Delia species in onion: assessment of damage and ovipositional preferences
LE3 .A278 2018
Bachelor of Science
Earth & Environmental Sciences
Onion maggot, Delia antiqua, (Meigen) (Diptera: Anthomyiidae) is considered the predominant Delia pest in onion (Allium cepa). It is unknown whether D. antiqua alone is damaging onion or if it is part of a complex with Delia platura, (Meigen) and Delia florilega, (Zetterstedt). Objectives of this research were to identify the Delia species present in commercial onion fields and quantify the impact of each species at various stages of onion development. This project had two components: 1. Commercial field assessments–to determine which Delia species were present in commercial onion fields and at what stage of development they are causing damage. 2. Host stage preference assessments – to determine whether Delia species (D. antiqua and D. platura) preferred particular plant growth stages for oviposition and which growth stages were most impacted by larval feeding under controlled conditions. Commercial field assessments revealed minimal damage from Delia species and the predominant species identified from sticky traps was D. platura. Results from the commercial field assessments found D. platura to have little impact on onion development while D. antiqua causes unmarketable damage to onions at all growth stages. Delia spp. host stage preference was tested in the field but results were inconclusive due to the small number of larvae recovered. Host stage preference was quantified in growth chamber studies using mating pairs of D. antiqua and D. platura. Although Delia spp. flies showed no preference for specific onion stages in the field, results from growth chambers studies suggest that D. antiqua females prefer to oviposit on post-germination seedlings at the 2 true leaf and 5-7 true leaf growth stages.
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