barking

[Karen]

It sounds like he is in charge. Has he ever been through an obedience class with you? Maybe it's time to do it again, if he has. You - the humans, need to be more in control here if you want a quieter dog. Right now, he thinks he's alpha, so needs to be on top of every situation - when really, if he knew someone else were in charge, he might be able to relax a little ...

[BC_MoM]

I would completely ignore him when he barks at objects - if you act upon his behaviour, you're reacting to it.

When you pick up a garbage bag and he barks, just carry on doing whatever you're doing with it.

Or try this:

Have a toy in one hand (one that he goes crazy over, or a treat!) when you go to pick up the garbage bag - when he starts barking, throw the toy/treat in the opposite direction and praise him when he grabs/eats it.