The sight of perpetual weed growth on your lawn is about a disheartening as it gets.
Do you ever find yourself wishing that you could kill the weeds in your yard before they sprout, and go to seed? Well, you can…
Pre-emergent herbicides give you a way to do just that. Once applied they stay in the soil between one to six months and, if timed and applied correctly, will stop weeds from germinating without killing your grass.
For best results, there are several factors to consider when determining which type of pre-emergent will work best for your lawn type. So I have compiled a pre-emergent herbicide list to simplify the puzzle and help you make the right selection for your lawn.
- How Does Pre-Emergent Herbicide Work?
- Pre-Emergence Herbicide List and What They Do
- What is the Best Pre-Emergent on the Market?
- When to Apply Pre-Emergent Herbicide
- How to Apply Pre-Emergent Herbicide
- Final Thoughts
- FAQ Pre-Emergent Herbicide List
The pre-emergent herbicides I’ll cover in this guide include benefin, dithiopyr, isoxaben, pendimethalin, and trifluralin.
While these are all pre-emergent herbicides, they don’t all act in the same way. Some chemicals, like benefin, work best for grasses and broadleaf weeds, while others, like pendimethalin, work best in food crop areas.
Read on to learn more about my experience of pre-emergents and hopefully the pre-emergent list below will provide insight and clarity.
How Does Pre-Emergent Herbicide Work?
When applied to soil, pre-emergent herbicides form a chemical barrier in the top layer of soil and prevent seeds from germinating and growing roots. They inhibit a seedling’s ability to perform cell division, therefore killing juvenile sprouts before they ever emerge from the topsoil.
Pre-Emergence Herbicide List and What They Do
There are several different types of pre-emergent herbicides that work best in different scenarios. I’ll cover five of the most popular types of pre-emergent herbicide active ingredients so that you can make an informed decision on which herbicides will work best for your yard.
Pendimethalin: Most Versatile
Pendimethalin is one of the most effective active ingredient chemicals for controlling broadleaf weeds and grasses in food crop areas and residential areas. In my experience, this herbicide was the best overall and most versatile.
Pendimethalin is a selective pre-emergent that halts mitosis and inhibits cell growth, preventing target weed seedlings from developing mature roots.
Pendimethalin is an exceptional herbicide for controlling broadleaf and grassy weeds. It’s primarily used to target weeds posing a threat to crop and agricultural areas. In addition to being a pre-emergent herbicide, pendimethalin acts as a post-emergent herbicide for early-stage weeds.
- Annual Bluegrass (Poa Annua)
- Evening primrose
I found Pendimethalin in granules, but it also comes in liquid form. It’s yellowish and can stain driveways and sidewalks.
Pendimethalin is non-toxic to birds, slightly toxic to humans and mammals, and very toxic to fish. When handling pendimethalin, wear proper safety gear and avoid using near bodies of water. Pendimethalin will not seep into and contaminate groundwater.
- Great for controlling weeds in food crop areas
- Liquid and granule form
- Doubles as a post-emergent for newly-sprouted weeds
- Highly toxic to fish
- Stains hard surfaces
Benefin: Great for Backyards
Benefin is the active ingredient chemical in pre-emergent herbicides that work exceptionally well for controlling grasses and broadleaf weeds. In my experience, Benefin was harder to find than pendimethalin, making it my runner-up choice.
Benefin is the shorthand term for the scientific name Benfluralin. Benfluralin is a dinitroaniline, meaning that it works by inhibiting mitosis in seedlings, which prevents cell division. The lack of cell division keeps roots from developing mature roots and emerging from the topsoil.
Benefin is a great pre-emergent herbicide for controlling broadleaf weeds and grasses. Some of the most widespread weeds that benefin controls are:
- Seeded alfalfa
- Red clover
- Seeded lettuce
I found that benefin usually comes in either liquid concentrate form or granule form. If using the product in granule form, be sure to water the product in after applying it to your lawn. Benefin takes about six hours on average to absorb into the soil. From there, it can begin inhibiting seed growth.
Benefin is a safe pre-emergent herbicide and has a low toxicity level for humans, mammals, and birds. It is toxic to fish, so avoid using products containing benefin if you live near a body of water.
- Kills broadleaf weeds and grasses
- Little to no toxicity to humans and mammals
- Toxic to fish
Dithiopyr: Best for Grassy Weeds
Dithiopyr is the active ingredient chemical in pre-emergent herbicides that are especially good for killing crabgrass and oriental grass. Dithiopyr is one of the most popular active ingredients in pre-emergent herbicides, so I had to test it for myself.
Dithiopyr works by inhibiting mitosis in a seedling’s roots and inhibiting spindle production, which prevents the plant from developing and maturing.
Dithiopyr is a good option for controlling the growth of different grasses. Some plants that products containing dithiopyr work well on include:
- Annual bluegrass
- Poa annua
Dithiopyr can even act as a post-emergent herbicide for crabgrass if you apply it to the weed before it tillers.
I found that dithiopyr comes in many forms, including powder, granule, and liquid concentrate. If using powder or granules, add water to the product after applying it to your lawn so that it can absorb into the soil properly.
Dithiopyr has low toxicity levels for humans, mammals, and birds, but it’s toxic to fish. Avoid using dithiopyr if you live near bodies of water or runoff areas.
- Kills various crabgrass and oriental grasses
- Doubles as a post-emergent for some species of crabgrass
- Available in a wide variety of products
- Safe for use on crop-land areas as well as turfgrass
- Toxic to fish
- Not great for broadleaf weeds
Isoxaben: Best for Broadleaf Weeds
Isoxaben is the active ingredient in pre-emergent herbicides that are great for selectively killing broadleaf weeds. Isoxaben is safe to use on turf and around ornamental plants. I used a product containing isoxaben on my turfgrass, and it did an excellent job preventing dandelions from growing.
Isoxaben prevents weed growth by inhibiting the production of enzymes needed for protein synthesis within the seed. This ultimately kills the seed before it has the chance to germinate and emerge from the ground.
Isoxaben works exceptionally well for nearly 100 species of broadleaf weeds, including:
Isoxaben can work as a pre-emergent herbicide for grasses and vines as well.
I found isoxaben in powder, granule, or liquid concentrate forms. You should water in the herbicide after applying to ensure that it seeps into the soil properly.
Pay attention to the concentration you’re using because isoxaben concentrations in popular herbicides range from just 0.25% up to 75%. The higher the concentration, the longer-lasting the effects will be. Isoxaben can work for as long as eight months with a single application.
Isoxaben has moderate toxicity to humans but can cause chronic harm to small mammals, birds, and fish.
- Various forms and concentrations
- Great for use on broadleaf weeds
- Not the best for grasses and other weeds
- Moderately toxic
Trifluralin: Best for Croplands
Trifluralin is a selective pre-emergent herbicide that works best on broadleaf weeds and annual grasses in food crops.
Trifluralin works by stopping mitosis and cell division in the roots of different weeds, preventing the seeds from emerging from the topsoil.
Trifluralin controls weeds of various different crops, including broccoli, cabbage, sugar cane, beets, and crops that provide food for animals. You can also use Trifluralin in residential areas to stop broadleaf and grassy weeds from growing around your turfgrass or ornamental plants.
I found Trifluralin in both granule and liquid forms. However, according to my research, it works best when applied as a liquid.
Trifluralin is non-toxic to birds but is highly toxic to fish, and the EPA classified it as a Class C possible human carcinogen. However, the likelihood of the chemical transmitting into the food is very low.
- Great for controlling broadleaf and grassy weeds
- Prevents weed growth on a wide variety of croplands
- Toxic to fish and potentially a human carcinogen
What is the Best Pre-Emergent on the Market?
Different pre-emergent work best for different target weeds. It’s important to research which pre-emergent herbicides will work best for your yard.
However, in my experience, I found that pre-emergent products containing the active ingredient pendimethalin had the broadest range of target weeds and uses. Herbicides containing pendimethalin are safe to use on both crop and residential lands, but they also act as a post-emergent if applied soon enough.
Pendimethalin’s versatility and wide range of uses make it the best pre-emergent herbicide, in my opinion.
Is There a Natural Pre-Emergent Herbicide?
In place of using a chemical pre-emergent herbicide, use corn gluten meal as a natural alternative.
Corn gluten meal is a byproduct of corn milling and contains no synthetic chemicals. When applied to yards and watered in, corn gluten meal can prevent broadleaf weeds and grassy weeds from sprouting.
Corn gluten meal remains in the soil for up to six weeks and reapplying a couple of times a year will help to ensure its effectiveness.
When to Apply Pre-Emergent Herbicide
Applying a pre-emergent at the right time is almost as crucial as determining which herbicide will target your weeds.
Different pre-emergent herbicides work in different ways. Most of the ones on our list only work once the seed has sprouted before emerging from the soil. If applied too early, the herbicide can drain from the soil before the seed begins to sprout, so your yard could be covered in weeds despite your efforts.
As a rule of thumb, pre-emergent herbicides should be applied to the soil once it begins to reach and maintain temperatures around 55 degrees Fahrenheit. Specific application times vary based on your location.
What Month Do You Put Down Pre-Emergent?
You should apply pre-emergent herbicides twice a year, once in the early spring and then in the early fall. The specific month varies based on your location, but for most temperate climates, apply in early March and then again in late August or early September.
Can it Be Too Late for Pre-Emergent?
Applying pre-emergent herbicides too late is the most common reason that a pre-emergent doesn’t work. If you apply a pre-emergent too late for example, when temperatures have exceeded 55 degrees Fahrenheit, the seeds will have already rooted and sprouted, and you will need to look into post-emergent herbicide methods for removal instead.
How to Apply Pre-Emergent Herbicide
Different types of pre-emergent herbicides need to be applied in different ways. The primary forms of pre-emergent herbicides are granules, liquids, and powders.
When applying a granule or powder, you can use a grass seeder to evenly cover your yard. Hit all the spots to avoid possible weed growth. When you use granule or powder herbicides, water them afterward so they can soak into the topsoil.
If you opt for a liquid herbicide, you prepare it according to the package and use a backpack or handheld sprayer of your choosing to evenly coat your yard. Furthermore, water your yard after applying a liquid pre-emergent so it can soak into the soil properly.
How Often Should You Apply Pre-Emergent?
It varies based on the product, but most pre-emergents work for up to 6 months. You should apply pre-emergent at least twice a year for optimal results.
Does Pre-Emergent Herbicide Need to Be Watered In?
Yes, pre-emergent herbicides should be watered immediately after application to soak into the soil and create a protective chemical barrier.
This article has covered my best pre-emergent herbicide list and how to use these herbicides for your yard based on my research and experience.
When choosing a pre-emergent, keep in mind what your target weeds will be and what type of land you are using herbicide on. In my experience, Pendimethalin gives the most versatile coverage and does the best job at killing its target weeds.
The best pre-emergent herbicide I’ve found containing Pendimethalin is Drexel Pin-Dee 3.3 T&O Pre Emergent Herbicide.
This is a professional-grade product that is suitable to use on many varieties of turf, hardscape, as well as crops.
It needs to be diluted with water, then administered via a sprayer.
On the other hand, Monterey Weed Stopper is a great product if you’re looking for a pre-emergent for your ornamentals or crop garden. If you’re searching for the best pre-emergent for grassy weeds, give a product such as Quali-Pro 40 WSB Herbicide that contains Dithiopyr a try.
FAQ Pre-Emergent Herbicide List
Now that we’ve covered the most popular pre-emergent herbicides and how to use them, you may have some questions. Below are the most frequently asked questions about pre-emergent herbicides.