Biology and ecology
How are the life cycle and development of D. suzukii varying with environmental conditions and how does its behaviour vary during the day?
The life cycle and environmental requirements (temperature, humidity, etc.) of D. suzukii are being assessed under various climatic conditions, both in the field and in the laboratory. Characteristics such as overwintering physiology and survival, generation times, lower and upper temperature thresholds, cold and heat tolerance are being gathered for all developmental stages and a day-degree model is being developed. In the field, studies are made along elevation gradients in the Alps. The circadian cycle, using simulated environmental conditions and field observations, is also studied since various characteristics related to the efficacy of control methods vary during the day (e.g. adult migration, insecticide resistance, metabolism, oviposition, mating).
What is the natural host range of D. suzukii and how is the fly distributed in complex landscapes?
Host range is investigated through large-scale field collections of wild fruits in Europe, China and North America. The relative levels of attack are also assessed. In the laboratory, no-choice and choice oviposition and development tests are carried out with cultivated fruits and the susceptibility and damage levels on various fruit varieties is investigated. The spatial ecology of D. suzukii is presently being studied with a large scale landscape approach to gather information on its distribution and the role played by the composition of the farmscape on its abundance. Habitat preference is investigated through surveys from farmscape dominated by monoculture to mosaics of fruit orchards and uncultivated area as well as urban areas. Spatio-temporal patterns are investigated also at the interface among different fruit orchards or between cultivated and uncultivated areas to characterize the specific role of these environments on D. suzukii spread.
What are the mortality factors affecting D. suzukii in native and invaded regions?
In this task, we collect the necessary information to develop biological control strategies against D. suzukii in T4.2. Partial life tables for D. suzukii are being built in Europe and China to investigate the relative importance of natural mortality factors throughout the life cycle of the fly, with emphasis on comparing the impact of natural enemies (parasitoids, predators and pathogens) in the regions of origin and introduction. Natural enemies are also the target of larger sampling programmes in various regions of occurrence in Europe, North America and East Asia.
Can we find better attractants to develop more efficient trapping systems?
Firstly, compounds from infested and non-infested fruits involved in the attraction of D. suzukii are being identified and compared with those already identified and presently used as attractants. Comparisons also include fruits infested with different yeast types that are specifically associated with D. suzukii. Secondly, we identify and test the attractiveness of compounds directly emitted by D. suzukii, such as those involved in courtship and mating behaviour. Information will be used to develop trapping methods for D. suzukii.
How does D. suzukii spread naturally?
Dispersal studies are being carried out with the mark-recapture technique. For this purpose γ-irradiated sterilized flies are released in a central point and recaptured in trap grid. This trial is carried out in cold and warm seasons to study the influence of weather conditions in fly dispersal ability. A flight mill based on designs used for aphids will also be tested to assess flight capacity of D. suzukii adults.
CABI (Switzerland/United Kingdom)