# SMARTerra, a High-Resolution Decision Support System for Monitoring Plant Pests and Diseases
## 3 Results
### Prediction Assessment: The Locust Egg Hatching  
Locust presence is monitored by LAORE through field surveys to observe and georeference insect growth. We were provided with survey data from the Ottana Plain area, collected from early spring until the end of May 2023. Each survey record includes the georeferenced location and the locust development stage (\"instr\"), which ranges from 1 (newborns) to 6 (adults). For our purposes, we compare the dates corresponding to instar 1 with the egg hatching dates predicted by SMARTerra at the same locations. An initial model run, performed with parameters taken from the literature (\(T_{\rm th}=30\,^{\circ}\)C, \(R_{\rm th}=100\,\)mm, \(D_{\rm th}=200\,^{\circ}\)C), shows (Figure 11, top left) values of \(\Delta_{d}\), the difference (in days) between the observed instar 1 date and the prediction of SMARTerra (Algorithm 1), spatially distributed in two homogeneous clusters. \(\Delta_{d}>0\) means that SMARTerra predicts the locust egg hatching earlier than observed, and vice versa. The light-grey observations have \(|\Delta_{d}|<30\) days and include predictions in good agreement with the observations, while dark-grey hexagons correspond to a distribution of records centered around \(\Delta_{d}=150\) days. Figure 10: Comparison of observed and predicted alert levels for rice blast disease in the Oristano rice districts. Observed (**top left**) and predicted (**top right**) alert levels for 17 July 2023. Observed (**bottom left**) and predicted (**bottom right**) alert levels for 18 July 2023. SMARTerra helps us understand the cause of this major misprediction. Analyzing Figure 11, middle left, it is evident that the red area corresponding to the dark-grey observations reaches the rainfall threshold \(R_{\text{th}}\) at dates (day\({}_{2}\)) approximately 3-4 weeks earlier than the orange area corresponding to the light-grey observations. This large difference in day\({}_{2}\) naturally affects the predicted egg hatching dates for day\({}_{3}\) (Figure 11, bottom left). In fact, the dark-green and light-green areas exhibit a significant difference of about 4-5 months. This can be explained as follows: since the accumulation of degree days is the summation of the difference, if positive, between the average daily temperature \(T_{\text{mean}}\) and the base temperature \(T_{\text{base}}=10\,^{\circ}\)C, the pixels in the dark-green area could continue accumulating during the still-warm days of October and November. In contrast, the summation for the pixels in the light-green area essentially halted during winter due to the low temperatures, requiring them to wait for the return of spring. However, predicted dates can change dramatically with even minor modifications in the model parameters. For example, running the model implemented in SMARTerra with the slightly different choice \(T_{\text{th}}=29\,^{\circ}\)C, \(R_{\text{th}}=105\,\text{mm}\), and \(D_{\text{th}}=200\,^{\circ}\)C (unchanged) results in a single-mode distribution of \(\Delta_{d}\), except for a few outliers, as shown in Figure 11, top right. The map in Figure 11, middle right, indicates that achieving the rainfall accumulation threshold \(R_{\text{th}}=105\,\text{mm}\) is slightly delayed in the area under examination compared to the middle left plot of the same figure. Consequently, only three observations fall in the dark-red area, while the others lie within the light-red and orange areas. Finally, Figure 11,  
Figure 11: Spatial distribution of \(\Delta_{d}\) for egg hatching predicted by the default (literature) model (**left**) and a slightly modified model (**right**), both with a superimposed OpenStreetMap layer (**top**), a map of the dates for day\({}_{2}\) when the rain threshold \(R_{\text{th}}\) is reached and the accumulation of degree days starts (**middle**), and a map representing day\({}_{3}\), the predicted dates of the hatching of locust eggs (**bottom**).