Winter fleshy‐fruited plants are the catalysts for spring populations of an invasive fruit fly

Abstract Winter is a critical bottleneck period for many insects and is particularly pivotal for pest species, being a major regulator of their populations. In winter, insect fruit pests such as the invasive fly, Drosophila suzukii , not only have to cope with harsh environmental conditions but also need to find alternative resources when cultivated fruit are scarce. This study aimed to disentangle the relative roles of climatic, landscape and local factors affecting fruit infestation rates of winter and spring host plants by D. suzukii . We assessed infestation in Aucuba japonica , Elaeagnus × submacrophylla (syn. Elaeagnus × ebbingei ), Mahonia aquifolium , M. japonica and Viscum album fruit in the north of France, between January and July 2022. Drosophila suzukii emerged from fruit of all plant species except M. aquifolium . The fly was the only species that emerged from fruit of A. japonica , E. × submacrophylla and M. japonica , but co‐occurred in V. album fruit with D. subobscura . Climatic factors (e.g. cumulative precipitation, the number of frost hours), landscape composition (e.g. grassland, shrubland and water cover) and local variables (e.g. resource abundance, vegetation architecture) influenced D. suzukii infestation, with effects varying between host plants. The fruiting succession of these five plants effectively provides a resource continuum from March to June, in which E. × submacrophylla , in particular, plays a pivotal role before commercial fruit become available (e.g. strawberries, cherries). Non‐crop plants should be considered in integrative pest management strategies as they could catalyse D. suzukii populations early in the season.