Field Observations on the Bean Seed Fly (Seed Corn Maggot), Chortophila cilicrura, Rond., and C. trichodactyla, Rond.

Abstract

Field observations on C. cilicrura and C. trichodactyla have shown that in Britain the larvae feed on beans, peas, cabbages, kale, cauliflowers, leeks, onions, cucumbers and lettuce. The importance of C. cilicrura as a pest of beans in spring was well known; its attack on cucumbers was suspected but had not been verified; but the infestation of leeks and brassicas in summer and spring cabbages in autumn had not hitherto been recorded in Britain. An association of larvae of C. cilicrura with rotting vegetation has not so far been established.Descriptions of adult and larval stages are given. Diagrams are given to illustrate specific differences between larvae of C. cilicrura and those of the onion fly, Hylemyia antiqua.Field observations have shown that C. cilicrura is on the wing from March to October and there is some evidence of slight activity during the winter months. There are 3–4 generations a year, and peak periods of fly activity occur during mid-April to mid-May, late June to early July, and in fine weather throughout the period August to October.Larvae have been taken throughout the period May to December. Peak periods of larval activity occur from mid-May to early June on beans, peas, cucumbers and cruciferous crops, during July on leeks and cruciferous crops, and during September to November on spring cabbages.The close relationship between cultural practice in south Worcestershire and the occurrence of high populations of C. cilicrura is discussed.A summary of control measures devised by other investigators is given. Modifications of cultural practice that would be likely to reduce attack by C. cilicrura are suggested. Results of preliminary trials with naphthalene and DDT emulsion are given.