ABSTRACT
Laboratory and field-cage experiments indicated that 6°C was the appropriate base temperature above which to accumulate day-degrees (D°) for forecasting the times of cabbage root fly activity under field conditions. The most appropriate way to record these accumulations was from integrating thermometers whose probes were placed 6 cm deep in the soil, the depth at which most of the insects’ development occurs. A total of 580D° accumulated, above a base of 6°C, at a depth of 6 cm in the soil was required for the cabbage root fly to complete a generation. The number of D° required to complete a generation remained constant throughout all three annual generations of the fly.
