The important points to remember from this video below are

1. be patient.
2. Help the dog learn to focus on you before the trigger gets him out of control.
3. The handler learns the dogs distance from the triggers that set him off. In this dogs case many things in the environment trigger the dog into excitement mode, especially trees. So the handler has to work with the dog very close to the beginning of the walk, so be it. watch as the dog get calmer with repeated attempts.
4. This is the type of training is when allot of food is effective. The tree containing squirrels are really, really exciting for a dog. So you have to become more exciting than a squirrel and the next better thing is usually food. Really yummy food. like chicken, lunchmeat or cheese. This method is called “counter conditioning”. The “conditioning” happened automatically when the dog learned to lung and bark at trees because some really fun stuff happened. To make staying with you on a polite walk a new habit, you have to make you more appealing then the fun of his learned doggie game of lunging/barking at trees. The process of doing it is called “counter-conditioning”. It takes a long time usually months of practice for a dog to give up an old habit and replace it with the new behavior you want

EXTREME LEASH PULLING, BARKING, LUNGING and JUMPING!