Predation on Drosophila suzukii within Hedges in the Agricultural Landscape

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.

Keywords: biological control; earwigs; molecular gut content analysis; predators; predatory bugs; semi-natural habitat; spiders.

Figure 1

Percent predation on pupae of Drosophila suzukii exposed during 2–5 days in 10 hedges across Switzerland. Predation according to (A) type of hedge and (B) according to exposure site. Different letters indicate significant differences (Tukey multiple comparisons: P < 0.05). The solid line indicates the median, the box goes from the first to the third quartile, whiskers indicate 1.5 × the interquartile distance and circles outliers.

Figure 2

Mean number of individuals per sampling period (period 1: 17 June–4 July; period 2: 8 July–25 July; period 3: 12 August–4 September; period 4: 17 September–16 October) and predator group. Different letters indicate significant differences (Tukey multiple comparisons: P < 0.05) between levels of the different predator groups (A–D, above the bars) and sampling periods (a–b, in brackets).