Studies were established to provide information on the efficacy of a novel bait treatment and to determine the best way to deploy the treatment to achieve maximum pest control with minimum application of active ingredient. The UK-based research was undertaken by Warwick HRI (WHRI) and Dow AgroSciences (DAS) using the population of carrot fly maintained in an experimental area at Wellesbourne. The carrot fly population is maintained intentionally at a high level at Warwick Crop Centre, Wellesbourne and damage levels are likely to be greater than those suffered by all commercial carrot crops grown conventionally in the UK. Apart from other considerations, conventional carrot crops are usually grown on wide rotations, both spatially and temporally, which reduces the level of colonisation from previous crops. Damage to the untreated carrots in both fields was very high and there was little evidence of damage reduction even with a standard pyrethroid spray programme, which was in itself surprising. There are a number of things to consider: • It is possible that the carrot fly population at Wellesbourne has become resistant to pyrethroid insecticides - although this does not impact directly on the performance of GF120. This has been reported to Syngenta. • It is possible that the spray programme with GF120 did not cover enough of the carrot fly activity period (last sprays applied 11 August). • A further possible explanation is that a relatively low proportion of the carrots in the trial were treated with insecticide, so that on a ‘field’ scale there was relatively little suppression of carrot fly numbers. Insecticide-free areas included the long bed drilled at the base of the plots, the untreated control areas and the spaces between the bands. Together these accounted for a large proportion of the trial area. In ‘conventional’ insecticide trials for carrot fly then the insecticide-free area would be likely to represent