small flies around thyme sprouts?

seeddrifterMarch 2, 2013

I am sprouting thyme from seed, and there seems to be small flies (much smaller than house flies) walking and flying around the soil and sprouts. There are other plants around like basil and cilantro. These are indoors (in the basement) being lit by florescent lights.

Is there something I can use to kill these flies? They seem to be multiplying. The thyme will eventually be used in food, so I don't want to do anything poisonous.


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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

They are called fungus gnats and are a result of keeping the soil in the containers way too wet. Letting the soil dry out well between watering will help control them but it takes one of the pesticides to eliminate them completely one they are established in the soil. Bt is an organic pesticide that works well.

See all the discussions linked below for more details.


Here is a link that might be useful: Fungus gnats discussions

    Bookmark   March 2, 2013 at 9:52AM
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Thanks Dave. I have sprinkled cinnamon around the soil to see if that will work. I'll post the results in a few days.


    Bookmark   March 2, 2013 at 10:27AM
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tanyuu((5/6 - South IN))

You can also try mosquito bits- they work with fungus gnat larvae by making them unable to eat and thus, unable to become fully fledged gnats.

    Bookmark   March 2, 2013 at 3:12PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

I have heard of using cinnamon to supposedly prevent soil fungus growth but never using it as a pesticide for fungus gnats.

Mosquito Bits that tanyuu mentioned are the Bt I discussed above. Bacillus thuringiensis (or Bt) is an organic insecticide. You just dissolve the bits to the "dunks" (another form) in water and use it to water the plants.


    Bookmark   March 2, 2013 at 4:03PM
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Kill fungus gnats by killing the eggs and larvae in the soil not the gnats themselves. Those flies you see only hatch out of the soil to mate and lay eggs in the soil and die. Killing them won't get rid of them because there will always be more hatching out. The larvae hatch from eggs in the soil and live in the soil eating plant roots and debris in the soil.

Getting them is nothing you did. The eggs were probably in the soil when you bought it.

Anyway they are very easy to get rid of. Mix about 1/2 teaspoon of dish soap or insecticidal soap in a quart of water and water the soil of the plants with it. The soap won't harm the plants but it will kill the eggs and larvae. As these are seedlings I'd wait until they are a bit dry so you don't over water. You can put some in a spray bottle if you want to spray and kill the flies if you get them to sit still long enough

Fungus gnats are nothing but a nusance. They won't harm food plants except for the larvae feeding on the roots

    Bookmark   March 2, 2013 at 6:40PM
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Using a fan to increase air circulation near the plants will help deter fungus gnats. The gnats don't like the air movement. Also the fan will help dry out the top of the containers.

    Bookmark   March 2, 2013 at 6:47PM
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