General Discussion:

house plant gnats

Messages posted to thread:

gwen in victoria01-Oct-03 07:24 PM EST 8a   
Judith in Innisfil02-Oct-03 07:39 AM EST 5a   
dm02-Oct-03 07:27 PM EST 3   
Will Creed, Interior landscaper03-Oct-03 11:37 AM EST   
gwen in victoria04-Oct-03 10:30 PM EST 8a   
Will Creed, Interior landscaper05-Oct-03 02:52 PM EST   

Subject: house plant gnats
From: gwen in victoria
Zone: 8a
Date: 01-Oct-03 07:24 PM EST

I believe they're fondly known as fungus gnats...they are whooping it up in most of the plants inside my house...they love african violets...what can one do to discourage the partying???

Subject: RE: house plant gnats
From: Judith in Innisfil
Zone: 5a
Date: 02-Oct-03 07:39 AM EST

Hi Gwen There is a rather peculiar method that works to get rid of the fungus gnats. Break up writing pencils into three or four inch pieces and insert into the soil - perhaps three or four around the perimeter of the pot. Initially lead pencils were used but they are now made of a different material and they still seem to work! I have been doing this for several years now.

Subject: RE: house plant gnats
From: dm
Zone: 3
Date: 02-Oct-03 07:27 PM EST

I just learned that my niece, who heard about the pencil tip on Ken Beattie's Get Growing, didn't have enough pencils for all her plants, so she got a small container of graphite from a hardware store instead. (Pencil "lead" is made of graphite.) She carefully sprinkled a little on the surface of each plant pot, including her orchids. She no longer has any gnats, and the plants do not seem to have been adversely affected. Might be worth a try.

Subject: RE: house plant gnats
From: Will Creed, Interior landscaper
Date: 03-Oct-03 11:37 AM EST

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 coir (coconut husk) or sand or diatomaceous earth on the soil surface. These substances have sharp edges that carve up the larvae. (I have never heard of the broken pencil technique and I don't understand why it would work.)

Another safe technique is to place ½ inch slices of raw potato on the surface of the soil. After a day or so, discard the slices along with the larvae inside. Repeat this until there are no more larvae in the potato.

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.

Subject: RE: house plant gnats
From: gwen in victoria
Zone: 8a
Date: 04-Oct-03 10:30 PM EST

thanks to all for responding...thanks Mr Creed...I was hoping to see your wise words appear here...I suspect the quality of bagged potting soil is the source of the problem...where does one obtain really good soil for our indoor friends??

Subject: RE: house plant gnats
From: Will Creed, Interior landscaper
Date: 05-Oct-03 02:52 PM EST

I have had pretty good luck with Pro-Mix brand potting mix. If that is unavailable, look for a bagged soil that is peat-based and does not have bark chips.

Another alternative is to make your own mix by adding one part perlite to 3 or 4 parts of peat moss. Add a little timed release fertilizer and you are all set.

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