When is a basal-bark herbicide treatment typically performed?

A basal-bark herbicide treatment is most effective when performed during the dormant season, when leaves have fallen from trees and shrubs. This timing is advantageous because the lack of foliage allows for better herbicide penetration into the bark, targeting the cambium layer where the herbicide can be most effective in killing the plant.

Applying this treatment during dormancy minimizes the risk of impacting surrounding vegetation that may still be actively growing and reduces the likelihood of herbicide movement through active sap or foliage. Additionally, the dormant season often corresponds to lower pest pressure, making it a strategic time for application.

The other options might suggest times when plants are actively growing or under environmental stress (like heavy rainfall), which can reduce the effectiveness of the herbicide application due to factors such as increased water runoff or the dilution of the herbicide.