Fall Pre-Emergent Application - Who Is Ready Now?

I know you guys appreciate when I walk you through the timing and thinking behind “when to apply fall pre-emergent” so I figured today would be a good time for that.

Fall pre-emergents are driven by soil temperatures. Coming out of summer and heading into fall, soil temperatures are on the downswing. We want to get down a pre-emergent herbicide that will create a barrier in the soil that stops certain weeds from growing. This is important because these weeds are called “winter annuals” which means they germinate now, in fall time, hibernate over winter, rage in spring and drop seeds in early summer, then die. Then in fall, the cycle starts all over.

The major winter annuals we have problems with are poa annual (annual bluegrass), henbit, chickweed and hairy bittercress. If you live further south where there is very little winter (such as south Texas, Mississippi Gulf Coast, Louisiana, Alabama or Florida) then you are also working to prevent spurge and Florida Pusley. These two weeds germinate all summer and into winter in our far southern climates. Especially with all the hurricane water you guys have gotten this year, weeds will be bad.
(also praying for you folks as you have one hitting you right now as I type this!!!)

Pre-Emergent Herbicides

In this article I’m talking to folks with many different grass types. Those of you who are ready to throw down right now are mostly cool season grasses, however, the areas coming into the “fall pre-emergent window” in the next couple-two-tree weeks are mostly across the transition zone, or for lack of a better word, the middle of the country where both cool and/or warm season grasses can be found. You guys are in the window.

So before we go any further, if you are going to seed your lawn, you should NOT apply pre-emergents. Many folks ask “what about after I seed, how long do I have to wait to apply a pre-emergent then?” I answered that in my podcast:


Now if you have not seeded, or you have any of the warm season grasses, here is who is ready to apply anytime between now and the next 10-14 days or so. I got these soil temperatures from the Greencast tool, but you can get yours for your exact house using our free lawn care app.

Ready to Throw Down Now

These areas, and those on a similar latitude will be ready to throw down in the
next couple-two-tree weeks:
We have a few options for you with pre-emergents - most of these will not be available at local stores. For some reason, the big box stores do not make room for fall pre-emregents on their shelves. My assumption is they are dominated by Scotts 4-Steps and those do not have any fall pre-emergent in them - just plain fert, maybe to keep costs low, dunno. But the fact is, you won’t find them at box stores. So here is what we have for you:

Least Expensive Option
Prodiamine WDG - this is the water dispersible granule formulation. You mix it in water and spray it. It’s not as difficult as it may seem and I have full training for you if you are new.
Cost of the WDG bottle is $19.99 but that is enough for a few applications on most lawns, so you will likely have some leftover for next spring which is great. If you have a 5,000 sq ft turf type tall fescue lawn, your fall application will cost you $9.15. Yep, less than $10 to treat a 5,000 sq ft lawn.
Fun Math:
Prodiamine WDG Cost: $19.99
Bottle Size: 5oz or 142g
Application Rate Fall App: 13g per 1,000 sq ft
Total Product Needed for 5,000 sq ft lawn: 65g
65/142 = .45
This means you will use 45% of the bottle to get this one application completed.
.45 x $19.99 = $9.15
Your fall app on a 5,000 sq ft lawn costs under $10 !!
Aren’t you glad that you paid attention in 8th grade math class? Now you can see just how affordable DIY lawn care is!

Easier For Most - Granular
I’ve been doing this for a long time and I know that a good majority of you prefer granular applications. I feel that way sometimes too and often will choose granular options for products. The good news here is we have a prodiamine granular option that comes in a 45lb bag. Let’s look at that next. Same deal here, let’s look at a 5,000 sq ft lawn. Pretty much all grass types are going to use the 3lbs/1000 rate here which will give you 90 days of pre-emergence control (last until just before Christmas - plenty of time for most of you)

Fun Math:
Prodiamine Granular Cost: $49.99
Bag Size: 45 lbs
Application Rate Fall App: 3lbs/1,000 sq ft
Total Product Needed for 5,000 sq ft lawn: 15lbs
15/45 = .33
This means you will use 33% of the bag to get this one application completed.
.33 x $49.99 = $16.50
Your fall app on a 5,000 sq ft lawn costs $16.50
Still not too bad! I bet you TruGreen would charge you somewhere around $50 for this app if you could even get them to do it!

We have one other option, granular dithiopyr, for those of you who may have used up your calendar year allotment of prodiamine. There is a max amount you are permitted to use. Others of you may just prefer dithiopyr. You can get that here in granular.

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