Which of the following factors is NOT a controlling factor for uniform backpack applications?

In determining which factor is not a controlling element for uniform backpack applications, it's important to understand the significance of the other factors listed. Nozzle size is critical, as it directly influences the spray pattern, droplet size, and the distribution of the pesticide applied, affecting coverage and efficiency. The time that the spray is kept on the target area also plays a vital role because it dictates how effectively the pesticide can penetrate or adhere to the surface, impacting the overall efficacy of the application. Pressure used during the application is another key factor, as it regulates the flow rate and the dynamics of the spray, which in turn can determine the effectiveness of the application and prevent issues such as drift or uneven coverage.

On the other hand, the temperature of the pesticide, while it can affect the viscosity and volatility of the chemical, is not a controlling factor regarding the uniformity of the application itself. This attribute primarily influences the behavior of the pesticide rather than how uniformly it is applied. Therefore, the choice indicating temperature as a non-controlling factor is accurate, as it does not directly impact the uniformity of application in the same manner that the other factors do.