HI XXXXXX,
First I would have it's health checked as Labs are prone to hypothyroidism and if this affects the dog even a little it can show aggressive behavior.
Second, you are right, do not let her off lead anymore or you are opening yourself up for trouble from another owner.
There is such a thing as fence aggression and this is when there are two dogs , both on opposite sides of the fence that want to get to each other but can't. From this they get riled up and some develop aggressive tendencies because of it. IF you had another dog with your Lab in your yard, what would happen is that the Lab would eventually go after your other dog because it can't get to the one on the street. Dogs do what works for them and in this instance what your dog is viewing is each time she acts aggressive toward the dog on the street from behind the fence , the dog eventually goes away from the property, your dog did not know that the other dog and owner were eventually going to go away from the property anyway, she thinks her actions made it happen.
So I would train her a few times a day on basic obedience inside the home where there are few distractions, then take her out to the garden and train then take it to the street. You want to stop her behavior before it even starts and you know that another dog coming your way is going to make her act out so you will want to teach her the leave it command in every training you do so you can give her this command before she gets into attack mode as another dog approaches. The leave it command means, "leave everything and anything you have your mind on alone and put your attention back on me and me only." So you dog must have this command down 100 % before you take her out to the street.
Heres is a site to help you with teaching basic commands. If you are currently using commands that she is not listening to then you must change the command. So if you use "Fido Come" you must change it to 'Fido Here' so she does not associate old commands with old behavior.
If you cannot be home with her to correct her actions at all times when she is in the garden then there is little you can do about it.
I would stop pushing her to the ground as this can make aggressive dogs more aggressive. Remember, "you catch more bees with honey" so you want your dog to want to listen to you because she thinks you're the greatest thing in the world to be with, not because she is frightened of what might happen to her. When dogs are frightened they eventually lash out.
Clicker training/positive method training
http://www.clickerlessons.com/
video http://www.clickertrainusa.com/clicker-training-videos.htm
Thanks very much. Will definitely have the health check done. Although her aggression is the exception rather than the rule.
I've heard that head halters can help control them. I've also heard that they can be dangerous if they get caught on something. What do you thinkg?
We did have another dog in the yard with her until he died of old age recently. She never attacked him. But from what you say am I right in thinking that we need to address the barking at the fence every time it occurs?
Head halters are fine for walking, but cannot stay on them as a rule just as you would not leave a choke chain on. Use only a buckle collar for daily use and to hold the tags. A head halter hooks to the regular collar because some dogs resist them so much they slip out of them then you have a loose dog. So you will have to train her how to get used to it before taking her into a distracting environment.
There are no pull harnesses that I have heard also work so you may want to look into that as well.
To address the fence problem she has to be trained first to commands and she would need to be on leash in the garden so you can guide her back to you. Giving her commands when she is loose can be tricky because if she does not listen to them that one time then she knows from that one time she does not have to listen as you cannot get to her. So it is imperitive she get the leave it command down first.
I do have to head out to work now but will be home around 1 pm and will check back with you if you have more questions.
dog training consultant
24 years training & behavior,pet first aide, Therapy dog eval., PA Animal Response Team