Which of the following best describes the impact of improper calibration on pesticide application?

Improper calibration during pesticide application significantly increases the risk of under- or over-application, making this answer the best choice. Calibration ensures that the equipment dispenses the correct amount of pesticide accurately and uniformly. When calibration is off, there may be too little pesticide applied, which might not effectively control the target pests or diseases. Conversely, too much pesticide can lead to unnecessary chemical use, causing potential harm to non-target organisms, including beneficial insects or aquatic ecosystems, and increasing the likelihood of pesticide resistance developing in target pests.

The other options do not accurately reflect the consequences of improper calibration. Increased efficiency cannot be achieved with inaccurate application rates, nor does improper calibration have no impact at all, as it directly affects both efficacy and environmental safety. Furthermore, it is unlikely to lead to reduced environmental impact, as over-application can contribute to pollution and harm surrounding ecosystems. Thus, understanding the critical nature of proper calibration is essential for effective and responsible pesticide use.