Welcome to the world of Black pines! If your talking about chopping them back the answer would be NO. Wait until spring for that. You can however trim CANDLES in the Fall and you should also remove some old needles. If the candles are more than 1 inch long you can remove up to 1/2 so it will back bud or produce shorter needles the following year. This would only be done on a branch that you would be keeping though. Let the top and a low branch go to help increase trunk size. This is just a very vague online of black pine work that needs to be done. You really need to get a good book on the subject and read. It takes a while to learn Black Pine.

Good Luck...you'll love working with them once yo get the hang of it!

A big factor in the treatment of your Japanese black pine would be its age, health, vigor, size, desired bonsai size, etc. Techniques vary greatly depending upon what you wish to achieve. You can spend a lifetime learning bonsai, and another lifetime learning Japanese black pine. But that's not to say you need a lifetime to learn the basics of training and caring for black pine, or to appreciate and enjoy them. I suggest you try out my articles on JBP.

Here is a link that might be useful: Sashi-eda Bonsai articles page