i dont like to chance on pulling the wrong plants either, but your plant looks mature enough to put into flowering. some say they can tell which sex it is there but i cant tell and wouldnt tell you to make a decision on it that way. i tried to guess before too, and got many right but some wrong, so im glad i didnt yank plants based on that. start flowering id say,and do a search on preflowers/preflowering and see if it helps.