# Spatial Dynamics of Olive Fruit Fly Adults in the Framework of a Monitoring Trap Network
## 1 Introduction  
Trap-based adult monitoring has been proven to be an essential part of managing fruit fly pests [1]. The olive fly, _Bactrocera oleae_ ([PERSON]) (Diptera: Tephritidae), is a key pest of olive groves in the Mediterranean and other areas in the world where the plant is cultivated [2]. The olive sector represents a major socio-economic pillar in many Mediterranean countries, where fruit damage by _B. oleae_ can severely impact both yield and oil quality [3]. Larvae attack the fruit mesocarp, causing significant quantitative and qualitative losses of the product with resultant consistent economic damages [4,5]. However, pest monitoring systems allow for the detection of early population increases, the implementation of appropriate and accurate management methods and ultimately the reduction of chemical inputs, while retaining beneficial species [6,7]. As a result, integrated pest management programmes always place a high priority on improving monitoring systems' accuracy.  
Trapping devices of various designs have been constructed and used so far to monitor adult olive flies. Attractive stimuli of various kinds have been used to make traps more efficient, for example, using a yellow colour, sexual pheromones or food attractants such as hydrolys protein baits and different ammonium salts [8]. Traditionally, human operators regularly inspect trap grids and collect data on catches across the specified control area. The purpose is to obtain information like female maturity and sex ratio and the presence of adult flies and their trend in the field [9]. Trap captures may feed various Decision Support System (DSS) software models to forecast population dynamics or to make the right management decisions [10,11,12,13]. However, monitoring traps provide a relative sample measure that is frequently not correlated to fruit damage [14]. In fact, traps only intercept the portion of the population that responds to attractive stimuli, influenced by factors related to the target pest biological status, the trapping system employed, and the climatic conditions that can act on both the attractant release or the activity of the flies [15,16].  
In extensive and cost-efficient sampling plans, the suggested trap density is usually 2-3 traps/ha [9,17], but it is still not entirely clear whether the given density is sufficient to have a reliable representation of flies in the olive grove and how the portion of the non-trapped population distributes in the field. Addressing this knowledge gap is crucial to adjust sampling strategies and strengthen the accuracy of decision support tools. In addition, testing these parameters using baited yellow panels will offer an additional benefit since, due to their advantages, they are used in e-traps [18], and any knowledge gathered on their potential to provide a realistic representation of the pest population in the field would be highly valuable for their integration in e-monitoring and decision-making systems.  
The aim of the present work is to answer the following questions: How substantial is the population not collected by the monitoring trap network in the field? Does the suggested trap density give a reliable representation of the population in the field? How does population density affect the distribution of _B. oleae_ in the olive grove? Do males and females follow the same distribution pattern in the olive grove?  
In order to investigate these questions, an experiment was planned, consisting of arranging a high-density network of unbaited sticky panels between monitoring baited traps deployed at the standard density of 2 traps/ha. The field tests were conducted across five orchards, each one representing a participating country in the experiment: Greece, Italy, Lebanon, Spain and Tunisia. The spatially explicit data were further analysed using SADIE analysis to measure the index of aggregation and the spatial association.