Fungus gnats

I think that's what they're called. I'm trying to grow soil sprouts, and the gnats run around in and under lumps of potting mix. They're about the size of fruit flies, but without the red eyes.

Their eggs hatch out into the awfullest maggots that eat roots and crawl around looking completely disgusting.

You might be able to pick out the gnat near the center of this photo, on the side of a pea.

I tried Diatomaceous Earth, but it doesn't deter them on broccoli seeds. I don't want to spray malathione or anything else on something I'm to eat within days. Neem doesn't work.

Any suggestions?

This is opinion, not experience. If someone with experience shows up, take their advice before mine! But I bet they also say "drier soil & less organic matter".

Sprouts might not need ANY fertilizer, organic OR chemical. I didn't know sprouts needed soil! I thought that was only needed for microgreens and baby leaves.


1.
Reduce excess moisture, especially on the soil surface.

Let the top 1-2 inches DRY OUT between waterings. Water less often, perhaps more heavily.

Maybe soak the seeds before sowing, or even pre-germinate them on coffee filters before sowing. Then you won't be tempted to allow soggy soil.

Set the pots or flats on a thick absorbent towel after watering, to pull away excess water. If the bottom of the soil isn't sopping, maybe the surface won't be soggy.

Make the air less humid, like by blowing a small fan onto the soil surface. Can you encourage a draft?

Remove the surface layer of mix and replace with something that sheds water faster, like coarse grit or bark chunks (not fines). But I don't know how deeply fungus gnat larvae/grubs/maggots burrow.

Next time, use a faster-draining soilLESS mix, something that retains less water. Less peat moss!

I would suggest re-potting to get rid of what sounds like TONS of eggs and larvae, but you said "soil sprouts", which i guess are like microgreens.
http://www.johnnyseeds.com/t-micro_greens_production.aspx?source=W_GrowersLibVegIndex_112015


2.
Reduce the amount of organic matter that feeds the fungus.

Next time, use a soilless mix, adding no compost.

Maybe: Don't fertilize containers with organic matter or compost. Use soluble (chemical) plant food.

If you must water containers with organic fertilizer, use less, and look for something that claims not to encourage fungus or fungus gnats.


3.
Knock down the amount of soil fungus somewhat, temporarily, if you can.

Water with 0.2% hydrogen peroxide (dilute drugstore peroxide by 16:1 - like 2 ounces per quart).
However, you can probably kill more eggs and larvae with "drier soil" than with chemicals.

Also, if you have wet soil containing much organic mater, the fungus will soon be back in large amounts no matter how much peroxide you use. Indoor containers can't support a soil ecosystem like the outdoor ecosystem. Nature is huge and contains near-infinite biological variety. Containers don't.


4.
Directly kill some gnats & larvae with something other than dryness.

There are chemicals, and some biological methods like Bt and beneficial nematodes.
You'll have to evaluate how effective and/or toxic each of those really are.
http://www.planetnatural.com/pest-problem-solver/houseplant-pests/fungus-gnat-control/

One website suggested "sticky yellow traps" to catch some of the adults. It also suggested starting out with fewer eggs and larvae - as if they don't multiply very rapidly. Good luck!

5.
It's the conditions, not the infection.

Some biologist in the last century (or maybe it was all the way back int he 1800s) said "Everything is everywhere". He meant that bacteria and insects are very good at spreading their eggs and spores. He was trying to tell people that they could not solve most biological problems by "killing all the agents" and then hoping they wouldn't come back. You can never kill them all unless you use an autoclave. Even if you could, you would have to seal them tightly inside glass to keep them from being re-infected about 5 seconds after being exposed to the air.

To solve a pest problem, you have to remove the conditions that encouraged the pest to thrive. Ideally, completely remove something they need. In this case, they need excessive soil moisture and fungus.

The fungus needs moisture and organics.

If you can reduce the soil moisture below what larvae need to live, they should die down to tolerable levels.

Next time, if you can keep excess organics out of the mix, they won’t even be attracted.

I grow orchids in high humidity and temps conducive to fungus gnats. Many of my plants are growing on live moss or have live moss covering the surfaces. The potted ones in organic mixes always have a gnat problem going into the greenhouse come fall. As mentioned by RickCorey, Bt is a safe and effective solution. It will knock out the larvae but not the gnats so it takes awhile. Maybe longer than your sprouts. :) I use pieces of mosquito dunks in a tank sprayer but have to net the dunks to keep the granules from clogging. Liquid Bt would be easier but I am looking to kill newly hatching larvae (the gnats are not the problem) over several weeks and the orchids get fertilized several times a week.

Wow! So sorry for the slow answer from me. What wonderful advice! I have come to believe the wetness was excessive, and now the gnats are "gone away"

Thank you so much for your time and trouble to reply.

What I am doing is called "soil sprouts" I'm using little bread pans, for now, with ProMix. I read a book by Peter Burke, "Year-round Indoor Salad gardening" Great book! Fresh greens in the winter, even in Vermont. In a window, not even needing a lot of sunlight. In ten days! I'm even getting a business license so I can sell the greens.

Best of luck with your business venture. It's great when you can profit from something you enjoy.

Congratulations on getting rid of the gnats.

You might want to try some Brassica rapa greens, like Bok Choy, Chinese cabbage, tatsoi and Komatsuna. The first two are VERY mild, and tatsoi is pretty mild. Komatsuna has a little "mustardy" flavor.

I don't know how they would be as sprouts, but as "microgreens" or "baby leaves", they are nice for salad. Do you eat the root and what's left of the seed?

Oooo, what is left of the seed, do you mean the seed coat? Never. That's where E Coli and that other one hids.

I am growing "Soil Sprouts" which are completely different from "jar" sprouts. I put a couple of inches of damp ProMix, which is a peatmoss mix, in small pans, scatter the soaked seed on top, then cover with folded, soaked newspaper. The newspaper keeps the seeds wet, and the growing sprouts have weight to press against when they are pushing their roots into the soil mix.

After three or four days in a dark cupboard, I bring them out into a bright window to green up and grow a little more. I get long stems this way. When they are right, I cut them just above the soil. The leftover soil mix, roots and all, go into the compost.

I learned this from a newly published book by Peter Burke, "Year-Round Salad Gardening" He fiddled with the technique for a whole winter, using his left over seeds from his summer time garden, in Vermont. GREAT BOOK!! Well thought out, and worth every penny. I really enjoy having a big pile of fresh cut greens on every plate of food I eat! And I feel the difference, too.

>> After three or four days in a dark cupboard, I bring them out into a bright window to green up and grow a little more. I get long stems this way. When they are right, I cut them just above the soil.

Cool! Do you harvest them more like microgreens (seedlings leaves plus maybe one small pair of true leaves) or like baby leaves (1-2-3 pairs of small true leaves)?

That's cool Adenium, great looking seedlings. Good luck with your business venture!

Sunflower, just as the first true leaves appear, but before they grow at all. I've found to NOT fertilize, just ProMix and water, they get astringent with too much food.

And here you might see a tray of cabbage that I just harvested this morning, the slow-to-germinate seeds are just showing through the (too many!) stems. I'm going to let them grow leaves--- I have a couple of trays with baby leaves after having harvested the tiny ones, cotyledons they are called. broccoli and beets.

I have a couple of books, one by Jean-Martin Fourtier, about making $100,000 a year on two acres growing vegetables. I really noticed his comment about how he's supplying two grocery stores with baby greens! And my only sprouts book, "Year-Round Indoor Salad Growing", about sprouts grown in "soil", harvesting ten days after planting. He mentioned a home business could bring in $35k a year.

Now I'm facebooking with others who are getting started. One fellow said he took some arugula sprouts to a restaurant, and they ordered two pounds right off the bat!

I'm eating big platefulls of greens now, easy! Yum!