Hello, I’m looking for some validation in the above instructions. For reference, I have a strip of land on the side of my house about 15 ft wide by 150 ft long that is 30% overrun by weeds from the neighboring property. I researched weed removal and narrowed down the pre-emergent to anderson’s barricade granular, and the post-emergent to 2,4-d spray with a surfactant (Celsius wg is pricey and I already have 2,4-d on hand).
The instructions seem backwards to me. I would have thought I’d pull the weeds manually, apply the post emergent to kill off any existing left over weeds, and then apply the pre emergent after to prevent new growth. However, the instructions I’m getting from ChatGPT seem counterintuitive to me. Are the instructions correct? Should I apply the pre-emergent first? I thought pulling weeds would disturb the barrier in the soil.
by lord_hyumungus
4 Comments
The common lawn pre-emergents (prodiamine, pendimethalin, and dithiopyr) work to help reduce the germination of certain seeds… Mostly grasses and only a handful of broadleaf weeds. The labels will list which weeds are targeted. To prevent more broadleaf weeds, a specialty broadleaf pre emergent like isoboxen is required.
Pre-emergents work by preventing the germination of seeds of the target species. So in order to be effective, a pre emergent needs to be applied BEFORE those seeds germinate. For winter annual weeds (annual weeds that are present in the fall, winter, and spring, like poa annua), a pre emergent needs to be applied in the fall before soil temps fall below 70F. In order to prevent summer annual weeds (like crabgrass), a pre emergent needs to be applied in the spring before soil temps reach 55F. (In very southern areas, timing can be more closely tied with periods of higher moisture AND climbing soil temps. Consult your state extension service for more specific guidance)
Pre emergents will not kill existing weeds. Pre-emergents alone will rarely control a weed problem. Pre-emergents are tools to **reduce** the need for post-emergents. They rarely eliminate the need for post emergents.
The labels of pre emergents have many important instructions and use restrictions. ALWAYS READ THE ENTIRE LABEL. For example, you are limited to 2 applications of each active ingredient per year.
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You’re essentially right. The “barrier” thing is kind of a myth, but its close enough.
So yea if you’re going to pull weeds, do that first, then spray if you’re going to do to that, and then pre emergent if you’re going to do that.
But I do have 2 important points to make:
– Like the automod comment says, lawn safe pre emergents are selective, meaning they only prevent the seeds of specific plants from germinating. They mostly target grasses, and only a handful of broadleaf weeds. So, read the label to be sure that the weeds you’re trying to prevent are actually on there.
– 2,4-d is a broadleaf weed killer, it only controls broadleaf weeds.
– 2,4-d should not be used alone, it should be used alongside atleast 1 other of the following: dicamba, mcpp (mecoprop), mcpp, fluroxypyr, triclopyr, quinclorac
Yea, those instructions make no sense to me either. Depending on the weed, you wouldn’t want to pull at all because that could actually produce more growth (nutsedge for example).
I would apply the pre emergent and water in. Then a day or so later once dry, apply post emergent and let the weeds absorb the herbicide and repeat applications as needed.
I generally spray prodiamine wdg for my pre emergent and mix in some image or similar post emergent that needs watered in so I hit two birds with one stone.
I wouldn’t pull weeds if you have selective herbicide like 24D. And Celsius would handle some weeds it would not. Understandable about budget though