Modelling
DEVELOPMENT OF TOOLS SUPPORTING RISK ANALYSIS AND RISK MANAGEMENT
The rational and sustainable management of P. japonica should take advantage of tools that allow to quantify the risk associated with this species in space and time. To develop scenarios of risk, it is necessary to better understand how the insect is influenced by the environment and to predict how its distribution and abundance may vary on the regional territory. For this purpose, there is the need of developing statistical and mathematical models able to describe, understand and predict insect biological and ecological characteristics that are useful for the design and the implementation of control strategies. The University of Brescia is developing three fundamental tools:
1. Spread models
Through the analysis of data related to the spread and the current presence of P. japonica in the regional territory, the GESPO Project is developing tools that allow to describe and to interpret the dispersal processes of the species in Lombardy. Under appropriate assumptions related to the movement of the species and taking into account land use, these models allow for the exploration of risk scenarios. These scenarios are based on the prediction of the means and the rates of colonisation of the new territories and are based on the development of dynamic risk maps. These models allow simulating the local dispersal of the insect (mainly due to the flight activity of the insect) but they can also take into account long-distance dispersal due to human activities and the consequent risks of new outbreaks.
Representation of the annual expansion front of Popillia japonica in the regional territory (updated to 2018).
2. Phenological models
Temperature is the environmental parameter that most affects the vital functions of all insects. Phenological models are able of predicting the succession of the phenological stages of a population of insects based on temperature data. Using air and soil temperature data, the GESPO Project is developing a tool that predicts the presence and potential abundance of the different stages of P. japonica (larvae, pupae, adults and eggs) and the main life cycle events (e.g. beginning of the larval trophic activity and adult emergence). This model provides a useful support for planning pest monitoring and control measures over time and space, towards a higher effectiveness of control measures and a reduced impact on the environment.
Time of emergence of the adult stage of Popillia japonica (on the x-axis the days of the year, and on the y-axis the percentage of emergence of the adult stage).
3. Habitat suitability models
The size of populations of living organisms grow more or less conspicuously according to the biotic and abiotic factors that characterise the habitats where the species lives. This is also true for invasive species such as P. japonica: its potential impact in the territories in which the species is present and in those where it may spread will depend primarily on the characteristics of the habitat. Habitat suitability models can produce maps of potential risk related to the species under investigation based on the knowledge of the characteristics of the habitat. The GESPO project is working on these models to produce risk maps for the entire territory of the Lombardy Region representing the potential impact of P. japonica as a function of important environmental variables such as climate, soil characteristics and land use.
The figure shows, with different color codes, the different types of land use in the western area of the Lombardy Region. The white and red points represent a subset of the areas where P. japonica was sampled.
The main results of the project will be made available to the stakeholders (Phytosanitary Services, farmers, floriculturalists, environmental resource management bodies, etc.) in order to provide indications for the sustainable management of the species at different spatial and temporal scales: from local to large-scale territorial management, and from short to medium-long term interventions.