How does lack of rainfall influence herbicide efficacy?

The correct answer highlights that drought-stressed plants absorb herbicides less effectively. During periods of low rainfall, plants often experience drought stress, which can lead to physiological changes. This stress can cause the plants to close their stomata to conserve water, limiting gas exchange and reducing the uptake of substances, including herbicides. As a result, the capacity of the plant to absorb and translocate herbicides diminishes, leading to reduced efficacy of the herbicide application.

This principle is crucial for those applying aquatic herbicides, as understanding the conditions that affect absorption and effectiveness can inform better decision-making about when and how to apply these chemicals for optimal results. Enhanced plant hydration can improve herbicide uptake, which is generally considered when planning an application during more favorable conditions.