It is common since the larva must ingest the BTI spores for them, the spores, to become active and start to digest the mosquito larva. The Mosquito Dunks will not prevent mosquito larva from hatching but they can keep the larva from becoming adult mosquitoes.

beanie, to answer your question, mosquito dunks have a very long shelf life (years) if stored properly: dry and cool. High humidity, freezing and/or stifling hot temperatures will cause them to deteriorate more quickly. You decide if you should replace your dunks or not.

thank you

Has anyone here tried using them on fruit flies before? They're also in the order Diptera. I'm giving it a shot at home.

BTI is also sold as Gnatrol which is used to control Fungus Gnats. Since the larva of fruit flies are on fruit there would be no good way to put some of this on your fruit. The simplest way to control fruit fly is to wash your fruit thoroughly as soon as you get it home.

Washing will not prevent an infestation of fruit flies, if you bring them in the house in the form of eggs that have been inserted under the skin of fruit. Washing won't even prevent egg laying from visiting fruitflies. In the home, you can prevent future problems by wrapping the individual fruits in paper towels or napkins for counter storage or putting them directly into the 'fridge.

Karen, are you certain that you have fruit flies? If so, you can very successfully trap the adults by putting a bit of apple cider vinegar and some dish soap into a small container with a little water for dilution. The adult flies will flock to that solution and sink to the bottom.

This will only work on fruit flies, not on fungus gnats or drain flies. It's a very simple and effective remedy. Bt will not be effective against fruit flies.

I've used traps like that, rhizo, and they do catch fruit flies -- but not all of them. There's always some left.

Yes, but the Bt will not control them. Trap the adults and keep trapping them. Their maggots will not feed on the Bt, simply because of where they are (under the skin of unprotected fruits and veggies). The adults don't feed at all.

Inside the home, fruitfly infestations can be prevented and halted, but Bt will not be part of that cycle. Sorry.

There are a number of different bacterial forms of BT, each specific to the insect being controlled. Some work on a worm's stomach where it changes the pH of the digestive system, and others prevent gill formation in aquatic larva, and the list goes on...but no one BT will do two jobs. Instar stages also determine the effectiveness of an application too.
Try mixing a quart of molasses to 3-gallons of water/BT mix to act as a sticker if you expect rain or might be slightly early with an application.
I've also used an old blender to turn dunks into a powder which can be broadcast for better coverage over wide areas.