Good morning, I'm relatively new to keeping houseplants again as I could just not keep them alive so recently I started again but did my homework. The issue is I've had persistent black fly for the past month or so. I've tried fairy liquid mixed in water and sprayed on the plants, I've tried gravel to prevent them laying eggs, restricting water to remove the dampness so any eggs will dry out and die, I've tried garlic infused water and shop bought black fly spray. I've also got up sticky catchers but they still persist. What else can I try? Any help or advice would be greatly appreciated.

James

Possibly fungus gnats! They will NOT harm the plants, or you.

Easiest way to control them is to let the soil surface dry out a bit more between waterings. They like it moist.

Thanks very much for taking time to reply with advice. I will try the suggestions and hopefully get rid of them. Thanks again.

James

BigBill said:Possibly fungus gnats! They will NOT harm the plants, or you.

Easiest way to control them is to let the soil surface dry out a bit more between waterings. They like it moist.

You're welcome!
Good to have you on board with the NGA!

with such a persistent problem, I wonder if you might even gently scrape off and dispose the surface soil where most larvae and eggs will be.

I had consider that as my next step if I couldn't find an alternative method. I changed the sticky pads yesterday and so far, no flys but I have seen one doing the rounds.

Thank you for your advice

James.

sallyg said:
with such a persistent problem, I wonder if you might even gently scrape off and dispose the surface soil where most larvae and eggs will be.

It sounds as if you've gotten ahead of them. Seeing just one is great, considering..

Fungus gnats tend to be cyclical for me. You'll see a lot of adult flies then they breed, lay eggs & die off. But then the eggs hatch, larva grow in the soil & eventually the cycle starts again. The point is keep doing what has been working even if you don't see adults. It may take a couple of cycles to get rid of them all.

Nuisance pests are seldom gotten rid of easily or quickly.
That's what defines nuisance!

dadduu70 said:I will try the suggestions and hopefully get rid of them.

If you grow fungus in your houseplant soils or your drains, the fungus gnat will come find you! As fungus / decaying matter is a food source for the larvae of the fungus gnat, and moisture helps this fugus grow, we have inadvertently provided the right conditions for the fungus gnat to complete its life cycle of egg, soil-dwelling larvae, and adult. And as they exist outdoors, indoors in your household drains, and prevalent in greenhouses, they probably will find you.
This article link below is about as good as any, and while I always suggest you get your information from an educational source (such as a university extension service or a university study,) this article in the NGA files is consistent with my experience with the fungus gnat and monitoring and control methods. I wish they had listed footnotes, so we all can check the actual sources like any university article or study would do. Most of the biological controls can be pricey if you have just a few plants, other than mosquito dunks or bits as your source of the BTi.
https://garden.org/learn/artic...

NOTE: get a positive ID on what your "persistent black fly" is, because what attracts & controls "fruit flies" (Drosophila melanogaster or similar) won't similarly work with "fungus gnats" (often Bradysia species.) If you have one on your 'yellow stickie,' look at it closely and match it to photos-sometimes the wing patterns viewed with a hand lens gives the positive ID. Put your yellow traps touching your soil, as these guys are bad flyers, and often appear to be skipping across the soil- I'm not sure if the yellow color is attracting them as much as their bad eyesight is allowing them to bash headlong into the trap.

Also NOTE that yellow traps and potato wedges (look that one up) are often referred to as "monitoring," and not control, as they won't be your total solution. Water less AND\OR change out your soil to quicker draining and non-larvae infested, if needed. It's a long fight, and be consistent.

Additional NOTE: I found the fun route-it's now a game! I use carnivorous plants (see below) now as my fungus gnat monitor (no more yellow traps,) and they are FAR MORE ENJOYABLE to me, and less disgusting to my family! While it certainly means learning to grow new plants, I have to admit I'm disappointed I don't see any gnats around my plants right now. If I swat a fly or squish a spider, it's gonna end up on the carnivore leaf! And yes, there are NO bugs on those leaves, so I'll probably need to feed them something else until the fungus gnats return again. And, yes, they will return, because apparently I grow fungus WITH my houseplants.

Pinguicula gigantea



Drosera capensis broadleaf

Thank you for such a comprehensive reply, I will definitely check out the link and make some changes where needed. I have 2 Venus fly traps (sorry, don't know the proper name for them) but the glues seem to avoid them completely 😕 hopefully with all your (everyones) advice. Very much appreciated.

James Baker

kenisaac said:
If you grow fungus in your houseplant soils or your drains, the fungus gnat will come find you! As fungus / decaying matter is a food source for the larvae of the fungus gnat, and moisture helps this fugus grow, we have inadvertently provided the right conditions for the fungus gnat to complete its life cycle of egg, soil-dwelling larvae, and adult. And as they exist outdoors, indoors in your household drains, and prevalent in greenhouses, they probably will find you.
This article link below is about as good as any, and while I always suggest you get your information from an educational source (such as a university extension service or a university study,) this article in the NGA files is consistent with my experience with the fungus gnat and monitoring and control methods. I wish they had listed footnotes, so we all can check the actual sources like any university article or study would do. Most of the biological controls can be pricey if you have just a few plants, other than mosquito dunks or bits as your source of the BTi.
https://garden.org/learn/artic...

NOTE: get a positive ID on what your "persistent black fly" is, because what attracts & controls "fruit flies" (Drosophila melanogaster or similar) won't similarly work with "fungus gnats" (often Bradysia species.) If you have one on your 'yellow stickie,' look at it closely and match it to photos-sometimes the wing patterns viewed with a hand lens gives the positive ID. Put your yellow traps touching your soil, as these guys are bad flyers, and often appear to be skipping across the soil- I'm not sure if the yellow color is attracting them as much as their bad eyesight is allowing them to bash headlong into the trap.

Also NOTE that yellow traps and potato wedges (look that one up) are often referred to as "monitoring," and not control, as they won't be your total solution. Water less AND\OR change out your soil to quicker draining and non-larvae infested, if needed. It's a long fight, and be consistent.

Additional NOTE: I found the fun route-it's now a game! I use carnivorous plants (see below) now as my fungus gnat monitor (no more yellow traps,) and they are FAR MORE ENJOYABLE to me, and less disgusting to my family! While it certainly means learning to grow new plants, I have to admit I'm disappointed I don't see any gnats around my plants right now. If I swat a fly or squish a spider, it's gonna end up on the carnivore leaf! And yes, there are NO bugs on those leaves, so I'll probably need to feed them something else until the fungus gnats return again. And, yes, they will return, because apparently I grow fungus WITH my houseplants.

Pinguicula gigantea



Drosera capensis broadleaf

Good luck! The Venus flytrap isn't a good fungus gnat catcher, as the trapping mechanism isn't small enough to constrain the small gnat, and you are also limited by the amount of paddles it has. The two plants I chose, a Mexican butterwort and a Cape Sundew, have leaves coated with sticky substances, like a yellow card. Anything small that contacts it can get stuck. Houseflies are much larger, and seem able to wiggle free and escape, eventually. It's not a control method, but sure is more fun than dealing with the sticky traps...

The Savage Garden, Revised: Cultivating Carnivorous Plants
By Peter D'Amato, 1997, page 37: said:

"Mexican butterworts and some larger sundews have been known since the Victorian age to be grown in greenhouses as a gnat controller"

Thank you. I will look into where I can get some from. I agree, the sticky traps are annoying and look ugly amongst my plants.

kenisaac said:Good luck! The Venus flytrap isn't a good fungus gnat catcher, as the trapping mechanism isn't small enough to constrain the small gnat, and you are also limited by the amount of paddles it has. The two plants I chose, a Mexican butterwort and a Cape Sundew, have leaves coated with sticky substances, like a yellow card. Anything small that contacts it can get stuck. Houseflies are much larger, and seem able to wiggle free and escape, eventually. It's not a control method, but sure is more fun than dealing with the sticky traps...