1College of Plant Protection，Shandong Agricultural University，Tai’an 271018，Shandong，China|2Entry-exit Inspection and Quarantine Bureau of Qingdao，Qingdao 266000，Shandong，China
Abstract：Explored the onion fly〔Delia antique（Meigen）〕adult oviposition selection in field cage and pot experiments and larval feeding preferences through indoor experiments．The results showed that the highest onion fly population occurred in onion，and the next population was in garlic and scallion，the lowest occurred in leeks through field cage experiments．The results of oviposition preference in pot experiments indicated the same trend as the field cage experiments．The lay eggs reached the most amount at onion，the lowest at leeks．The most favorite plant of the 1st larvae was onion，the next was scallion and the least were garlic and leek．The 3rd instars larvae showed the same preference as the 1st larvae．In a word，the most favorite host plant of onion fly was onion，the next was scallion and garlic，the least was leek．Moreover，we found that the oviposition selection of onion fly was the important factor in its population occurrence．So trapping and killing adult flies have applicable value in controlling onion maggot．
