Lisianthus and Fungus Gnats!!!! Hurry before they all die!

rinomanfroni(7)February 7, 2010

My seedlings of Lisianthus (hundreds!) have been decimated by Fungus Gnats. They kill seedlings in a matter of less than one day.

Is there anything I can buy at the Home Depot to kill these insects?

Thanks, I need help as soon as possible because they are dying even right now!


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You may have both Fungus Gnats and Damping Off. Damping Off can kill seedlings quickly. The Fungus Gnats themselves (the adults) probably aren't hurting your seedlings, but they lay eggs that hatch into maggots that feed on the roots of your seedlings. They wouldn't kill your seedlings so quickly, but certainly could stunt their growth.

I control Fungus Gnat maggots in the soil by watering with a solution that includes some powdered Mosquito Dunks. I use them because I happen to have them on hand. They should be available locally in a home store or garden center. I place a dunk, or a piece of one, in a Ziploc bag, place it on a hard concrete surface, and pound it into powder with a hammer. I add that powder to the water that I water my seedlings with. Don't breath the dust and wash your hands after. However, any product that contains Bt and is labeled for fungus gnats should work.


    Bookmark   February 8, 2010 at 1:50AM
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rhizo_1 (North AL) zone 7

The most important element here is probably the overly moist condition of your potting medium. That's what causes the assorted diseases that cause 'damping off' in seedling, as well as fostering a healthy fungus gnat larvae population.

What kind of seed germination set-up do you have; what's your potting soil like; soil temperatures vs. room temperature, air circulation, etc. If we had some further information, we could do more to steer you in the right direction next time.

    Bookmark   February 8, 2010 at 9:00AM
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I treated the seedlings with a Bayer Advanced insect killer and also a fungicide. I sprayed thoroughly over the trays. Today the seedlings that were still alive have not disappeared! I hope it will continue to be like this for a long time!

This is how I created my little greenhouse in the patio closet. The three round pots are those where the Lisianthus are growing.

    Bookmark   February 8, 2010 at 2:03PM
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