Ravaged by fungus gnats???

[Lemuel714]

I started noticing gnats a while ago but didn't worry about them too much as it didn't look like they were actually damaging my plants. I was getting a lot of stunted growth but didn't connect the two. After a while the gnats got thicker and my plants started turning yellow, drying up and dying. Long story short, I read up a little on the gnats and went to war with them. First of all I keep two rooms. I've got one room for vegetative growth with a couple of t5s and a flowering room with some bigger lights and better fans. I've seen a few gnats in the flowering room but most of them have been in the vegetative room. So after a little research i put out a bunch of sticky traps and I watered all the plant in the v room with a solution of 4 parts water and one part hydrogen peroxide while I ordered and waited for nematodes and mosquito dunks. Three or four days later I put 5 million nematodes in about 7 gallons of water and watered everything in both rooms. I repeated that about 3 days later. In another 3 days I still wasn't seeing any progress so I crumbled up about a half dozen mosquito dunks and spread the dust over the soil in all the pots. I put a couple more dunks in a five gallon bucket and have been watering the plants from that ever since. About 3 days after that (2 or 3 days ago) I began noticing a big drop off in the number of gnats. Now I'm only seeing one or two when I water the plants. When I started out I had nearly 150 plants ranging from a week to probably two and a half months old in the v room. I've probably lost two thirds of them and the ones that are left range from healthy to very sick looking. They still seem to be dying off albeit at a much slower pace. I'm wondering if this is all due to the gnats or am I dealing with another problem in addition to the gnats? Any help or advice would be greatly appreciated. I will put up a couple pics. Thanx.

Lemuel714 Reviewed by Lemuel714 on 01-05-2014. Ravaged by fungus gnats??? I started noticing gnats a while ago but didn't worry about them too much as it didn't look like they were actually damaging my plants. I was getting a lot of stunted growth but didn't connect the two. After a while the gnats got thicker and my plants started turning yellow, drying up and dying. Long story short, I read up a little on the gnats and went to war with them. First of all I keep two rooms. I've got one room for vegetative growth with a couple of t5s and a flowering room with Rating: 5

[tlranger]

They will hit the roots first, before they emerge from soil, imo. :joint1:

[ThePinkJina]

The sticky traps work great for the flying gnats, for the larvae in the soil you'll need to let the soil dry out completely, to the point where it looks like your ladies are very sad and droopy. Gnats love moist soil. This could be part of your problem as to why they aren't dying as fast. Another thing you can do is purchase a pound or two of (Sterile) Sand, and put about 1/2" to 1" on top of your soil, I would do this about 3 days after watering. The sand is too heavy and dense for the larvae to crawl out. As long as you let your soil dry out completely between watering, you'll notice more and more dead gnats.

I also use a shot glass or small lid (shallow), pour a small amount of wine or beer in the lid, set it at the base of the plant or on top of the soil. Come back the next day and you have a glass/lid full of drunken dead gnats.

Also, look up a drench solution called "Azamax". It's simple, easy, and effective. Just add the specified amount of solution to water and drench your soil with about a 1/4 run-off. Repeat this process once a week or until soil is completely dried out, for about 3 weeks. This product also fights mites/insects of all kinds as well as fungus, and mold!

[Lemuel714]

I definitely appreciate the input but I think I've pretty much got the bugs under control. Being that I'm down to almost zero gnats I'm guessing that the larvae have been mostly dead for a week or so now. What I'm asking is whether or not one would expect their plants to continue dying off this long? My plants are still continuing to turn yellow, dry up and die (although, at a much slower pace) and I'm starting to wonder if I have another problem in addition to the gnats.

[OMB]

At this point I would repot them all in fresh soil. Get a good look at the root's on the sickest one, probably a sacrificial lamb though. What soil are they in? Did they germinate in that soil?

[Lemuel714]

Actually, I have repotted a few of them. I cleaned them up and put them in water overnight and back into new soil the next day. Four out of five of them look like they're gonna make it. The fifth one is still questionable. They are in Scotts potting soil. Some of them are clones and some are from seeds. I put clones and seedlings into jiffy pellets and then into the soil. Not sure that's the best thing to do but it is how I started my plants years ago when I grew outside.

[KeiserSozeh]

Sounds like you're well on your way to getting the gnats under control. I'd say that is most of the problem, because even with the gnats dead, you still have root damage which will take a while to heal (if it does), or it could be permanent that causes eventual death. Really depends on how strong the plants/clone strain is and how well they can tolerate the root damage and how quickly they can regrow a (or grow a new) root system.

I had the gnat problem myself and realized it came from buying cheap dirt. Not to say Scott's is cheap.... I really have no idea on that one. I can say that since I popped for the actual miracle grow I have not had this problem. Something about the way they treat their soil. When I ran into this issue, a friend recommended NEEM oil. A little bit in a spray bottle with your regular water goes a very long way. Treat once a week, soaking the soil down with the spray and the gnats were gone completely after 2 treatments.

As for the continuing yellowing/leaves dying that would seem to be a factor of a poor root system. When I'm doing my clones, I put the cutting straight into water and leave them there until they get a nice, thick root system. I was using a rooting hormone to start with, but found out just the water by itself seems to perform about as well. Using just the water like I do may add a few days to the rooting cycle, but I've notice doing it this way seems to work best for me. Just my two cents!

[Chromophore]

If fungus gnats become a serious problem, that indicates other issues. Namely, your soil is drenched and somewhat anaerobic. Having a few around is no big deal, but as others have pointed out, if the larvae become dense enough in populatipon, they run out of microrhizzae to consume and start eating roots. Bummer. But the fact that this is happening points to other problems, which may persist even after the (current) batch of gnats is knocked down. You MUST have soil that drains easily and does not allow stagnation around the roots. Fungus gnats thrive under those conditions. But those conditions also mess up the transport of nutrients and oxygen into the roost, so the overall problem is compounded. Use the best soil you can find (Foxfarm Ocean Forest may be the best soil I've ever used in terms of drainage and proper water retention) and make sure you water through. Don't allow the holes in the pot bottoms to sit in water. Forgive me if you already know everything I've said, but I deal with fungus gnats in a greenhouse constantly. We use them like the "canary in the coalmine". If we see a lot of them, we know our water/soil situation has a problem.

[Lemuel714]

How long do them in water? Scott's is decent but it is fairly cheap and may be where they came from. I've been doing this for a year now and have probably had the gnats for three months. So it hasn't always been a problem. I'm sold on Nematodes and mosquito dunks and will continue to use both as a preventive measure. I just repotted several plants and a few of them just had NOTHING left for roots. No wonder they're looking so bad.

[Chromophore]

Yes you indeed had a serious infestation. Once those larvae get a taste for roots they're off to the races. The roots become weaker as the stagnant water suffocates them. Free lunch. Personally I hate all commercial potting soils. There are many threads in this forum dealing with this issue, but if I'm going commercial I will only use the best. Screw cost; you get what you pay for. But in the event that you simply cannot find good soil like Foxfarm, just make sure that you're letting the soil dry out a bit before watering again. At least the top inch or so should be dry, and NO standing water in the lower levels of the rootball. Drainage, drainage, drainage. In nature there is a limitless soil horizon around each plant and water can diffuse away. In a pot things are much more restricted and problematic.