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Why Should I Apply Fall Pre Emergent Herbicides? - Weed Prevention Tips

By DoMyOwn staff

Getting a pre-emergent barrier down in the fall can help prevent winter weeds that emerge in the spring like poa annua, chickweed, and clover. Using a pre-emergent will save you time and money.

 Why Should I Apply Fall Pre Emergent Herbicides?  - Weed Prevention Tips Video Play

Video Transcript

Hey guys! I'm Amber from and today I'm going to talk to you about pre-emergent herbicides and why should put them down in the fall. There's a whole host of other weeds that will germinate across the fall and winter months… weeds like poa annua, chickweed, and a variety of others are gonna pop up in your yard in the spring if a pre-emergent isn't used in the fall.

Using one in the fall also helps make sure that you save time and money. It's important to get a barrier down in the fall to make sure that you're getting ahead and keeping your lawn healthy for the next season.

You may want to look at doing a split application as well depending on the temperatures in your area and what kind of weed control you're looking to achieve. We have a great video on how to do split applications that you can see on our site, and this will show you exactly why it's important and how to do this step by step. Basically the short version of it is it's going to help extend your weed control and give you a much healthier and nicer looking lawn all season long. 

When should you apply a pre-emergent herbicide? There's typically two times a year that we're gonna focus on: spring and fall. Now as we go into the fall season you're going to start looking for temperatures to drop between 80, 70 and going lower. You can use a soil thermometer to test the temperatures in your area to make sure that you're at the right time and get your application down for the best results. Now, for the fall a lot of times these temperatures are going to range around the August and September timeframe.

This is when you want to start looking to put down your first pre-emergent application especially if you're planning to do a split. Split applications are normally going to be done about five to eight weeks apart so you'll want to make sure to keep that in mind and mark that on your calendar if you start doing your pre emergent application soon.  

Some of you are in areas of the U.S. that never really seem to get cold. It's just kind of just... hot all year round. In that case, your pre emergent window is going to be a little bit wider than most. Areas like Arizona and Florida often run into needing to put a pre-emergent down later in the season, potentially even closer to October and November to make sure that your barrier really lasts. UV rays and lots of rain can break down your product so you want to make sure that you're getting a good application down to sustain any weather that mother nature might throw at your yard. 

What do I need to know to make sure I'm choosing the right pre-emergent for my lawn and my needs? The first step which is the most important is finding out what type of lawn you have. You want to make sure that you're using products that are safe for your grass type. If you don't know your grass type, you're welcome to send in photos to our team to try and identify it or you can pair up with your local Master Gardener's office to find out the turf type in your lawn or in your area. The next most important step is going to be finding out what weeds you have. Knowing this is crucial to make sure you're choosing the right selective herbicide for your needs.

You want it to be safe for your turf type and you want to make sure that it's going to control everything that you have. Pre-emergents, like we mentioned before, are going to prevent weeds from coming up so if you do have something in your yard currently, you want to look at some of our selective herbicides for post-emergent control currently. 

When doing applications, you want to make sure that you're being careful and following all the label instructions, being sure to follow all of that PPE that's going to be listed things like gloves, closed toe shoes, long pants, and any other directions that it may provide to make sure that you stay safe and so does your lawn. 

There's a ton of different pre-emergent options out there...there's liquids there's granules and we get asked which one should I use? As far as the application goes,  you can choose granular or liquid: whatever meets your needs.

With products like granular pre-emergents, you're going to want to make sure that you calibrate your spreader before your use and make sure that it's going to deliver that even application that you're looking for.

You'll want to make passes back and forth in your yard trying to get as much of an even coating as possible. Be sure to sweep any granules that may land on concrete areas like sidewalks and driveways back into the yard, rather than washing them off, to be sure that no herbicide is going to stain any of the areas around your home. 

For liquid applications, we recommend going with tank sprayers. This is going to ensure ultimate accuracy across the yard and make sure that you're getting a good even application. You can use an approved tank mix post emergent herbicides with your pre-emergent at the same time.  This will help eliminate the weeds that are currently there while your barrier of your pre-emergent is getting you ready for the following season.

For some of you that may be using herbicides that you're just not really comfortable with or you're not sure that you're going to get your application even you can add in a marking dye with your solution to make sure you can see where you have applied. Marking dye will normally fade within about one to two days at most and it's not going to stay in any of your yard and change the color of it. It's just going to help you see where you've applied so you don't overlap and do too much herbicide in the same area.

Again, there's tons of options out there as far as what pre-emergents you can use. Some of the most popular ingredients out there are dithiopyr, pendimethalin and prodiamine.

Out of those ingredients we typically recommend one like the dithiopyr in the spring because it's great on crabgrass and really helps get a lot of those spring weeds controlled very well. For the fall, we tend to recommend ones that have pendimethalin in them. They work great to prevent poa annua and a variety of other weeds.

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