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Organic Gardening: Fungus gnat under row covers

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Forum: Organic GardeningReplies: 6, Views: 71
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Central Valley, CA
(Zone 9a)

April 3, 2010
2:36 PM

Post #7677394

It has been cool and rainy here for the past week. I've noticed fungus gnats flying around under my tunnels. The seedlings seem very healthy and are growing well. So, I am not too worried.

I have been trying to read up a bit on these insects. From what I gather, they mainly consume fungus and decomposing OM. Not suprised my this. There are tons of micromushrooms poping up everywhere. I added quite a bit of OM at all stages of decomposition to the beds. They must be having a feast. I read that the larvae eat plant roots. Is this a given or just when their main food runs low, like slugs, snails, mealbugs and other detritius feeders?

The weather is suppose to warm up considerably and dry out next week. Is there much damage they can do until then?

P.S. I don't want to overcover my tunnels too long to let it dry out due to the cold and windy conditions.


Charlotte, NC
(Zone 7b)

April 5, 2010
8:32 AM

Post #7681265

Yellow sticky traps will catch and kill fungus gnats. If your seedlings have a good root system, the larvae should not do too much harm. However, without adequate control the population can explode, especially under a row cover where natural preditors are absent.

Another control tip: Put out containers that are yellow and have water in them. Fungus gnats are drawn to the color yellow and they will drown themselves!
Conroe, TX
(Zone 9a)

April 5, 2010
3:15 PM

Post #7682172

HoneybeeNC, thanks for this tip.

I have about a zillion of them this year. We had a very cold winter and a wet spring. Maybe this had something to do with it. I wish the hummingbirds would arrive. They love fungus gnats.


Charlotte, NC
(Zone 7b)

April 6, 2010
8:33 AM

Post #7683983

I thought the hummingbirds had already arrived in Texas. I'm still waiting for my first one here in Charlotte, NC


Pueblo, CO
(Zone 5b)

April 11, 2010
3:54 PM

Post #7697684

Bt for mosquitos will work on the larva stage of fungus gnats - it isn't an instant kill, it takes about a week.
Central Valley, CA
(Zone 9a)

April 12, 2010
1:19 PM

Post #7700137

There has been two major series of storms in our area with a warm week break in between. I have turned up the row covers on short dry breaks during the stormy beds. I've completely uncovered the beds on the warm, sunny dry days. It seems that the fungus gnats have not done any damage. The plants are all very healthy and growing fairly fast.

The gnat population seems to die down on dry days only to mystereiously boom on wet days. They must be either hiding in the straw bedding on the sides of the beds. Or they can repopulate that fast. Probably, both.


Charlotte, NC
(Zone 7b)

April 14, 2010
8:35 AM

Post #7704924

dlbailey - I don't think the actual gnats do any damage - it's their larvae that eat the roots.

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