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Fungus gnats?

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by syl726 on June 19, 2004 04:52 PM
In the past week I've seen maybe 3-4 tiny black bugs around my Dieffenbacha [scaredy] I didn't pay much attention at first since the plant sits by the front door and the opening and closing may have let them in. I've read about fungus gnats; could it be [dunno] If so...WHAT ARE SOME CURES????????? [critic]
by barleychown on June 19, 2004 06:51 PM
I often have a problem with fungus gnats during the winter, mostly 'cause that's when I spend more time fussing over and watering my house plants. [grin]

They like it when you water all the many suggested to me to water less. That worked on most of my plants, but for those that cannot go without watering lots, I found that sand on top of the soil works, as well. [Wink]

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We do not see things as they are, we see things as we are.
by Will Creed on June 21, 2004 12:31 AM
If you suspect fungus gnats, then place inch slices of raw potato on the surface of the soil. The potato will attract the gnat larvae that live in the soil. After 24 hours look at the bottom of the slices and see if there are some tiny worm-like things burrowing into the potato. If you do find them, then here is what you need to know.

Adult fungus gnats fly around and are an annoyance, but they are not harmful to people. Each gnat lives for about 5 days. The trick is to get rid of the next generation - the gnat larvae that live in the top layer of the soil. The larvae feed on decaying organic matter. Decaying pine bark in potting mixes and decaying plants roots feed the larvae.

Try to keep the soil as dry as possible. Remove all loose soil from the surface and put a light layer of coarse coir (coconut husk) or sand or diatomaceous earth on the soil surface. These substances have sharp edges that carve up the larvae. (Recent studies indicate that fine-textured peat moss also deters gnat larvae.)

Another safe technique is to place inch slices of raw potato on the surface of the soil to attarect the larvae. After a day or so, discard the slices along with the larvae inside. Repeat this until there are no more larvae in the potato.

For more serious infestations try Knock-Out Gnats to treat fungus gnats available from Gardens Alive for about $20. See

Another bio-control method is Gnat Not, a parasite that destroys gnat larvae and other soil pests. It comes on a sponge in plastic (5 weeks shelf life) that is rinsed into water and applied to the soil. For information, go to

Detection trick: Add a little water to the soil and then look very closely for tiny fungus gnat larvae swimming in the water as it pools on the surface. You need good light and good eyes to see them. If you don't, then your plant is probably gnat free.

Prevention is often the best remedy. Use sterile potting mixes that are free of bark chips. The potting mix should have ample drainage material, such as perlite so that it drains well and allows the soil to dry out frequently. Fungus gnats can nearly always be traced back to overwatering and/or poor soil quality.

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