This is a chicken/egg type question. 

Now I'm not sure what I have are really fungus gnats.  I have not seen any of the larvae with the black heads.  But I've recently noticed a bunch of gnats around my cuttings.  I've also had to give up on two or three cuttings that had died and rotted pretty significantly before I had noticed.  Now I can see them flying around, and little wormies in some of the cups of healthy ones, etc.

My question is, did the cuttings die because the gnats got to them and started eating them, thereby causing them to decay?  Or did the cutting die due to other causes (too much water, lack of vitality, mold, etc), after which the gnats moved in and started to multiply?

And now that I have the gnats around, will they start attacking the healthy cuttings and kill them?

Probably a simultaneous thing. The gnats are opportunists that find orgiastic delight (they multiply) in soggy soil conditions - the same conditions the damping off group of fungi find so attractive. Cuttings prefer damp conditions - not wet. Plants don't drink water; rather, they absorb it a molecule at a time in the form of vapor found in soil pores and the thin film of water on soil colloidal surfaces. Gnats generally are attracted to organic particles that remain moist and break down quickly - the reason they find fish emulsion and other organic nutrient sources attractive in container media. Gnats/larvae WILL feed on roots if nothing else is available, but they prefer rotting vegetation and animal products (hoof/feather/other meals, e.g.) over all else.

Al  

Perfect timing of question.  I had a potted plant given to me and this afternoon I find gnats on this pot. Any remedy suggestion Al ?

Cuttings prefer a medium that is VERY well aerated/drains quickly. The medium should hold very little or no perched water; this, so the end of the cutting is never 'immersed' in the perched water table or covered by a film of water that blocks oxygen movement into the cutting. If you're using a soil like this, and keeping the soil damp instead of wet, gnats are usually never an issue; so an appropriate rooting medium accompanied by good watering habits will go a very long way toward thwarting their getting established. Allowing the top of the soil to become quite dry before watering also discourages them. A nonchemical remedy is the Bacillus thuringiensis israelensis (Bti) bacteria that's quite easy to find. I know soil drenches with Imidacloprid are very effective, but I've never had to use it on soils I have cuttings in, so I can't vouch for whether or not it is too stressful to be used with no ill effects. I've used it on other young plants with no problems, though. Gnatrol is also sure to work.

Al

It looks like that type of neonicitinoid, Imidacloprid is at least substantially responsible for CCD in bees. It is likely harming native bees as well, who live underground mostly. Who knows how many billions have been lost by keepers and farmers? Bayer crops science is making money of course and we can expect them to keep selling the stuff. Maybe they will invent a reanimation spray for bees next so we all don't die because our farming industry collapsed, zombie bees to the rescue! Or people could just stop using it.

Paully, dust the surface of the container with DE, try one of those sticky traps, use the mosquito dunks, or get pet tree frogs ; ) Some potting mixes have FNs, and they fly in from outside so they can be tough to eradicate.

If you want to steer clear of the bee-killing pesticides that are too often suggested, you can also try putting 1/4 inch slices of raw potatoes on the soil surface to entice the larvae. If nothing else, you'll see if you have the larvae. Then pick them off. You won't get them all this way, but you might reduce the population. That and the yellow sticky traps and diatomacious earth that hoosierbanana mentioned.

I might agree about the Imidicloprid comments in principle, but not in practicality. First, a soil drench on a couple of trees isn't like wholesale spraying of the landscape. Second, while I'm certain that trees in bloom attract bees, most of my trees bloom in the spring when soils are cold/cool and gnat activity is nil. Also, I've never seen a bee hovering around my fig trees - closed inflorescence and all that. Bees, wasps, other beneficials and their larvae can all end up as secondary casualties to other methods (BTI, DE, other insecticides), so there is often collateral casualty associated with even the best IPM plan once you reach the treatment stage.

I offered 4-5 suggestions, all of which would be variably effective at controlling gnats, applied individually or in combination. I think that of all the suggestions, the imidicloprid would be fastest, most effective, and the longest lasting. If there are politics associated with its use, I'll let others wrestle with that issue. That's probably for the OP to decide - I wouldn't presume to substitute my value set or a personal ideology for someone else's.

I never have infestations of the beasts. In my mind, the best cure is prevention, and I've found that well-aerated soils and discipline in watering habits to be excellent prevention, and that's what I suggest, not only because of the gnats, but because of other far reaching benefits much more important than gnat control.

I live in a nice neighborhood on a good size cul de sac with about (I'm counting) 18 homes on it. Of the 18 homes, at least 2/3 - 3/4 have a lawn service. Grubs are a major problem in our area, so I'm sure all or nearly all and probably some of the others w/o lawn service are using Merit or some other form of imidicloprid on their lawns to control the grubs. I think that if we want to look for offenders, we should look first to agribiz and other SIGNIFICANT users of imidicloprid, not to the poor sole who has a few trees in pots to dose via a soil drench.

That's just my take. Like I said, I agree in principle but not in practicality. I have some very surprisingly valuable bonsai trees. My first line of defense against scale is imidicloprid. I use it responsibly, and can't make the connection between how I use it and the destruction of our food supply.

BTW - the effectiveness of DE is significantly reduced when it's wet or damp due to the clumping effect and the fact that water acts as a lubricant and inhibits DE's ability to absorb the insect's waxy cuticle - a mechanism quite different from the commonly held belief that it's the abrasive/cutting effect that causes desiccation.

Take care.

Al

You made some very good points Al, I doubt you are doing much harm the way you are using it. I am angry at the FDA and Bayer, and still in shock since this is a new development. Mostly I would like to put a dent in Bayer's pocketbook by making people think twice about buying a bottle, since they have been so reckless.

I do appreciate your advice Al, I did not mean to aim any anger at you. Have a great season.

I lost 90% of my hives four years ago. Strange thing about it was that there were no dead bees in any of the hives. the hives had no bees at all, well except for about ten dead ones. The hives still had a full super (box) of honey left in them at the end of winter so they probably dissappeared late fall.  If they die of starvation through the winter there are masses of dead bees in the hive come unwrapping time in the spring. That spring I moved and got out of my bee keeping hobby.
As far as the gnats go I got some from the potting soil too and I just catch them very well with with Tangle Trap (insect trap coating) brushed on some plastic placed near my soil. And yes I am watering less now.

Don't worry, Brent. I'm slow to anger but tend to be matter of fact, which some people take as snotty or short. I don't mind disagreement at all, and I understand exactly where you're coming from. In a way, it reminds me of my own propensity for patronizing local businesses instead of corporate entities, or not doing business with companies whose political leanings or MO conflict with my own value set. The important thing is we're all here trying to make things better for each other. Every grower can't implement every suggestion (I've seen so many people fall into horticultural ruin by trying) ;-) so they're going to have to decide what they want to do. All we can do in our effort is present our case & hope they make the right decision - no matter what they decide.

Sammy - Brent mentioned CCD, which stands for Colony Collapse Disorder. Some researchers think that imidicloprid plays a significant role in the malady because they can replicate it with doses of imidicloprid above a certain threshold. Other scientists aren't that sure and attribute the disorder to a combination of effects, with imidicloprid perhaps being one of them of unknown significance. In CCD, the bees are unable to find their way back to the hive. As always, use your best judgment and follow directions carefully anytime you use insecticides of any type.

I forgot to mention that the yellow sticky traps are fairly effective at removing the adult gnats, too. What Sammy said about the Tanglefoot reminded me.

Take care.

Al  

I hate fungus gnats!
In the past they were a real, real; pain, pain (you know where).
This year not so much, :)
I bought some 'soil addivite', I think from Garden Alive, that seems to work.
In the past it was liquid, last year it was granules.
Not sure what they are up to now...

http://www.gardensalive.com/product.asp?pn=3440

While reading this thread and enjoying a pint of Guinness, gnat fell into my glass. I'm out on the deck grilling. I drink the gnat along with my pint. Way I see it, it's just another source of protein.

Pete

HELLO ROB,

http://blogs.scientificamerican.com/observations/2012/04/06/common-pesticide-implicated-bee-colony-collapse-disorder/

>>> enjoying a pint of Guinness, gnat fell into my glass...

One of them (flutter), managed to sneak upstairs into my bedroom
and then get close enough to get inhaled through my
nose (think-wing-flutterrr!).

3 years ago bought a bag og MG potting soil & I had a hard time with those gnats. Now I used regular top soil that I have left out in the cold for 8 months and no problems. Wold never go back to MG soil.

LOL. Way to go Pete. Protein is good but if I have to go to the "can" every 15 minutes after the extra protein I would need one of those large headrest pillow used in airplane as my "high chair" to fix my bottom problem. No thanks for  extra protein that way. Best laugh for the day Pete. Thanks.

I think there is probably 2 ways to read the blip that Gina provided. On one hand, if you are already predisposed to believe that imidicloprid is an awful chemical, it can be read to support that position. If you're critical about what it actually says ...... well, let's read it together with emphasis added.

Farmers worldwide have been using one popular neonicotinoid, imidacloprid, for about a decade to keep harmful insects off their cotton, corn, grains, potatoes, rice, vegetables and other crops. Like other neonicotinoids it targets the nervous system of insects, resulting in paralysis and death. Because honeybees (Apis mellifera) are insects, too, biologists have long suspected [not very conclusive - the author isn't sure] neonicotinoids as a possible [this is very vague - it's possible that it could also be any one of several thousand other causes] force in colony collapse disorder. [The first thing I thought of was 'intentionally scary with no real substance, and the entire article is laced with 'mights & maybes']

 
Researchers have now found that repeated low-dose exposures are perfectly capable of gradually killing of whole hives of bees [sic]. [I'm having trouble imagining an insecticide that doesn't/wouldn't act in such a manner, along with thousands of other common substances that if 'fed' to bees in repeated low doses wouldn't kill them] In fact, 94 percent of hives whose bees had been fed the pesticide died off entirely within less than six months, according to a new paper that will be in the June issue of Bulletin of Insectology.

I really have no opinion one way or another about whether or not anyone should or shouldn't use imidicloprid. I don't think the manner in which I use it is worth my fretting over. I do think that if I was invested in determining if there was a moral obligation for me NOT to use it, I'd be looking for something scientific. I'm not even saying that something scientific and definitive doesn't exist - there may well be studies that conclusively show that imidicloprid use is indeed a significant cause of diminished bee populations. What I'm saying is that I'd quickly bypass the article in Scientific American because it doesn't show/conclude anything and because of the bias that's so obvious in the manner in which it was written.

Finally, the Bayer toxicologist said the concentrations were unrealistic. The reply to this assertion was, “Our experiment included pesticide amounts below what is normally present in the environment.” As I read this, the question I wanted answered is, if doses lower than what is normally present in the environment are killing bees, why are there bees? Shouldn't they ALL be dead because the amount of imidicloprid normally found in the environment is greater than a lethal dose?  

Al  

I found it neat that Gina's article mentioned 94% and that I lost 90%.

Of course the missing bees could be added to the list of masses of birds and fish showing up dead all of a sudden all over the world. (just joking here)

Thanks Al and Gina.

I hate gnats.  And I have more this year than I ever did in the past.  

Just placed some potato slices in my pots and cups to try Gina's suggestion.  My cuttings are all in my attached garage.   For many  of us...those of us with  less than 30 or 40 cuttings...would a couple shots of an aerosol insecticide around the base of our cuttings really be so bad?  I mean...we are talking about a very small amount of insecticide here.

Having said that...my cats come and go throughout the house and into and out of the garage, so I won't be doing it.

But again...for someone with a small amount of cuttings and no other issues...

I use "gnats" as a swear-word.
With fungus gnats, I allow the soil to dry down more between waterings, and scratch up the surface of the soil with an old fork.
Klobbers 'em in short order.
And be friendly to spiders, they'll eat them if you don't want too.

Dave - You might be interested in knowing that if you use one of the flea control medications that you apply on the back of your pet's neck, you're applying imidicloprid. It's also used remedially and prophylactically for ear mites, heart worm, and a variety of intestinal parasites (worms).

Al 

Thank you Al.  Sounds like a good idea.  I will most definately look into that, with an eye to dosage and application concentrations and methods.

Hi, Viv - mosquito dunks contain a bacteria (BcI) That's been mentioned several times upthread and it's effective against the larvae, so helps prevent future generations.

The Frontline you use is another systemic neurotoxin that is effective on insects, used widely on crops, and is also toxic to bees.

*****************************************

I'll make it clear that I'm not advocating for the use of any particular chemical or treatment regimen - imidacloprid in particular. My only goal was to list effective methods of controlling gnat populations. I did want to point out that taking for granted that knee jerk reactions or badly biased information is always correct is often self limiting. If (the collective) you choose not to use any one of the methods mentioned, it won't hurt my feelings one little bit. We're all big people & able to make our own decisions. The best we can do is get the right info into each other's hands, or at least work toward providing a view that's as objective as possible. That's not always an easy thing to do. I'm very certain that in spite of the fact I try to be objective, I have my biases - human nature. One thing though ..... I promise if you ask if my outlook is objective and based only on known facts, I'll take the time to reflect on it and answer straightforwardly.

I hope the rest of every one's weekend is relaxing. I'm looking for the Red Wings to win in a few minutes. I'll record it & watch it with my son after he & my wife return from golfing.

Take care.

Al  

Paully, you know I'm thinking my infestation might be from the Miracle grow organic potting mix as well.  I had been using Fafards/perlite mix through most of the winter, but couldn't get that for a while and had to switch to the miracle grow.  Then, after a few weeks with that stuff, I've got fungus gnats.  Coincidence?  Maybe.  But I know it's far from sterile, because there are little seedlings of something popping up here and there in it, and it also tends to mold.  Will not use it again.

I may have to resort to the insecticides soon.  The fly strips certainly catch a bunch, but not all. 

I have had fairly good success by keeping the surface of the soil light and fluffy (the top 1/2 to 1 inch) and by bottom watering only.  The idea behind having the surface fluffy is that it will dry very quickly.  If the soil surface is dry there is no (or very little) fungus growing on damp, decaying organic surface material, which means the gnats are not attracted.  If the surface is packed down, it may wick water from below even if you bottom water, and it will be slow to dry.  Gnats burrow a bit into the soil so if the fluffy surface is too thin, they may still be attracted to the damp and decay that is just below.

A few years ago I had an infestation near the grow lights in my cellar, I think from a "sterile" planting mix that I bought.  I went around to every pot/planter and scratched up the top 1/2 inch so that it was fluffy and in a few weeks the gnat population went down to maybe one every few weeks.  Unfortunately, every spring I have many dozens of seeds starting (tomatoes, peppers, etc) in very small containers and it is impractical to keep the top of the soil fluffy and dry.  So for a month each spring there is usually an infestation.  But once those go outside, the dozen pots that remain inside are maintained fluffy and dry on the surface and the gnat population drops back to zilch in a week or two.

I suppose instead of fluffing the top 1/2 inch, you can replace it with something which will drain and dry quickly.  I've heard a suggestion that putting a half inch of vermiculite on the surface of each pot/planter works.  My guess is that it works because it drains and dries quickly, again providing a surface with no decay and fungus to attract the gnats.