Its about soil temps, apply preemergents when soil temps start reaching around 55 degrees for several days straight(to deter summer weeds) and do it again later in the year when the soil temps start dropping just below 70 degrees (to deter winter weeds).

Sometimes Nature does not stick to the same schedule you want. Generally in the north the time to apply preem in the spring is when the forsythia first bloom. If you have a regimented garden calendar, you will see that that date can vary. Check the bag to see when to reapply. There is a time to apply in the fall, too. This application gets the plants that germinate in the fall, sprout and immediately go dormant, and then arise with the sunlight and rain in the spring. Those have to be caught in the fall, though.

In the south it is easier to go from rainstorm to rainstorm. Apply preem at the first big rainstorm after winter and the big rainstorm after summer. Again, no set date for those applications, because Mother Nature will not cooperate with our calendar.

My lawn is 1/2 acre so I know what you mean about the backpack sprayer. The backpack is ideal for spot spraying but for anything beyond that you need a pull behind sprayer. I bought a 31 gallon from Northern Tool and it is perfect for any application where you need to blanket spray the entire lawn. Yes, it's $279 but over the next 4 to 5 years it will pay for itself as the Prodiamine WDG is far cheaper than granular pre-m applications. Just do a few "dry" runs using only water until you get a good feel for the spray pattern and can put down an even coat. Here's a link to the one I bought: https://www.northerntool.com/shop/tools/product_200645939_200645939   They also make the same unit in a 21 gallon model that's a little cheaper.

For the POA, you need to put down a pre emergent late summer as it usually germinates in the early fall and then winters over and comes on strong in the spring. Some will also germinate in the spring. Not sure when you would need the fall app but around here it's early September. The spring app for me is usually mid to late February to catch all the spring weeds. The nice thing about prodiamine is you can adjust the length of coverage by how much you put down. Even if your spring app is done early you can adjust it to last until a little before you intend to do the fall app. If you won't need to overseed this fall then by all means do the pre-emergent sometime in August/September and your POA problem should be way better next year.

Thank you all for the advice. Just to narrow it down I have decided to use the Prodiamine. Sorry, but I am a little unclear on a couple of things.

Forsheems, I was looking into the tow behinds but I was wondering if it is a pain to make turns since I have a zeroturn mower. What do you think? What happens when you need to slow down, does the sprayer keep spraying causing you to apply too much?

1) Ok so typically when forsythias bloom would be the first application of Prodiamine 65 wdg. How much should I put down since I over-seed every September 1st.

2) I assume the late summer application of Prodiamine 65 wdg should not be done because it will interfere with new grass seeds, correct?

3) When should fall application of Prodiamine 65 wdg be applied? How long after over-seeding?

4) Going forward, when weeds are under control, is it OK to still apply the Prodiamine 65 wdg twice a year and every year for preventive maintenance or not? what is typically done going forward.

I have a Hustler X-One zero turn and that's what I use to pull mine. With a ZTR it is easy to turn too sharp and jack knife it so you just have to be careful there. Otherwise it's really easy once you get used to it. While using the pull behind you will be going pretty slow anyway. There's an on/off switch on the power wire that connects to the battery. I zip tie that to the roll bar so it's easily accessible and you can turn the pump on and off as needed.. You may find a spot that works better for you. Again, practice with plain water until you feel comfortable with it.

1- I prefer to get mine down a little early if possible. I can't remember the exact numbers but I plan mine to run out about August. The label lists the different rates and how long it will typically last. Just plan accordingly so it will run out just prior to seeding.

2- If you are overseeding then no, DO NOT put out prodiamine.

3- Read the label to double check but I believe it's either 60 days or after the new grass has been cut 4 times. Again, don't take my word on this because I'm going off of memory.

4- I do a pre-m every year. Around here we get a lot of rain during the spring when temps are ideal for weed seeds to germinate. Last year spring came way early and I didn't get my pre-m down and weeds were a problem. This year I got it down mid February and weeds so far have not been an issue.

I wish a fall app would work for me but having to overseed every fall kills that. My main problem is winter annuals like chickweed and henbit but spot spraying those is pretty easy and has worked for me.

Didn't you apply pre-emergent through the sprinkler system last year?

Thank you Forsheems for the advice. I'll probably be getting the tow behind unless I can find some way to rig a rack on the back to hold a tank. Other than that, have you found that the 31 gallon was overkill for a half acre? If you could buy again, would you go for the same size?

Also, if I over-seed September 1st, and waited 60 days, that would bring me right to Nov 1st. Would that be too late for a fall application since weeds germinated already and spring application is so close anyway?

Lawniac, you are somewhat correct. It was 2 years ago and I chose not to ever do that again after a few people brought it to my attention how bad that is incase of back flow. It was kind of a great idea lol.

Yes, I would definitely buy the 31 gallon again. There are times when it is slightly overkill but most of the time it's not. I just applied a fungicide this week and used 2 full tanks to put it down. I've learned the speed I need to go to use up the full tank.It takes some time and practice but once you get it figured out it's super easy.

Applying the pre-m in November probably won't do much for the POA as it will have already germinated by then. You could use Tenacity for a pre-m at time of seeding. It will last about 30 days and will prevent most of the POA from germinating but not effect the grass seed. Just make sure you read and fully understand the application rates. Then drop the prodiamine at the 60 day period. As I said earlier, I don't worry to much about the broadleaf weeds as a spot spray of Triclopyr will wipe them out in a hurry but the grassy weeds like POA can be difficult to control.

I split my lawn in half and use about 25 gallons per half. The way the nozzles are set up on the Northstar sprayer they overlap in the middle just about the width of the mower. Then you have an outer band on each side where it doesn't overlap. What I do is run strips the width of the mower so in reality the entire lawn gets 3 passes with the sprayer to get an even application if that makes sense. I had borrowed a Fimco sprayer several years ago that didn't overlap in the middle so I used a different pattern with it. Each sprayer seems to have a slightly different pray pattern which is why you will need to play with it to figure out how to get a good even coverage.