Revised Comments Rainfall Required for Herbicide Activation Peanut Notes No. 60 2021

— Written By NC State Extension

Good morning all,

I wanted to clarify the sentence I marked in red from yesterday’s article about water requirements for preemergence herbicide activation:

“Some product labels are quite vague in their language about rainfall minimum requirements for preemergence herbicides. I believe 0.25 inches is sufficient to activate most preemergence herbicides. Another complication to consider is that some preemergence herbicides will sit on top of dry soil and resist breakdown and when rainfall comes, the herbicide will activate (albeit less than the amount you applied). In summary, if a dry period follows a preemergence herbicide application, plan on spraying the first postemergence herbicide application sooner and always tank mix a preemergence herbicide with that first postemergence treatment to extend the soil residual activity on weeds in the field.”

If a dry period follows a preemergence herbicide application, plan on spraying the first postemergence herbicide(s) application sooner and tank mix a residual herbicide (such as Dual Magnum, Warrrant, Outllok, Zidua, etc) with it. This will extend the soil residual activity on weeds that have not emerged yet in the field.

Michael W. Marshall, Ph.D.

Extension Weed Scientist

Edisto Research and Education Center

Clemson University

64 Research Road

Blackville, SC 29817

Mobile:  (803) 522-1415

Office: (803) 284-3343 x228

Twitter:  @ClemsonWeedSci