Sachin Dhanda, Former weed science postdoctoral researcher, Sithin Mathew, Weed science graduate student, and Debalin Sarangi, Extension weed scientist Soybean field treated with postemergence Cobra herbicide (within the label cutoff) showing temporary leaf injury. Photo: Sithin Mathew) As postemergence herbicide spraying is ongoing in Minnesota this week, this is a reminder that all the applications should follow the growth stage cutoffs specified on herbicide labels for postemergence applications and to comply with the preharvest interval (PHI) which is legally required. The PHI represents the minimum time between the last herbicide application and the crop harvest. The restrictions are in place to prevent potential crop injury, herbicide carryover, environmental or food safety issues, and other concerns. If tank mixing two or more herbicides, the cutoff is determined by the most restrictive labels. Always consult herbicide labels prior to application to ensure ...
Sachin Dhanda, Former weed science postdoctoral researcher, Sithin Mathew, Weed science graduate student, and Debalin Sarangi, Extension weed scientist Corn field planted in mid-May requires postemergence herbicides for weed control. Photo: Debalin Sarangi Herbicide labels typically specify growth stage or crop height cutoffs (whichever comes first) for herbicide application, and the preharvest intervals (PHI) indicate the minimum time required between the last herbicide application and crop harvest. The restrictions are crucial to prevent potential crop injury, herbicide carryover, environmental or food safety issues, and other potential concerns. When tank mixing herbicides, the most restrictive label determines the cutoff. Always consult herbicide labels before application to ensure compliance. Below is an updated table (as of June 17, 2025) summarizing field corn growth stage or height cutoffs and PHI for commonly used postemergence herbicides. The growth ...