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This study investigated the dynamics of land use and land cover (LULC) modelling, mapping, and assessment in the Kegalle District of Sri Lanka, where policy decision-making is crucial in agricultural development where LULC temporal datasets are not readily available. Employing remotely sensed datasets and machine learning algorithms, the work presented here aims to compare the accuracy of three classification approaches in mapping LULC categories across the time in the study area primarily using the Google Earth Engine (GEE). Three classifiers namely random forest (RF), support vector machines (SVM), and classification and regression trees (CART) were used in LULC modelling, mapping, and change analysis. Different combinations of input features were investigated to improve classification performance. Developed models were optimised using the grid search cross-validation (CV) hyperparameter optimisation approach. It was revealed that the RF classifier constantly outstrips SVM and CART in terms of accuracy measures, highlighting its reliability in classifying the LULC. Land cover changes were examined for two periods, from 2001 to 2013 and 2013 to 2022, implying major alterations such as the conversion of rubber and coconut areas to built-up areas and barren lands. For suitable classification with higher accuracy, the study suggests utilising high spatial resolution satellite data, advanced feature selection approaches, and a combination of several spatial and spatial–temporal data sources. The study demonstrated practical applications of derived temporal LULC datasets for land management practices in agricultural development activities in developing nations. [ABSTRACT FROM AUTHOR]

Insect Growth Regulator (IGR) novaluron is an alternative to synthetic neuro-inhibitory insecticides. Present study was designed to assess appropriate dosages of novaluron for dengue vector control. Larvae of Aedes aegypti and Ae. albopictus were exposed to a concentration series of novaluron (Rimon EC10) for two fixed exposure periods of 7-days and 14-days to determined LC50 and LC99 values. Inhibition of adult emergence (IE50 and IE99) was determined by a 14-day exposure. Semi-field experiments were conducted by exposing cohorts of Ae. aegypti larvae to IE99, 2 × IE99 and 10 × IE99 novaluron concentrations in water storage buckets (10 L) and plastic barrels (200 L). For the 7-day exposure, LC50 values were 0.047–0.049 ppm and LC99 were 0.144–0.151 ppm. For 14-day exposure, these values were 0.002–0.005 ppm and 0.006–0.01 ppm respectively. For both species, IE99 was 0.001 ppb under semi-field conditions, and was effective for nearly 2 months. Novaluron concentration 0.01 ppb was effective up to 3 months, with an IE of 89–95%. Authorities should critically review a reduction of the presently recommended field dosage of 200 ppm novaluron by × 100 or more. This would provide the same efficacy but mitigate environmental pollution, development of vector resistance, and financial losses. [ABSTRACT FROM AUTHOR]

Pyrethroid resistance has imposed a severe threat to the control programmes of dengue vectors Aedes aegypti and Ae. albopictus in Sri Lanka. Present study investigated the resistance status and underlying mechanisms of these mosquitoes in six provinces of Sri Lanka. Mosquitoes were collected from Badulla (Uva Province), Batticaloa (Eastern), Colombo (Western), Jaffna (Northern), Kandy (Central) and Kurunegala (Northwestern). Adults were exposed to discriminating dosages of permethrin, deltamethrin, λ-cyhalothrin, cyfluthrin and DDT according to WHO guidelines. Survivals from bioassays were tested for kdr type mutations. Elevation of insecticide metabolizing enzymes and insensitivity of acetylcholinesterases, the target site of organophosphates and carbamates, were also tested. A total of 4875 mosquitoes (2687 Ae. aegypti, 2188 Ae. albopictus) were subjected to bioassays. All the populations had high resistance to DDT though it has not been used in the country for more than four decades. In general, Ae. aegypti populations showed more resistance towards pyrethroids. Glutathione S-transferase (GST) activities were enhanced in most of the populations with no enhancement of carboxylesterase and monooxygenase activities. Acetylcholinesterases were not altered in both species. Aedes aegypti showed high resistance to pyrethroids, mainly due to three kdr type mutations; V1016I, S989P and F1534C found in the voltage gated sodium channel which is the target site of pyrethroids and DDT. Both species were highly resistant to DDT mainly through a GST based mechanism. In the absence of elevated esterase-based and insensitive AChE mechanisms, organophosphates and carbamates can be recommended as alternatives for future dengue vector control programmes in Sri Lanka. [ABSTRACT FROM AUTHOR]

Avian blood parasites have been shown to have significant health effects on avifauna worldwide. Sri Lanka, a tropical island rich with resident and migratory birds, has not been properly evaluated for avian blood parasites or their vectors. We investigated the presence of avian haemoparasites in Sri Lankan birds and the potential mosquito vectors of those pathogens. Blood samples were collected from local/migratory birds captured by standard mist nets from Anawilundawa bird sanctuary, Hanthana mountain range, and the University of Peradeniya park. Mosquitoes were collected from Halgolla forest reserve and the forest patches in Kurunegala and Gampola areas in addition to the above mist-netting localities. Part of the mitochondrial cytochrome b (cytb) gene was amplified and sequenced to detect the presence of haemoparasites from avian blood samples (86) and mosquito samples (480). Blood parasites of the two genera, i.e., Haemoproteus (4 species; Haemoproteus sp. 1-4) and Plasmodium (5 species; Plasmodium sp. 1-5) were identified from seven bird species (four resident and three migratory). Among these, three bird species (Red-vented bulbul (3/16), Asian Brown flycatcher (1/1), and India pitta (1/1)) were positive for Plasmodium spp., while four (Yellow-browed bulbul (1/4), oriental white-eye (1/4), brown-headed Barbet (1/4), and Indian blue robin (1/1)) were positive for Haemoproteus spp. Two mosquito species were also positive for Plasmodium (3) and Haemoproteus (1) species. Phylogenetic analysis and haplotype networks created using positive sequences of haemoparasites showed that a Plasmodium clade was shared by Cx nigropunctatus mosquitoes and the migratory bird, Indian pitta. The majority (85%) of the Plasmodium and Haemoproteus sequences of this study were not linked to the well-characterized species suggesting the distinct nature of the lineages. Associations between mosquito species and blood parasites of birds suggest the possible vector status of these mosquitoes. [ABSTRACT FROM AUTHOR]

Tropical agricultural soils have been claimed as a source of carbon. As agricultural systems in the tropics are highly diverse, it is useful to study soil organic C (SOC) of different agricultural systems. We quantified the SOC fractions, available nutrients, and aggregate stability in eight different tropical agricultural systems, including annual crops under different management scenarios, such as organic, inorganic, and combined fertilizer applications. Annual crops treated with organic fertilizer only (A–OF), inorganic fertilizer only (A–IF), both organic and inorganic fertilizers (A–O/IF), perennial crops (PC), home gardens (HG), and abandoned home gardens (AHG) in Eutrustox soils and annual crops with organic fertilizer only (A–OFS) and uncultivated land on Quartzipsamments soil (USR) were studied. The links between SOC fractions, available nutrients, and aggregate stability in these soils were analyzed. Regression models were fitted for SOC fractions and available nutrients. Our results indicated that the different land use types exhibited significant variations in organic carbon fractions, aggregate stability, and available nutrients in soils. The available macro and micronutrients, except for nitrogen, showed a significant positive correlation with either total organic C (TOC) or carbon fractions indicating the synergy between them. The differences in soil C stocks clearly reflected the differences in litter fall and soil disturbance, as indicated by the highest C stocks in AHG. The dry weight of collected litter showed that AHG accumulated the highest litter content (97.38 g/m2) compared to the lowest (37.63 g/m2) in A–I/F. Organic matter addition to soil also increased the C stocks, even in annual crops. Aggregate stability showed a positive correlation with C fractions. The regression models developed in this study can be used to predict available nutrients by measuring TOC or C fractions in similar land use types in the tropics. This study confirmed that tropical agricultural systems that include annual crops have potential for storing and maintaining C in soils, if appropriately managed. The beneficial influence of SOC on available nutrients and aggregate stability could be a driving force to increase carbon stock in tropical agricultural systems. [ABSTRACT FROM AUTHOR]

A miniature incubator was used in combination with a cryofocusing inlet system and GC-TOFMS in order to determine the rate of hexanal production during myoglobin (Mb)-induced lipid peroxidation of phosphatidyl choline containing arachidonic acid. The cryofocusing inlet system allowed for rapid preconcentration of the volatile products of the peroxidation reaction, yielding a total analysis time for hexanal of less than 4 min. Each reaction was sampled repetitively, and the production of hexanal was determined in real time, as the reaction progressed. Myoglobin-induced lipid peroxidation produced hexanal linearly over 40 min, maximizing at an average concentration of 1 ppm after 60 min. In reaction mixtures containing basal levels of hexanal, presumably due to autoxidation occurring during storage, greater amounts of hexanal were formed at a faster rate of production, though the production was not linear for more than 15 min. The rapid preconcentration and nondestructive sampling are advantageous; the sampling time can be adjusted in order to detect and quantitate minor products, and the instrumentation can thus be used for full profiling of the volatile products of lipid peroxidation. [ABSTRACT FROM AUTHOR]