Possible fungus gnat problem & question

DanaB_2109(6)December 4, 2011

I think I might have a fungus gnat problem. Today while I was fixing myself a late-night snack, I saw two tiny bugs flying around my amaryllis plants. I think they might be fungus gnats, which puzzles me a little because as a rule, I tend to underwater my plants. Regardless, I plan on getting some Schultz 3-in-1 spray tomorrow; am I correct in assuming that this is the proper course of action? I also intend to water from the bottom from now on, just to make sure that the surface of the soil doesn't get too wet.

I have another question as well: Five of my amaryllis plants have scapes that I expect to bloom soon. Will it hurt to spray the plants when the flowers are so close to opening? Thanks for your help.


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Me again! :)

I just wanted to add that I think (but am not certain) that I've seen these same kind of flies flying around my bananas before I ever had plants in my kitchen. Are they fruit flies? Fungus gnats? I'm curious now...


    Bookmark   December 4, 2011 at 10:29PM
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Could be either, Dana... I notice fruit flies if I keep fruit around a lot, and I do... we're big fruit eaters. When the fruit is moved or consumed, they tend to hang around my plants under the grow lights.

I've found that the yellow sticky fly strips will attract them, so I'll hang one from a grow light. I've also found a great product for eradicating fruit flies... can't recall the name, but the item is shaped and colored like a small apple and comes with a liquid attractant/insecticide that you pour in. Flies fly in, but they don't fly out. Cost was about $6 for one little kit. It was worth it! I found it at our local farm oriented store, but I'm sure Home Depot or Lowe's, or somewhere like that might carry it.

For root health reasons, I avoid bottom watering. There's a reason why it's best to water thoroughly from the top, when watering is necessary... you're forcing fresh oxygen in, and accumulated gases out, which helps maintain root health. Of course, roots are much healthier when the structure of the medium you use has the ability to maintain plenty of tiny air pockets for decent aeration.

I'm sure you've seen me link to an article at the Container Gardening Forum about container soils and water retention... everything is explained within that one article, including proper watering, the purposes soil serves, what happens under the soil surface within a pot, etc. I've linked it below.

Quit honestly, Dana, more plants are killed by improper watering than by any other one thing, but it's very difficult to properly water when the soil used is a fine, silty, water retentive medium that can't hold its structure and compacts, losing any aeration.

Fungus gnats like a moist environment... and the medium you choose is the foundation of any containerized planting... so if you're using a medium that can't hold perched water and dries out in a decent amount of time, there shouldn't be anything for fungus gnats to be attracted to.

In the meantime, try a 3 in 1 spray or a systemic insecticide... and hang up a yellow sticky fly trap or get an actual fruit fly trap... and check out the article I linked about soils and water retention. Even though the surface of your soil may seem dry, my guess is that there's a lot more moisture at the root zone than you may think there is.

Happy Growing!

Here is a link that might be useful: Container Soils - Water Movement & Retention XIV

    Bookmark   December 5, 2011 at 2:29AM
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Actually Dana, I don't think you have to spray the whole plant if is fungus gnats, I would just spray the soil and or drench the soil..that's where the gnats live, start their families, and do all their dining..in the soil ;-)


    Bookmark   December 5, 2011 at 10:20AM
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Many thanks to both of you! I didn't get to the store today for the 3-in-1. My four-year-old was sick--it's just been one of those kinds of days...

Jodi, I'll definitely check out that link and continue watering from the top. I haven't seen any gnats or flies around my plants today, but then I haven't had much time to really examine them. I'll check again later when the kids go to sleep, and hopefully, I'll get to the store tomorrow.

Donna, thanks for the tip about spraying only the soil. I didn't want to hurt those soon-to-be-open flowers!


    Bookmark   December 5, 2011 at 4:11PM
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The bulk of roots is/are situated at the bottom of the container. Everybody can verify this for themselves. Thus, it makes absolutely sense to water from the bottom. Which was the breakthrough in my cultivation of Hippeastrums. I challenge other people to present me their balcony boxes with two rows ÃÂ 8 seedlings that, at least from DIP, can bloom in a percentage of 50 to 75 % after just two years from seed.

When the surface remains totally dry, then it can be maintained "hostile" for any arthropod life form by spraying in intervals, with long lasting insecticides. IF an infestation becomes obvious from the bottom, then an agent can be applied, that contains Thiamethoxam, Imidacloprid or Thiacloprid, being added to the lukewarm water.

    Bookmark   December 5, 2011 at 4:31PM
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I'm BronxFigs. I asked this same question of the forum members not too long ago, and they gave me some very good advice on how to rid myself of my Fungus Gnat problem. Check out all the information that was previously posted about these little pests.

Here it is short and sweet. Replant your bulbs into a quick-draining mix. I did and the gnats were gone in one day. There's plenty of information about this gritty, quick-draining mix posted on many of the forums. Use the link that was provided to learn about the correct way to formulate container mediums for growing plants. Too much moisture trapped in planting mediums could mean the kiss-of-death to your plants.

Good luck, and I hope all the information posted here helps.


    Bookmark   December 5, 2011 at 7:37PM
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Hans and I have differing opinions when it comes to soils and watering technique... and that's fine... what works for Hans doesn't work for me. We live and garden in different environments, halfway around the globe from one another.

In any growing situation, if we want optimal results, we must ask ourselves why we use the materials and methods we use, and we must understand how they work. It helps immensely if we know what the functions of soil are, how water moves through soil, and what actually happens under the surface of soil in a containerized environment, with respect to the roots of a plant.

Aeration and drainage are the most important considerations in a container planting... the soil is the foundation.

Past experience and learning have shown me that quite a bit of the more commonly accepted and circulated information about growing plants is riddled with fallacy, misinformation and half truths.

The medium I use is a larger particulate that holds its structure and aeration very well, is sharp draining, mostly inorganic in nature, and provides the roots of my plants with the environment they need to be healthy... with a little help from a good watering and nutrition regimen. Bottom watering wouldn't work very well in my situation because of the medium I use, and because I want to flush the medium of gases created at the root zone and allow for fresh, and needed, oxygen to enter the soil. The action of thorough watering from the top does this quite well. It also helps flush out any accumulated salts.

That's not to say that Hans is wrong... for his situation, his methods give him the results he feels happy with. But most of us aren't consummate growers with quite so much experience, or the exact same environmental variables in place.

I'm a huge believer in going with what basic science and physics tell me, and when I add the science and physical aspects that I've learned about soils and water movement to the other pieces of my own growing puzzle, it calls for a more open soil watered from the top, thoroughly, when necessary. The roots of my plants colonize the entire pot... not just the sides or bottom, or close to the surface.

It is my belief that successful bottom watering comes with a few caveats... one must have the proper knowledge of how and why such methods work, and have the right materials and other factors in place.

I've tried the peat and cocopeat based soils, and I've used bottom watering in the past. Such methods weren't workable for my growing situation, so I abandoned the finer soils prone to compaction and holding perched water, and opted for a more fast draining medium that allows the roots the proper exchange of oxygen and gases, good root function, metabolism and growth.

I would pose the question to Hans... have you ever read the article I frequently link? And if so, what is your opinion of the ideas contained therein?

    Bookmark   December 5, 2011 at 8:02PM
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Hey Jodi, you remember you told us that you lost most of your collection to the narcicuss bulb fly, is it because you left your bulbs outside for summer? Well I lost all my bulbs due to that darn bulb fly, so I cut each bulb in 4 pieces and then put them in small baggies with vermiculite and they have bulbletd, i`m glad I got something out of them, nature is amazing in it`s own way! :)

    Bookmark   December 6, 2011 at 12:16PM
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Actually, no... my bulbs were housed indoors, with the exception of one. During the warmer months, our windows are opened partially to help circulate some fresh air, and I'm afraid the little buggers came in through the window gaps... or it's even possible they came in through the stairwell, where the outside door is quite often left open for dogs to enter and exit... or, they could have come in on a bulb or other plant that was purchased... I'm just not sure.

The bottom line is... I was so afraid of NBF, and I didn't really have a protected spot outdoors... that I kept my plants indoors... and they got attacked anyway. I should have risked it, and then they could have had much better light from the sun. They get enough through the windows and through supplemental lighting, but the garden would have been much better.

Next spring, I'm taking the remainder of my collection outdoors, re-potting into fresh gritty medium, and using decent doses of systemic on everything.

I did manage to save a few pieces of some bulbs... so we'll see.

    Bookmark   December 6, 2011 at 2:14PM
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Thanks for the advice, everyone. Even when it conflicts, I still find it edifying, and I'm grateful for the help. :)

    Bookmark   December 6, 2011 at 9:30PM
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You're very welcome, Dana... if anything, conflicting information and/or opinions are good reason and offer opportunity to research further, finding vetting for the various methods and materials offered for your consideration.

I'm certain that once you learn the purposes a medium serves, and what actually happens beneath the soil surface in a container planting... once you know the "how & why" of it all... you will be able to determine what path to take toward success, keeping your own environment in mind.

Happy Growing!

    Bookmark   December 7, 2011 at 6:18AM
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