A pre-harvest interval is the amount of time that’s required between a product application and cutting the crop in anyway — not just harvest. A PHI can always be found on a product label, and following the recommendation can help the crop dry down faster and keep product residues within maximum residue limits.
“When it comes to harvest, we’re not just talking about combining, we’re actually talking about cutting the crop,” says Andrew Reid, technical marketing specialist of herbicides with BASF. There is sometimes a misconception that after spraying a pre-harvest aid, you can go out the next day or so and start swathing, which Reid is here to clear up in this episode of Canola School.
“If you spray a pre-harvest aid on a standing crop of canola, and then there’s a hail storm or frost and the crop needs to be knocked down, if the PHI is three days, you still have to wait those three days,” says Reid. (Story continues below video)
“The most important thing to remember with a PHI is if you’re using more than one product in a tank mix combination, you have to go with the most restrictive PHI, which means the longest PHI,” says Reid. For example, if one tank mix partner has a PHI of three days but the other has a PHI of seven days, you have to wait the seven days.
Market access and product residue issues have been the focus of discussion lately. A PHI is in place to minimize a product residue as much as possible, and by following it, growers are better equipped to comply with maximum residue limits.
Remember that spraying earlier because there’s more time between application and harvest, does not actually minimize residues, in fact you can end up with more product residue in the grain if you spray too early. Double check your crop’s staging and application timing according to the label and be sure to follow those PHIs.
Related: Pre-harvest cautions and no glyphosate in Mexico
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