Efficacy and residues of chlorpyrifos applied against root maggots attacking cole crops in British Columbia


  • J. R. Mackenzie Research Station Agriculture Canada Vancouver, B.C.
  • R. S. Vernon Research Station Agriculture Canada Vancouver, B.C.
  • S. Y. Szeto Research Station Agriculture Canada Vancouver, B.C.


Chlorpyrifos proved to be as effective as chlorfenvinphos, and more effective than fensulfothion and diazinon for cabbage maggot control in root and stem crucifers. For short season crops such as cauliflower, broccoli and cabbage, the granular formulation applied at seeding, followed in 21 days with a single drench of the emulsifiable liquid formulation was adequate. In Brussels sprouts, the slowest of the stem crucifers to mature, a minimum of two drench applications were necessary for acceptable control. In rutabaga, another long season crop, chlorpyrifos 15G applied at seeding followed by 3 drench applications (i.e., at 21-day intervals) after seeding was necessary to produce rutabagas with acceptable damage levels at harvest. In the sandy-clay loam where these studies were undertaken, chlorpyrifos applied at the dosage rates and at the times prescribed for the stem and root crucifers studied did not give rise to appreciable residues at harvest. These studies show that a pre-harvest interval of 32 days would be appropriate for the 5 crops studied.


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