What is the term for pesticides that when mixed together do not stay uniformly mixed in the spray tank even with adequate agitation?

• A. Antagonism
• B. Synergism
• C. Physical incompatibility
• D. Chemical incompatibility

Answer: (C)

When two pesticides mixed in a spray tank don’t stay evenly mixed despite adequate agitation, it indicates physical incompatibility. This describes instability in the mixture’s physical state, so the components separate, form layers, or a precipitate appears rather than staying as a stable suspension or solution. It’s about how the ingredients physically interact in the liquid, not about a chemical change or a biological effect.

That’s different from chemical incompatibility, where a chemical reaction occurs between components that can alter active ingredients or produce new, unwanted compounds. It’s also distinct from antagonism or synergism, which refer to how the pesticides affect pests, not how they behave in the tank.

To prevent this, use products that are labeled as compatible, perform jar tests with your specific water and tank setup, follow the recommended mixing order, and avoid combining products that are not physically compatible. If mixing isn’t compatible, don’t force the blend; use separate applications or find a compatible tank-mix if approved.