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Fungus Gnats.. Ugh

LordHill

LordHill

Everytime I buy a commercial potting mix to start my plants, I get over run with fungus gnats. What is the best way to manage/destroy them? I cant water any less often without my plants not coming back from their drooped stage of thirst... Ive used many sticky traps over the last couple of years.. they get covered and replaced in days... the problem is sticky traps catch adults that just happen into them. They don't stop the larvae. Is there anything I can do? I was thinking Diatomaceous Earth. I have read to add a layer of sand to the top of the pots and bottom water, but that isnt really an option for a couple of my plants. Any suggestions?
 
I can't get mosquito dunks. I did buy nematodes which work really well, I see a reduction in gnats fairly quickly. I tried sand last year, it did not work at all. 
 
I always microwave my potting soil for 1:45 seconds on high to kill anything in the soil like flies and mites. And sand on top of soil will help. You can set traps of apple cider vinegar in a cup with a drop or two of joy. They will dive in and die.
 
96strat said:
I always microwave my potting soil for 1:45 seconds on high to kill anything in the soil like flies and mites. And sand on top of soil will help. You can set traps of apple cider vinegar in a cup with a drop or two of joy. They will dive in and die.
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96 is spot on !  He taught me that a few years ago , when the first year i had fungus gnats ,but since then i microwave first and not a critter ! Thanks teach !    
 
Thinking ahead - I buy Fox Farms soils in the Fall, keep them outside so they freeze a couple of times, put the soil into the shed, and when it's time to use in the Spring - I have very few fungus gnats.  So far this season I've caught 2 gnats on the sticky traps.
 
I also use crumbled mosquito dunks when I mix the soil for transplants.  A little Bt goes a long way.
 
LordHill said:
Everytime I buy a commercial potting mix to start my plants, I get over run with fungus gnats. What is the best way to manage/destroy them? I cant water any less often without my plants not coming back from their drooped stage of thirst... Ive used many sticky traps over the last couple of years.. they get covered and replaced in days... the problem is sticky traps catch adults that just happen into them. They don't stop the larvae. Is there anything I can do? I was thinking Diatomaceous Earth. I have read to add a layer of sand to the top of the pots and bottom water, but that isnt really an option for a couple of my plants. Any suggestions?
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My best advice (for this specifically) is to see if the soil mix bags say if the soil has been sterilized or not. If it has, you are very unlikely to get pests from the soil directly.
 
 
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mrgrowguy said:
My best advice (for this specifically) is to see if the soil mix bags say if the soil has been sterilized or not. If it has, you are very unlikely to get pests from the soil directly.
 
 
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Even if it has, if the bags have even the tiniest little opening, they will find their way in. Sterilized at the bagging site does not ensure sterility at the retailer. Far from it...
 
Thus the "very unlikely" part. I hate dealing with absolutes unless I absolutely know it's absolute. And anything can be infiltrated, sterilizing simply helps. If I had to pick a bag that is less likely to have bugs between a sterilized bag and one that is not, I'll choose the sterilized one every time. Otherwise, you're betting against probability. And it doesn't pay out as big in gardening.
 
FFOF had a bad run for about a year where they sterilize their bags, but whatever they did in transit or storage, a huge number of their bags were infested with fungus gnats. I want to say that was about 2 or 3 years ago.
 
Unfortunately for me, I was on the receiving end of at least a good handful of those bags. But the last few batches I've bought were 100% bug free.
 
Fortunately, I learned how to deal with fungus gnats! Pretty easy really, with good watering habits and a few other measures.
 
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solid7 said:
Even if it has, if the bags have even the tiniest little opening, they will find their way in. Sterilized at the bagging site does not ensure sterility at the retailer. Far from it...
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"they [could] find their way in."
 
My bad, they actually *do* find their way in. I stand corrected.

Our local hydro store tells customers upfront that the sterilized media they sell often gets contaminated in transit. (they sell putting mixes as well as hydro stuff)
 
LordHill said:
Everytime I buy a commercial potting mix to start my plants, I get over run with fungus gnats. What is the best way to manage/destroy them? I cant water any less often without my plants not coming back from their drooped stage of thirst... Ive used many sticky traps over the last couple of years.. they get covered and replaced in days... the problem is sticky traps catch adults that just happen into them. They don't stop the larvae. Is there anything I can do? I was thinking Diatomaceous Earth. I have read to add a layer of sand to the top of the pots and bottom water, but that isnt really an option for a couple of my plants. Any suggestions?
Click to expand...
I use these yellow sticky things:
 
http://www.seabrightlabs.com/trap.htm
 
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