Characterising Hot Spots of Mediterranean Fruit Fly Infestation in Apple Orchards: Implications for Pest Monitoring and Management

The Mediterranean fruit fly (medfly, Ceratitis capitata [Wiedemann]) (Diptera: Tephritidae), is a significant pest causing sizeable economic burden and fruit damage to crops worldwide, especially in the Mediterranean area. In deciduous orchards, monitoring the population of Mediterranean flies is an intensive and expensive process. This study aimed to explore alternatives to optimise the time and effort-intensive practice of medfly field monitoring, and promote site-specific management strategies, such as targeted pesticide applications or mass trapping, which could be implemented in high-density areas identified within orchards. In our previous work, the medfly population was found to begin infestation in small locations (few trees) within the orchard. This dynamic often precedes the infestations in the rest of the orchard. This study aims to characterise the differences between these locations (termed ‘hot spots’) and areas representing the rest of the orchard (termed ‘cold spots’). We examined differences in microclimate conditions (temperature, humidity and leaf area index) in apple orchards and quantified fruits nutrient level. The results characterised hot spots (HS) with a higher leaf area index, lower temperatures and higher humidity than cold spots. In addition, the fruits in the HS had higher nitrogen levels. To deepen our investigation, we also used remote sensing validation with thermal images to assess its potential for future hotspot detection. The differences we found can help to identify HS in other orchards and provide guidelines for using this knowledge to optimise pest control.