SCIOSLUGCONTROL · The potential use of sciomyzid flies as novel biocontrol agents of pest slugs in Europe and the USA, with particular reference to Ireland and California

Final Activity Report Summary - SCIOSLUGCONTROL (The potential use of sciomyzid flies as novel biocontrol agents of pest slugs in Europe and USA, with particular reference to Ireland and California)

It has been estimated that approximately USD 75 billion of global food production is lost annually to pest organisms before it reaches the consumer. Of these, slugs are among the most important and are the primary pests in temperate regions of the world including most parts of the United States (US) and Europe. The initial objectives of this fellowship were to elucidate the potential of using sciomyzid flies as biological control agents of pest slugs in Ireland and California. However due to high levels of mortality during transit, all attempts to import these flies into quarantine in California failed. Nevertheless, since the slug fauna was practically unresearched in the state, the first new aim of the fellowship was to complete a comprehensive slug survey. This resulted in the collection of over 1 750 specimens representing 12 species (including two new species to the state). All of these except one were invasive European species which are now serious economic pests throughout California. Following on from this survey, a guidebook to the invasive and native slug fauna of the state was written by the fellow and has now been published by University of California Press. It is the first guide ever to be published on the slugs of the state. However, these pests still represent a serious challenge to control practitioners because many species are very difficult to identify on external characteristics alone. Even the use of traditionally reliable characters such as genital structure can be problematic e.g. in immature slugs. Chief among this group are slugs in the genus Arion which are widely distributed and are major pests in California. Since accurate pest identification is a crucial prerequisite to successful control, a second aim of the fellowship was to design a method which resulted in accurate slug identification. Given that the composition of DNA is unique for every species, there is a possibility that genetics could be used in identification. The approach involves isolating and sequencing a particular gene from slugs called COI and then using commercial enzymes to fragment the isolated DNA into various numbers and sizes of fragments. By selecting specific enzymes these fragments and their sizes can be unique for specific species. The results of such digestions can then be observed using standard gel elecrophoresis enabling a positive identification to be made. Unlike colour and genital structure, the composition of DNA does not vary with age, climate and time of the year, so it provides a reliable method of making accurate identifications. A molecular identification key for invasive species of the genus Arion in California has now been successfully designed. Molecular biology was also used to investigate the population genetics of the gray garden slug (Deroceras reticulatum) in California where it was one of the most abundant invasive slug species. The initial aim of the research was to determine whether its presence in California was the result of a multiple invasion (metainvasion) or the result of a single invasive event. This method is based on the premise that individuals from different populations will have evolved different base pair alignments in the COI gene and hence the number of invasive populations in an area can be determined by sequencing this marker. Results showed that there were relatively little differences in sequence composition between the different Californian populations which suggested that the occurrence of D. reticulatum in the state was the result of a single invasive population. The final aim of the fellowship was to identify the European origin of this population. Since, D. reticulatum is native to Europe sequences from individuals collected throughout that continent were compared with those from Californian populations. Our results suggested that Californian populations, originated from United Kingdom and parts of Belgium. This information is important as it highlights those shipments from Europe where stricter inspections are required and those areas where natural enemies should be collected for classical biological control programs.

Data: CORDIS, © European Union