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PHI / REI Lookup.

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PHI / REI Lookup

Pre-Harvest Interval and Re-Entry Interval reference for common pesticides — organic and conventional.

Important

Always verify intervals on the specific product label. Same active ingredient may have different intervals across formulations and crop labels. PHI and REI on labels are legally binding under FIFRA. The values below are typical for reference; the label governs.

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Type a pesticide active ingredient, brand name, or pest target.

PHI vs REI

TermMeaning
PHI (Pre-Harvest Interval) Minimum days between last application and harvest. After PHI, residues are below regulatory tolerance and crop is legally harvestable.
REI (Re-Entry Interval) Minimum hours after application before workers may enter the treated area without specific PPE. Set by EPA Worker Protection Standard (WPS).
FRAC group Fungicide Resistance Action Committee classification. Rotate between FRAC groups to prevent disease resistance.
IRAC group Insecticide Resistance Action Committee classification. Rotate between IRAC groups to prevent insect resistance.

Why these matter

PHI is a legal requirement. Harvesting before PHI elapses is a FIFRA violation and produces residue that can fail food safety testing. For organic-certified or FSMA-relevant operations, PHI compliance is part of your audit trail.

REI is worker safety. Sending workers into a treated area before REI elapses without proper PPE is an OSHA and WPS violation. Documentation matters: who applied what, when, and when workers re-entered.

Rotation matters. Repeated use of the same FRAC or IRAC group accelerates resistance. Powdery mildew resistant to FRAC-3 fungicides has been documented in cannabis; spider mite resistance to abamectin (IRAC 6) is widespread. Rotate.

Resistance management — basic rotation

Modern integrated pest management (IPM) calls for rotating active ingredients across applications. The principle: never use the same FRAC or IRAC group twice in a row, and aim for 3+ different groups in a season for any given pest.

For example, a powdery mildew rotation might look like:

  1. Application 1: Bicarbonate (FRAC NC — non-classified, contact)
  2. Application 2: Sulfur (FRAC M2 — multi-site contact)
  3. Application 3: Bacillus subtilis (FRAC BM02 — biological)
  4. Application 4: rotate back, varying with disease pressure

For spider mites, IRAC rotation might use: bifenazate (IRAC 25) → spirotetramat (IRAC 23) → predatory mites (biological) → repeat. Tetranychus mites readily develop resistance to single-mode-of-action pesticides if not rotated.

Tracking applications

For any commercial operation — and especially organic-certified, regulated cannabis, or FSMA-relevant — record-keeping is non-negotiable. For each application, log:

  • Date and time of application
  • Product name + EPA registration number
  • Active ingredient(s) + FRAC/IRAC group
  • Rate / dilution applied
  • Area treated
  • Applicator name + license number
  • Weather conditions at application (wind, temp, rain forecast)
  • PHI start date (= harvest blocked until)
  • REI end timestamp (= worker re-entry safe at)
  • Required PPE (per label)

OAT Manage tier captures these as `chemistry.foliar_applied` events automatically; the audit packet generator produces inspector-ready records.

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Free under CC BY 4.0. Cite as "OAT PHI/REI Lookup (openagriculturetechnology.com)". Always verify on product label; label governs over reference values.