Prediction of the potential geographic distributions and risk assessment of four trade impacting invasive insect pests in Australia and China

This thesis explores biological invasion through the potential pest distribution and risk analysis of tomato potato psyllid (TPP), Bactericera cockerelli; fall armyworm (FAW), Spodoptera frugiperda; Bactrocera bryoniae; and Bactrocera neohumeralis. Through better understanding of the pest distribution and risk analysis agricultural management policies can be implemented, and containment and eradication actions taken. The TPP is a psyllid native to North America that has recently invaded Australia. The potential for economic losses accompanying invasions of TPP and its associated bacterial plant pathogen Candidatus Liberibacter solanacearum (CLso), has caused much concern. Here, we employed ecological niche models to predict environments suitable for TPP/CLso on a global scale and then evaluated the extent to which global potato cultivation is at risk. A total of 86 MaxEnt models were built using various combinations of settings and climatic predictors, and the best model based on model evaluation metrics was selected. Climatically suitable habitats were identified in Eurasia, Africa, South America, and Australasia. Intersecting the predicted suitability map with land use data showed that 79.06% of the global potato production, 96.14% of the potato production acreage in South America and Eurasia, and all the Australian potato production are at risk. The information generated in this study increases knowledge of the ecology of TPP/CLso and can be used by government agencies to make decisions about preventing the spread of TPP and CLso across the globe. Fall armyworm (FAW), S. frugiperda is native to the Americas and it has rapidly invaded 47 African countries and 18 Asian countries since the first detection of invasion into Nigeria and Ghana in 2016. It is regarded as a ‘super pest’ based on its host range (at least 353 host plants), its inherent ability to survive in a wide range of habitats, its strong migration ability, high fecundity, rapid development of resistance to insecticides/viruses and its gluttonous characteristics. In order to better understand the seasonal geographic distributions of S. frugiperda, we employed ecological niche models of MaxEnt to predict potential year-round breeding and seasonal distribution for S. frugiperda on a global scale and in Australia. A total of 74 MaxEnt models were built using various combinations of regularization multiplier, feature class and climatic variables, and the best model based on model evaluation metrics was selected, with an evaluation of dominant climatic factors that control its distribution. The results suggest that the temperature factor was the most important variable affecting the seasonal distribution of S. frugiperda. No matter where in the world, the year-round breeding distribution model predicted smaller portions of fall armyworm's ranges than the seasonal model. S. frugiperda had a high remaining invasion potential in Australia, posing a significant threat to its biosecurity, food security and agricultural productivity. Bactrocera bryoniae and Bactrocera neohumeralis are highly destructive fruit flies and considered major biosecurity/quarantine pests of fruit and vegetable in the tropical and subtropical regions in the South Pacific. Ecological niche modelling MaxEnt was employed to predict the potential geographic distribution of B. bryoniae and B. neohumeralis across the world and particularly in China with the occurrence data of these two species. B. bryoniae and B. neohumeralis exhibit similar potential geographic distribution ranges across the world and in China, and included southern Asia, the central and the southeast coast of Africa, southern North America, northern and central South America, and Australia. While within China, most of the southern Yangtze River area was found suitable for these two species. Notably, southern China was considered to have the highest risk of B. bryoniae and B. neohumeralis invasions. Our study identifies the regions at high risk for potential establishment of B. bryoniae and B. neohumeralis in the world and particularly in China and informs government officials to develop policies for inspection and biosecurity/quarantine measures to prevent and control their invasion

Fabrication and Characterization of Antifungal Essential Oil-In-Water Nanoemulsion Delivery System Targeting Fusarium Graminearum In Vitro and During the Malting Process

Fusarium mycotoxins represent the most food safety concern for the malting industry. The complete prevention of Fusarium mycotoxins in the grains by limiting toxigenic fungi in the field and during storage is not practical. The common way to control Fusarium mycotoxins in malting industry is to avoid infected grains. However, avoidance is not always possible. To ensure the quality and safety of food products, development of food-grade antifungal strategies that can be applied in food processing, would benefit growers and the food industry. Recently, plant-based essential oils (EOs) have received considerable attentions in the food industry due to broad-spectrum of antifungal activities and inhibitory effect against mycotoxin biosynthesis. However, direct application of EOs during the malting process is impractical. In this project, parameters that impact on the formation of EO-in-water nanoemulsions and functional properties including antifungal and mycotoxin inhibitory efficacy were evaluated in vitro. The proper-designed EO-in-water nanoemulsions were then applied in micro-malting process. Results indicated that physically stable EO-in-water nanoemulsions can be fabricated by incorporating either ?75 wt% of corn oil or ?50 wt% of medium chain triacylglycerol (MCT) into EO before homogenization and homogenized under optimized processing conditions (68.95 MPa and 2 passes). In general, the mycotoxin inhibitory efficacy of EO was enhanced considerably in nanoemulsion form than bulk oil. Among all selected five EOs, thyme and clove oil-in-water nanoemulsions had the greatest antifungal and mycotoxin inhibitory activities. In terms of emulsifiers, the antifungal activity was mainly dominated by EO rather than emulsifier to alter mycelial and spore cell membrane integrity. At last, clove oil-in-water nanoemulsions stabilized by three different emulsifiers (Tween 80, bovine serum albumin, quillaja saponins) were selected to apply in micro-malting process according to our germinative energy test of barley seeds. All clove oil-in-water nanoemulsions had the capability to inhibit fungal growth and DON production during the micro-malting process. Among the three emulsifiers, Tween 80-stablized clove oil nanoemulsion displayed largest reduction of mycotoxin and least flavor impact on the final malt. The overall project showed a great potential for utilization of EO-in-water nanoemulsion as antifungal agent and mycotoxin inhibitor in the food industry

Performance Characterization of Coagulation Pretreatment for Two Industrial Effluents

In this work, performances of coagulation and flocculation were tested for two different industrial effluents. Coagulation-Flocculation and activated carbon adsorption were applied for the remediation of oil sands process-affected water (OSPW), generated from oil sands operations in Alberta, Canada. OSPW is a complex mixture of suspended solids, various suspended and dissolved organic compounds. Alum and natural coagulant Opuntia ficus-indica (OFI) were used as the coagulants, and the process was optimized to improve the removal of turbidity and dissolved organic carbon (DOC). The maximum removal of 98% and 63% in turbidity and DOC from OSPW, respectively occurred at pH=6.32, with an alum dosage of 190.44 mg/L and activated carbon at 0.28 g/L. Whereas a comparable removal of turbidity and DOC from OSPW occurred at similar pH and carbon loading at a much higher dosage of 780 mg/L for natural coagulant. Adsorption on polymer seems to be the mechanism of removal of DOC from OSPW during coagulation. Natural coagulant increases the DOC of water due to dissolution of sugars and carbohydrates from natural coagulant, but these compounds are highly biodegradable and should not be a problem when treated water is disposed of in natural environment. Large volumes of bilge water are generated by the ships across the world. Due to the abundance of saline water on-board, performance of sodium chloride/ calcium silicate as a coagulant for oily waste water was determined and compared with that of alum/ calcium carbonate. Almost 93% of the oil was recovered at the top and bottom when 100 mg alum/L and 1 g calcium carbonate/L was used, and a very clear effluent was produced in the middle section of the treatment vessel. 5 wt% of NaCl was effective in coagulating the bilge water, but at a much higher dosage than alum

Risk estimation and prediction of the transmission of coronavirus disease-2019 (COVID-19) in the mainland of China excluding Hubei province

In December 2019, an outbreak of coronavirus disease (later named as COVID-19) was identified in Wuhan, China and, later on, detected in other parts of China. Our aim is to evaluate the effectiveness of the evolution of interventions and self-protection measures, estimate the risk of partial lifting control measures and predict the epidemic trend of the virus in the mainland of China excluding Hubei province based on the published data and a novel mathematical model.; A novel COVID-19 transmission dynamic model incorporating the intervention measures implemented in China is proposed. COVID-19 daily data of the mainland of China excluding Hubei province, including the cumulative confirmed cases, the cumulative deaths, newly confirmed cases and the cumulative recovered cases between 20 January and 3 March 2020, were archived from the National Health Commission of China (NHCC). We parameterize the model by using the Markov Chain Monte Carlo (MCMC) method and estimate the control reproduction number (R; c; ), as well as the effective daily reproduction ratio- R; e; (t), of the disease transmission in the mainland of China excluding Hubei province.; The estimation outcomes indicate that R; c; is 3.36 (95% CI: 3.20-3.64) and R; e; (t) has dropped below 1 since 31 January 2020, which implies that the containment strategies implemented by the Chinese government in the mainland of China are indeed effective and magnificently suppressed COVID-19 transmission. Moreover, our results show that relieving personal protection too early may lead to a prolonged disease transmission period and more people would be infected, and may even cause a second wave of epidemic or outbreaks. By calculating the effective reproduction ratio, we prove that the contact rate should be kept at least less than 30% of the normal level by April, 2020.; To ensure the pandemic ending rapidly, it is necessary to maintain the current integrated restrict interventions and self-protection measures, including travel restriction, quarantine of entry, contact tracing followed by quarantine and isolation and reduction of contact, like wearing masks, keeping social distance, etc. People should be fully aware of the real-time epidemic situation and keep sufficient personal protection until April. If all the above conditions are met, the outbreak is expected to be ended by April in the mainland of China apart from Hubei province