All of the gnats died

[leum]

Not complaining, but fought an especially pitched battle and appeared to be losing. Gnatrol, Gnatnix, yellow stickies. Even imagined the gnats had mutated to a smaller pheno to get through the physical barrier. They didn't seem to be doing much damage, so I gave it up.

Then, suddenly, no gnats - at all. What happened? I'm two weeks into flower. Added a dehumidifier. Otherwise, no recent changes that could account for it. Any ideas? I want to figure it out so that I can avoid the infestation altogether.

 

[Smorf]

Interesting
Maybe what you were doing worked slowly and they all died off. They like when the soil stays wet so maybe the dehumidifier helped too.

 

[Arthur]

I vote the drop in humidity...what's the difference in rh?

 

[leum]

It's a big drop. The reduction in the gnat population corresponds to moving the dehumidifier under the plant. It's a thermo-electric type, the largest available, in a 2 x 4 closet grow. Also using air-pots. Gnats love those.

They seemed thirsty at the end. Buzzing around the reservoir.

 

[Waira]

leaum, what's the time line here? with biological controls, there's lag time as you kill off the larval generations, and adult expire normally,.. also, new recruits coming in,... how well the Bt gets distributed into the pot is a factor too,.. I like to make a tea of sorts out of the Gnatrol, pucks/granules, whatever.... as long as it the bacterial agent Bt,... if you have granules, or grind up pucks, make up enough to give a good watering for each plant,.. for say a gallon, clean no Cl water, use 2 fat T, with 2T molasses and a dash of nutes,... put it someplace warm, get an airstone in there for best results, and let it brew for a day or so to activate the Bt and get then multiplying,... then water away, stirring up to get granules into the pots too,...

 

[BII]

@Waira: I am interested in learning why you (and seemingly everybody else) presume that totally crude, non-sterile/non-aseptic (dirty, environmental bacteria- and fungi-contaminated) culture with molasses or any other simple sugar mixture is an effective and appropriate culture medium to selectively grow/replicate/expand the specific bacterium (or any other beneficial microorganisms) that you want to grow. Do you have any knowledge concerning dilute molasses actually being a suitable selective culture medium for Bt bacteria, or is this a blind presumption? Have you ever seen any Bt product actually labeled with such a recommendation?

I would presume aerated Bt culture is molasses/sugar water will result more in rapid growth of fungi and other bacteria, microorganisms that multiply faster in sugar water; and that there is more risk or no upsides vs. just using the Bt by just adding it to feed water and the letting the spores do their thing naturally. Even if Bt grows in molasses culture, is this under the right conditions to form Bt toxin? You don't even control temperature and pH during this attempt to culture Bt. If molasses use with Bt is associated with any improvements, it's probably from the molasses, not from any expansion of the number of live Bt bacteria and/or Bt toxin crystals. Mixed culture (with many other microorganisms present) could also well result in breakdown of Bt crystals already present or as new crystals are formed, further reducing efficacy. That molasses-cultured Bt works may be more attributable to enough Bt surviving to kill larvae, not from any increase in live Bt bacteria.

 

[Waira]

... yes, this is anecdotal, no it's not selective...I didn't come up with this either, some excellent gardeners made this recommendation,...Also, how do know that it doesn't? Can you show us something that should put this in doubt, even anecdotally? ..Devils advocate aside,... Molasses is well recommended in other brews/teas for the same reason, along with mineral nutritional benefits, ditto for adding it into soils,... glucose is something they can take into their bodies, it's instant fuel... So once in the brew the spores activate and start doing their thing, feed and multiply,.... Besides, this is an every day practical application, not a science experiment..... Bottom line, I've run batches with and without, and being a largely an outdoor grower the fight against gnats is unending, so I see plenty of results... the speed of population reduction is notably faster with that brew than just letting them soak in water overnight with nothing, and worlds better than surface application/watering in alone,.... I've had zero issues ever personally or from others telling me about some sort of microbe population imbalance from adding this solution, especially in healthy soil with a good population of beneficials,...
No label recommendations for this, indeed,... can you figure out why?--- because it's not made for treating gnats by intent, right?... it works only because gnats and mosquito's are closely related enough that this strain of Bt will hurt them both... You won't get good results using the strain made for killing caterpillars, BTW... and nobody is going to put molasses into their ponds either, that would be foolish....
As for sterility, a bucket that's relatively clean and stays dry almost always is not going to be an overwhelming source of contaminant microbes, especially in that short of time,... at least not that I've seen so far... I'm sure if left to brew for too long other things will dominate...

Even if Bt grows in molasses culture, is this under the right conditions to form Bt toxin?

.... what do mean "right conditions"? They make this toxin regardless of where they are,... inside their bodies first, right? Only after ingested does the toxin release, damage the gut wall and allow free access into the bodies of the victims, multiplying and making more toxins..basically infecting and poisoning at the same time....

You don't even control temperature and pH during this attempt to culture

I said warm, no need for exacting control here, for the same reason-- limited time brewing,.. as long as it's not overly hot, or too cold, there's plenty of flexibility on this,... unless in RO/Di/super low hardness water, pH isn't likely going to go wildly off either,.. I use tap, with significant hardness, and have had no pH issues in the brew,... have you seen anything from others that makes you think this is a genuine problem, or brewed up a batch yourself and measured pH?

If molasses use with Bt is associated with any improvements, it's probably from the molasses, not from any expansion of the number of live Bt bacteria and/or Bt toxin crystals.

.... this makes no sense dude,... what do you mean by improvements? How is molasses going to improve the speed and effectiveness of larval gnat population reduction if not by increasing the bacterial count?

Mixed culture (with many other microorganisms present) could also well result in breakdown of Bt crystals already present or as new crystals are formed, further reducing efficacy. That molasses-cultured Bt works may be more attributable to enough Bt surviving to kill larvae, not from any increase in live Bt bacteria.

... again, that's going to be a question of contaminant microbe types and populations; who said anything about using some debris caked skanky bucket? ... "could" doesn't mean "is", and that's also assuming these other microbes are actively consuming the toxins made by the Bt,... sorry, but I have serious doubts about that,... Are you suggesting that the molasses will cause such overwhelming counts of contaminant microbes that it will actually reduce the population of what was originally inoculated?? ...sure, maybe, if you literally tried to make that happen, as per the first sentence above,...

 

[leum]

Hi, @Waira! I prepare Gnatrol as directed and use it as my initial soak when preparing pots for planting. Thanks for the tips!

Anyway - I have a new theory. The plant killed them. Under the canopy, there's a strong, unmistakable odor of mosquito repellent. I never used any. so the plant must be producing it herself. That's what terpenes are for, after all. She's an especially vibrant plant, SAD fast F1. Burst out of the ground in one day and hasn't slowed down since.