Ability of Muscidifurax raptorellus and Other Parasitoids and Predators to Control Drosophila suzukii Populations in Raspberries in the Laboratory

Abstract

Drosophila suzukii is an invasive pest and economic threat to berry crops in Europe and the Americas. Current methods of control of this pest rely primarily on frequent applications of insecticides; therefore, there is a need for alternative control methods to reduce insecticide reliance. In this study, we evaluated the biological control potential of three parasitoid wasps: Diglyphus isaea, Muscidifurax raptorellus and Pachycrepoideus vindemmiae, and four predators: Chrysoperla carnea, Dicyphus hesperus, Orius insidiosus and Podisus maculiventris. Experiments were conducted for 15 days under controlled conditions in experimental arenas with D. suzukii females and raspberries, allowing for all life stages of D. suzukii to be available to natural enemies. Results showed the first evidence of M. raptorellus's ability to parasitize D. suzukii, resulting in a 40% reduction. Orius insidiosus, P. vindemmiae and C. carnea were also efficient, reducing D. suzukii numbers by 49%, 43% and 32%, respectively. Predator preferences for each D. suzukii life stage were assessed. The clutch size, sex ratio and adult size variability of D. suzukii pupal parasitoids were also evaluated. This study expands the list of species that can effectively parasitize D. suzukii and provides new insights into the biological responses of M. raptorellus to D. suzukii pupae.

Keywords: Drosophila suzukii; biological control; host-parasitoid interactions; invasive pest; predation.

Figure 1

Means (± SE) of D. suzukii cumulative life stages (larvae, pupae, and dead and alive adults) recovered after 15 days when exposed to female parasitoid wasps. Each arena (n = 8 per parasitoid wasp species) contained five D. suzukii mated females and raspberries at the beginning of the experiment, with 18 larval parasitoids added on day 4 and 18 pupal parasitoids added on day 9. Cumulative means with the same letter were not significantly different (Tukey’s HSD, p < 0.05).

Figure 2

Means (± SE) of D. suzukii cumulative life stages (larvae, pupae, and dead and alive adults) recovered after 15 days when exposed to predators. Each arena (n = 8 per predator species) contained five D. suzukii mated females and raspberries at the beginning of the experiment, with 18 predators added on day 3. Cumulative means with the same letter were not significantly different (Tukey’s HSD, p < 0.05).

Figure 3

Mean (± SEM) number of D. suzukii life stages recovered after 24-h exposure to predators (either larval C. carnea, adult D. hesperus, adult O. insidiosus or nymph P. maculiventris). Each arena (n = 15 per predator species) contained six D. suzukii (either eggs, larvae, pupae or adults) and one predator. Means for each life stages with the same letter were not significantly different (Kruskal–Wallis post-hoc Dunn’s test, p < 0.05).

Figure 4

Total number of individuals (a) and means (± SE) of left hind tibia length (b) of M. raptorellus and P. vindemmiae parasitoids that emerged from D. suzukii pupae at various clutch sizes in raspberries under laboratory conditions. Controls were M. raptorellus that emerged from M. domestica pupae and P. vindemmiae that emerged from D. suzukii pupae used in the rearing colony. Asterisks above bars in panel (a) indicate male: female ratios different than 1:1 for each clutch size (Chi-square, p < 0.05), and bars with the same letter in panel (b) are not significantly different (M. raptorellus: Kruskal–Wallis post-hoc Dunn’s test p < 0.05; P. vindemmiae: Student’s t-test, p < 0.05) for each sex and parasitoid species. Numbers in bars in panel (b) are the individuals measured.

Figure 5

Size differences between host D. suzukii and M. domestica pupae. (a) parasitized D. suzukii pupa; (b) parasitized M. domestica pupa.