Where do you live?

What kind of grass do you have?

I'm in Houston. I have palmetto st. augustine.

I'm in Houston too--Both these guys are on the move right now for some reason. For number 1, check out my thread on doveweed from this week. Several treatment options are discussed but it's a nasty one.

Number 2 is spurge, a true PITA. See one, pull one. It drops seeds the size of sand grains from the leaf nodes, so spray the spot with preM after you pull. Roundup or Fluazifop will kill it, but that'll kill everything else too. Sulfentrazone claims to control it but I haven't had much luck. Just turns it red & the spurge keeps kickin.

what preM would you suggest? Will Weed Free Zone by Fertilome work well?

are you absolutely sure #1 isn't buttonweed?

#1 looks like buttonweed to me. Tough to control. 3-way herbicides work when they're young, as they mature triclopyr works better.

are those safe to use on St. Augustine? I put this sod down in March so its fairly established...but its still hot so i'm worried something too harsh will kill the grass.

which 3-way herbicide would you suggest and should I spot treat or treat the entire yard?

I don't think those are safe for St. Augustine. I'll let someone else familiar with that grass recommend something appropriate.

Spot treat only. Virginia buttonweed doesn't grow down here but theyre very commonly confused from my research. It sure had me confused for a few weeks! Weed free zone looks like a 3-way & it's labeled for St. Aug, but I can't tell if it has a preM included. I use bonide Sedge Ender because it has prodiamine mixed in already, but as I said the sulfentrazone did not do much to either of these weeds. It's fantastic on nutsedge & Crabgrass though, so you'll use it eventually in Houston. Honestly though, buy yourself a bottle of prodiamine if it's in the budget. A little goes a long way.

I don't spend a lot of time on herbicides even for St Augustine, but the one that seems to wipe out everything except St Augustine is atrazine.

Oh yeah, I forgot about that! Only St. Aug can handle atrazine, secret weapon time.

Careful on temps with atrazine, read the label for sure. You could routinely just look for the buttonweed and pull it out. Sort of rake it up with your hand without pulling it out to separate it from the SA grass, then you'll find where that section of the buttonweed is originating from and you can pull that part out of the soil. You could just hand pull most of it and throw down a good pre-em layer. You'll have to keep checking for new growth though because it can spread vegetatively, and from the part you left in the soil (as well as seed). Keeping your grass high and not watering too often will help. Bonide sedge ender had a mild effect (a worse effect on my grass actually), but I spent so much time checking to see how it did on the buttonweed I ended up just hand pulling it, should have just done that in the first place (so I'm on the lookout for regrowth there). Celsius controlled buttonweed for me, but required two apps. You can go the Celsius route, the only drawback I see is that in high temps Celsius stunts the growth of my saint Augustine grass, so it conflicts with trying to get the grass to grow tall and thick to choke out weeds. On my front yard that is nice and thick, it's easy for me to just look for weeds when checking the mail and pull as required. In my large backyard, it's more of a mess, so I go the Celsius route. No time for the attention the grass needs... I've done the google thing over this buttonweed earlier this summer, so hopefully I've given good information, but I am certainly not an expert.

Can you recommend a good preM that would be safe to use? It looks like temps are coming down, so I can wait until highs are below 90 degrees before I apply atrazine.

Prodiamine & dithiopyr or dimension are common around here. Prodiamine is available in granules or spray, dimension is harder to find & I think granules only. Honestly the best preM is the one you can get reliably at your local store of choice. Otherwise you can buy a bottle of prodiamine online & that'll last a long time

Look for something with prodiamine or dithiopyr for a pre-emergent.

Keep us in the loop on how the atrazine works. I'm curious about the buttonweed.