Which of the following factors could reduce the effectiveness of pesticide application?

Pesticide resistance in pests significantly reduces the effectiveness of pesticide application. When pests develop resistance, they evolve mechanisms to survive treatments that were previously effective against them. This can occur due to repeated exposure to the same type of pesticide, allowing the few resistant individuals to survive and reproduce, leading to a population that is increasingly difficult to control.

In contrast, increased application frequency generally enhances the pest management strategy by reducing pest populations effectively. Optimal weather conditions, such as appropriate temperatures and humidity, facilitate better pesticide performance by preventing issues such as evaporation or wash-off. Proper storage conditions for pesticides ensure that the products retain their effectiveness over time. Thus, while these factors contribute positively to pesticide application success, resistance in pests creates a significant challenge, undermining the whole application process.