You wrote: "Now my plants are starting to die!! "

If the bulbs, perhaps just done for the season?

If other things, what are they, what size when planted, and what happening (specifically) now?

Beyond that, does the container have drain holes?

The plants are brand new, i only planted them in late Feb. The plants are a hosta, an astilbe, and an oxalis triangularis. The oxalis' leaves are drying up, browning and shirveling. And the astilbe's leaves are browning. I purchased them in a package, as blubs (roots), and they have just started to pop out of the soil a few weeks ago. So i don't think they're done for the season.
Yes the container has drain holes, 5 total.

I googled gnatrol and found these 2 websites where you can order it:
http://www.amazon.com/BetterGrow-Hydro-Gnatrol-32-oz/dp/B0012KT6IY
http://www.planetnatural.com/site/gnatrol.html

Also, fungus gnats were discussed (a long time ago) on gardenweb.

Here is a link that might be useful: gardenweb gnats

fungus gnats should not be a problem that has to be treated outdoors ... IMHO.. avoid the chemical use ...

they proliferate in soil that is maintained too wet ...

and perhaps the problem came in the bag of CHEAP potting soil...

the easiest solution .... is to buy some fresh soil ... pot up your plants.. dump out the CHEAP potting soil ... and then replant the potted stock ... washing all the old soil off the plants before replanting in new soil ...

it will probably be cheaper than buying a large container of gnatrol... that will just sit in the garage for 100 years ...

another problem comes to mind.. they may be attracted to a ripe new barrel .. while it is empty.. you might want to scrub it down with a 10% bleach solution to rid it of any of the fermentation byproduct that might be left in the wood ... be safe .. i once had a barrel.. full size.. that smelled of whiskey for a year ... lol ... since our market is near canadian club in windsor Ont .... or in the alternative... smelled like ginger ale.. since vernors is/was local ... IMHO.. there is a strong chance that there is something emanating from the barrel that is attracting them.. and it might be the barrel ...

ken