# Detecting Symptoms and Dispersal of Pine Tortoise Scale Pest in an Urban Forest by Remote Sensing
## 4 Discussion
The full reflectance spectra of the pine canopy from the PRISMA earth observation system proved useful in clearly differentiating the presence/absence of PTS symptoms, probably due to the very high spectral resolution and spectrum, as previously reported in other studies [67, 68]. The availability of the SWIR channel, sensitive to the reflectance of the water content and the biochemical composition of leaves, can be considered PRISMA's main asset over other techniques, such as proximal sensing [69]. The latter technique, conversely, may feature frequent revisit times and higher spatial resolutions that, in turn, may enable multi-temporal studies [33]. This confirms its usefulness in large-scale forest vegetation studies where spatial resolution or temporal resolution are not limiting factors for the detection of canopy stress [70]. It should be noted that although a specific hyperspectral reflectance signature for the PTS infestation on stone pine is potentially feasible, it was not among the objectives of this study. In the future, numerous satellites for Earth Observation will be launched, such as the IRIDE constellation [71] and CHIME [72], which will include hyperspectral sensors with characteristics and sensitivities similar to those of PRISMA but with shorter revisit times. This will make any pest detection model developed for PRISMA reusable for the remote sensing monitoring of forests, as well as for early warning detection systems such as those that are available today based on multispectral sensors or synthetic aperture radar sensors [73, 74]. Airborne dispersal in the study site, originating from the PTS onset infestation hotspot detected in 2018, was found to account for 22% of the spatial variability of its detected presence in pine forests, cumulating years from 2019 to 2021, signaling that other dispersal media like animals, other insects, human-induced transport, or any combination of them in addition to wind and air currents, might be responsible [31]. Although the dispersal direction is downwind for wingless insects and very weak fliers [29], we could not find strong evidence that PTS's spatial distribution was mediated by the direction of the prevailing winds [49]. This is possibly due to a mitigation effect of sea breezes alternating with land breezes that dominate coastal wind systems during the spring months in the study site. The net effect of an alternating dispersal of PTS could slow down its net forward motion potential from the infestation hotspot and enable the public administration to design effective pest-management control strategies or identify potential predators and parasites. Limitations of the wind models developed in this study include the coarse spatial resolution of the PTS detection map (30 \(\times\) 30 m) that did not allow for the inclusion of microclimate, terrain, or canopy effects. Permanent windbreaks on land or artificial wind tunnels, such as wide, straight, and coast-inland roads, if present, could also modify the wind profiles and the distribution and dispersal of PTS [29]. The extent to which these confounding drivers could add to the alternating sea/land breeze wind system effect in slowing down PTS dispersion through the prevailing winds is not yet known. Nonetheless, we suggest monitoring the spread of PTS in coastal areas in all directions from the onset hotspot, regardless of the local wind systems, due to the currently increasing probability of the occurrence of windstorms [75].