Optimization of Agriotes sordidus monitoring in northern Italy rural landscape, using a spatial approach

A spatial analysis of Agriotes sordidus (Illiger) (Coleoptera Elateridae) was carried out on data collected by means of pheromone traps in a farm of 500 hectares in northern Italy. The main objective of the paper was to analyse the spatial distribution of this economic pest, in order to optimise the monitoring; another aim was to understanding the spatial patterns of this insect in relation to the geographic and agronomic management of the site investigated. Spatial distribution was studied by means of geostatistical analysis of the total number of captured individuals per year (variable Sum) and the peak of population density (variable Peak). Data were analysed using the total of traps and reduced datasets by means of re-sampling simulations. The semi-variograms showed that adults of A. sordidus exhibited a strong aggregative pattern in the investigated area, confirming previous preliminary studies. Kriging contour maps were used to describe spatial aggregation of A. sordidus. Cross-validation analysis demonstrated that the simulations with 50% of the total of traps produced maps with a good concordance between estimated and measured values, with the caution to maintain a uniform distribution of the sample points within the monitored area. Simulations by means of geostatistics were suitable to optimise the monitoring in order to obtain a compromise between precision and feasibility. This study provided an interpretation of the spatial dynamics of A. sordidus adults on meso-scale, leading to an estimation of the riskzones for pest damage. Further studies are needed in order to understand the role of a number of agronomic variables on the populations of A. sordidus, to design zones of different risk of infestation and to optimize the monitoring and management of this economic pest in northern Italy.