What the pre-harvest interval is
The PHI is the number of days that must pass between the last treatment and the harvest so that residues in the grapes stay within the permitted limits. You find it on the label and in the product's instructions for use.
Some Slovenian labels say the interval is "ensured by the time of use": the product may only be used up to a given growth stage of the vine, so there is no separate number of days.
How to calculate it
Date of the last spray + the PHI in days = the first day you may harvest.
Example: last spray on 10 August, PHI 28 days — harvest on 7 September at the earliest.
What applies to a tank mix
If several products went into the same tank, the longest PHI among them applies. For a parcel, what counts is the spray whose interval ends last — not necessarily the latest spray.
The PHI in Kletio
For every spray you record, Kletio reads the PHI from the product register, takes the longest one in a tank mix, and shows on the parcel list how many days remain or from when harvest is safe.
The PHI is stored with the record when you save it, so a later change to the register never rewrites a past record. Product data is for information — the label always prevails.
A general explanation, not advice on using any product. Always check the dose, the number of treatments and the PHI on the label.