J Appl Entomol. 2020;00:1–6. wileyonlinelibrary.com/journal/jen | 1 © 2020 Blackwell Verlag GmbH 1 | INTRODUCTION The onion maggot (Delia antiqua Meigen) is an economically import- ant pest of Allium crops worldwide. Found primarily in temperate climates, D. antiqua is well established in onion growing regions in the Americas, Europe and Asia where crop losses due to this pest can range from 50 to 100 per cent on onions ( Allium cepa L.), garlic ( Allium sativum L.), scallions ( Allium fistulosum L.) and chives ( Allium schoenoprasum L.) if left unmanaged (Ellis & Eckenrode, 1979; Ning, Wei, & Feng, 2017; Nault, 2007; Nault, Straub, & Taylor, 2006; Nault, Zhao, Straub, Nyrop, & Hessney, 2006). Intensive management of this pest has become a necessary component of effective onion pro- duction in many parts of the world and severe damage from this pest continues to occur in areas where Allium crops are grown without rotation or where populations resistant to insecticides have devel- oped (Martinson, Nyrop, & Eckenrode, 1988; Nault, Zhao, et al., 2006). Delia antiqua is a primary pest in part due to its lifecycle. It is multivoltine with three generations per year in the Northern United States (Eckenrode, Vea, & Stone, 1975; Hoepting, Scott-Dupree, Harris, & McDonald, 2004). Larvae feed on plant roots and allium bulbs causing the damage associated with this pest. First-generation infestations are particularly devastating as early feeding by D. anti- qua larvae can kill seedlings (Nault, Zhao, et al., 2006; Nault, Straub, et al., 2006). In addition, damaged plants become more suscepti- ble to infestation by subsequent generations and plant pathogens (Eckenrode & Nyrop, 1986; Nault, Straub, et al., 2006). Even if plants are not completely killed by D. antiqua larvae, feeding damage often renders the bulbs unmarketable. Management of this pest has relied on prophylactic insecticide applications at planting (Nault, Straub, et al., 2006). A variety of organophosphate and carbamate insecticides have been used and discontinued (Nault, Straub, et al., 2006). Chlorpyrifos is commonly used as a drench treatment in combination with either the cyroma- zine seed treatment (Trigard) (Nault, Straub, et al., 2006) or the seed treatment package containing thiamethoxam, spinosad and several fungicides (FarMore FI500). Cultural practices such as crop rota- tion, removal of cull and volunteer onions from fields, and delayed Received: 3 October 2019 | Revised: 20 January 2020 | Accepted: 22 January 2020 DOI: 10.1111/jen.12740 ORIGINAL CONTRIBUTION Field monitoring of onion maggot (Delia antiqua) fly through improved trapping Denis S. Willett | Camila C. Filgueiras | Jan P. Nyrop | Brian A. Nault Entomology, Cornell AgriTech, Cornell University, Geneva, NY, USA Correspondence Denis S. Willett, Entomology, Cornell AgriTech, Cornell University, Geneva, NY, USA. Email: deniswillett@cornell.edu Abstract Onion maggot (Delia antiqua) is an economically important pest of Allium crops in temperate regions throughout the world. Management of this pest is necessary to achieve economic returns and depends on insecticide regimes and cultural manage- ment. Current cultural management especially altering planting date, field location and crop rotation depend on monitoring. We evaluated the effect of shape, size, colour and chemical attractants on trap catch of field populations of adult D. antiqua flies in upstate New York. White, large diameter, spherical traps in conjunction with Delia Lure attractant performed the best in attracting and catching D. antiqua adults. These results suggest an improved means of attracting and capturing D. antiqua pop- ulations which could be useful in monitoring efforts and development of attract and kill strategies for pest control. KEYWORDS attract-and-kill, attraction, Delia antiqua, Lure, onion maggot, onion management, sticky-trap