Browsing by Author "Wickramarachchi, Suranga R."

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Antifungal properties of chitosan microcapsules containing cinnamon oil and lemongrass oil against aspergillus flavus isolated from stored rice
(ACTA CHEMICA IASI, 2020) Paragodaarachchi, Yashodha L.; Subasinghe, Prarthana; Wickramarachchi, Suranga R.
Essential oils have long been attracted as substitutes for synthetic chemical pesticides because of their antimicrobial properties, low mammalian toxicity and wide public acceptance. Essential oils of lemongrass and cinnamon leaf were encapsulated using chitosan, a biodegradable polymer by emulsion formation/ionotropic gelation technique. A. flavus was isolated from stored rice. In-vitro antifungal efficacy of oil loaded microcapsules against A. flavus and its time profile were determined. Based on morphological and molecular characteristics the fungus was identified as Aspergillus flavus. Both lemongrass and cinnamon leaf oil and their respective microcapsules were fungicidal against A. flavus. The Minimum inhibitory oil load of lemongrass and cinnamon leaf oil microcapsules were 0.5 g and 0.75 g respectively. Lemongrass showed a comparatively higher activity than cinnamon against the test fungi. However, cinnamon possessed the antifungal activity for a longer duration than lemongrass. Encapsulation of oil within chitosan may effectively reduce the evaporation rate of oil thus increasing its bioavailability. Microcapsules of cinnamon and lemongrass oil have the potential to be developed as a natural fungicidal formulation to control A. flavus.
Extracellular extracts of antagonistic fungi,Trichoderma longibrachiatum and Trichoderma viride, as larvicides against dengue vectors, Aedes aegypti and Aedes albopictus
(2023) Perera, Dinusha S.; Tharaka, W.G. Hiruni; Amarasinghe, Deepika; Wickramarachchi, Suranga R.
Aedes aegypti and Aedes albopictus are the responsible vectors of transmitting dengue in Sri Lanka. Excessive use of chemical pesticides causes insecticide resistance.Therefore, mosquito biolarvicides remain to be an important method for mosquito control. The use of fungal metabolites can be considered a tool to overcome the issues related to insecticide resistance and environmental pollution. The present study focused on the evaluation of the mosquito larvicidal efficacy of Trichoderma longibrachiatum and Trichoderma viride aqueous and crude extracellular metabolites against Ae.aegyptiand Ae.albopictusunder the laboratory conditions. Fungi were grown in Richards' broth medium for collection of fungal biomass. Eight test concentrations of extracellular aqueous and crude fungal filtrates in a range from 12.5 gL−1 to 175 gL−1 were prepared and batches of 25 laboratory-reared third instar larvae of Ae.aegypti and Ae.albopictus were exposed to each test concentration separately with three replicates. Control bioassays were conducted with distilled water and larval mortality was recorded after 24 hours and 48 hours of exposure periods. The study revealed that LC values and LC values for extracellular crude metabolites for two fungal species were lower than the values obtained for extracellular aqueous extracts. All the LC values obtained for Ae.albopictus were lower than that of Ae.aegypti. LC values obtained for T.viride aqueous extracellular metabolites were 81.46 gL and 87.75 gL in 24 hours, 70.66 gL and 77.93 gL in 48 hours for Ae. albopictus and Ae. aegypti respectively. LC values obtained for T.longibrachiatum aqueous extracellular metabolites were recorded as 103.35gL and 108.79gL in 24 hours and 93.05gL and 102.1gL in 48 hours for Ae.albopictus and Ae.aegypti respectively. It was revealed that LC values obtained for T.viride crude extracellular metabolites were 34.42gL and 47.27gL in 24 hours, 30.29gL and 41.56gL in hours for Ae.albopictus and Ae.aegypti respectively. LC values obtained for T.longibrachiatum crude extracellular metabolites were 49.84gL and 59.24gL in 24 hours, 40.73gL and 51.49gL in 48 hours for Ae.albopictus and Ae.aegypti respectively. It can be concluded that there is a potential for using T.viride as an effective larvicide against dengue mosquitoes.
Mycosynthesis of Silver Nanoparticles (Trichoderma viride, Trichoderma longibrachiatum) and their Mosquito Larvicidal Efficacy on Dengue Vectors and Acute Toxicity on Moina macrocopa
(Asian Journal of Chemistry, 2023) Perera, Dinusha s.; Tharaka, W.G. hiruni; Wickramarachchi, Suranga R.; Amarasinghe, Deepika; De silva, Channa R.; Gunawardana, Thilini N.
Current study is based on the larvicidal effect of mycosynthesized siver nanopartices (AgNPs) from Trichoderma longibrachiatum (Tl-AgNPs) and Trichoderma viride (Tv-AgNPs) on Aedes aegypti and Aedes albopictus dengue vectors and non-targeted aquatic crustacean, Moina macrocopa. Mosquito larvae were exposed to each test concentration (10 to 50 mg L-1) of Tl-AgNPs and Tv-AgNPs separately with three replicates containing 25 larvae each. The AgNPs characterization confirmed the formation of Tl-AgNPs and Tv-AgNPs in the UV-Vis spectrum with the surface plasmon resonance (SPR) band at 430 nm, existence of biomolecules and stabilizing agents on the AgNPs in FTIR spectroscopy and the presence of spherical shape AgNPs in a size range of 15-20 nm in TEM. The total larval exposure period was 48 h in order to evaluate 24 and 48 h larval mortalities and the toxicity effects on Moina macrocopa were also evaluated. LC50 were recorded as 14.68 mg L-1,14.05 mg L-1 after 24 h and 13.4 mg L-1, 12.94 mg L-1 after 48 h of exposure to A. aegypti and A. albopictus, respectively for Tl-AgNPs. The LC50 for Tv AgNPs were recorded as 12.08 mg L-1,14.05 mg L-1 after 24 h and 13.4 mg L-1, 12.94 mg L-1 after 48 h exposure for A. aegypti and A. albopictus, respectively. The Tv-AgNPs are reported to be more toxic for M. macrocopa after 48 h exposure with LC50 0.167 ppm, LC90 0.291 ppm for Tl-AgNPs and LC50 0.155, LC90 0.248 ppm for Tv-AgNPs. This study concludes Tl- AgNPs and Tv-AgNPs could be used as potential larvicide for dengue vector control. Results confirmed that Tv-AgNPs are more effective than Tl-AgNPs in controlling mosquito larvae. However, there is a potential threat to other non-targeted organisms in the practical aspects of this treatment.