Seasonal morphotypes of <i>Drosophila suzukii</i> differ in key life-history traits during and after a prolonged period of cold exposure

Seasonal polyphenism in Drosophila suzukii manifests itself in two discrete adult morphotypes, the “winter morph” (WM) and the “summer morph” (SM). These morphotypes are known to differ in thermal stress tolerance, and they co-occur during parts of the year. In this study, we aimed to estimate morph-specific survival and fecundity in laboratory settings simulating field conditions. We specifically analyzed how WM and SM D. suzukii differed in mortality and reproduction during and after a period of cold exposure resembling winter and spring conditions in temperate climates. The median lifespan of D. suzukii varied around 5 months for the WM flies and around 7 months for the SM flies. WM flies showed higher survival during the cold-exposure period compared with SM flies, and especially SM males suffered high mortality under these conditions. In contrast, SM flies had lower mortality rates than WM flies under spring-like conditions. Intriguingly, reproductive status (virgin or mated) did not impact the fly survival, either during the cold exposure or during spring-like conditions. Even though the reproductive potential of WM flies was greatly reduced compared with SM flies, both WM and SM females that had mated before the cold exposure were able to continuously produce viable offspring for 5 months under spring-like conditions. Finally, the fertility of the overwintered WM males was almost zero, while the surviving SM males did not suffer reduced fertility. Combined with other studies on D. suzukii monitoring and overwintering behavior, these results suggest that overwintered flies of both morphotypes could live long enough to infest the first commercial crops of the season. The high mortality of SM males and the low fertility of WM males after prolonged cold exposure also highlight the necessity for females to store sperm over winter to be able to start reproducing early in the following spring.</p

Overwintered <i>Drosophila suzukii</i> are the main source for infestations of the first fruit crops of the season

The mechanisms allowing the widespread invasive pest Drosophila suzukii to survive from early spring until the availability of the first fruit crops are still unclear. Seasonal biology and population dynamics of D. suzukii were investigated in order to better understand the contribution of the early spring hosts to the infestation of the first fruit crops of the season. We identified hosts available to D. suzukii in early spring and assessed their suitability for the pest oviposition and reproductive success under field and laboratory conditions. The natural infestation rate of one of these hosts, Aucuba japonica, was assessed over springtime and the morphology of the flies that emerged from infested A. japonica fruits was characterized under field conditions. Then, these findings were correlated with long-term monitoring data on seasonal reproductive biology and morphology of the pest, using a cumulative degree-days (DD) analysis. Field sampling revealed that overwintered D. suzukii females were physiologically able to lay eggs at 87 DD which coincided with the detection of the first infested early spring hosts. The latter were continuously and increasingly infested by D. suzukii eggs in nature from early spring until the end of May, in particular Aucuba japonica. Individuals emerged from most of these hosts were characterized by a poor fitness and a rather low success of emergence. In the field, only few summer morphs emerged from naturally infested A. japonica fruits around the end of May-beginning of June. However, field monitoring in orchards revealed that D. suzukii individuals consisted solely of winter morphs until mid-June. These observations indicate that overwintered D. suzukii females are the predominant source for the infestations in the first available fruit crops of the season. We discuss these findings in the context of possible pest control strategies

Correction: Approaches to identify the value of seminatural habitats for conservation biological control

We would like to change the authors’ names and email addresses on page 195 of paper [1] from: John M. Holland 1,*, Philippe Jeanneret 2, Anna-Camilla Moonen 3, Wopke van der Werf 4, Walter A.H. Rossing 5, Daniele Antichi 6, Martin H. Entling 7, Brice Giffard 8, Herman Helsen 9, Mark Szalai 10, Carlo Rega 11, Caroline Gibert 12 and Eve Veromann 13 1 Farmland Ecology Unit, Game and Wildlife Conservation Trust, Fordingbridge SP6 1EF, UK 2 Agroecology and Environment, Agroscope, CH-8046 Zurich, Switzerland; [email protected] 3 Scuola Superiore Sant’Anna, Agroecology Group, Institute of Life Sciences, Via Santa Cecilia 3, 56127 Pisa, Italy; [email protected] 4 Wageningen University & Research, Crop Systems Analysis, Droevendaalsesteeg 1, 6708PBWageningen, The Netherlands; [email protected].</p

Correction: Approaches to identify the value of seminatural habitats for conservation biological control

We would like to change the authors’ names and email addresses on page 195 of paper [1] from: John M. Holland 1,*, Philippe Jeanneret 2, Anna-Camilla Moonen 3, Wopke van der Werf 4, Walter A.H. Rossing 5, Daniele Antichi 6, Martin H. Entling 7, Brice Giffard 8, Herman Helsen 9, Mark Szalai 10, Carlo Rega 11, Caroline Gibert 12 and Eve Veromann 13 1 Farmland Ecology Unit, Game and Wildlife Conservation Trust, Fordingbridge SP6 1EF, UK 2 Agroecology and Environment, Agroscope, CH-8046 Zurich, Switzerland; [email protected] 3 Scuola Superiore Sant’Anna, Agroecology Group, Institute of Life Sciences, Via Santa Cecilia 3, 56127 Pisa, Italy; [email protected] 4 Wageningen University & Research, Crop Systems Analysis, Droevendaalsesteeg 1, 6708PBWageningen, The Netherlands; [email protected].</p

Approaches to Identify the Value of Seminatural Habitats for Conservation Biological Control

Invertebrates perform many vital functions in agricultural production, but many taxa are in decline, including pest natural enemies. Action is needed to increase their abundance if more sustainable agricultural systems are to be achieved. Conservation biological control (CBC) is a key component of integrated pest management yet has failed to be widely adopted in mainstream agriculture. Approaches to improving conservation biological control have been largely ad hoc. Two approaches are described to improve this process, one based upon pest natural enemy ecology and resource provision while the other focusses on the ecosystem service delivery using the QuESSA (Quantification of Ecological Services for Sustainable Agriculture) project as an example. In this project, a predictive scoring system was developed to show the potential of five seminatural habitat categories to provide biological control, from which predictive maps were generated for Europe. Actual biological control was measured in a series of case studies using sentinel systems (insect or seed prey), trade-offs between ecosystem services were explored, and heatmaps of biological control were generated. The overall conclusion from the QuESSA project was that results were context specific, indicating that more targeted approaches to CBC are needed. This may include designing new habitats or modifying existing habitats to support the types of natural enemies required for specific crops or pests