That looks like false daisy. In this heat you're pretty limited on your options. One option is Image the original Imazaquin, not one of their other formulations. It is labeled for false daisy and there are no temp restrictions on the label. Wouldn't be surprised if you do get some yellowing of your turf, but should recover quickly. Seeing your other pic your St. Aug looks healthy and should handle an herbicide app pretty well. You could always spray a test spot of 10x10 or so and give it a few days and see how the Aug handles it. Try to spray early morning or at dusk. If you're just needing to spot spray a few areas buy the quart concentrate and mix your own in a gallon sprayer per label directions. When spot spraying the weeds need just a very light coating, not a 5 second soak down to the point of runoff. More is not better.