Ferran Garcia-Marí

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 scale...

The introduced parasitoid wasp Aphytis melinus, the most widespread natural enemy of the California red scale (Aonidiella aurantii) and the superior competitor, has displaced the native Aphytis chrysomphali from most citrus areas of the Mediterranean basin and other citrus areas all over the world. However, our extensive survey data on the scale parasitoid populations collected in 2004-2008 show that in large citrus areas of eastern Spain both parasitoids coexist. Using field data from 179 orchards spatially divided in five citrus-producing agroecosystems, we examined the mechanisms that could explain displacement or coexistence between both Aphytis species in relation to weather conditions. The distribution and abundance of the parasitoid species are related to the mean summer and winter temperatures and relative humidity of each ecosystem. The relative proportion of A. melinus is higher during the warm months, and the abundance of A. chrysomphali increases from south to north, being higher in the cooler northern areas. Aphytis melinus has displaced A. chrysomphali from hot and dry areas, whereas regions with mild summer temperatures and moderate relative humidity present the optimal conditions for the coexistence of the two parasitoids. The more negative effects of winter temperatures on A. melinus allow the earlier use of the available host resource in late winter and spring by A. chrysomphali and the coexistence of both parasitoids in the same orchard via temporal niche partitioning. We combine previous literature on the behavior of Aphytis species in the laboratory under different temperature and humidity conditions with our field results to confirm the role of spatiotemporal weather conditions and seasonal changes in host stages on the variation of Aphytis relative abundance and parasitoid coexistence.