Which of the following methods can be classified under mechanical pest control?

Handpicking pests off plants is classified under mechanical pest control because it involves the physical removal of pests from the affected area. This method is direct and does not involve the use of chemicals or biological agents, making it a straightforward approach in pest management. The primary goal of mechanical pest control is to reduce pest populations through non-chemical means, and handpicking is an effective technique, especially for larger pests or those found in manageable numbers.

In contrast, applying herbicides involves the use of chemicals to kill or inhibit the growth of unwanted plants, which falls under chemical pest control rather than mechanical. Using genetically modified crops typically leverages biological resistance to pests and diseases, thereby aligning with biological control methods rather than mechanical ones. Rotating crops seasonally is a cultural control strategy that helps manage pest populations by disrupting their life cycles but does not fit the mechanical category as it does not involve any physical means of pest removal.