Dormant oil can cause injury if applied under which condition?

• A. Below freezing
• B. Above freezing
• C. On a windy day
• D. During rain

Answer: (A)

Dormant oil poses the greatest risk of plant injury when temperatures are below freezing. At subzero temperatures the oil can solidify and form a strong film on winterized tissues, which, combined with cold stress, makes buds, bark, and other tissues more susceptible to damage. The plant isn’t actively growing, so it can’t recover quickly from this added stress. In contrast, above-freezing temperatures, windy conditions, or rain don’t create the same risk of tissue injury from the oil itself—the main concern with freezing is the heightened vulnerability of the plant and the potential for the oil to exacerbate frost damage.