During which condition should postemergence applications of herbicides be made?

Postemergence applications of herbicides are most effective when plants are healthy and not under stress. When plants experience moisture or heat stress, their physiological functions may become compromised, leading to reduced uptake of the herbicide and diminished effectiveness. Healthy plants are better able to absorb and translocate the herbicide through their system, resulting in improved control of the targeted weeds.

Moreover, applications during conditions of high stress can also increase the risk of harming desirable vegetation and lead to phytotoxicity, as stressed plants may react adversely to the chemicals. Considering temperature and wind conditions also plays a role in the successful application of herbicides; extreme temperatures and wind can lead to vaporization or drift, further complicating herbicide efficacy and the potential for harming non-target species. Thus, making applications when plants are not experiencing moisture or heat stress ensures the highest efficacy and less chance of negative environmental impacts.