https://www.um.edu.mt/library/oar/handle/123456789/10660 Sun, 06 Sep 2026 14:50:37 GMT 2026-09-06T14:50:37Z https://www.um.edu.mt/library/oar/handle/123456789/148637 Title: Formulation of plant-based pesticides Abstract: The increasing reliance on synthetic pesticides in modern agriculture is raising concerns regarding environmental contamination, biodiversity loss, pesticide resistance, and risks to human health. Because of this there is an increasing interest in botanical pesticides as a sustainable alternative to synthetic pesticides. Because of its warm Mediterranean climate, Malta faces this challenge in various crops, particularly in the production of brassica crops such as the cauliflower. which are economically important crops affected by caterpillar pests. This study evaluated the potential of Nicotiana glauca-based formulations as botanical insecticides through an integrated assessment of biological efficacy, toxicity, and residue persistence. The research focused on cauliflower (Brassica oleracea var. botrytis), one of Malta's most commonly cultivated brassica crops, and targeted two major pest species, the Small White Butterfly (Pieris rapae) and the Large White Butterfly (Pieris brassicae), both of which can cause substantial crop damage and economic losses to farmers. Three complementary approaches were employed: an in vivo caterpillar assay, a residue analysis in cauliflower tissues using UV-Vis spectrophotometry, and a brine shrimp lethality assay (BST) with probit analysis for LC₅₀ determination. The caterpillar study demonstrated that all treatments, including Nicotiana glauca (Ng) and its combination with garlic (T), significantly reduced survival over time. Although the synthetic insecticide (E) induced faster initial mortality, botanical treatments achieved comparable lethality within the experimental period. The BST assay confirmed dosedependent toxicity for all treatments, with strong linear probit-log dose relationships (R² = 0.88-0.99). The combined treatment (T) exhibited the highest toxicity (LC₅₀ = 19.82 µg/mL), followed by Ng (29.60 µg/mL), while nicotine showed the lowest toxicity (78.86 µg/mL). Statistical analysis revealed significant differences in both slopes and intercepts of doseresponse curves, indicating distinct toxicological profiles. Residue analysis showed that alkaloid-related compounds from Nicotiana glauca degraded rapidly in cauliflower tissues, with half-lives of approximately 1 day and DT₉₀ values around 3 days. In contrast, the synthetic insecticide exhibited significantly greater persistence (DT₉₀ ≈ 10 days). These findings indicate that botanical treatments provide strong biological activity while minimising long-term residue accumulation. The integration of results demonstrates that Nicotiana glauca-based formulations are effective and rapidly degrading bioinsecticides. However, the measurable toxicity of the control formulation highlights the importance of considering formulation effects. Overall, the study supports the potential of botanical pesticides as environmentally favourable alternatives to synthetic insecticides, while emphasising the need to balance efficacy, persistence, and formulation in their development. Description: M.Sc.(Melit.) Thu, 01 Jan 2026 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/148637 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/148055 Title: Assessing the conservation status of selected insects in the Maltese Islands Abstract: The main aim of this dissertation is to present an evaluation of the conservation status of selected groups of insects of the Maltese fauna, including a reassessment of selected species listed in Schembri and Sultana (1989). Species were evaluated using IUCN criteria based on data from literature published over the last 30 years. Selected species within 48 selected families from Coleoptera, Diptera, and Lepidoptera were considered on the basis of the information available. The conservation status using IUCN categories as well as notes are provided for each species that was (re)evaluated. Overall, a total of 381 species were successfully (re)assessed, including 95 species from Schembri and Sultana (1989). The overall percentages of IUCN categories that were evaluated is as follows: ‘Least Concern’ – 6.3%, ‘Near Threatened’ – 5.5 %, ‘Vulnerable’ – 13.6%, ‘Endangered’ – 27.3%, ‘Critically Endangered’ – 15.5%, ‘Possibly Extinct’ – 13.6%, ‘Data Deficient’ – 17.6%, and ‘Not Applicable’ 0.3%. There was a significant change in the IUCN conservation status of selected species that were mentioned in Schembri and Sultana (1989), with 59% of species evaluated being in a threatened or near threatened category, an increase from 1% to 11% of species classified as ‘Possibly Extinct’, and from 0% to 3% in the ‘Least Concern’ and ‘Near Threatened’ categories; and a decrease in the ‘Vulnerable’ (from 21% to 18%) and the ‘Endangered’ (from 30% to 24%) categories. This may be due to using a more objective approach when evaluating the species with the standardised IUCN criteria, rather than the previous subjective approach. When comparing distribution type (endemic vs nonendemic), no significant difference was found on extinction risk. This was probably due to the fact that even non-endemic species are frequently threatened at the local scale because of their small extent of occurrence and area of occupancy at the national scale, in turn largely a consequence of the small size of the islands. Moreover, the last recorded locations of ‘Critically Endangered’ and ‘Possibly Extinct’ species, as well as all the distribution data for threatened species, were visualised on QGIS maps, which display clustering in locations such as Buskett, Marsa, Salina, Mġarr, Rabat, Dingli, Marsaskala, Marsaxlokk, Girgenti, Mellieħa, Għar Lapsi in Malta, and Ramla, Marsalforn, Victoria and Xlendi in Gozo. These locations include habitats such as sand dunes, salt marshes, and freshwater pools, and are considered vulnerable due to human impact, climate change, and habitat loss. Therefore, these locations should be of conservation priority. In conclusion, long-term monitoring as well as further research into the ecology of the species evaluated, as well as assessment of both direct and indirect impacts that are contributing to insect population decline, is recommended in order to develop better conservation strategies for the preservation of the Maltese insect fauna. Description: M.Sc.(Melit.) Thu, 01 Jan 2026 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/148055 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/148053 Title: Evaluating the influence of temperature fluctuations on soil state in the Maltese Islands using remote sensing techniques Abstract: Increasing temperatures and droughts present growing environmental challenges in the Mediterranean region, particularly for small island environments like the Maltese Islands where water resources are limited and climate pressures are intensifying. This study examined the spatial and temporal variability of soil surface temperature and soil dryness across the Maltese Islands over a ten-year period (2015–2024) using remote sensing techniques. The analysis focused on seasonal and interannual changes in Land Surface Temperature (LST) and the Temperature Vegetation Shortwave Dryness Index (TVSDI), and on evaluating the relationship between surface temperature and soil dryness under semi-arid conditions. Wet and dry seasons were analysed separately to capture the strong seasonal contrasts characteristic of the Mediterranean climate. Statistical analyses, including correlation and regression tests were applied to assess relationships between LST and TVSDI across districts and seasons. The results revealed a clear seasonal contrast, with dry-season LST values consistently exceeding wet-season values across all districts. While district-level differences in LST were not statistically significant once seasonality was considered, spatial patterns showed persistently higher temperatures in urbanised districts and cooler conditions in rural districts and hydrologically active areas. TVSDI values remained relatively uniform during the wet season, reflecting the homogenising effect of winter rainfall, but exhibited pronounced spatial and temporal variability during the dry season. The South Eastern, Western and Gozo districts consistently recorded the highest dryness levels, with extreme conditions observed in 2016, 2020 and particularly 2024. A strong and statistically significant positive relationship between LST and TVSDI was identified during the dry season, indicating that surface temperature is the dominant driver of soil dryness under moisture-limited conditions. In contrast, weak wet-season relationships highlighted the moderating role of rainfall. Overall, the findings demonstrated the effectiveness of LST-based remote sensing indices for monitoring soil dryness in semi-arid island environments and provided insight into emerging drought trends under ongoing climate change. Description: M.Sc.(Melit.) Thu, 01 Jan 2026 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/148053 2026-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/144851 Title: Recapping and mite non-reproduction in the endemic honey bee subspecies of Malta : Apis mellifera ruttneri Abstract: Scientific literature concerning Apis mellifera ruttneri, the endemic honey bee of the Maltese Islands is still limited. Recently, its behaviour and development gained an increasing attention particularly in relation to Varroa resistant traits. Nevertheless, the effect of recapping on mite reproduction remains controversial. In October 2021, a standardized study was set up for the evaluation of two resistant traits: recapping and mite non-reproduction (MNR). In total 40 colonies (A.m.ruttneri n = 20, and Buckfast n = 20, sister queens) of approximately the same size, were distributed across two apiaries, one in Wardija and the other in . Hygienic behaviour evaluated by the pin-test method was higher in the Buckfast than in A.m.ruttneri, but this was not significant. In contrast, A.m.ruttneri produced significantly more honey than the Buckfast group. MNR is very restricted for analysis due its strict requirements in the right number of mites in relation to the brood. A Varroa treatment in December 2021 was applied to reduce mite loads, subsequently the first MNR/recapping assessment occurred in June 2022 and continued until April 2023. The measurements were repeated three times across a ten-month period, but samples could not be further collected due to insufficient mite infestation and colony losses emerging from to constant strain of the mites. High recapping rates and low mite reproductive success were consistent in A.m.ruttneri. In the Buckfast group, both at the colony level and at the cell level elevated rates of recapping were linked with MNR. However, this direct outcome of recapping on mite reproduction was not observed in A.m.ruttneri. Even though, both traits seem to mainly be driven by seasonality and apiary environment, this effect was stronger in A.m.ruttneri. Brood infestation related to an increased non-targeted recapping in A.m.ruttneri but not in the Buckfast. Despite brood infestation was relatively high, most colonies preceded by A.m.ruttneri still survived until the end of the study, and afterwards. All this implies that A.m.ruttneri shows a certain degree of tolerance and resistance expressed both through MNR and an extensive mite infestation tolerance. This is likely due to a combination of recapping and possibly other traits such as VSH, physiological adaptations along with the rhythm of brood dynamics amalgamated to the seasonal changes of to the Maltese Islands. Description: M.Sc.(Melit.) Wed, 01 Jan 2025 00:00:00 GMT https://www.um.edu.mt/library/oar/handle/123456789/144851 2025-01-01T00:00:00Z