What is the minimum soil temperature required for effective fumigant volatilization?

• A. 85
• B. 75
• C. 65
• D. 55

Answer: (D)

Volatilization of a fumigant depends on the gas phase formed in the soil air, and how readily that gas can move through soil pores to reach pests. Temperature drives this because higher soil temperatures raise the fumigant’s vapor pressure, making more of the chemical turn to gas and diffuse through the soil. If the soil is too cool, very little fumigant becomes gas, so distribution through the root zone or pest habitat is inadequate and control will be poor.

The minimum temperature is the lowest end of the practical range at which enough fumigant can volatilize to achieve effective movement and pest contact. Warmer soils will enhance volatilization and spread, but the threshold is the point you don’t want to fall below if you need reliable results.