During which season is it appropriate to apply dormant oil?

Applying dormant oil is most appropriate during the winter season. This practice is typically done in late winter or early spring before buds begin to break but while trees and shrubs are still dormant. The purpose of dormant oil is to control overwintering pests such as scale insects, aphids, and mite eggs, which can be present on plants.

During the winter, the oil can effectively suffocate these pests and reduce their populations for the growing season ahead. The key to using dormant oil is that it must be applied when temperatures are typically above freezing, ensuring that the oil can spread effectively over the plant surfaces without being washed away or rendered ineffective by cold conditions.

The other seasons are less suitable for applying dormant oil due to factors such as active plant growth or the presence of desirable insects. In spring, for instance, applying dormant oil can disrupt the awakening of beneficial insect populations and may interfere with the growth of buds and new leaves. Summer and fall also pose similar risks due to the activity of both pests and beneficial organisms, which can lead to unintended side effects. Thus, winter is the optimal time for this type of treatment, maximizing its efficacy while minimizing harm to the broader ecosystem.