Board Thread:Questions and Answers/@comment-70.31.139.90-20130701230202/@comment-8540798-20130702103313

The config you need to enable is this line;

"# Whether or not to generate rubber trees during map generation

B:WorldGen.RubberTree=false"

Change the false to true, and you'll be fine. That line's in the General Section of the file, third from the bottom on the list.

No idea if this will bug your game with the IC2 Rubber Trees appearing as well though.