Fungus Gnats!

[SueCT]

I was so happy to have an indoor herb garden this winter. I was surprised how well they did under the lights I usually use for my seedlings.




Well I started my seeds last week next to my herb garden, and most have germinated. The last couple of days I have started to see fungus gnats. I am concerned for my new seedlings. Is it worth fighting them with watering in BT or should I just buy tomato plants again this year? I have not have insect, fungal or other problems with my seed starting in 5 or 6 years. I have read it takes weeks to get rid of the gnats using BT. Would it help the tomato seedlings to put the herbs outside and let them go if they are not hardy enough, like the Basil? I don't have time to spend weeks on getting rid of the gnats and then maybe still have to restart seeds and have good sized plants in time to set out.

[Al@NC]

I had a big problem with fungus gnats last year, it reduced the number of seedlings I ended up with come plant out time. It was so bad for me that several seedlings basically quit growing due to the gnats eating their roots. I literally took cuttings of seedlings and put them in cups with water to try and save time over regrowing seeds!

Last year I was in Canada called Sticky Stiks and bought a product which is basically just yellow paper with adhesive sticky to catch flies and gnats. It works pretty good and i've seen online where people just buy yellow double sided tape or make diy projects to setup sticky paper to catch them with.




This year I'm also using "mosquito dunks", so far it's working great. You can buy mosquito dunks at Lowes for about 10$ for 6 dunks. Some people mix the dunks into the water they give their plants to kill the baby gnats down in their soil but there are also others that say they get good results by crumbling the dunks and sprinkling them on the soil of their plants. One guy actually says he beats the dunks with hammers before he opens the package.

Al

[Cole_Robbie]

Mosquito Dunks are cheap BT. Just soak them in the water that you use for watering. (edit: Al and I just posted at the same time)

I would cover the top of your media with dry perlite, and then bottom-water from them on, trying to keep the perlite dry. That makes it hard for the eggs to hatch. Don't breathe the perlite dust.

[SueCT]

Thanks, I have a mosquito dunk soaking now so that I can use the water tomorrow. I just moved the herbs to the garage. I spritzed the seedlings because they getting a little dry and I did not see any thrips. I have only seen a few and killed them but I know I need to be proactive to save the seedlings. I will try to get to HD and see what they have for the sticky traps also. I am just afraid those few I saw laid tons of eggs before I got them. I found in the past I had more problems bottom watering, because the soil in the bottom would be too wet by the time it reached the soil at the top with the tiny seedling. It is probably my technique, but I just did not do it well. I have found watering lightly when it starts to dry out has worked in the past, but I realize I might need to try something else if these little buggers persist. How do you prevent water logging of the soil in the bottom of the pot? I will keep the soaking mosquito dunk next to the seedlings. I find they drown themselves in the water if I leave standing water near by. I find dead ones floating in it the next day. Maybe they will die in the BT water instead of the soil. It is also an indicator to me if they are still around. Hope it doesn't help them breed.

[Cole_Robbie]

What mix are you using for the seedlings? It shouldn't get "too wet." It might need perlite added to it if it is getting too mucky.

[SueCT]

I use a peat based seed starting mix, Jiffy at times in the past, but one from Garden.com this year. I haven't had any problem with it being too wet since I stopped bottom watering a number of years ago. Part of the problem now is that all the seeds are started and 75-80% of the pots have germinated, so it would mean re-potting very delicate seedlings that don't even have true leaves yet. I would try it rather than loose them all, but I think it would be a rather delicate, time intensive process.

[Bulldog]

I read to use boiling water to moisten the seed starting mix before using it. Also to freeze it before using to kill the eggs.

[brownrexx]

This won't help you now but I started putting my bags of seed starting mix in the freezing temperatures outside for a few nights before using it in the spring. I have not had gnats since I started doing this.

I have also read that a slice of raw potato placed on top of the soil will attract the larvae and then you can remove it and throw it and the larvae away. I have not done this so I don't know if it works but bt should work.

[ginger2778]

We had a fungus gnat issue last season at the community garden, a disaster because the larvae ate the tender roots of seedlings destined for a plant sale, We reseeded, hit them with BT (Thurcide) and all was well. It worked right away. No more losses and the new seeds mostly all germinated and formed strong plants. Just to be safe, we used the BT at the next couple of waterings.

[Johnniemar]

I had fungus qnats this year also. Raising about 200 tomato seedlings. Bought mosquito dunks and soaked them in my watering can. It took about 4 weeks but the gnats are all gone now. Plants recovered nicely and are now about 8" tall and ready for plant out. A few got stunted but after the gnats were gone they recovered. Good luck. Yours will be fine.

[TC_Manhattan]

Anyone ever use cinnamon?

I just found this and think I'll try it next time I seed:

http://therustedgarden.blogspot.com/...ings-stop.html

Here's another article about the gnats:

http://http://www.smallfootprintfami...ts-organically

[gorbelly]

Originally Posted by TC_Manhattan

Anyone ever use cinnamon?

I used cinnamon when I had problems with fungus gnats a few weeks ago. It isn't any kind of quick fix, and it won't work well if you already have a problem. The gnats aren't bothered by it at all, and it only really helps by reducing the fungal growth on which the larvae like to feed. It's a fairly mild antifungal, as far as I can tell, so it's not going to fix an already established gnat problem or bad damping off issue.

Where I think it might be helpful is from the very beginning of the seed starting process, sprinkled on top of seed starting medium that is sterile already, where it can contribute its mild, antifungal properties to a more robust antifungal, anti-gnat regimen. I don't think it will do very much on its own, and I know for a fact that it won't do anything once you already have fungus gnats in your seedlings.

What worked for me was a mild hydrogen peroxide drench 1:4 drugstore concentration H2O2 to water and covering up the seedlings right afterward to keep the gnats from getting to the soil again. I'm sure BTi is really the way to go, so I plan to make sure I have some on hand next year.

[bower]

I tried cinnamon once - it was a horrible cold wet year and a lot of early blight and botrytis. I bought a bulk dispenser of it and sprinkled on the soil as well as trying it on pruning cuts to stop mold from growing. Didn't work, but it smelled great. Dipping the pruners in bleach works a lot better.

I did think the plants liked the cinnamon, although it didn't bother fungus much. I afterwards read it is quite high in salycilates. So a bit like giving them an aspirin, too.

[bower]

Mosquito dunks will kill the larvae in the soil, but from what I read it is most effective on a certain stage of the larvae, younger ones I think. This is why sometimes you have to keep hitting them with the BT for a while, before the next generation doesn't make it.
Also you need the sticky traps to take out adult gnats. The BT does nothing to them, and they keep laying eggs until they're dead so they need to be trapped. Our dollar stores often have large sized sticky squares for $2 a pack. You can catch more (they say) by laying the sticky horizontal across the edge of the pot, but anywhere near the soil is a good bet.
I find the gnats are harder on peppers than tomatoes, at least, once the tomatoes get big enough, they seemed to tolerate them at a certain level (mind you, I kept at em with the mosquito dunks and mosquito bits - those are the ones designed to toss in the pot and water over em.)
Good luck...

[TheUrbanFarmer]

Try crumbling mosquito dunks and adding them directly to the soil as opposed to trying a wet application. Given it is a bacteria, you can increase and maintain it's populations in a soil system. Not to mention with each watering you are utilizing a controlled release application of sorts.

I did this for years, but now use Dipel Pro DF. A very small amount (a tsp per cu ft of media) is all that is needed. I never have issues with gnats unless I forget to mix it into the soil.