Which factor can contribute to herbicide control failure related to weather?

Excessive rainfall is a significant factor that can lead to herbicide control failure. When heavy rain occurs shortly after herbicide application, it can wash away the pesticide from the targeted area, reducing the effectiveness of the herbicide. This loss can prevent the herbicide from being absorbed by the targeted weeds or grass, making it unable to control or eliminate the unwanted plants. Additionally, excessive moisture can promote the growth of weeds and other vegetation, further complicating control efforts and potentially leading to increased competition for desired turfgrass.

Other factors, while they may influence herbicide efficacy, do not have the same immediate and drastic impact as excessive rainfall. For example, too little sunlight may affect plant growth generally but does not directly wash away herbicides. Low humidity can affect the rate of evaporation, but it does not pose as direct a threat as excessive rainfall. Finally, high wind speeds can cause drift, which may lead to application issues, but it is less commonly a direct cause of control failure than the washing away of herbicide due to rainfall.