Pests and Diseases forum→Pretty sure I got fungus gnats... Help?

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Name: João V.
Lisbon - PT (Zone 10b)
Greetings from Portugal!
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Wallknocker
Apr 1, 2021 11:19 AM CST
Hey everyone!

I'm pretty sure I got a small infestation of fungus gnats, but wanted to make sure… This is in a small indoor space. Crying

Here are some adults I trapped:
They are about 1/10 of an inch, or 2 mm.

Thumb of 2021-04-01/Wallknocker/3fbf36
Thumb of 2021-04-01/Wallknocker/1b7e28

If they are indeed fungus gnats, I could use some help to know he best way to get rid of them.

So far, I've set some vinegar traps and some yellow stick traps, but as the weather is warming up, they are visibly increasing in numbers by the day (yesterday I trapped 1 and killed 2, today the traps got 6 and I killed another two, so far).

I have 4 small lemon tree seedlings (that I'm pretty sure originated the problem), but now the gnats are spreading to 14 fairly grown cacti and succulents, and about 60 small pots with succulent props, so I would really like to avoid repotting all of them with fresh soil to remove the larvae. Sighing!

I just got some neem oil, some hydrogen peroxide and some diatomaceous earth, all ready to go, but I'm not sure which is the best one to use in the situation (or even if there is another, better way) Confused

Any help would be appreciated! Thank You!





(Sorry for any eventual bad english! ^^")

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ElPolloDiablo
Apr 1, 2021 12:06 PM CST
Yes, they are Fungus gnats alright.
Please leave the homemade remedies alone since they may even harm your plants, head over to eBay and buy a product called "Gnatrol": it's specifically designed to kill Fungus gnats and it's completely harmless to bees, pets and humans. Bonus point: you can use it to kill Tiger mosquito larvae as well.
Gnatrol is used as a soil soak, just follow instructions on the label. And it's scaringly effective.

PS: I live in Italy and got the 2oz bag for $25 shipped and it lasted me for two years. Fungus gnats were gone after two months and I sued the rest to kill off mosquito larvae. Great product, just check shipping time.
The Saviour.
Name: João V.
Lisbon - PT (Zone 10b)
Greetings from Portugal!
Image
Wallknocker
Apr 5, 2021 9:01 PM CST
Hey sorry for the late reply!

Thank you for the tip, I ended up giving them a soak of a hydrogen peroxide solution because the problem was notably worse by the day and I didn't find any shipping delivery that could get some Gnatrol to Portugal in less than 2 weeks (I ordered it anyway)

The problem was clearly reduced but it wasn´t gone completely. One of the cactus is still riddled with them, so now I am waiting for the Gnatrol to arrive so I can get rid of the gnats for good.

Thank You!
(Sorry for any eventual bad english! ^^")

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ElPolloDiablo
Apr 6, 2021 12:44 AM CST
If the number of adults is out of control, you can reduce their number by using a high quality pyrethrins or pyrethroids insecticide, with a warning: as with all insecticides pyrethrins cost an arm and a leg in Europe and they are getting harder and harder to get.
The Saviour.

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