Fungus Gnats

Alshain(8a-8b east-TX)April 2, 2012

I have some peace lily plants I recently separated. I've had trouble with Fungus gnats in the past using bagged soil so I tried Al's 5-1-1 mix thinking a better soil would help.

It didn't. Suffice to say, the problem is now worse. I've never seen so many gnats in one place in my life and they are in my office!

Before you say something, it's not over watering. In fact it's been 3 weeks since watering any of them, and they still swarm around it.

I tried EcoSmart Garden insecticide, that didn't do anything (it really wasn't meant for gnats I think, someone else bought it so I tried it).

I can't figure out how to get rid of these things... well actually there is one way. It involves a dumpster, which is about to be the solution. I have one last chance to get rid of them and save my plants. Does anyone have any idea how to stop this?

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Alshain(8a-8b east-TX)

Well good news, I may have solved my own problem with Dawn.

    Bookmark   April 2, 2012 at 3:02PM
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rhizo_1 (North AL) zone 7

Just curious, are you going to share your method?

    Bookmark   April 2, 2012 at 4:05PM
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Alshain(8a-8b east-TX)

Researching around with Google I learned that soap will not harm the plants. Suggestions included misting the leaves and soil with water mixed with drops of dish detergent all the way to mixing 2 tbsp/gallon when watering the plant. I think the mist was to immediately control a problem while the watering was to prevent them from coming in the first place.

Something about the soapy film make the soil inhospitable.

    Bookmark   April 2, 2012 at 4:29PM
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Joe1980(5)

If you can go 3 weeks without watering, I suspect you may have your plants overpotted, which means you have soil that is staying wet all the time. If soil is left to dry out, fungus gnat eggs will die. I used to have trouble with fungus gnats when I used bagged MG soil. I switched some of my plants to 5-1-1, and a lot to gritty, and haven't seen a gnat since. However, I have never gone 3 weeks without watering, because the free draining mixes dry out in 1 week or so, 1.5 max.

Joe

    Bookmark   April 2, 2012 at 5:15PM
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tapla (mid-MI z5b-6a)

I'm not sure what's happening, but I've not had gnat problems with either the 5:1:1 or the gritty mix. Are you fertilizing with fish emulsion or some other form of organic fertilizer?

The fact is, soils that are comprised of or contain ingredients that readily decompose and that remain wet at the surface for extended periods are what drive gnats to an orgiastic frenzy. Those aren't characteristics associated with either soil, especially since you've ruled out the possibility of over-watering, but neither is '3 weeks between waterings' something usually associated with either soil, so something is amiss. Glad you have things under control, though!

Al

    Bookmark   April 2, 2012 at 11:21PM
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JessieC777(Washington State 5)

I was having problems for awhile with those darn things! I ended up putting a layer of sand on the top of all of my plants and then sprinkling cinnamon around them as well. This was before I changed my soil to a grittier mixture. It worked like a charm though!

    Bookmark   April 3, 2012 at 1:15AM
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eayeary(5)

Cinnamon. Pour it on top of the soil and it kills the fungus that the gnats eat. I had to do this for a plant I rescued off clearance.

    Bookmark   April 3, 2012 at 9:11AM
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Alshain(8a-8b east-TX)

Thanks for all the replies. The good news is, the soap is definately working and plants don't seem any worse for wear. Still a few buzzing around, but no swarming this morning.

The soil is all Pine Bark, MG Perlite, MG Sphagnum, GardenLime, and MG 12-4-8 liquid. That's it... and water of course.

As for over potting, I don't think so. I did separate the peace lily but the root structures are huge. I think some of the pots are too small really. Even if I did overpot, it's a peace lily so it won't be overpotted for long... but I really don't think I did.

The top inch of the soil is completely dry, but yet they are still after it for some reason. I was under the impression they only laid their eggs 1" deep.

    Bookmark   April 3, 2012 at 9:14AM
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rhizo_1 (North AL) zone 7

earyeary, fungus gnats don't feed on fungus. The LARVAE feed on organic matter in the soil. In outdoor soil, that would mean compost, decomposed leaf litter, clippings, etc. They are part of the recycling team.

In our container plants, they are attracted to the peat moss, primarily. If they become numerous, they will feed on tender plant roots.

These insects are associated with fungus because they are attracted to the same kind of environment where mushrooms and molds would be common....moist and organic-y.

    Bookmark   April 3, 2012 at 4:47PM
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JessieC777(Washington State 5)

When you put a layer of sand on top, it prevents them from getting out when they hatch. They die and the cycle stops.

    Bookmark   April 3, 2012 at 6:05PM
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rhizo_1 (North AL) zone 7

Sand can also prevent the gnats from laying their eggs. It can be a very useful tool.

    Bookmark   April 3, 2012 at 11:24PM
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Joe1980(5)

Applying sand to your 5-1-1 mix would be counterproductive in regards to the whole point of using it: Drainage. It would just get watered into the mix, where it would start to clog your good draining soil.

Joe

    Bookmark   April 5, 2012 at 6:19PM
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orchids41

I've found that drenching the soil with BT...can't recall the proportions...does the trick.

    Bookmark   April 5, 2012 at 8:04PM
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orchids41

I've found that drenching the soil with BT...can't recall the proportions...does the trick.

    Bookmark   April 5, 2012 at 9:34PM
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dellis326 (Danny)

May not be anything you're doing. Heard on the news today that in some parts of the country, due to early spring temps there are unusual increases of insect swarms and fungus gnats were one of the types mentioned.

    Bookmark   April 5, 2012 at 11:21PM
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Alshain(8a-8b east-TX)

Well I appreciate the vote of confidence, but I had em last year when using bagged soil. It still might not be anything I'm doing, I may just be a victim of my surroundings.

I live in East Texas. If you've never been here, they call it the Piney Woods and it lies between the plains of the Dallas Texas area and the Swamps of Louisiana. Suffice to say, bugs are a way of life.

The Dawn Dish Detergent does work if I can keep it up. After a misting application, the adults won't touch the surface of the soil right after and I think that is enough to break the cycle. This time I went ahead and mixed 2 tablespoons in a gallon and watered the plants with it before the long weekend.

    Bookmark   April 5, 2012 at 11:45PM
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