Yes the weeds will develop a resistance to a product. What happens is a few are naturally resistant to the product. They multiply so the following year there are more that are resistant. Ans so on year after year.

You need to alternate herbicide groups. Prodiamine, dithiopyr, and Pendimethalin are group 3 while Indizaflam is group 29. I do not know what weeds you are concerned about so cannot suggest which herbicides to use. You can look up on the labels themselves. But alternate at least two.

 

I had a crabgrass break through and it's bad. I'm changing my pre emergent strategy and using Esplanade 200sc, dual Magnum, and prodiamine

 

Prodiamine has eliminated 99% of my weeds! Been using it 4 years. I do split apps.

This is the first year of results that good, I've had less and less weeds year over year though. Only have an issue with prostrate spurge.

How healthy of a stand is your turf for the last seven years?

How are you timing and applying your applications?

When I'm done with my Prodiamine I'm switching to Esplanade 200sc, if I choose another product.

 

Indizaflam for the win. Eliminated 90+% of poa first application last fall for this past winter. Same thing this summer. I have a few area weakening now with drought or that I’ve removed an old storage building that didn’t covered, but yards 98% weed free (except for sedges).