In a tank mix of two pesticides, the re-entry interval after application should be based on the product with which characteristic?

• A. The shorter REI
• B. The longer REI
• C. The average REI
• D. Unknown REI

Answer: (B)

When two pesticides are mixed and applied together, you have to protect anyone who might enter the treated area from both products. The re-entry interval is the waiting period after application before it’s safe to re-enter. Because a worker could be exposed to residues from either product, the overall restriction must reflect the longer waiting period. Using the longer REI provides a safety margin that covers the needs of both products, whereas relying on the shorter REI could allow entry while one product still has restrictions. Averaging or guessing isn’t acceptable—follow the label that imposes the strictest re-entry. So, the tank mix should be treated as having the longer REI.