Do you also have black gnats everywhere in the potting soil and don't know what to do? Supposedly, coffee grounds help against fungus gnats. What is really in the home remedy, I tell you today!
There is hardly anything more annoying than the small, black mosquitoes that cavort in the potting soil. They multiply incredibly fast and harm the plants.
Especially small vegetable plants, such as tomatoes, cucumbers or peppers can perish from the larvae of the mosquitoes.
When you want to work undisturbed in the office, another mosquito buzzes around your head. A second one lands in the water glass, and if you have your desk near the flower pot, you've lost anyway.
But what can you do about it?
Have you also heard that coffee grounds help against fungus gnats? I was on fire when I heard about it and tried it right away.
But first, I'll tell you everything you need to know about coffee and fungus gnats.
After that, I'll tell you about my self-test in which I used coffee grounds on the office plants to combat fungus gnats.
Table of contents
Why do fungus gnats harm plants?
Fungus gnats are very small, black gnats that live in the potting soil. Their larvae feed on the roots of the plants. The feeding damage leads to the fact that the plants can no longer absorb nutrients.
This weakens the plant and can even lead to its death. Especially young seedlings are very sensitive and quickly fall victim to the larvae of the fungus gnat.
A single female fungus gnat lays up to 200 transparent eggs in moist soil. After 7 to 8 days, the larvae hatch and feast on the roots.
Therefore, you should react as soon as possible if you see small, black flies in the soil.
Take action against fungus gnats today if you don't want your plants to become a snack for them!
Can coffee really help against fungus gnats?
Coffee grounds contain an acid that is supposed to make life difficult for fungus gnats. They should no longer be able to lay their eggs in the soil
In addition, coffee changes the pH of the soil. The new, acidic environment does not like the mosquitoes.
Coffee grounds are used to prevent the upper layer of soil from becoming moist. After all, this is exactly what the mosquitoes want. The development of the larvae can only succeed if the upper centimeters of the soil are wet enough.
Coffee grounds additionally contain caffeine, which is nothing else than nerve poison. The sensitive mosquitoes are disturbed in their development and eventually die.
By the way, coffee grounds are also a great fertilizer for most plants. You can read here how you can use it as a natural fertilizer use.
Attention for sensitive plants
But beware of sensitive plants: coffee grounds change the pH of the soil. It makes it more acidic, which can work wonders against mosquitoes.
However, sensitive plants do not react well to it. Here, other means can be more helpful, such as neem oil. You can read about it here: "How neem oil works against fungus gnats“
Which coffee grounds is the right one?
Regardless of what type of coffee you typically brew - fresh ground or pre-ground beans - both can help effectively control fungus gnats.
In addition to the coffee grounds from the filter or the fully automatic machine, you can also use the remains of used coffee capsules, but this is a little more time-consuming.
Keep in mind, however, that already used coffee (=coffee grounds) does not contain very much caffeine.
Depending on the variety, the caffeine content of coffee can vary widely - Arabica varieties contain about 0.8 to 1.4 %, while Robusta beans contain 1.7 to 4 %.
However, when the coffee beans are mixed with water, their caffeine content is diluted. After the preparation of coffee, the set contains 0.06-0.1 % caffeine.
8 unusual ways to use coffee grounds!
How do I use coffee properly for mosquito infestation?
You can either use coffee grounds or put on a strong coffee to water the plants with.
Good to know: Fungus gnats live for five days. Their entire development cycle from larva to mosquito is about 13 days. You must therefore use coffee grounds more often to catch them all.
Coffee grounds against fungus gnats
The following applies to coffee grounds: dry them before you use them. Otherwise, mold can form, which is equally harmful to the plant. Put it on a baking tray and dry it in the shade. The thinner you lay it, the faster it will be ready for use.
- Pour the dried coffee grounds into a container with a screw cap.
- Sprinkle the coffee powder on the potting soil with a spoon. The layer should be about two centimeters thick.
- Repeat the procedure every 2 to 3 days.
- Water the plant only from the bottom. Thus, the coffee grounds remain dry, which is not at all pleased fungus gnats.
Coffee approach against black mosquitoes
You can also try it with coffee. I pour the old coffee grounds with water and make a decent strong coffee. You can also use fresh coffee, but it's frankly too bad for me.
- Dilute fresh coffee 1:1 with water. If you use coffee grounds, then take 3 tablespoons of coffee grounds to 200 ml of water.
- Let the coffee stand until it has cooled.
- Water the plants with the coffee brew. Let the soil dry a little and then sprinkle with quartz sand.
The quartz sand prevents the mosquitoes from laying new eggs and the freshly developed mosquitoes from reaching the surface.
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My self-test: coffee grounds against fungus gnats
Now that I am well informed, I dare to take the test. I have little to lose.
To get a feel for how bad it really is and to trap live mosquitoes, I stick yellow tags in the ground for two days.
The mosquitoes are attracted to it and stick to it. Each caught mosquito can therefore already at least times no longer reproduce.
However, you can only really defeat the pests if you get down to the larvae.
I put coffee, dilute it with water and water the infested plant with it. Now I let the soil dry again and in the meantime dry the coffee grounds from the coffee maker.
I put a two-centimeter layer of it on the soil. After three days I repeat the procedure with the dried coffee brew.
On closer inspection, however, I can see the mosquitoes making their way through my coffee layer.
When I noticed hardly any improvement after a week, I quickly switch and reach for neem oil.
I ordered three bottles right away and will water properly with it in the next few days. In addition, I have used mosquito plugs overnight. Whether that helps, I do not know, but at least it can not hurt.
The neem oil significantly reduced the infestation after only three days. In addition, I put as many yellow boards in the soil as possible. You should also leave the yellow plates in the potting soil for a while after the infestation.
So a few larvae in the soil are enough to start the infestation all over again. My tip is to water again with neem to get the last larvae.
My conclusion
That coffee grounds help against fungus gnats, I can confirm only conditionally. I tested it for a few days, but could not notice any improvement. Who knows, if I had held out longer, it might have gotten better. But I did not want to risk that. In addition, the mosquitoes are quite annoying, if you constantly have one in front of the nose at work.
Against this, neem oil has quickly shown the first effect. I hope that I can quickly get the infestation under control.
Good luck in your fight against the pests!
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