Lanka Sustainable Energy Authority in 2007.

In the arena of industries, location of industries in industrial estates and conducting Strategic Environmental Assessments (SEA), voluntary standards like ISO 9001, ISO 14,001, Green building concepts, the Green Tax, Cleaner production initiatives, Clean Development Mechanism (CDM) benefits have provided incentives to reduce GHG in this sector. Many national initiatives are underway in reducing the GHGs in waste sector too. As a country with a high canopy forest cover of 23.5% and a forest cover of 40% in general the potential to act as a GHG sink in forestry sector is very high. While ensuring the sustainable development efforts this will help the country to obtain benefits from CDM or Reduced emissions from Deforestation and Land Degradation (REDD and REDD+) programs in the future.

Corticolous lichens as indicators of forest management regimes in the Dotalugala area of Knuckles mountain range – Sri Lanka

G. Weerakoon1, S. Somaratne2, P.A. Wolseley3 and S.C. Wijeyaratne1
1
Department of Botany, University of Sri Jayewardenepura, Sri Lanka
2
Department of Botany, The Open University of Sri Lanka
3
Department of Botany, The Natural History Museum, United Kingdom

Lichens have been widely considered as bioindicators of forest health and ecological continuity as well as atmospheric pollution. The use of lichens as bioindicators in tropical zones has been hampered by the lack of taxonomic and ecological knowledge. The purpose of the study was to assess the variation of lichen diversity in different forest management regimes under different environmental conditions on the basis that their potential uses as bioindicators of environmental alterations in different habitats in the Knuckles mountain range. The sampling sites were chosen to include pristine forest of montane and sub-montane and six different disturb vegetation types. Lichen species, their frequency and cover values were recorded together with environmental parameters in 20 sites of 100 m2 plots. Ten trees were sampled randomly in each plot. The collected data were analyzed to assess the relationship between lichen diversity and environmental conditions in different forest management regimes using one-way analysis variance, least significant difference- LSD (mean comparison) and Regression tree analysis.

There were 192 lichen species recorded from the natural vegetations, where as 148 lichen species present in the disturbed vegetation types. The results of the study have shown that there is a considerable variation in the lichen diversity along different vegetation types and their degree of disturbance. The statistical analysis revealed a significant variation in lichen diversity between the disturbed and undisturbed vegetation in the area (F = 6.213, df = 1; p ≤ 0.05). Similarly, lichen diversity in different vegetation types also indicated a remarkable variation (F =3.21, df = 7; p ≤ 0.05). The results obtained from regression tree analysis indicated that there were three important variables that determined the lichen diversity of the study area; type of vegetation, altitude and association with other cryptogamic communities.

There are distinct lichen communities associated with tree boles in disturbed forests including weedy taxa and low diversity with few forest lichen species.  The analysis of epiphytic lichen diversity showed significant difference in the natural vegetation and disturbed vegetation.

This may be due to the heterogeneity of microclimatic conditions and specialist lichen communities associated with pristine tropical forests. Thus, there is utmost importance to identify lichen communities that can be use as indicators of reflecting forest health for the purpose of sustainable management.