Abstract/Summary

Raspberry is a soft fruit of economic importance across the globe. The production of raspberries, which are often grown under plastic-covered polytunnels, is threatened by many insect pests. One such pest, the invasive Spotted Wing Drosophila (Drosophila suzukii), damages fruit by laying eggs in the epicarp. The subsequent larval feeding then damages the quality of the fruit and increases risk of pathogens. Drosophila suzukii is found on every continent except for Antarctica and is an increasing problem globally, particularly in the face of a changing climate, evidence of resistance and increased restriction on use of Plant Protection Products (PPP). There is an urgent need for more sustainable approaches to manage pests such D. suzukii in soft fruit which also take into account beneficial insects such as natural enemies and pollinators. To help support sustainable production of raspberry crop this thesis had 3 objectives. The first was to explore the influence of non-crop habitats on the abundance of D. suzukii in and around fruit farms and quantify how this is affected by season, crop and management type. Building on this, the second objective was to test the impacts of insect mesh as protective barriers on polytunnels on D. suzukii abundance and damage to fruit taking into account tunnel microclimates, fruit quality and pest and natural enemy abundance. The final objective was to characterize the main pollinators of raspberries in England, quantify the contribution they make to yield and quality and explore how they’re impacted when commercial bumblebee colonies are introduced to tunnels. The results indicate that crop edges and woodland neighbouring fruit farms are an important habitat for D. suzukii and that D. suzukii are found in greatest numbers in these habitats over winter. Pest management approaches to control D. suzukii should be targeted at areas with the greatest vulnerability. Additionally, by reducing D. suzukii oviposition in fruit and with only limited effects on tunnel microclimates, natural enemy abundance and fruit quality, insect exclusion mesh has potential as a useful tool employed as part of a wider IPM strategy. Finally, honeybees and bumblebees were identified as the most frequent visitors to raspberry flowers with wild pollinators much less abundant. Honeybee visitation was impacted by the presence of commercial bumblebee hives. Given the significant contribution of pollinators to raspberry yield and quality, approaches are needed to maximize the contribution of both wild and managed pollinators in polytunnel systems. The outcomes of this thesis provide farmers with a better understanding of the pest and beneficial insect communities that interact in tunnel-grown raspberries in the south of England. This thesis helps to guide management recommendations to produce more sustainable and environmentally friendly IPM programmes in protected raspberry crops, helping control key pests such as D. suzukii while considering beneficial insects such as natural enemies and pollinators.