How can you determine if a pesticide is incompatible with another you plan to mix with it?

• A. Check both labels for compatibility information; perform a jar test if allowed; do not mix if incompatible.
• B. Mix first and ask questions later.
• C. Assume compatibility unless told otherwise.
• D. Only test on a small scale.

Answer: (A)

Verifying compatibility before mixing relies on using the product labels and, when allowed, a jar test to mimic the tank mix. The labels often include explicit compatibility information or charts that show which products can be combined and with what additives. Use the same water source and follow the same mixing sequence you would in the sprayer. A jar test involves mixing small amounts of each product in the same proportions, then shaking and observing for a short period. You’re looking for signs of physical incompatibility: separation, cloudiness that won’t settle, precipitates, gels, or excessive foaming. If you see any of these, do not use the mixture in the tank. If the jar test stays stable and the label allows the combination, you can proceed, but still follow all label directions regarding pH, water quality, adjuvants, and application timing. Some products can be chemically incompatible even when they look fine in a jar, so always rely on label guidance and manufacturer compatibility resources. Jumping straight to mixing, assuming compatibility, or testing only on a tiny scale without proper guidance can lead to crop injury or ineffective pest control.