Carrot Rust Fly: Monitoring Adults to Determine Whether to Apply Insecticides

Catches of carrot rust fly (CRF), Psila rosae (F.), on Bristol Board traps varied with location in the Holland Marsh, Ontario. When decisions to apply insecticides (diazinon or parathion) by spraying vs. 1st generation adults were based on trap-catch data, the number of applications required was reduced as compared with routine spraying at 7–10 day intervals. From 1973–77, using a trap catch of at least 1 fly/plot as the criterion for spraying, 0.03 to 4 ha test plots located in areas of low CRF activity required from 0 to 5 applications in contrast to the 5–6 applications that would have been applied in a routine program. Resulting infestation levels were economically acceptable.