|Authors: ||S. Finch, R. H. Collier|
Laboratory and field experiments indicated that the number of day-degrees /D°/ required for the cabbage root fly to complete a generation was approximately 580 D° above a base temperature of 6 °C, measured at a soil depth of 6 cm.
The times to 10 % oviposition by this fly could be forecast as accurately using D° accumulated on integrating thermometers as using D° calculated from data collected at a nearby weather station.
The original forecast was based solely on accumulated D°. Apart from the over-riding influence of temperature, however, cabbage root fly activity in the field is influenced considerably by a/ the times the flies emerge from the overwintering puparia, b/ aestivation and, c/ the effect of day-length.
By including these 3 factors, both seasonal and local variations in cabbage root fly infestations can be forecast with satisfactory accuracy.
A comparable system is being developed for the carrot fly.
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