Spray know-how
What is a surfactant, and do you need one?
That little bottle of “spreader-sticker” can be the difference between a spray that works and one that beads off.
If you’ve ever sprayed a weed killer exactly by the label and still gotten weak results, the missing piece might not be the product, it might be a surfactant. It’s one of the least understood parts of spraying, and one of the easiest ways to get more out of the products you’re already using. Here’s what a surfactant actually is, in plain English, and how to know whether your spray job needs one.
What a surfactant actually does
A surfactant is a spray additive, it’s not a weed killer or a fertilizer itself, and it doesn’t control anything on its own. Its whole job is to change how your spray behaves once it leaves the nozzle. The word is short for “surface-active agent,” and the simplest way to picture it: without a surfactant, spray droplets tend to bead up on a leaf like water on a waxed car, and a lot of them roll right off onto the ground. A surfactant breaks that surface tension so the droplets spread out into a thin, even film that clings to the leaf.
Why does that matter? Because the active ingredient can only work on the plant tissue it actually stays in contact with. More coverage that stays put means more of the product you paid for gets absorbed by the weed, instead of dripping onto the dirt. A surfactant doesn’t make a herbicide stronger, it helps the herbicide reach its target.
Do you actually need one?
Not every spray job needs a surfactant, some products already have one built in. The first thing to do is read your herbicide label: it will usually say whether a surfactant is required, recommended, or already included. Beyond that, a surfactant helps most in these situations:
Waxy or hairy-leaved weeds. Plants like ivy and many tough weeds have surfaces that naturally repel water, exactly where a surfactant’s spreading action helps most.
Hot, dry conditions. Some surfactants also slow evaporation, giving the product more time to absorb before the droplet dries up.
When the label calls for it. If your herbicide, fungicide, or insecticide label says to add a non-ionic surfactant, that’s the clearest signal, and skipping it can noticeably reduce results.
If your product already contains a surfactant and you’re treating easy-to-wet weeds in mild conditions, you may not need to add one. When in doubt, the label is the deciding voice.
A versatile option
Agrifac Pro
A general-purpose, non-ionic surfactant, an 80% blend of alkylpolyoxyethanol and humectants. It’s compatible with a wide range of products: herbicides (including glyphosate formulations), fungicides, insecticides, and fertilizers, so it works across most spray programs rather than being tied to one product. Typical tank-mix rate is 1 to 2 quarts per 100 gallons of water.
Non-ionic surfactant · humectant blend for dry conditions
How to use one correctly
Follow the rate, don’t overdo it. More surfactant isn’t better, too much can cause excess runoff or even leaf injury. Use the labeled amount (for Agrifac Pro, 1 to 2 quarts per 100 gallons).
Check compatibility with a jar test. Before mixing a surfactant into a tank with multiple products for the first time, combine them at the intended ratio in a clear jar and watch for separation or clumping.
Always read the product label too. Check the label of whatever you’re mixing the surfactant into, not every product wants a surfactant added, and some specify a particular type.
Common questions
What does a surfactant do in a weed killer mix?
It reduces the surface tension of the spray so droplets spread into an even film on the leaf instead of beading up and rolling off. That means more of the herbicide stays in contact with the weed and gets absorbed, improving coverage and results, without making the herbicide itself any stronger.
Do I always need to add a surfactant?
No. Some products already contain one, and easy-to-wet weeds in mild conditions may not need it. Always check your herbicide label first, it will say whether a surfactant is required, recommended, or already included. A surfactant helps most on waxy or hairy weeds and in hot, dry conditions.
Is a surfactant the same as a weed killer?
No. A surfactant doesn’t kill anything on its own, it’s an additive that improves how another product performs. You mix it into the spray tank with your herbicide, fungicide, insecticide, or fertilizer to help that product spread and stick better on the plant.
Can I use too much surfactant?
Yes. More is not better, too much surfactant can cause the spray to run off the leaf or, in some cases, injure the plant. Stick to the labeled rate; for a general-purpose surfactant like Agrifac Pro, that’s about 1 to 2 quarts per 100 gallons of water.
Will a surfactant work with any product?
A general-purpose non-ionic surfactant like Agrifac Pro is compatible with a broad range of herbicides, fungicides, insecticides, and fertilizers, including glyphosate. But always confirm on the label of the product you’re mixing it into, and run a quick jar test for compatibility before combining several products in one tank for the first time.
Get more out of every spray
Contact Agrisel to find a reseller carrying Agrifac Pro for your spray program.