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Pest, Disease & Weed Timing CalendarsPre-Harvest Interval Calendar
A pre-harvest interval is a hard stop on the calendar, and the simplest way to respect it is to plan backward from your harvest dates.
Key points
- Work backward from harvest using the interval on the current label.
- Repeated-harvest crops need the interval counted before every pick.
- Restricted-entry and pre-harvest intervals are different rules.
- Document dates and keep label copies.
- Build a safety margin into the clear date so weather and early ripening do not push you past the limit.
What is a pre-harvest interval?
The pre-harvest interval, often shortened to PHI, is the minimum number of days that must pass between the last application of a pesticide and harvest of the crop. It exists to let residues decline to levels that meet legal limits for food. Residue limits are set by federal rules, and the interval on the label is how growers meet them in practice, which is why shortcuts can create real problems at the market or processor.
The interval is printed on the label and differs by product and crop. The label is the law. This article explains how to schedule around intervals, not what to apply.
Intervals may also differ for different crop uses, such as fresh market, processing or animal feed, so confirm which use applies.
How do you plan backward from harvest?
Start with the earliest expected harvest date for each field or planting. Count back the label's interval and mark that day as the last allowed application date. Then add a safety margin for weather delays and early ripening. Share the finished calendar with harvest crews, buyers and anyone else who needs to know which blocks are off limits and until when.
For example, if you expect to begin picking on a given date and the label requires a set number of days, the last application day is that many days earlier. Use the label's numbers for your product and crop, and update if harvest moves.
Add a few extra days to your planned clear date if weather could speed ripening. A small buffer protects you from compliance trouble.
What about crops picked many times?
For crops with repeated harvests such as beans, tomatoes or berries, the interval applies before each harvest. If you spray, you may not pick from that block until the interval passes, which can mean lost picking days. Stagger blocks so some are always ready. Walk through every planned application on paper before the season, so you can see conflicts with your harvest plan while there is still time to change them.
Plan sprays on one block at a time and mark the clear-to-pick date on a visible board for workers and buyers.
- Mark spray date and clear-to-pick date
- Post it where harvest crews can see
- Label sprayed blocks in the field
- Keep a backup block ready
How does the re-entry interval differ?
The restricted-entry interval is a separate time during which workers should not enter treated areas without protective equipment. It protects people, while the pre-harvest interval protects consumers. Both may apply and both come from the label and worker protection rules.
Check the Worker Protection Standard guidance for your state, and train crews on posting, notification and protective equipment where required.
Keep protective equipment, posting signs and notification records ready before the season starts.
What can change the plan?
Weather, ripening speed and market demand can move harvest earlier. A heat wave can shorten the time to maturity, and a buyer may ask for early picking. Build flexibility into your calendar, and never shorten an interval to meet a deadline.
If harvest must occur before the interval has passed, choose a different management option or lose that picking window. The legal limit is not negotiable.
Talk with buyers and pickers early about the schedule so no one is surprised by a restricted block.
How should you document intervals?
Record the application date, product name as on the label, label interval, calculated clear date and actual harvest date. Many buyers and food safety audits ask for these records, and they protect you if a question arises.
Keep label copies, since label text and intervals can change. Always use the current version.
If an inspector or buyer asks for records, being able to produce a complete log quickly shows careful management.
What mistakes are most common?
Counting from the wrong date, forgetting about repeated harvests, misreading the crop on the label, and ignoring the interval when moving a crop to a different use are frequent errors. Another is letting hired help spray without knowing the harvest schedule. Add a reminder in your phone for each clear-to-pick date.
A shared calendar and clear communication solve most of these problems.
Review your process after each season and fix the weak points before the next one.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.