Predation on Drosophila suzukii within Hedges in the Agricultural Landscape

SIMPLE SUMMARY: Drosophila suzukii is an invasive species that feeds and reproduces on various cultivated and wild fruits and moves between agricultural and semi-natural habitats, such as hedges and forest patches. These semi-natural habitats are known to harbor a diverse community of natural enemies of pests. When we exposed D. suzukii pupae in dry and humid hedges, we found that on average 44% of them were predated within four days. The most common predators in the hedges were earwigs, spiders, and ants. Using a molecular assay that detects the DNA of D. suzukii in the gut of predators, we could show that 3.4% of the sampled earwigs, 1.8% of the spiders, and one predatory bug had fed on D. suzukii. This small proportion may be due to methodological constraints. However, the overall predation rate helps to reduce D. suzukii populations, in particular in hedges that are scarce of host fruits. ABSTRACT: The invasive Drosophila suzukii feeds and reproduces on various cultivated and wild fruits and moves between agricultural and semi-natural habitats. Hedges in agricultural landscapes play a vital role in the population development of D. suzukii, but also harbor a diverse community of natural enemies. We investigated predation by repeatedly exposing cohorts of D. suzukii pupae between June and October in dry and humid hedges at five different locations in Switzerland. We sampled predator communities and analyzed their gut content for the presence of D. suzukii DNA based on the COI marker. On average, 44% of the exposed pupae were predated. Predation was higher in dry than humid hedges, but did not differ significantly between pupae exposed on the ground or on branches and among sampling periods. Earwigs, spiders, and ants were the dominant predators. Predator communities did not vary significantly between hedge types or sampling periods. DNA of D. suzukii was detected in 3.4% of the earwigs, 1.8% of the spiders, and in one predatory bug (1.6%). While the molecular gut content analysis detected only a small proportion of predators that had fed on D. suzukii, overall predation seemed sufficient to reduce D. suzukii populations, in particular in hedges that provide few host fruit resources.