Patterns of change in population abundance of citrus pest species obtained from an area-wide field survey and monitoring network established in eastern Spain

Abstract: The establishment of scientifically sound warning, forecasting and early diagnosis systems is one of the priorities established by EU directives for pest management. These field monitoring programs generate also information useful to define patterns of change in pest abundance and to identify possible influencing factors. We present pest population patterns obtained from data of an area-wide survey and monitoring network established by the autonomic Government of the Comunitat Valenciana in the 180,000 ha citrus belt in eastern Spain between 2004 and 2009. The network was established for quarantine purposes and to assist farmer in pest management decisions. Four hundred orchards were monitored biweekly all along the year, determining population levels of 22 pest species. Weather data from 30 climatic stations in the area were also collected. Our results show that species of citrus have a strong influence on abundance of some species (diaspidid scales) but not on others (coccid scales). Some pests show intense fluctuations in abundance from year to year (Tetranychus urticae, Paraleyrodes minei, Ceroplastes floridensis, Closterotomus trivialis), whereas others remain stable (Phyllocnistis citrella, Planococcus citri, Aphis spiraecola, Aonidiella aurantii). Some pests are linked to the same geographic area year after year (Paraleyrodes minei, Icerya purchasi, Ceroplastes sinensis), whereas others change geographic preference from year to year (Panonychus citri, Planococcus citri, Aleurothrixus floccosus, Phyllocnistis citrella). Finally, population trends in abundance along the year remain stable year after year in some cases (Aphis spiraecola, Aleurothrixus floccosus, Icerya purchasi) but not in others (Tetranychus urticae, Paraleyrodes minei, Saissetia oleae). Differences in abundance and trend patterns observed are likely related with differences in interacting factors which regulate and/or condition pest populations, either ecological (climate, biological control, plant physiology, food availability) or biological (dispersal, voltinism, growth rate).