Hi all,
  Some folks have commented that they use BTi biological larvicide every time they water as a preventative measure for keeping the fungus gnats at bay.  I was doing this semi-regularly last summer/fall and have continued the practice with the figs I brought into the house to extend the season.  Specifically, I am using a product called Gnatrol WDG (Water Dispersable Granules).  I know that others on the Forum use this product as well.
  As a matter of convenience I would mix up a couple of gallons at a time in milk jugs, and I often had some left over.  In fact, I would often specifically mix more than needed and keep it on hand so that it was ready to go.  I finally got to wondering whether or not this was really the right thing to do.
  A couple of days ago I contacted Valent, the manufacturer of the Gnatrol products, and described my practice to them.  I was informed that the effectiveness degrades pretty quickly once it is mixed in suspension with water.  For example, after a couple weeks there would not be much "insecticidal property" left.  I was advised to mix up only as much as I needed and use it as soon as possible.

  It was very nice that they called me back to answer my questions.  I missed the call and am just recounting the gist of the voicemail message they left.

  I'm now wondering about a followup issue, which would be the use of Gnatrol WDG for makeup water in SIP or SWC pots.  I don't currently use SIP/SWCs now, but I'll be starting in the spring.  The water in the reservoir is wicked up into the planting medium, so the BTi would be delivered where it needs to go I guess.  I don't suppose it is the case that it will be sitting there at the bottom of the planter for a long time...

  Does anyone have any insight/experience with this?  It might be worth a follow-up call.
Cheers,
Jim

I use the powder you mix with water I also mix weak mg about 1/4 stringth. I mix a gal at a time and have some left over I have seen maybe three gnats altogether but have lost no cuttings to them just a few that I messed up myself.

Jim, I don't keep a gnatrol/water suspension for more than a day once mixed up because I was worried it might not stay viable.  Thanks for making the phone call and confirming my suspicion.

Also you raise a good point about SIPs.  I've been adding gnatrol (relatively dilute suspension) every other time I add water to my SIPs.  All seems well so far.  I have both SIPs and non-SIP cups/1 gallon containers never see more than one gnat buzzing around.  I also have a couple of carnivorous plants which put a dent in the adult population.

Don't have the answer about the SIPs, but I'm here to save you guys money.

I've searched long and hard because of issues with fungus gnats, and it is very expensive to get a strong dose like Gnatrol. Look up this stuff called Microbe Lift BMC. You can find it for anywhere between $15 and $25 and it is a SUPER concentrated liquid in a dropper. It is sold in the pond/water garden market to treat for mosquito larvae, so each tiny bottle can treat around 500 gallons! Literally, you can put just a few drops in a gallon of dechlorinated water for your plants. It will last months and months. 

I also like using a little diluted natural Neem oil from Dynagro as well. It kills those little guys in time, is healthy for the plants, kills the bad fungi, and is actually a systemic! So it helps protect against leaf eating plants as well, such as spider mights.

I just did a quick websearch of Microbe Lift BMC (Biological Mosquito Control).
http://www.microbelift.com/products/pond-and-water-garden/mosquito/bmc/
http://www.microbelift.com/files/1013/2812/2879/MSDS-BIOLOGICAL-MOSQUITO-CONTROL.pdf

It is a source of BTi...like the Gnatrol WDG product.

Microbe Lift BMC claims "up to 14 days activity depending on application site"...so this reinforces the whole "don't mix it and leave it sitting around, use it right away" notion.


"2 oz. (BMC2) Treats 400 gals. for 2 years"...this implies that the 2 oz bottle has a shelf life of at least 2 years.  (Note: one rationale behind the "water dispersible granules" formulation of Gnatrol was to improve the shelf life of the product, which it claims as 2 years.  Presumably Gnatrol's liquid version is less.)

EDoukas -- does the label on the Microbe Lift BMC bottle say what the shelf life is?

Cheers,
Jim

It just says up to two years. I've heard that refrigeration is good for shelf life so I store it that way.

Also says 6 drops for 100 gallons for pond use. That is concentrated!

Jim,
All the BTi instructions are to re apply on a 7-14 day schedule to break the reproductive cycle of the Fungus Gnats. Since they do not "live" in water the SIP reservoir doesn't actually need to be treated with BTi, but if needed a chunk of Mosquito Dunk will last for 30 days in water. I grater the Donut, mix it with water or mix it into the top 1 -2 inches of damp soil, where the eggs are laid and the larvae emerge and are active. Good Luck.

http://www.summitchemical.com/mosquito/

I usually mix up a gallon, use what I need and save the rest for next time.  I'll start making less!  Thanks.

Since this Microbe Lift BMC sounds super concentrated, and obviously you can't go sub 1 drop... will it hurt anything if you were to mix a concentrated batch of say 1 drop per gallon?  Or would it just kill more gnats!!!   :)
Ever since I found out these things were bad I'm starting to hate the little buggers.  Time to make em pay.

EDoukas - How effective has the Microbe Lift BMC been for you?  How much have you been using to treat?

Also, for everyone, how do you water with these products on cuttings in Uline bags on 7 day intervals and not soak the soil and create root rot?  I mean it seems like by drenching the bag with this stuff I'm going to be solving one problem and creating a bigger one...what am I missing?

Doug,
I completely agree. As explained in the linked Topic

Microbe Lift BMC claims "up to 14 days activity depending on application site"...so this reinforces the whole "don't mix it and leave it sitting around, use it right away" notion????

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