Spillover of agricultural pests into adjacent desert habitats

The high productivity of arable fields within the season increases the density of insect pest populations and may result in an export of organisms to the surrounding landscape. Spillover from crops is likely to affect the dynamics of food webs in natural habitat patches. In desert agroecosystems cropland and arid natural habitats contrast strongly in productivity. In this study, we investigated the spillover of prey species from intensively farmed agricultural “islands” in the hyper-arid Arava Valley, Israel. In this area a mandatory crop-free period is imposed from mid¬ June to mid¬ August for reasons of sanitation. Our working hypothesis is that agriculture herbivores will move from agricultural areas into adjacent desert habitats. We investigated the movement of pests from agricultural fields into surrounding non-crop habitat as a function of time in the season and distance from the crop. We monitored the movement of two agricultural pests, Bemisia tabaci and Frankliniella occidentalis, using sticky traps in three different habitat types over four phenological seasons of the crops at increasing distances from agricultural fields. Both species arrived at traps placed in the desert up to 300 m from crops, and also in nearby villages. During the sanitation period, the pest abundance was higher in villages than in desert habitats, however both pest species could be found in desert habitats. Thus, pest spillover may be subsidizing some desert predators or scavengers and could subsequently affect the desert food web.