Which of the following is an example of a phytosanitary treatment?

Heat treatment to eliminate pests is recognized as a phytosanitary treatment because it actively aims to remove or neutralize harmful organisms that can adversely affect plant health and agricultural systems. This method uses elevated temperatures to kill or reduce the population of pests, such as insects and pathogens, present on or within plant material.

Phytosanitary treatments are essential for ensuring that plant products meet international standards for pest and disease management, allowing for safe trade and transport across borders. These treatments help prevent the introduction and spread of invasive species, thereby protecting native ecosystems and agricultural productivity.

The other options provide benefits to plants but do not specifically address pest elimination in the context required by phytosanitary regulations. For instance, watering with organic fertilizer, maintaining regular feeding schedules, and using natural pest predators focus more on plant nutrition and overall health or biological control rather than the immediate need to ensure that plant materials are free of harmful pests and diseases as is the primary focus of phytosanitary treatments.