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.

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.

Comparison of sampling techniques to estimate tree diversity and aboveground biomass in Sinharaja forest Sri Lanka

M.D.P. Kumarathunge, R.O. Thattil, S.P. Nissanka and P. Pathinayaka

The use of correct sampling techniques is of paramount importance since the precision of estimates greatly depends on it. Different methods of sampling have to be investigated to find out the best sampling technique for a given situation. This study was conducted to determine the best sampling technique to estimate tree diversity and aboveground biomass in Sinharaja forest.

Tree sampling techniques, such as quadrat method, transect method, and point centered quarter method PCQ) were evaluated in this study. A total of 25, 15×15 m plots for quadrat method, eleven, 5×100 m strips for transect method and 120 sampling points for PCQ method were used for sampling. All stems greater than 5 cm diameter at breast height (DBH) were taken in to consideration and their species level and the tree height, DBH was recorded. Sampling techniques were compared for tree density, basal area, tree size distribution, aboveground biomass and diversity indices estimated by each technique. A simulation was done to estimate the minimum sampling area required to assess the number of tree species of the study area.

According to the results, PCQ method gave the highest precision for most of the parameters estimated. There were no significant variation between the parameters estimated by PCQ method and quadrat method for most of the situations. PCQ technique recorded the highest number of species per 100

individuals enumerated (18.12%). The negative exponential functions fitted for the species – area (quadrat method) and species – point (PCQ method) relationships estimated that the minimum sampling area required to assess the number of tree species (in an area of 50 ha) of Singharaja forest as 6000 m2 for Quadrat method and 160 sampling points for PCQ method. But it was difficult to estimate the minimum sampling area required to estimate the above ground biomass in Sinharaja since there was no underlining relationship between biomass and number of sampling units.

The results of the study emphasized that the PCQ method is a precise sampling technique that can be used to estimate the tree density, tree diversity and above ground biomass in natural forests. The random distribution of individuals is not necessary for tree diversity and biomass estimation by PCQ method if the site stratification and random placement of sampling points in the study area are performed. Considering the highest precision of estimates and the saving of time and cost, the PCQ method can be recommended as an effective sampling technique for tree diversity and biomass studies.

M.D.P. Kumarathunge, R.O. Thattil, S.P. Nissanka and P. Pathinayaka

Department of Crop Science, Faculty of Agriculture, University of Peradeniya, Sri Lanka.

Forest woodland ecosystem: An insight into the addition of litter through teak plantation

A. K. Mani, S. Manivasakan, S. Vijayabaskaran

Teak is an important tree species grown under plantation conditions for timber requirement. Being a deciduous tree, it favours for accelerated nutrient cycling. A field experiment was conducted in an eighteen year old teak plantation at Forest College and Research Institute, Mettupalayam, Tamil Nadu, India to study the litterfall, their composition and rate of decomposition. The litter collected were separated into leaf litter, flowers, fruits and twigs. All were subjected to decomposition by using nylon bag technique. The total annual litterfall accounted for 11,255 kg ha-1. Of the total litter, leaf fall in a year was 9216 kg ha-1 (81.9%) followed by 726 kg ha-1 (6.5 %) by twigs, 707 kg ha-1 (6.3 %) by fruits and 607 kg ha-1 (5.3 %) by the flowers. Among the litter components, flowers decomposed rapidly than the other components. The highest decomposition constant (K) was recorded for flowers (2.39) and the least for fruits (0.70). The per cent remaining of the absolute amount of dry matter of leaf litter, flowers, fruits and twigs after one year of decomposition was 17.3, 9.2, 49.5 and 19.6, respectively.Keywords: Forest woodland ecosystems, Teak plantations, Litter fall Decomposition

A. K. Mani, S. Manivasakan, S. Vijayabaskaran

Regional Research Station, Tamil Nadu Agricultural University, India

Growth, biomass and carbon accumulation among rubber (Hevea brasiliensis), teak

N. Appuhamy, L. Samarappuli and S. Karunaratne

The study was conducted to compare the biomass accumulation and carbon stocks among rubber, teak and mahogany. Above Ground Biomass of each species were calculated using the allometric models. Mean total tree height of rubber, teak and mahogany were ranging from 0.87 m to 20.32 m, 3.41 m to 11.05 m and 1.65 m to 7.53 m, respectively, between 1 to 10 years of age. For height and age, regression logistic standard curves were fitted to teak, rubber and mahogany with the R2 of 0.845, 0.916 and 0.921 respectively. The mean dbh of rubber, teak and mahogany were varying from 2.19 cm to 19.63 cm, 1.97 cm to 12.84 cm and 1.75 cm to 8.14 cm, respectively, within the selected age series. Exponential curves for rubber (R2=0.976) and teak (R2=0.915) and logistic curve for mahogany (R2=0.913) were fitted for dbh vs. age. Mean total tree biomass and carbon stock in rubber were significantly higher from other two species in all selected age series, except first year; biomass and carbon stock varying 0.89 kg/tree to 262.61 kg/tree and 0.45 kg/tree to 131.30 kg/tree, respectively. For other two species, it was ranged from 0.74 kg/tree to 88.87 kg/tree and 0.37 kg/tree to 44.35 kg/tree for teak and 0.49 kg/tree to 23.83 kg/tree and 0.24 kg/tree to 11.91 kg/tree for mahogany. For Biomass and age regression logistic, critical exponential and exponential standard curves were fitted to rubber (R2=0.965), mahogany (R2=0.862) and teak (R2=0.874). The relationship of Height vs. dbh showed a high degree of association for rubber (R2=0.918), teak (R2=0.859) and mahogany (R2=0.976). Moreover, the relationship of biomass vs. height recorded a high degree of association for rubber (R2=0.911), teak (R2=0.862) and mahogany (R2=0.962).Keywords: Biomass accumilation, dbh, treeheight, teak, Mahogany, Rubber

N. Appuhamy1, L. Samarappuli2 and S. Karunaratne1

1Department of Plantation Management, Faculty of Agriculture and Plantation Management,

University of Wayamba, Sri Lanka

2Department of Soils and Plant Nutrition, Rubber Research Institute of Sri Lanka.

Effect of particle size of Coco peat for Greenhouse Tomato (Lycopercicum esculantum

H.K.M.S. Kumarasinghe1 and D.G.D. Ransimala2

Coco peat is a by product of extraction of fiber from coconut husk. It is 100% natural, biodegradable, fibrous and spongiest material. It has high C: N ratio, therefore it take long period to decompose. Also it has high water holding capacity, approximately 7-9 times its own weight. Coco peat contains antifungal and antibacterial properties. In addition, it contains high Cation Exchange Capacity (CEC) and moderately high pH value. Considering above properties, Coco peat is very good plant growth substrate, after adjusting several properties in soil less cultivation such as green house vegetable nurseries.

Before start the experiment, raw coco peat were taken from bulk and checked for EC and pH, then put into the soaking tank and added Ca(NO3)2 super soluble fertilizer (rate 2kg per one ton of wet raw coco peat). Then washed out four times up to 600 μS/cm and sun dried up to 13% moisture level. Coco peat were graded according to the particle size; particle size greater than 4mm (coarse particle), particle size between 4 mm – 0.5mm (medium particle) and particle size less than 0.5mm (fine particle) and unseived materials (row coco peat). Above four different sizes of particles were used as treatments and studied the nursery performances by using tomato seeds. The experiment was arranged as Completely Randomized Design with four replicates. Germination percentage was measured up to 7 days. Plant height and number of leaves were taken up to 3 weeks.

Result revealed that seed germination was significantly higher (p>0.05) in medium size particles (88%), compared to all other particle sizes. Also highest plant height and number of leaves were observed in medium size particles throughout the nursery period. Results can be concluded that the most suitablepartial size for tomato nursery in green house is medium size coco peat particles.

Keywords :- Antifungal, Coco peat, Plant growth substrate, Vegetable Nurseries.

H.K.M.S. Kumarasinghe1 and D.G.D. Ransimala2

1Department of Crop Science, Faculty of Agriculture, University of Ruhuna Sri Lanka

2Ceyland International (Pvt) Ltd, Kuttigala, Embilipitiya, Sri Lanka