Puppy aggression at dog park with new dogs

Question
Hi, I own an American Bulldog she is about 7 months old. I have taken her to the (off leash) dog park since we got her at about 8 weeks and is quite comfortable with the regular dogs that attend, they play well, small and big.
However when a new dog (usually smaller than her) comes she immediately runs up to check it out along with the other dogs but then she starts bullying a little eg. barking and lunging at the dogs and sort of trapping them from getting away, and if they run she will chase and I cant catch her, she is practically impossible to grab or distract from her chase and bullying. I dont beleive she has ever bitten another dog and she is very placid generally shes just all bark and chase, in those situations.
I have today tried a spray bottle which distracts her but she is very clever and actually started dodging me as well. So I end up frantically chasing her around and its awful for the other dog owner (obviously)
Please make some suggestions as to how I can get her to stop or I think Im going to have to stop taking her as I cant control her. (She isnt de-sexed)

Thank you

Answer
Dear Gaenor,

Good for you for bringing your pup to the dog park regularly!  Good dog (owner)!  In my experience, most dogs' personalities change as they approach their first birthday, and their puppy sense of humor often disappears at their second birthday.  So it's really important that you keep bringing her to the dog park to continue her socialization.  

What I recommend is that you keep bringing her to the park but when a new little dog enters, put your dog on her leash for the first several minutes, until she's met the dog and a little calmed down from the excitement of a new kid in class.  Keep your water bottle and use it for inappropriate on-leash lunging etc. -- she won't be able to dodge the water when she's on leash.  

If possible, sneak her a treat very quickly when she's being good, but don't do this if she has any food aggression at all (or if another dog in the park does).  Use lots of praise instead of the treat if so (use praise either way when she's being good.  When you think she's going to behave, let her off leash and watch her like a hawk.  If she starts up again, leash her and keep praising or squirting, whatever she has earned, then let her off again when you think you can.

If you haven't already, get her into a good positive reinforcement obedience class (you may have to spay her to do so, but I strongly recommend you do for many, many reasons which I won't list here).  You need better verbal control of her for when she's unleashed at the park.  She needs a solid "come" and "stay" for these situations, and a group class is the only way she'll learn to pay attention to you in a group dog situation.  Go to http://www.apdt.com for a good trainer in your area, but make sure it's a group class.

Whatever you do, don't stop socializing her, and thanks for writing!
Suzanne Harris, BSc, CPDT
http://www.dogdaysusa.com