Senior Advisor
Posts: 3,228
Registered: ‎04-30-2010

Rain Needed For Herbicide Activation

Here is a 2007 ISU study which cites a 1997 UI site.  The chart tells it all.

Bottom line - 1" for full control of foxtails.  1/2" gives 85-90% control.  Up to 1/4" shows about 50% control.

So, it looks like 1/2" gives most of the results but for full results we need an inch.