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

Abstract

1 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. 2 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. 3 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. 4 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.

Predicting Landscape Configuration Effects on Agricultural Pest Suppression

“…Syrphids, parasitoids, predatory wasps, and staphylinids were more abundant in fields surrounded by landscapes with higher edge densities, and these configurational effects dwarfed the effects of the amount of seminatural habitat. The same has been found for insectivorous wasps in wheat [17], parasitoids in cucumber [18], and coccinellids in rice [19]. In North America, edge density appears to have similar effects on aphid predators in cereal crops, with more chrysomelids, nabids, and overall higher aphid enemy richness in fine-grained landscapes [15,16].…”

“…We need more information on how grain size affects herbivores, rates of suppression, crop damage, and yield. Evidence on herbivores is biased toward aphids ( Figure 1), and variously suggests that finer-grained landscapes can have more [18,19,23] or fewer [27] herbivores, or the results were inconsistent [28] or showed no effects [29,30]. The recent synthesis of data from Europe provides more clarity; pests overwintering outside of fields decreased with edge density, whereas pests overwintering in crop fields were mostly unaffected [14].…”

Short Communication: Landscape composition alters parasitoid wasps but not their host diversity in tropical agricultural landscapes

“…The presence of natural habitats has important contributions for natural enemies (Tscharntke et al 2016), especially to support shelter, alternative hosts, and alternative sources of pollen and nectar (Gagic et al 2011). However, a previous study with cucumber field in Bogor showed a different pattern in that landscape with higher proportions of natural habitats did not influence the abundance of parasitoid wasps and herbivorous insects (Ulina et al 2019). From 12 species of lepidopteran larvae, only 5 species were found to be parasitized by parasitoid wasps ( Table 2).…”

“…This research was conducted in agricultural landscapes located in six villages in Bogor District, West Java, Indonesia (Figure 1). The characteristics of agricultural landscapes in Bogor consist of patchy croplands and the presence of semi-natural habitats (Ulina et al 2019). In each village, a crop field was selected with the distance between crop fields in other villages being at least 2 km apart in order to avoid overlapping landscapes and spatial autocorrelation (Tischendorf and Fahrig 2000).…”

“…Crop habitats might also provide more important resources for parasitoids than non-crop or natural habitats (Sann et al 2018). At landscape scale, a study by Ulina et al (2019) showed that the patch number of croplands can influence parasitoid diversity and suggested that the management of agricultural landscapes needs not only to preserve non-crop habitat, but also to increase the patch number of croplands. Therefore, studies on the relationship between landscape composition, either patches of crops or non-crops, and parasitoid communities are still needed in order to enrich existing knowledge to understand and develop management strategies to achieve sustainable agriculture.…”