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fungus gnats on vegetable seedlings

Posted by love2garden-nc 7 (My Page) on
Fri, Jul 13, 12 at 23:18

looking for suggestions on getting rid of these pests. I just saw 3 or 4 of them tonight for the first time flying around my flats with fall veggie seedlings. I have read about mixing soap with water and spraying plants and soil. anyone know if this works and recommended amounts of soap to water? Also read about mixing mosquito dunks in water used to water seedlings-is this ok to use on veggies? any other suggestions? i appreciate any ideas-this is my first attempt at starting my own seedlings. btw seedlings range from 2-4 weeks old.


Follow-Up Postings:

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RE: fungus gnats on vegetable seedlings

The BT ingredient in mosquito dunks works on the larvae in the soil which is what does the plant damage. It will not harm the plants at all. Al


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RE: fungus gnats on vegetable seedlings

In the future, don't use peat. Fungus gnats are a sign of too-wet conditions. Never seen any unless there was peat involved.


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RE: fungus gnats on vegetable seedlings

thanks for the info. i made a note in my notebook that its ok to use the dunks with veggies plants-the old memory just isnt what it use to be. on the peat- i used miracle gro seed starter mix. i looked at the ingredients and it does include peat. the top layer of soil seems to get crusty-is that normal? what is your favorite starter soil to use? thanks again for all the info-i am really enjoying the fall seedlings.


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RE: fungus gnats on vegetable seedlings

I have found a good way to control and prevent fungal gnats. Even when growing indoors in low ventilation, with a little TLC and control measures you will be fungal gnat free!

I mix spray bottles of water and Murphy's Oil Soap (About 2-3 tbsp per spray bottle) Spray the leaves and soil once daily for about 7 days. ensure that you check the undersides of the leaves as well.

Make sure you liberally apply, as the gnats should be soaked in it.

It will NOT hurt the plant to have the solution on the leaves, i've used it for years and have yet to have a problem.

-Mitchell Haase


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RE: fungus gnats on vegetable seedlings

I sow veggie seeds directly outside, and don't try to grow things that won't do well that way, but certainly understand the desire and commend your efforts! I know whatever I've grown won't have any nasty stuff on it, and it's easier and healthier to avoid an avoidable problem by not allowing the abundance of moisture required for fungus gnats to live. House plants have taught me this but the gnats don't care what kind of plants they are as long as there is moist organic material in which to breed. Indoor seed sowers usually tout the benefits of sterilization (of the soil and pots) so you may want to investigate that for next time, in conjunction with cutting back on the water a bit.


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RE: fungus gnats on vegetable seedlings

Nearly all soilless potting mediums use peat as the primary ingredient; seed germinating mixes are just finer textured. That's not about to change anytime soon. But it is not that difficult to prevent fungus gnat infestations. It's great to get a several week jump start on our veggies and flowers, but not if those gnats become a nuisance.

I'm going to suggest that you fill your flats with a good potting mix....one that you might use for your houseplants....perhaps with perlite added for even better porosity. Then add a good dusting of your seed starting mix on top.

Water your flats thoroughly with a gentle spray so that you don't compress all of the air out of the mix. Sow your seeds on top of the moist and drained flats, then dust a layer of the starting mix on top. Use a plant mister to completely saturate the seeds and that final layer. After draining again, cover the flat so that you won't have to water again while the seeds are germinating.

Once the seeds have germinated, begin to expose the flats to real air and sunlight. If the top layer becomes crusty, keep the surface gently stirred. Use a pencil or a bamboo skewer for the job.
A crust will prevent the flat from drying uniformly and can create a great environment for the fungus gnats.

Seedlings should NOT stay in that fine-textured starter mix for any longer than it takes for them to reach a transplanting size. That is just a matter of days. If you are growing plants in that stuff....stop. Adapt to that dusting technique and your seedlings will be much better off.

The secrets to preventing these pests aren't secret at all. Use a good, porous soilless medium with only a tiny layer of the starter stuff; provide good air circulation and lots of light; do not over water. I never sterilize my potting or propagating mediums.
Mosquito dunk-water works great....use it only when you would ordinarily water, not more.

I would be remiss if I didn't mention that lots of people have problems with Miracle grow. The peat must be too finely milled
to create a porous, fast draining medium.


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RE: fungus gnats on vegetable seedlings

Just wanted to say thanks for sharing your knowledge. I never saw anymore gnats--I did cut back on the watering for a bit. So I guess I jumped to conclusions to quickly. Anyhow, I made note of all this info and will know what to do if I do get them next time. And I'm looking for a different soil--thanks again and have a wonderful day:-)


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