Kill Slugs with Ammonia? [Yes, it’s a Real Slug Killer]

A hosta with slug damage

Slugs can be a nasty pest in your garden or yard, especially if you have hostas. Trying to save your plants can send you searching for alternatives, and I know that I was surprised when I found out that you can kill slugs with ammonia.

Many people don’t know this fact, but it’s very important. I’ve seen people use ammonia as a fertilizer, but I wanted to use it as a pesticide to get rid of the slugs without pouring nasty chemicals into my hostas like I’d get with some commercial-grade pesticides.

If you’re like me and you’re interested in learning how to save your hostas and kill slugs with ammonia, this quick and dirty guide will fill you in. Are you ready? If so, let’s dive in!

Ammonia: What Is It?

WARNING: Household ammonia is considered hazardous by OSHA. Take the same care using this chemical outside as you would in your home. Keep children and pets out of areas where out of areas where you are using ammonia solutions.

Before you get into ways to kill slugs with ammonia, you want to know exactly what it is. Ammonia is a very irritating and colorless gas that has a very sharp odor. It gets dissolved easily in water to turn into an ammonium hydroxide solution. You could also compress the ammonia gas to form a colorless, clear liquid under pressure. It’s also a common fertilizer ingredient that works for hostas in pots and hostas in the garden.

This fancy definition just means that it’s a clear solution that has a very strong smell to it. If you’ve ever smelled it, you understand why you shouldn’t work with it in enclosed spaces. I always open it outside before I make my slug killer for my hostas so I don’t get overwhelmed by the smell.

How Do You Kill Slugs with Ammonia?

Does ammonia kill slugs? If so, how do you apply it without causing damage to your plants? Luckily, there are a few ways you can apply ammonia to and around your hostas to get at the slugs without damaging your plant. Depending on which way you choose, you may have to dilute the ammonia.

Ammonia works on snails and adult slugs. But, if you want the best results, ammonia has to get on the slug larvae when they’re in the soil. It’ll kill the larvae and stop the slug’s lifecycle. Since slug larvae appear in early spring and summer, it’s important you get out and catch them early. Now, how exactly do you apply it?

Spraying the Plants

Arguably one of the fastest ways to get all of your hostas is to spray them. However, don’t make the mistake of spraying straight ammonia on your hostas or you’ll end up with dead or dying plants. Instead, you want to dilute the ammonia with water, and there are several dilution methods you can try.

Since there is no exact rule when it comes to dilution, you can experiment a bit. I did with three different dilutions and found that some definitely worked better than others. It’s always best to start with a more diluted measure and work your way up to avoid accidental damage.

Some people claim 1:4 or 1:9 are the key dilution ratios while other people like 1:10 or 1:16. I’ve even heard of people using 1:18 or 1:20. This means that you’d add one part ammonia for 4, 9, 10, 16, 18, or 20 parts water. Which one is best depends on who you talk to.

Many hosta grows prefer 9 or 10 parts water for the initial dose, and even lighter doses in the summer. For me, this is all way too complicated and I was never a fan of math. So, I just use a 10% solution for everything. This is the 9:1 ratio.

Drenching the Soil

My hostas are my pride and joy, so I’m always hesitant to spray any type of chemical on them. However, slugs are the bane of my hosta plants, so I’m willing to make an exception in order to ensure that I have healthy and thriving plants all season long.

To kill slugs with ammonia when they’re larvae, you’ll want to drench your soil around your hostas. Again, there is a debate on which dilution ratio works best, by 9 or 10 parts water to 1 part ammonia seems to do the trick. Make sure you don’t get this on your hosta leaves because it can burn them.

I mentioned that slug larvae start showing up in the early spring and summer months, so I go out and drench my soil right after the frost leaves. I’ll do the 9 or 10 parts water stronger solution for the first round. Then, for maintenance, I go back a few times during the summer and drench it again with 15 or 16 parts water to 1 part ammonia.

Will Ammonia Kill Eggs?

You can use ammonia to kill pest eggs around your hostas in the soil. Ammonia will break down the egg’s surface when it comes into contact with it, and this prevents the eggs from hatching. However, the ammonia has to come into direct contact with the eggs for it to work.

This is where the drenching the soil method comes in. You can spray too, but you have a higher chance of missing eggs. If you miss them, the ammonia won’t kill the eggs and they’ll hatch.

What Kind of Ammonia to Use in the Garden?

One thing you’ll learn is that there are many different types of ammonia available, and not all types are created equal. Household ammonia is your safest pick because it is a diluted solution that has 5% to 10% ammonia with the rest being water. Never use any type of ammonia that you can’t purchase over the counter. High concentrations of this chemical are extremely dangerous, and you should take steps to protect yourself with the proper safety equipment.

You want to avoid cleaners with a bunch of chemical additives. Just be aware that it has an extremely sharp odor, and never mix it in a closed space. Take it outside or in a well-ventilated area.

Risks of Using Ammonia

Will ammonia kill your plants? Just like anything else, too much of a good thing can be bad. Ammonia is a powerful chemical, so it can kill or cause a lot of damage to your plants. You’ll really see this happen if you splash non-diluted ammonia onto the hosta leaves or around the base.

So, never spray pure ammonia onto your hostas or surrounding plants unless you’re trying to kill them. Also, if your hostas are surrounded by other types of plants, be very careful. For example, if you planted hostas with roses, the roses could be more sensitive to any ammonia you apply where it won’t bother the hostas.

If you have any doubt, test. Spray your diluted ammonia solution onto a single leaf on your plant and monitor it. If it gets damaged, you need to dilute it more and test it again before you douse the area. If there isn’t any reaction, you’re most likely safe.

Remember, what works for one person may not work for another. So you can ask for advice, but always test everything out before you spray entire areas to kill the slugs. You may have to make adjustments if you’re working around different plants around your hostas.

Short and Long Term Results of Killing Slugs with Ammonia

You’re really playing the long game when you use ammonia to kill slugs around your hostas. But, you can see some short-term results too. You should notice a decrease in the number of slugs around, especially if you choose to drench the soil.

Ammonia works to kill aphids, and it’s toxic to a range of insects. So, this is both a short and long-term result you can get when you use ammonia to kill slugs. It has an immediate effect, but the amount of insects and pests will gradually taper off year after year with continued use.

Ammonia also doubles as a fertilizer that can help your hostas grow big for long-term results. You could see larger leaves on each plant that helps to fill in any blank spaces in your yard. Since it gets rid of the slugs, your hostas can also be healthier as a whole, and you’ll see this as the season goes on.

Frequently Asked Questions

1. Can ammonia hurt plants?

Yes. It can easily burn the leaves. Ammonia can also kill your hostas and any plants around it because it’s a strong chemical, and this is why it’s important to use the chemical with forethought and care.

2. Is household ammonia good for hostas?

Yes and no. It’s good in the sense that it can eliminate slugs and a few other pests as well as make a small amount of fertilizer available in the soil. It’s bad in the sense that if you use it improperly, you can kill your plants or even harm you. However, this is true of many different garden chemicals you use.

3. Will ammonia kill bugs?

Yes. Along with working on slugs and aphids, ammonia is a great bug deterrent because it has such a sharp and strong odor. Ammonia also works well to kill bacteria.

4. What does ammonia do to soil?

Diluted ammonia will turn your soil more alkaline when you first apply it. Over time, the ammonia can get converted to nitrate to increase your soil’s acidity. Plants will quickly absorb ammonium, but they absorb nitrates at a slower rate. This makes nitrates safer to use. Ammonium will also cause your lawn to grow quickly, but it can also easily burn and turn brown. Your plants will absorb ammonium and nitrate through the assimilation process. Once they do, they convert them into organic molecules with nitrogen.

Closing Thoughts on Kill Slugs with Ammonia?

Finding out that you can kill slugs with ammonia can open the door to a whole new opportunity to treat a slug infestation in your garden and save your hostas. Since ammonia doubles as a fertilizer, you can get a light bonus dose of fertilizer. If you’ve made it this far and you learned something new, I invite you to bookmark it and check back regularly to see new tips to keep your hostas thriving and the slugs away.

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