IRSPAS 2018
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Item Effect of aqueous extracts of Annona glabra plant and extracellular metabolites of two Trichoderma species on the survival of larval Culex quinquefasciatus and eggs of Aedes aegypti(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Aberathna, A. A. A. U.; Ranasinghe, H. A. K.; Rajapaksha, R. D. T.; Amarasinghe, L. D.Phytochemicals constitute a rich source of bioactive chemicals and some microbial products carry selective toxicity to many insect species, hence those are considered as alternatives to chemical insecticides. This study aimed to determine the potential of concentration gradient of Annona glabra aqueous leaf and fruit extracts for the mortality of third instar larvae of Culex quinquefasciatus; and to determine the ovicidal activity of extracellular metabolites of Trichoderma harzianum and Trichoderma viride at concentration gradient of 100, 200, 300, 400, 500 g/L on field collected eggs of Aedes aegypti with four replicates including controls for all bioassays. For the bioassays, aqueous crude extraction of plant materials was done by overnight shaking and extraction of extracellular metabolites of T . harzianum and T . viride was done using Richard ’ s broth . Study revealed that LC50 for A . glabra aqueous leaf extract for third instar larvae of Cu . quinquefasciatus was 16.26 g/L and 8.29 g/L in 24 hr and 48 hr exposure respectively (Minitab 14, Probit analysis). LC50 for A . glabra aqueous fruit extract, for third instar larvae of Cu . quinquefasciatus were higher than the LC50 for A . glabra leaf extract; 422.54 g/L and 114.01 g/L in 24 hr and 48 hr exposure respectively. 100% mortality was observed in mosquito larvae under 69.86 g/L of leaf and 1000g/L of fruit extract treatments after 24 hours of exposure. Mosquito larvae mortality compared to those in the control group reveals that the mortality of mosquito larvae may be due to the toxic compounds found in the plant. Although literature has shown that most Trichoderma strains produce volatiles and non-volatile toxic metabolites, significant ovicidal activity of extracellular metabolites of T . harzianum and T . viride on field collected eggs of Ae . aegypti was not observed (One-Way ANOVA; P>0.05) after 24 hr of exposure. The results of the study revealed that, both A . glabra fruit and leaf extracts are potential mosquito larvicides for Cu . quinquefasciatus. This may contribute to the formulation of an environmentally friendly measure to control Cu . quinquefasciatus vector mosquito species, which is a vital need to overcome the use of synthetic insecticides.Item Abundance and distribution pattern of Aedes aegypti and Aedes albopictus in selected urban, sub-urban and rural areas of Gampaha District, Sri Lanka(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Dalpadado, C. P. R. D.; Amarasinghe, L. D.The abundance and distribution of Aedes aegypti and Aedes albopictus, vectors of dengue fever, were determined at six localities in Gampaha District, which is the district with the occurrence of second highest number of dengue cases during last five years. Negombo and Wattala areas were selected to represent urbanized communities, Gampaha and Attanagalla to represent sub-urban communities and Dompe and Divulapitiya were selected for the rural communities based on population density. Percentage of premises infected with Aedes larvae (Premise Index) and the number of positive containers for 100 premises inspected (Breteau Index) were used as a proxy to determine the abundance of vectors. Larval collections were done monthly during April 2016 to June 2018 using random sampling technique for minimum 100 houses within a radius of 300 m. Potential breeding places in each site were identified and categorized accordingly. Out of 7916 premises examined, 1011 (12.8%) premises were found to be positive for Aedes mosquitoes. Among them 10.1% and 89.9% were found to be positive for Ae . aegypti and Ae . albopictus, respectively . Ae . aegypti was mostly prevalent in highly urbanized MOH areas (73%) while it showed low abundance in sub urban (21%) and rural (6%) areas. On contrary, abundance of Ae . albopictus was highest in sub-urban areas (47%) and lowest in urban areas (18%). Premise index (PI) for Ae . aegypti in urbanized areas were significantly higher than that of sub-urban (F=9.13, p<0.05) and rural areas (F=15.49, p<0.05) in Gampaha District and there was no significant difference (F=4.04, p>0.05) between PI of Ae . aegypti in sub urban and rural areas. The PI of Ae . albopictus in sub-urban areas was significantly higher than that of urban areas (F=15.43, p<0.05). There was no significant difference (F=1.44, p>0.05) between PI of Ae . albopictus in sub-urban and rural areas. Similarly, there was no significant difference between mix indices for Ae . aegypti and Ae . albopictus in Gampaha district (p>0.05). There was a strong correlation between the Breteau Index and the number of dengue patients reported in urbanized areas (r<0.5). Higher correlation was recorded with Ae . aegypti than Ae . albopictus. Therefore, occurrence of dengue epidemics are strongly correlated with Ae .aegypti indices in city areas of Gampaha District and present study suggests that Stegomyia indices can be used as a proxy to determine dengue transmission risk.Item Indoor resting preference of Aedes (Stegomia; Culicidae) mosquitoes in urban human dwellings of Gampaha District, Sri Lanka(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Dalpadado, C. P. R. D.; Amarasinghe, L. D.The current study was designed to identify the preferred resting height, place and surface of Dengue vectors, Aedes aegypti and Aedes albopictus, near human dwellings located in urban cites in Gampaha District, Sri Lanka during August 2017 to February 2018. Adult mosquitoes were collected systematically using manual aspiration technique, during 6:00 a.m. and 9.00 a.m. and 4:00 p.m. and 7:00 p.m. from all the resting localities from 280 premises. At each station, resting place, nature of the resting surface and resting height were recorded and mosquitoes were identified down to species level. In total, 378 Aedes mosquitoes (Aedes aegypti 82.3%, Aedes albopictus 17.7%) were collected and of the collected Aedes mosquitoes, 1:8 male to female ratio was observed. 68.3% of Aedes mosquitoes preferred to rest closer to the ground level and 24.9% mosquitoes rested between 1 m to 2 m above the ground level. 4.8% Aedes mosquitoes were found resting between 2 m to 3 m of height and only 1.5% Ae . aegypti mosquitoes were found resting 3 m above the ground level and none of the Ae . albopictus was recorded above 3 m from the ground level. There was no significant difference (p=0.001<0.05) between males and females in resting height for both vectors. Bedrooms were more frequently visited by resting Ae. aegypti mosquitoes (51.8%), followed by living rooms (28.5%) and kitchen (12.4%) while 52.4% female Ae . albopictus were found resting on living rooms and 28.6% in bed rooms. Identified indoor resting places were significantly different for Ae . aegypti and Ae . albopictus in Gampaha district (χ2= 20.895, P< 0.05). Majority of Aedes female mosquitoes were found resting on cloth hangings and curtains (49.3% Ae . aegypti, 77.8% Ae . albopictus) followed by under furniture (24.3% Ae . aegypti, 22.2% Ae . albopictus) . The mean number of mosquitoes per positive premise was 1.35 and maximum total number of Aedes mosquitoes collected at a premise was 7. The maximum number of females collected was 6 and maximum for males were 2 per premise. Higher abundance of Ae . aegypti in the region increases the transmission risk greatly, since Ae . aegypti bites more than one host to complete one blood meal. Since females were found resting closer to floor level especially in hidden locations such as cloth hangings, curtains and under furniture, indoor space spraying should be strengthened targeting these locations to control dengue in future.Item Nematicidal activity of Annona glabra aqueous plant extract and extracellular metabolites of two Trichoderma species on root knot nematode Meloidogyne incognita(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Lakmini, W. V.; Amarasinghe, L. D.The root knot nematode, Meloidogyne incognita, is the most widespread and serious nematode pest damaging root systems of a variety of agricultural and ornamental crops in tropical and subtropical countries throughout the world. Management of this nematode species by integrated application of synthetic insecticides and variety of non-chemical methods are suggested but many are not very effective. Even though, mature leaf extraction of Annona glabra (pond apple or alligator apple; Family Annonaceae), contains some insecticidal properties, there is no clear evidence of its nematicidal effect. This study was conducted to find the efficacy of aqueous leaf extracts of A . glabra, on root knot nematode species, M . incognita attacking spinach plants in comparison to the extracellular metabolites of two species of antagonistic fungi, Trichoderma harzianum and T . viride. Polythene bags were filled with nematode free soil. Single spinach plants having 6 leaves were transplanted into each pots. 10-12 mature adult female nematodes were added to spinach plant pots. These pots were kept outdoor for 2 weeks prior to inoculating the treatments. Above ground growth parameters such as number of total leaves, length of stem, below ground growth parameters such as number of root galls, root length were used to determine nematicidal effect on the nematode infested plants. One-way ANOVA was performed to test whether there is significant difference (95% confidence interval) between each concentrations of treatments. Results revealed that spinach plants treated with A . glabra plant aqueous leaf extract showed highest stem length and higher number of leaves compared to the control treatment. Nematicidal effect of A . glabra aqueous extract is more effective than T . viride but lower than T . harzianum when considering above ground plant growth parameters. 125 g/L of A . glabra plant aqueous leaf extract and 140 mg/L of fungal mycelium T . viride extract and 100 mg/L of T . harzianum concentrations showed the highest effect for controlling root knot nematodes. This study concludes that there is a nematicidal activity of A . glabra aqueous plant leaf extract even at lowest concentration (100 mg/L) and extracellular metabolites of T . harzianum and T . viride on M . incognita.Item Prevalence of micro-fauna associated in rice field habitats in Kurunegala district in Sri Lanka and potential mosquito larvicidal effect of Vorticella microstoma(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Ranasinghe, H. A. K.; Amarasinghe, L. D.Micro-fauna are associated with most of the mosquito larval breeding habitats in tropical climate. There may be parasitic, pathogenic or even predatory species among these biota to mosquito larvae and their potential use against mosquitoes is a new avenue of study in vector control. Rice fields are common breeding sites for certain vector mosquito species in Sri Lanka. The objective of the present study was to find the prevalence of micro-fauna in order to search for potential parasitic or pathogenic taxa/ species associated with mosquito larvae inhabiting rice field breeding habitats and to carry out bioassays for potential taxa. Sampling was done from paddy fields (n=12) in Kurunegala district using a metal larval scooper and the samples were preserved using Rose Bengal solution. Twelve micro-fauna species were recorded; the highest abundance was recorded from Vorticella microstoma (62.68%). Other micro-fauna species recorded were Zoothamnium sp., Diurella stylata, Keratella valga, Lecane luna, Monostyla bulla, Philodina citrina, Acanthocystis aculeata, Canthocamptus staphylinus, Daphnia longis, Notholca acuminata, Arcella arenaria . Also, 98 . 60 % of mosquito larvae which were collected from rice fields belonged to the genus Culex . Culex gelidus and Culex tritaeniorynchus represented the majority of samples (76.26%) and the highest abundance was recorded from Cu . gelidus . Study revealed that Vorticella microstoma trophont stage was lethal to Cu . tritaeniorynchus and Cu . quinquefasciatus larvae. Bioassay resulted that, 32.14% of Cu . quinquefasciatus died 05 days after infection with lab maintained V . microstoma cultures . Pupation was also delayed compared to the duration of normal life-cycle and only 10.71% of population emerged as adults. 100% mortality was recorded from Cu . quinquefasciatus in 2 days of infection with V . microstoma. The mean mortality percentage of two mosquito species studied were significantly different from each other (IBM SPSS Software, One-Way ANOVA: P<0.05). Trophonts of V . microstoma were infected to thorax, abdominal segments and anal papillae regions of larvae. The results of study revealed that Vorticella microstoma could be used as killing agent of mosquito larvae in future studies and would be a new avenue to work on environmentally agreeable manner in reducing the Culex spp . mosquito populations .