When pesticides are mixed, the level of risk you protect against should reflect the higher hazard indicated by the signal words. The signal word on a label shows acute toxicity potential, so if two products have different signal words, the mixture could present at least the higher level of danger. Treating the mixture as the more hazardous signal word ensures you use the appropriate PPE, application methods, and handling precautions for the worst-case scenario. Choosing a less cautious approach could leave you exposed to greater risk, and assuming the hazard is only the lower level isn’t safe. If in doubt, always follow the label and safety data sheets for the combination, but the standard practice is to default to the higher hazard.

When you mix pesticides, you must follow the most restrictive signal word shown on any of the labels. Signal words reflect acute toxicity and guide how carefully you should handle and apply the product. If one component says WARNING and another says CAUTION, the mixture is treated as WARNING because WARNING represents a higher level of hazard than CAUTION. This ensures you use the higher level of protective equipment and follow the stricter handling precautions that come with WARNING. A DANGER label would apply only if any component carried DANGER, which isn’t the situation here. A CAUTION-only result would occur if all components were CAUTION, and UNKNOWN isn’t appropriate because there is a clear hierarchy among the signal words. So the mixture should be treated as WARNING.

When you’re using a pesticide under a Special Local Needs label (24c), the exact directions you must follow are defined by that 24c label. Because these labels can specify different uses, rates, timing, crops, and safety requirements than the federal label, you need to have a copy of the 24c label with you at the application site. Having the copy on hand ensures you can reference the precise instructions and comply with the local authorization, and it also serves as documentation in case of inspection or questions about how the product was used. This requirement isn’t about whether a label generally exists; it’s about following the specific locally authorized use. Therefore, it’s not optional or only for some products—the correct practice is to have the 24c label copy in possession whenever you apply under that label.

Doubling the pump pressure will not double nozzle output. For a fixed nozzle orifice, the flow rate increases with the square root of pressure, so doubling pressure raises flow by about sqrt(2) ≈ 1.41 times, not 2 times. In other words, going from 20 psi to 40 psi might increase output by roughly 41%, depending on the nozzle and system, but it won’t double. Higher pressure can also affect droplet size and drift, so pressure changes don’t translate to proportional changes in output.