While much of Manitoba’s canola crop is already in the swath or being combined, Alberta and Saskatchewan fields are at or approaching proper swath timing. Unfortunately, late season pests like bertha armyworm are also building substantially in many areas. Why is this an issue? Because of the pre-harvest interval (PHI) required for many insecticide products.
The PHI is days between application and the crop being CUT, not harvested. For some actives, like Lambda-cyhalothrin (Matador/Silencer) or Deltamethrin (Decis 5EC), the PHI is seven days but with chlorpyrifos (Lorsban/Citadel/Pyrinex/Nufos) the PHI is 21 days. For some products, it’s as much as 30 days. The decision to spray and the decision on swath timing have to jive; which is the greatest risk? Spraying but extending the stand time or not spraying but cutting at optimal timing? Either way, if you’ve already sprayed, you must wait the required days before cutting — even if the swath will sit for two to three weeks. Why? The Canola Council of Canada spells out the risks on its website: tests for detecting residues are very sophisticated. One part per billion is equivalent to about nine seeds of canola in a ‘Super B’ grain trailer, says the Canola Council; finding the residue either here or overseas could result in serious fines.