###### Abstract
The degradation rate of these compounds during storage is influenced by their initial concentrations [15], but storage conditions also play a critical role in determining the chemical stability and quality of EVOO over time [14; 15]. Olive oil production--both in terms of yield and quality--is affected by numerous factors, including environmental conditions, cultivation practices, and genetic characteristics [17]. While the olive tree is considered drought-tolerant due to its adaptive mechanisms for coping with limited water supply [18], its performance can still be impacted by climatic variability. It is well adapted to the Mediterranean climate [10; 19; 20], which features dry, hot summers and cool, wet winters, and can produce high-quality products under such conditions [10]. However, intensified cultivation [21], combined with the effects of climate change--such as increased temperatures and irregular rainfall during critical phenological stages [19; 21]--may compromise both yield and oil quality [21]. In response, modern irrigation strategies have been developed to optimize water use while maintaining production levels and quality [20; 22]. Another factor that can adversely affect olive production is weed competition. Depending on species and density [23; 24], weeds compete with olive trees for vital resources like water and nutrients, ultimately reducing fruit yield and quality [25]. Effective weed management is therefore crucial to maintaining high productivity [23]. Given the limited data available on the impact of _Ailanthus_ on tree crops, the observations from this experiment are interpreted in the context of its broader ecological behavior as an invasive species. Like other aggressive weeds, _Ailanthus_ poses a significant challenge to agricultural production, as it can compete with crops for essential resources such as water, light, nutrients, and space [26; 27]. This competition can result in reduced crop yield and quality. As a fast-growing species with high adaptability to harsh environments, _Ailanthus_ may outgrow cultivated plants, causing shading, reduced photosynthesis, stunted growth, and lower fruit quality [8]. In terms of water management, its presence may increase the need for irrigation to meet crop demands and could also negatively affect plant nutrition [28]. In this context, the findings of the present experiment offer valuable insights into the potential competitive and ecological impacts of _Ailanthus_ on neighboring crops. In Greece--currently the second-largest olive oil producer in Europe [12]--the spread of _Ailanthus_ poses a growing threat to olive cultivation [3]. The olive tree holds significant cultural and economic value in the country. Among the various cultivars, 'Koroneiki'stands out globally for producing high-quality olive oil. Given that many Greek olive groves are rainfed, competition from _Ailanthus_ could exacerbate water stress and further threaten productivity. The objective of this study was to investigate the potential stress effects of _Ailanthus altissima_ on the yield and oil quality characteristics of the 'Koroneiki' olive cultivar, under both full and deficit irrigation conditions.