What practice involves modifying a plant's growing environment to reduce unwanted pests?

Cultural control refers to the practices that modify a plant's growing environment to make it less favorable for pests while supporting healthy plant growth. This can include techniques like crop rotation, selecting pest-resistant plant varieties, altering planting times, and managing soil health. By improving environmental conditions and reducing the suitability for pests, cultural control methods can effectively minimize pest populations and their impact on crops without the direct application of pesticides.

The other options, while related to pest management strategies, do not fit the definition as precisely. Chemical warfare typically refers to the use of chemical pesticides to eliminate pests, which doesn't necessarily involve modifying the environment. Biological control uses natural predators or pathogens to manage pest populations, but it does not focus on altering the plant's environment. Mechanical control involves physical methods to remove pests or barriers to prevent their access but does not alter the growing environment itself. Therefore, the concept of altering the growing environment aligns closely with cultural control, making it the correct answer.