What are some problems that can result from mixing two or more pesticides?

• A. Incompatibility of chemicals can result in dangerous or volatile mixtures that could explode, start on fire, or release harmful vapors.
• B. Mixing pesticides always improves safety.
• C. Two pesticides never interact.
• D. Mixing can reduce the effectiveness but pose no hazard.

Answer: (A)

Mixing pesticides can create chemical incompatibilities. When different products are combined, their ingredients and carriers can react with one another, sometimes producing heat, gases, or new, unstable compounds. These reactions can form dangerous or volatile mixtures that could explode, start a fire, or release harmful vapors, especially in poorly ventilated areas. Labels often prohibit mixing unless the products are specifically approved to be combined, and a compatibility test or small-scale trial should be done before full use. Because safety depends on how components interact, mixing does not always improve safety and can actually introduce hazards and reduce effectiveness. The idea that mixing always improves safety, that pesticides never interact, or that mixing only reduces effectiveness without hazards isn’t accurate.