To have a stranglehold on something means to have control over it and prevent it from being free or from developing. These companies are determined to keep a stranglehold on the banana industry
a wrestling hold in which the arms are pressed against the opponent's windpipe complete power over a person or situation; "corporations have a strangelhold on the media"; "the president applied a chokehold to labor disputes that inconvenienced the public
complete power over a person or situation; "corporations have a strangelhold on the media"; "the president applied a chokehold to labor disputes that inconvenienced the public"