Simazine herbicide is a pre-emergent, selective herbicide used to control broadleaf weeds and annual grasses.
It is available in several main formulation types, including wettable powder, liquid suspension or flowable, granular, and water-dispersible granules.
Common product names include Simazine 4L, Simazine 480, and Simazine 90DF.
| Name | Formulation Type | Active Ingredient | Notes | Region Where Popular |
|---|---|---|---|---|
| Simazine 4L | Liquid (Flowable) | 4 lb/gal (≈480 g/L) | U.S. customary unit version | United States |
| Simazine 480 | Liquid (Flowable) | 4 lb/gal (480 g/L) | Metric equivalent of 4L | Europe, Canada, Australia |
| Simazine 90DF | Dry Flowable | 90% by weight | Granular powder, mixes with water | United States, Australia |
Contents
Active Ingredient
The active ingredient in simazine herbicide is simazine, a chemical compound belonging to the triazine class of herbicides or to Group 5 herbicide.
Its chemical name is: 6-chloro-N²,N⁴-diethyl-1,3,5-triazine-2,4-diamine.
It works by blocking photosynthesis in weeds. It stays in the soil and is taken up by the roots of young plants. Once inside, it stops the plant from making food from sunlight, so the weed runs out of energy and dies.
How long does it take to work?
The herbicide starts working right away after it is absorbed by the weed’s roots. First signs usually appear within 1 to 3 weeks, depending on the weather, soil, and plant type.
The first visible signs appear on the leaves, even though the herbicide enters through the roots. You will then notice that the weed stops growing normally, followed by leaf burn and browning.
The entire plant dies within 2 to 6 weeks, depending on conditions.
Where to Apply It
You can apply simazine herbicide in several types of areas from agricultural crops to ornamental plantings, but it’s important to follow label directions to avoid harming non-target plants.
Orchards, vineyards, corn fields, nut groves, fence lines, roadsides, industrial sites, railway embankments, storage yards, woody ornamentals, and tree plantations are areas where the herbicide can be used.
Weeds Controlled by Simazine
This herbicide controls most annual broadleaf and grass weeds such as:
| Alyssum | Knawel (German Moss) |
| Annual Bluegrass | Lambsquarters |
| Annual Morningglory | Nightshade |
| Annual Ryegrass | Pepperweed |
| Barnyardgrass | Pigweed |
| Burclover | Pineappleweed |
| Carelessweed | Prickly Lettuce |
| Carpetweed | Purslane |
| Common Chickweed | Ragweed |
| Crabgrass | Rattail Fescue |
| Downy Brome | Redmaids |
| Fall Panicum | Russian Thistle |
| Fiddleneck | Shepherdspurse |
| Filaree | Signalgrass |
| Fireweed | Silver Hairgrass |
| Fivehook Bassia | Smartweed |
| Flora’s Paintbrush | Spanish Needles |
| Florida Pusley | Speedwell |
| Foxtails | Tansymustard |
| Goosegrass | Wild Mustard |
| Groundsel | Wild Oats |
| Henbit | Witchgrass |
| Junglerice | Yellow Flower Pepperweed |
Herbicide mix ratio
It does not have a one-size-fits-all mix rate. The amount you need to apply can change based on the type of plant, crop, or location where it’s used.
For example, fruit trees, field crops, turfgrass, and nursery plants all have their own specific mixing instructions.
Some situations allow for a single application, while others permit split treatments across the season.
| Crop / Use Area | Mix Ratio | Comments |
|---|---|---|
| Almonds / Nectarines (CA) | 1–2 qts/acre in 2–4 ft (0.61/1.22 m) band | Apply before weeds emerge. Trees must be older than 3 years. Avoid soils with less than 1% organic matter. |
| Apples, Pears, Sour Cherries | 2–4 qts/acre | Apply once per year. Do not exceed 4 qts/year. 150-day pre-harvest interval for apples. |
| Avocados (CA, FL) | 2–4 qts/acre | Avoid use on sandy soils. One application per year only. |
| Blueberries, Caneberries | 2–4 qts/acre or 2 qts spring + 2 qts fall | Minimum 40 gals water/acre. Use half-rate on young plants. Avoid when fruit is present. |
| Filberts (OR, WA) | 2–4 qts/acre or 2 qts fall + 2 qts spring | Do not apply on sandy soils or during nut drop. Max 4 qts/year. |
| Grapes | 2–4 qts/acre | Use only in vineyards 3 years or older. One application per year. |
| Grapefruit, Lemons, Oranges (AZ) | 1.6 qts spring + 1.6 qts fall | Do not exceed 3.2 qts/year. |
| Grapefruit, Lemons, Oranges (CA) | 2–4 qts/acre or 2 qts fall + 2 qts spring | Do not apply in Imperial, Coachella, or Palo Verde Valleys. Max 4 qts/year. |
| Grapefruit, Oranges (FL) | 4 qts/acre (up to 8 qts with 50% band) | Use with contact herbicide if weeds are present. No fall application if spring was treated. |
| Grapefruit, Oranges (TX) | 4 qts/acre | Do not exceed 4 qts/year. Max 2 applications per year. |
| Macadamia Nuts | 2–4 qts in 50 gals water/acre | Apply before weed emergence. Do not apply during nut drop. |
| Olives | 2–4 qts/acre | Repeat annually in midwinter. One application per year only. |
| Peaches (CA) | Max 2 qts/acre in 2–4 ft (0.61 to 1.22 m) band | Apply once per year before weeds emerge. Do not apply to sandy or gravelly soil. |
| Peaches (other states) | Max 2 qts/acre | Same rate as CA, no banding requirement. Apply in late fall to early spring. |
| Plums, Sweet Cherries | 2–4 qts/acre | Apply once per year in late fall or early spring. Use only in MO and states east of the Mississippi (except TN). |
| Pecans | 2–4 qts/acre | Use only on trees older than 2 years. Avoid during nut drop. Max 1 application per year. |
| Strawberries (OR, WA only) | 1 qt/acre | Apply after harvest during bed renovation. Use only once/year. Wait 4 months after transplanting. |
| Walnuts | 2–4 qts/acre | Do not apply during nut drop or on sandy soil. Avoid soil disturbance after treatment. |
| Nurseries (Woody Ornamentals, Trees) | 2–3 qts in ≥25 gals water/acre | Apply fall or spring, min 1 year after transplanting. Spot treatment only if by pressurized handgun. |
| Christmas Tree Plantings | 2–4 qts in ≥25 gals water/acre | Apply after transplanting. Do not treat transplants <3 years old. Max 4 qts/year. Spot treatment only if using handguns. |
| Christmas Tree – Quackgrass | 4 qts fall or 2 qts fall + 2 qts spring | Apply after quackgrass begins growth. Do not exceed 4 qts/year. |
| Christmas Trees – Simazine + Surflan | 2–4 qts Simazine + 2.67–5.33 lbs Surflan 75W or 2–4 qts Surflan A.S. |
Apply uniformly. Irrigate after overtop sprays. Avoid use on seedbeds or greenhouses. |
| Sod Turfgrass (Florida – Muck/Peat) | 4 qts/acre | Apply to old beds within 2 days of lifting sod. Additional 2 qts allowed if weeds return. Water in if >2 qts used. |
| Sod Turfgrass (Florida – Sandy Soil) | 2 qts/acre | Apply 3–4 days after sprigging. Apply again if weeds return. Water in if >2 qts used. |
| Sod Turfgrass (Other States) | 1–2 qts/acre | Apply after Sept 1. Use lower rate for annual bluegrass, 2 qts for other weeds. Max 2 apps/year. |
| Turfgrass for Lawns & Similar Areas | 1–1.6 qts/acre | Use 1 qt for annual bluegrass; 1.6 qts for other weeds. Irrigate after application. Max 2 apps/year. |
Tank Mix
Simazine 4L can be mixed with liquid fertilizers, crop oils, spreaders, or other pesticides, but you should always test first to make sure they are compatible. Mixing without testing can cause clumping, separation, or spray problems.
Here’s a simple test you can do at home or on the farm:
- Take two clean one-quart glass jars with lids.
- Pour 1 pint of the fertilizer into each jar.
- In one jar, add ¼ teaspoon of a compatibility agent (equal to 2 pints per 100 gallons of spray). Close the lid and shake well.
- Add the correct amount of herbicide to both jars. For dry herbicides, you can add 1.5 teaspoons per pound per acre. For liquid herbicides, try to add 0.5 teaspoons per pint per acre.
- Shake the jars for 1 minute, then let them sit for 15 minutes.
- Mixing dry herbicides in a bit of water before adding them.
- Splitting the compatibility agent: put half in the fertilizer and half in the herbicide.
- Prepare your equipment.Try to clean the sprayer thoroughly and ensure proper calibration and uniform spray output. Use nozzles with screens no finer than 50 mesh.
- Put your protective gear on..To make sure you are protected, wear a long-sleeved shirt, long pants, waterproof gloves, and shoes with socks. Use coveralls if required for the crop or application method.
- Check the weather conditions.If the wind speed exceeds 10 mph or conditions are gusty, choose another day to spray the herbicide. Also, do not apply during temperature inversions.
- Mix the solution. First, fill in the spray tank partially with clean water. After that start agitation and slowly to add the product. If you using other products, check the label and add them in the correct order. Keep constan agitation to maintain suspension.
- Apply to soil. You should spray before weeds or crops emerge and target bare or prepared soil. Avoid spraying directly on plant foliage unless allowed for that crop. Make sure you apply it uniformly.
- Post-application moisture. Allow natural rainfall or irrigate after application to move the product into the root zone. If conditions are dry, use shallow cultivation to help with activation.
- Clean up equipment. Wash the sprayer with water and detergent immediately after use. Also, wash PPE separately from other laundry.
Check the jars. If you see large flakes, oily layers, gel, or lumps, the mix may not be safe.
If the mixture only separates slightly but mixes again when shaken, it may still be usable. Just make sure you use constant stirring during spraying.
If the mix doesn’t work, you can try:
If it still doesn’t mix well, do not combine these products in your sprayer.
| Herbicide Mix | Mix Ratio | Crop(s) |
|---|---|---|
| Simazine + Bromacil 80W | 4 qts Simazine 4L + 3–4 lbs Bromacil 80W per acre in 40 gal water | Grapefruit and Oranges (Florida only) |
| Simazine + Gramoxone Extra | 1.5–2.5 qts each in 50–200 gal water per acre | Apples, Pears, Peaches, Almonds |
| Simazine + Roundup | Simazine (label rate) + 1–5 qts Roundup per acre + 0.5% surfactant | Grapes, Apples, Peaches, Pears, Almonds, Macadamia nuts, Citrus, Plums, Walnuts |
| Simazine + Solicam DF | Simazine (label rate) + 4–5 lbs Solicam DF in 20–100 gal water per acre | Oranges, Grapefruit, Lemons |
| Simazine + Surflan 75W | Simazine (label rate) + 2.67–5.33 lbs Surflan 75W in 20–40 gal water per acre | Almonds, Apples, Grapes, Oranges, Peaches, Pears, Plums, Walnuts, Avocados, Cherries |
| Simazine + Surflan A.S. | Simazine (label rate) + 2–4 qts Surflan A.S. in 20–40 gal water per acre | Same as above |
| Simazine + Atrazine 4L | 1–1.2 qts each (coarse soil), up to 1.2–1.5 qts each (fine soil) in 10–40 gal water | Corn (Preplant and Preemergence) |
| Simazine + Sutan+ 6.7E | 2–6 pts Simazine + 4.75–7.33 pts Sutan+ 6.7E per acre in 20+ gal water | Corn (Preplant incorporated) |
Corn Crop
This herbicide can also be used on corn crops. You can mix nitrogen solutions or complete liquid fertilizers with SIMAZINE 4L instead of water, or use them together.
Try not to use it after the corn has started to grow, because the liquid fertilizer may damage the plants. If you use a pressurized hand sprayer, it should only be used for spot treatments on sweet corn.
The correct way to apply it is before weeds or corn begin to grow.
You can use up to 2 quarts per acre if the soil does not erode easily, or if it does but has at least 30% plant residue.
If you need to apply the herbicide again during the same year, the total amount used should not be more than 2.5 quarts per acre.
If the soil erodes easily and has less than 30% plant residue, apply no more than 1.6 quarts per acre.
Before planting, you can apply the herbicide in the spring after plowing. You can use it before, during, or after preparing the seedbed. If you work the soil after applying, avoid mixing it in too deeply.
For the best results, apply the herbicide within two weeks before planting. In dry weather, applying before planting may provide better weed control.
| Soil Texture | Broadcast Rate per Acre |
|---|---|
| Coarse-textured soil: Sand, silt, and loam that is low in organic matter | 2 qts. |
| Medium-textured soil: Soil containing a moderate amount of clay and organic matter | 2.4 qts. |
| Fine-textured soil: Loam that is high in organic matter and clay (including dark prairie soils of Corn Belt) | 2.5 qts. |
| Organic soil: Peat, muck and high organic clay | 2.5 qts. |
How to Apply It
To achieve great results and ensure safe, legal use of this product, it is important to follow a proper application process.
The following steps shows you how to prepare, apply, and clean up effectively, while minimizing environmental risks and protecting both the applicator and the crop.
Simazine 4L needs rain or irrigation to be effective because it works through root uptake. It’s not labeled as “rainproof” in the sense of resisting being washed off, but it relies on moisture to move the active ingredient into the soil where weeds absorb it.
Make sure rainfall or irrigation is expected soon after application, as moisture is needed for activation.
Weed Resistance Management
Over time, using Simazine and similar herbicides again and again can cause some weeds to become resistant, meaning they no longer die when treated.
If you notice that certain weeds are not being controlled as they used to be, it may be a sign of herbicide resistance.
What you can do is avoid letting them go to seed. Try using a different herbicide (from another group) or apply physical control methods like hoeing or tilling.
A good practice is to switch to herbicides from different groups each season, or even within the same season.
Some of the herbicides recommended on the label for mixing with Simazine 4L are Bromacil 80W, Gramoxone Extra, Roundup, Solicam DF, Surflan 75W, Surflan A.S., Atrazine 4L, and Sutan+ 6.7E.
Also, clean your equipment before moving it to another field to prevent spreading resistant seeds.
Limitations and Restrictions
When it comes to how much you can use, don’t go over 2.5 quarts per acre per year on corn. That’s the maximum.
Other crops and soil types might have different limits, so always check the exact rate allowed for your specific situation.
There are also rules on how you apply it. Aerial spraying is not allowed, and you can’t apply it through irrigation systems like chemigation.
Also, it’s not approved for use in Hawaii, Alaska, or any U.S. Territories, including Puerto Rico.
Be careful with young crops or trees too because some types can’t be treated until they’re at least 1 to 3 years old, depending on the plant.
After you spray, you can’t go back into the treated area right away. The re-entry time varies by crop, but it’s usually between 12 and 48 hours.
Weather conditions are important too. Don’t spray if it’s too windy, and never spray during a temperature inversion, which can cause drift.
Also, make sure the boom height stays under 4 ft (1.22 m), and use a coarse spray to reduce the risk of off-target movement.
Finally, this product is not suitable for every crop.
It’s only approved for specific fruits, nuts, vegetables, turfgrass, and trees.
And you should know that some crops, like soybeans, sugar beets, small grains, and legumes, can’t be planted in treated soil the following year, or you might risk crop damage or illegal residues.
EPA Registration Number
The EPA registration number of the Simazine 4 L herbicide is 9779-296 and for Simazine 90 DF is 9779-295.
