Faculty of Graduate Studieshttp://dr.lib.sjp.ac.lk/handle/123456789/34352024-03-28T15:35:37Z2024-03-28T15:35:37ZNatural Grain Protectants: Growth Regulatory Effects of Neem (Azadirachta indica) Seed Oil nn the Rice Moth, Corcyra cephalonica (Stainton)Amarakoon, A.M.T.M.Karunaratne, M.M.S.C.http://dr.lib.sjp.ac.lk/handle/123456789/45952022-02-24T05:30:12Z2015-09-11T00:00:00ZNatural Grain Protectants: Growth Regulatory Effects of Neem (Azadirachta indica) Seed Oil nn the Rice Moth, Corcyra cephalonica (Stainton)
Amarakoon, A.M.T.M.; Karunaratne, M.M.S.C.
Corcyra cephalonica (Lepidoptera: Pyralidae) is considered a major pest of stored cereals and cereal commodities that causes substantial loss in quality and quantity. Growth regulators are found to be one of the best sources of protection against insect pest attack, affecting the oviposition, egg hatchability and adult emergence. The present study was thus carried out to assess the growth regulatory effects of neem seed oil against C. cephalonica, in the search for a more environmentally sound and an effective approach in stored grain protection.
To evaluate the growth regulatory effects, five different concentrations of neem oil in n-hexane (0.5, 1.0. 2.0, 3.0 and 4.0%v/v) were tested. Oviposition deterrence, egg hatch inhibition and adult emergence were used as indices of growth regulation. All bioassays were carried out under ambient laboratory conditions (29±2°C and 84±2% RH). A single-choice and a dual-choice bioassay were used where the number of eggs laid on neem oil treated and untreated surfaces by mated female moths was taken as a measure of oviposition deterrence. Inhibition of egg hatching was evaluated by recording the number of hatched eggs exposed to different oil treatments for 3 hours. Adult emergence was determined by recording the number of adults emerging from 15 -17d old larvae fed on neem oil seated food medium.
The results revealed that oviposition deterrent effect increased with the increase of oil concentration. The lowest number of eggs indicating the highest deterrence (24.6±4.9) was observed at the highest concentration (4.0%v/v) when compared with the control (203.1±7.1). The results of egg hatch inhibition also showed that the highest concentration was the most effective, indicating 100% ovicidal property of the oil. Similarly, neem oil has evoked 100% reduction in adult emergence at the highest concentration. Neem oil has also induced physiological disturbances leading to growth abnormalities in the adults. The incidence of inhibition in the development was most prominent at higher doses and abnormal forms of adults exhibited varying degrees of wing deformities. The overall results of the study demonstrate a high possibility of utilizing neem oil as a protectant for sustainable insect pest management in stored grains.
2015-09-11T00:00:00ZEco-Frlendly Alternatives for Storage Pest Anagement: Leaves of Ruta graveolens (Aruda) As a Repellent Against the Rice Weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae)Perera, A.G.W.U.Karunaratne, M.M.S.C.http://dr.lib.sjp.ac.lk/handle/123456789/45942022-02-24T05:29:33Z2015-09-11T00:00:00ZEco-Frlendly Alternatives for Storage Pest Anagement: Leaves of Ruta graveolens (Aruda) As a Repellent Against the Rice Weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae)
Perera, A.G.W.U.; Karunaratne, M.M.S.C.
In view of worldwide interest and greater public awareness in finding plant products as the most promising, ecologically safer, and economical alternatives for synthetic insecticides for post-harvest protection of stored rice, present study was undertaken to explore the potential of leaves of Ruta graveolens (Aruda) as a repellent against Sitophilus oryzae infestations. Leaf powder and solvent extracts of R. graveolens were evaluated under laboratory conditions (29 - 2° C and 84x2 % RH) for their contact and fumigant repellent properties against seven day old S. oryzae adults. In contact repellency test, weevils (20 each) were exposed to 1.0 g, 3.0 g, 5.0 g. and 7.0 g o f leaf powder mixed with white raw rice grains (30 g) in a modified cup bioassay apparatus. Fumigation repellency of leaf powder was tested using same dosages and number of weevils in a fumigation-repellencv chamber. Number of weevils that moved from the bioassay chamber was recorded one hour alter weevil introduction. To evaluate the repellent action of leaf extracts, leaves o f R. graveolens were extracted in hexane, ethyl acetate, methanol and distilled water. Four extracts of different concentrations 10, 50, i00% (v/v) were assessed separately for repellent activity by means of an area preference bioassay. In all experiments, ten adult weevils for each were tested and the number repelled was recorded 30 minutes after weevil introduction. Both contact and fumigant repellent effects of plant powder against S. oryzae were significantly high at all doses and the results indicated that repellency rate increased with the increase of dose. Highest contact and fumigant repellent effects were elicited by 7.0 g o f leaf powder resulting in repellency of 96% and 95% respectively, whilst lowest dose also produced more than 50% weevil repellency indicating extremely strong repellent action of the plant powder. In comparison, aqueous leaf extract exhibited the most potent repellent activity (91%) while hexane, ethyl acetate and methanol extracts also produced 72%. 79% and 84% of repellent effects on weevils respectively at the concentration of 100% (v/v). Overall findings of the study suggest that both powder and extracts o f R. graveolens leaves could be used as eco-friendly agents for post-harvest rice protection.
2015-09-11T00:00:00ZPotential Use of NS1 Ag Strips to Detect Denv Infection in Field Collected Female Aedes Aegypti Mosquitoes from Dengue High Risk Areas in Colombo DistrictDayananda, P.D.Seneviratne, D.B.De Silva, B.G.D.N.K.http://dr.lib.sjp.ac.lk/handle/123456789/45892022-02-24T05:29:21Z2015-09-11T00:00:00ZPotential Use of NS1 Ag Strips to Detect Denv Infection in Field Collected Female Aedes Aegypti Mosquitoes from Dengue High Risk Areas in Colombo District
Dayananda, P.D.; Seneviratne, D.B.; De Silva, B.G.D.N.K.
Dengue has become the major mosquito borne viral infection in Sri Lanka. Prevention and control of dengue relies heavily on surveillance and vector control. Since entomological and human-virological surveillance is less effective in predicting outbreaks, virological surveillance of dengue vectors has now become an area of interest. Potential of dengue NS1 Ag strips (Standard Diagnostic Inc. Korea) to detect dengue virus (DENV) infection in field caught adult, female Aedes aegypti mosquitoes from selected dengue high risk areas in Colombo District was examined in the study. Three areas (Maharagama, Boralesgamuwa, Nugegoda) were selected. Mosquitoes were collected daily, identified and stored in 80 °C for NS1 antigen detection. Sampling of mosquitoes was carried out during the period of dengue outbreak (May, 2014) in Maharagama, whereas it was carried out in Boralesgamuva (March, 2014) and Nugegoda (April, 2014) during the period just after a dengue outbreak. Heads and thoraxes of mosquitoes were separated, homogenized (as singles, pools of 8-10 mosquitoes) with PBS and each homogenate was used on NS1 Ag strip. Laboratory infected and uninfected Ae. aegypti mosquitoes were tested as controls.
Study revealed the presence of NS1 antigen in field collected mosquito samples, from single mosquitos: 41% (n=24). 36% (n=22). 19% (n=3 1) and from pools: 2 of 5, 1 of 3 and 2 of 5 respectively of Maharagama, Boralesgamuwa and Nugegoda. Results illustrated the presence of DENV infected Ae. aegypti vectors in three sites. Study confirmed the potential use of NSI strips for detection of DENV in Ae. aegypti for the first time in Sri Lanka, as a rapid approach that can easily be used under field conditions with minimal training. The study suggests, adult mosquito screening for NSI Ag, as a practical approach that provide promising results in risk assessment for DENV transmission in Sri Lanka.
2015-09-11T00:00:00ZA Preliminary Study to Analyze Aedes aegypti Diversity in Sri Lanka Using Mitochondrial DNA VariationsFernando, H.S.D.Hapugoda, M.D.De Silva, B.G.D.N.K.http://dr.lib.sjp.ac.lk/handle/123456789/45882022-02-24T05:29:13Z2015-09-11T00:00:00ZA Preliminary Study to Analyze Aedes aegypti Diversity in Sri Lanka Using Mitochondrial DNA Variations
Fernando, H.S.D.; Hapugoda, M.D.; De Silva, B.G.D.N.K.
Aedes aegypti is the primary vector of dengue- which has become a major public health problem in Sri Lanka during the recent past. In the absence of an effective drug and vaccine, mosquito control appears to be the only way to protect human from this deadly virus. This in turn reveals the need for more detailed understanding of the diversity and distribution of this mosquito species in Sri Lanka. A preliminary study was done to analyze genetic variability of COI region in Aedes aegypti mosquitoes in Sri Lanka. Mitochondrial Cytochrome C Oxidase subunit I (COf) gene was sequenced and analyzed from 50 mosquito samples collected from five districts, Colombo. Jaffna, Galle, Ratnapura and Batticaloa. DNA was extracted from sampled adults and larvae- which were reared to adults. PCR amplification was carried out for COI region. Post PCR products were sent to Macrogen
Inc. Korea for sequencing and the results were analyzed using DnaSP, v. 5.0.
A total of 9 haplotypes were identified from the fifty individuals sequenced. Mainly two haplotypes were shared among populations. Haplotype 1 was present in all districts except Ratnapura, whereas haplotype 6 was present in all districts. Majority of haplotypes (4) were only found within a single district. Haplotype 7 was only present in Colombo and Ratnapura district whereas haplotype 5 was present in Galle, Ratnapura and Batticaloa populations. The nucleotide diversities were characterized in 13 polymorphic sites, of which 12 sites were parsimony informative. The overall nucleotide diversity per site was 0.01099± 0.00056. whereas haplotype diversity was 0.726 ±0.051 indicating low levels of genetic diversity.
This is the first study to analyze the genetic diversity of Ae. aegypti populations in Sri Lanka using mitochondrial DNA variations. Although low levels of genetic diversity among the populations is revealed, the need for further studies exists in order to have an insight into the role of control programmes in shaping the genetic composition of the mosquito populations. Further, the study would pave the way in predicting the dispersal patterns and the behavior of the mosquito species enabling more effective mosquito control.
2015-09-11T00:00:00Z