Does composition of tropical agricultural landscape affect parasitoid diversity and their host-parasitoid interactions?

The expansion of agricultural fields is the main cause of landscape simplification and changes in the composition and configuration of landscapes. These landscape changes influence pests and their natural enemies, and may influence their interaction and the biological control services to which they contribute. However, the effects of landscape composition can vary between region and insect species. The present study was conducted on cucumber plants in 16 different sites of varying landscape composition in Bogor and its surrounding area, West Java, Indonesia. Sampling of insects was performed on lepidopteran pests and their parasitoids. The results obtained showed that landscape composition (i.e. patch number of cropland) had a positive impact on the abundance of parasitoids and their host (lepidopteran pests). Yet the proportion of natural habitat did not influence parasitoid abundance and their host-parasitoid interaction. The presence of Apanteles taragamae (i.e. the most abundant parasitoid) in the agricultural landscape was affected by the abundance of its hyperparasitoid and its host (Diaphania indica) and not by landscape composition. The findings of the present study suggest that the higher proportion of patchy cropland in tropical agricultural landscapes, as well as agricultural practices, can maintain parasitoid abundance and functional diversity and, finally, an enhanced parasitism rate.