What weather condition can lead to reduced control of herbicides due to wash-off?

Heavy precipitation can significantly impact the effectiveness of herbicides by causing wash-off. When it rains heavily shortly after application, the rain can wash the herbicide off the target site before it has had the chance to effectively penetrate or adhere to the weeds. This wash-off leads to reduced efficacy as the active ingredient may be diluted or removed entirely from the area it was intended to control. Effective herbicide application relies not only on proper timing and method but also on weather conditions, and heavy rainfall poses a risk to successful application, especially in the initial hours or days after treatment.