Monitoring and control of the carrot fly (Psila rosae fabr.) in northern Norway

A 4‐year study (1991–94) focused on (1) the use of yellow sticky traps to monitor carrot fly activity, (2) insecticide control trials, and (3) analyses for insecticide residues in carrots in northern Norway. There was only one generation of flies each year. In most fields, first flies appeared in the second part of June, with a peak fly activity occurring in the first part of July. The maximum difference in peak activity from one year to the next was 3 weeks. In five trials in which the fly infestation was high, 10–100% of the roots were damaged and marketable yield was reduced by 30–100%. Satisfactory control was achieved by drenching the crop with the organophosphorous insecticides diazinon or fenthion, timed according to catch on traps. Seed coating (isofenphos) had an unreliable, often lacking, effect. Residue levels of the fenthion in the carrots at harvest were unacceptable, even when this insecticide was applied at the recommended rates.