If you’re trying to time a herbicide application as late as possible, here are the limits for some key herbicides. Please note that many of these require tolerant seed traits.
R1 (first flower): Liberty, Pursuit, Raptor
R2 (full flower): Cadet, Enlist One, FirstRate, Roundup, Warrant
Varies by State: Xtendimax, Engenia, and Fexapan, the dicamba products for Xtend crops. This is a tricky one, because the label says either R1 or no more than 45 days after planting, whichever comes first. However, state rules may limit application further. Most states say June 20 or June 30 for a cutoff. Typically, our advice is to spray before June 15, but whatever you do, make sure you find out the last spray date for your state and your situation.
If weeds come up after your field is blooming, the best option to stop the weeds and not hurt yield is to hand-pull the weeds. It’s possible you could cultivate the field, but before you do that, I’d suggest digging in between the rows to see how far across the root systems are. In our fields, the roots are all the way across our 30-inch rows, and I would be reluctant to consider cultivation because it will likely hurt yield by pruning off roots.
If you’re dead set on spraying an herbicide after R2, there are a few that still get used:
Cobra: R6 (full seed) or 45-day PHI (preharvest interval), whichever comes first
Resource: 60-day PHI
Select Max: 60-day PHI