Which of the following is a non-chemical method of termite control?

Heat treatment is a non-chemical method of termite control because it utilizes elevated temperatures to eradicate termites and their eggs. This method involves raising the temperature of the infested area to a level that is lethal to termites, typically above 120 degrees Fahrenheit, for a sustained period.

This approach is particularly effective because it targets the termites directly without the use of chemical pesticides. Additionally, heat treatment can penetrate into walls and other structural components, ensuring that hidden infestations are also addressed.

In contrast, the other options involve the use of chemicals or pesticides, which do not align with the definition of non-chemical control methods. Liquid termiticides and soil fumigation are chemical treatments that aim to create barriers or eliminate termites through the use of toxic substances, while pesticide baiting relies on feeding termites poisoned bait. Thus, heat treatment stands out as an environmentally friendly, safe alternative for controlling termite infestations.