Help! Fly Attack

Hello! I'm growing my seedlings in the garage with heat and under a dome and lights. I've recently noticed very small fly's (?) buzzing about and running into and over the soil. They seem to be multiplying at an exponential rate and are snacking on my seedlings! At about the same time I also began to notice a small amount of white, fluffy fungus looking stuff on the soil? Any suggestions on what this could be or what to do? I tried "Organicide" which is supposed to kill 52 plus pests, but to no avail!

The flies are probably Fungus Gnats http://gardening.about.com/od/gardenproblems/a/FungusGnats.htm . The tiny flies themselves don't damage your plants, but they lay eggs and their young larva are maggots that live in your growing mix and feed on the roots of your seedlings. The white fluffy stuff on your soil is a natural fungus that is breaking down organic matter in your seedling mix. It is probably harmless and not related to your Fungus Gnat problem.

Based on your mention of "Organicide", I guess you are an organic gardener. I am not an organic gardener myself, because I don't believe that "chemicals" are necessarily evil, but I use many organic methods. There are organic methods of preventing Fungus Gnat damage. I powder up Mosquito Dunks http://www.planetnatural.com/site/mosquito-dunks.html (available in Home and Garden stores), mix the powder with water, and water my seedling beds with that. Fungus gnat maggots can do very serious damage, so before I plant my seeds, I dampen the growing medium with the Mosquito Dunk mix (which I keep in gallon jugs that I label as "Seedling Water"). When I repot my seedlings, I reapply the "Seedling Water" to maintain protection.

ZM
(Not associated with any product or vendor mentioned)

Zen Man,

Thanks so much for the info. I think you really hit it on the head - I'm going to run out and load up on mosquito dunks now! A number of my seeds have germinated but are not growing, mostly just sitting looking sad. Based on what I read at the links you provided, I think this is probably becuase the larvae have been munching on the roots. Any idea if they will recover post-dunk or do you think I should just trash them and go back to square one? btw - I'm not really a organic gardener, just ended up with the organicide by chance, so if you have any other non-organic suggestions, I'd love to hear them!

ps - what is the dunk powder / H2O ratio you use?

DG

DG,

"...what is the dunk powder / H2O ratio you use?"

The exact ratio isn't critical. I use one powdered Mosquito Dunk per gallon of water to make a stock solution. I make my "Seedling Water" by filling an empty gallon jug about one-quarter full with the stock solution and add "regular water" to make a gallon and then I put the lid on the jug and shake it to mix the stuff together. So a single Mosquito Dunk makes four gallons of Seedling Water. There will always be a bunch of pieces of un-powdered Mosquito Dunk floating around in the Seedling Water, but that is fine, because they will be of some lasting benefit when they get poured or sprinkled on your seedlings.

I am looking for a better way of powdering the Mosquito Dunks, but my current method is to seal a Dunk up in a big Ziploc bag, put the bag on a smooth hard concrete surface, and pound the Dunk repeatedly with a hammer. Try to hit the dunk, or its pieces, "flat on" so as to avoid cutting the Ziploc with the edge of the hammer. But if you do damage the Ziploc some, don't worry about it. Just try to get most of the powdered Dunk into a gallon jug. Toss what is left of the Ziploc bag into the trash. Incidentally, a suitably-sized funnel will be a big help in this operation.

If I see a blender cheap at a garage sale, I may buy it with the idea of using its "Puree" setting to blend the Mosquito Dunk mix better. I wouldn't want to use a blender for food if the blender had been used for blending Mosquito Dunks, even though the Dunk stuff probably isn't dangerous. I have no idea how well a blender will actually work with a Mosquito Dunk, so I don't want to get much money invested in that approach. The Ziploc bag & hammer method works well enough.

As for your maggot-munched seedlings, whether you try to nurse them back to health or discard them depends on the value of the seeds. If the seeds were expensive, I would try to nurse them back. Once you kill the maggots, your seedlings will be able to grow new roots that don't instantly become maggot food. Even though I didn't buy the seeds, I consider my baby zinnias as valuable, because I hand-hybridized their seeds and I have a vested interest in discovering how each one of them is going to turn out.

If your seeds were cheap, discard the maggot-infested media and start over, this time with media that is initially treated with the Mosquito Dunk water. Prevention is the best cure. If a Fungus Gnat female fly lays eggs in your pre-treated germination medium, the maggots either won't hatch or will die while still microscopic in size.

ZM

ZM,

Thanks again for all the info. Per your suggestion, I've made 'seedling water'. Just having a 'plan' has made me feel a TON better. I transplanted any viable looking plants out into the coldframe and doused the remaining possibly viable plants that are still under lights. Ended up throwing out two flats of goners, but I think it had to be done. Washed the emtpy containers, etc in a water/bleach solution just to be sure. Mixed in the seedling water with the potting soil into the plants I sent out to the coldframe. The gnat situation doesn't seem to be as bad outside, but I'm going to go ahead and spray everything in the frame - just to be safe. I'll keep you posted!

Good luck with your zinnias!
ps - I really dislike these suckers!

DG