Abstract/Summary

Apple is a globally important crop that is suscepMble to many pests and diseases. PromoMng natural pest control could increase crop yield and quality and reduce reliance on harmful pesMcides. The addiMon of nectar and pollen rich floral habitat is a commonly used management pracMce in agricultural ecosystems. This pracMce has been demonstrated to increase the abundance of predators and parasites of orchard pests(natural enemies), although there is less evidence of the extent to which this could improve pest control services, yield or profit. This thesis aimed to evaluate the ecological and economic effects of perennial flower margins in UK apple orchards for control of an economically significant global crop pest, Dysaphis plantaginea, rosy apple aphid. Empirical data collected over two years from different locaMons in commercial orchards, either with or without flower margins, revealed that flower margins provided a disMnct plant community, and their presence increased natural enemy diversity in orchard ground vegetaMon compared to orchards without flower margins. However, there was no evidence of broad differences between natural enemy taxa abundance, diversity, or community structure on the apple trees. Despite this, there was reduced spread of D. plantaginea on aphid infested trees in orchards with flower margins, and subsequently a reduced number of trees with fruit damage, from 80% to 48%, with effects seen up to 50 m from the flower margin during a year with higher aphid infestaMon levels. The reducMon in the spread of D. plantaginea, and percentage of trees with apple damage, varied between the two years and at different distances from the orchard edge. An economic model of these benefits when compared to the costs associated with flower margins, revealed that flower strips bordering the crop area could be a promising economic investment for D. plantaginea control if they do not replace apple trees. If non-crop land were not available and apple trees were being replaced by the flowers, establishment of a flower strip in the centre of an orchard instead of the edge, could recoup opportunity costs. The economic model showed that installing a flower strip in the centre of the orchard for 5 years could return £2997 per hectare per year if aphid infestaMon levels were high. However, the results suggest that this is context-dependent, and a similar flower strip could cost £210 if placed on crop land as a margin instead of in the orchard centre. This work is the first to demonstrate a reducMon in fruit damage by D. plantaginea at harvest in orchards with a flower margin compared to a control orchards with mown primarily grass margins, and one of few to evaluate the economic effect. The results highlight the potenMal for established perennial flower margins to deliver orchard-scale, sustainable, economically viable D. plantaginea control benefits, and provides insights into the spill-over distance of the effects. Flower margins could be used as a tool to support more sustainable producMon in apple orchards. The factors that influence the extent of these potenMal benefits are discussed.