# Detecting Symptoms and Dispersal of Pine Tortoise Scale Pest in an Urban Forest by Remote Sensing
###### Abstract
seedlings. Pine forests in the Mediterranean area yield resources that are still the backbone of a number of economic activities [27], including tourism and leisure pastimes [28]. Monitoring, eradication, and the setup of containment measures in buffer zones against PTS infestations have been mandatory at the national level since 2021. The boundaries of the PTS-infested areas and the buffer zones surrounding the symptomatic area, at least 5 km wide, have been established in Lazio and were last updated in 2023. Patterns of insect dispersion are little understood and difficult to predict. The wind is one of the most important factors that can influence the local as well as long-distance dispersion of insects, for example, between agricultural fields as well as between forest stands and plantations, particularly in those ecosystems where the wind is a pervasive climatic factor of the environment [29] and is aided by orography or man-made structures that can channel the wind more effectively. For wingless or very weak-flying insects, such as scales, the main direction of dispersion is downwind up to a few meters away or, more rarely, a few hundred kilometers [30]. PTS was recorded as being carried up to 5 km in [31; 32], although its downwind dispersion in relation to prevailing winds has never been investigated. Large-scale detection of pest infestation, including the use of proximal- [33] and remote-sensing [34], can help assess the local dispersion patterns [35] and contribute to the development of mitigation and containment systems. Multispectral remote sensing has become widely established as a means of monitoring biotic and abiotic anomalies in forests by detecting breakpoints or anomalous trends in phenological patterns. Phenology is one of the most sensitive biological indicators of changes in underlying growing conditions, whether due to a changing climate or any occurring anomaly, such as pest outbreaks [36; 37]. There has been much focus on reflectance measurements in the visible (VIS, 450-700 nm), near-infrared (NIR, 700-1400 nm), and short-wave infrared (SWIR, 1400-2500 nm) wavelengths. Changes in these spectral regions are associated with several physiological and biochemical traits [38], including absorption of solar radiation by chlorophyll a, b, and carotenoids (VIS); the scattering of individual leaves and whole plant canopies driven by the internal leaf structure and canopy structure (NIR); and the SWIR, which can be indicative of the water content and the biochemical composition of leaves [39; 40; 41]. Recent developments in the cloud computing approach to elaborate long-time series of optical images enable the assessment of anomalous spectral changes and the automatic assessment of forest disturbances [42]. There is still uncertainty regarding the use of hyperspectral remote sensing, as such sensors have only recently been deployed in orbit, granting freely available products [43; 44; 45; 46]. PRISMA (Hyperspectral Precursor of the Application Mission) offers global coverage, with a spectral resolution of 12 nm and a spatial resolution of 30 \(\times\) 30 m, and has a repeat cycle of approximately 29 days. The VIS-NIR and SWIR sensors are integrated with a panchromatic camera [46]. In this context, we assessed the effects of the PTS outbreak in a stone pine urban forest located along the Tyrrhenian coast in Central Italy using hyperspectral PRISMA imaging. Since the first outbreak in Rome in 2018, PTS has spread toward the coastal forests, seriously affecting stone pines. This research aimed to (i) spatially detect the symptoms of defoliation on stone pines infested by PTS in an extensive protected area, (ii) evaluate how the prevailing winds had affected the spread pattern of the pest since its onset, and (iii) assess the potential of using PRISMA hyperspectral imaging to detect pest outbreaks in an urban forest in terms of accuracy and sensitivity.