What can excessive sunlight do to pre-emergence herbicides?

Excessive sunlight can cause pre-emergence herbicides to break down due to photodegradation. When these herbicides are exposed to high levels of ultraviolet (UV) light, the chemical compounds in the herbicides can undergo reactions that alter their structure, reducing their effectiveness. This breakdown process diminishes the herbicide's ability to prevent weed seed germination and can lead to ineffective weed control.

While factors like temperature and moisture can influence the performance of pre-emergence herbicides, excessive sunlight specifically contributes to their degradation. Understanding this effect is crucial for proper application timing and ensuring optimal conditions for herbicide activity, which helps maintain effective pest control in turf and ornamental settings.