What method is most effective to avoid causing brownout when controlling trees along a highway?

The basal application in the winter is the most effective method to avoid causing brownout when controlling trees along a highway. This technique involves applying herbicide to the lower portion of the tree trunk, which minimizes the likelihood of non-target plant injury during the growing season.

In winter, many trees are dormant, and the risk of herbicides affecting surrounding vegetation is significantly reduced, thus preventing brownout, which is the undesired browning and loss of foliage in non-target plants. Additionally, the dormant season means that herbicides will not be taken up by actively growing foliage, further reducing the risk of unintentional plant damage.

Other methods, such as foliar application in the summer, pose a higher risk of drift and impact on surrounding plants that are actively growing during that season. Cut-stump applications in the fall can also lead to unintended effects if the herbicide migrates through soil or roots during active growth periods. The soil drench method can be effective but carries a risk of affecting other plants due to root uptake, particularly if applied during a time when other plants are vulnerable to herbicide effects. Thus, the winter basal application stands out as the most suitable option for safe and effective tree control without causing brownout.