Abstract
Simple SummaryDrosophila suzukii is an invasive fruit fly that have became a key pest of soft-skinned fruits during the past decade. Today, the control of this pest relies strongly on broad-spectrum insecticides. Deploying attractive traps to control the pest population (mass trapping) could be part of the management strategy of D. suzukii. The present study analyses whether mass trapping with different attractants could be viable for D. suzukii control and how far traps should be maximally spaced in a grid. Traps in a grid compete for the same insects when they are spaced close enough and their radii of attraction overlap. Since the traps on the corners of a grid have fewer competing traps around than fully surrounded centre traps, the ratio of the catches in the corner traps and the centre traps indicates whether the traps are spaced close enough. By quantifying that trap interference in 4 × 4 trapping grids, it was found in this two-year field study that workable trap densities can be expected to control D. suzukii. From June onwards, synthetic lures in dry traps show equal or better results than the same traps with a reference liquid bait (apple cider vinegar).The invasion of Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) worldwide has disrupted existing or developing integrated pest management (IPM) programs in soft-skinned fruits. Currently, with a reliance on only broad-spectrum insecticides, there is a critical call for alternative control measures. Behavioural control is one of the pillars of IPM, and, in the present study, it is investigated whether mass trapping could be viable for D. suzukii management. By quantifying trap interference in 4 × 4 replicate trapping grids, an estimate of the attraction radius for a certain attractant and context can be obtained. Traps designed for dry trapping (no drowning solution, but a killing agent inside) and synthetic controlled released experimental lures were tested in a two-year field study. Apple cider vinegar (ACV) was included as a reference bait and trials were performed with 5, 10 and 15 m inter-trap spacings at different seasonal timings. Clear trap interference and, hence, overlapping attraction radii were observed both in spring and summer for both the synthetic lures and ACV. In early spring, ACV shows the most potential for mass trapping, however from June onwards, the experimental dry lures show equal or better results than ACV. Based on our findings, workable trap densities are deemed possible, encouraging further development of mass trapping strategies for the control of D. suzukii.
Highlights
The spotted wing Drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), native to Asia [1–3], became a worldwide invasive key pest of soft-skinned fruits over the last decades [1,4–11]
In the trial at 5 m inter-trap spacing in May 2018 (34 days, from 27 April to 31 May), there were significantly more D. suzukii flies caught in the corner traps than in the centre traps for apple cider vinegar (ACV) (GLMM: z-ratio = 4.85, p < 0.0001, n = 16) (Figure 1a)
In the trial at 5 m inter-trap spacing in May 2020 (35 days, from 24 April to 29 May), there were significantly more D. suzukii flies caught in the corner traps than in the centre traps for ACV (GLMM: z-ratio = 5.23, p < 0.0001, n = 16) (Figure 1b)
Summary
The spotted wing Drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), native to Asia [1–3], became a worldwide invasive key pest of soft-skinned fruits over the last decades [1,4–11]. As D. suzukii is a serious economic pest [12–15], its invasion forced fruit growers to revert to calendar-based sprays with (broad-spectrum) insecticides [1,13,16,17]. There have been numerous research efforts to devise alternative control measures and to develop integrated pest management (IPM) programmes [18]. The identified attractive chemicals have been tested by adding them to known baits [24,34] or fruit juices [51] or have been applied in controlled release dispensers [24,52–59]. D. suzukii populations are known to shift olfactory preferences throughout the year [70], so it is important to test attractants at different (relevant) seasonal timings
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